Research ArticleStudy of Tunnel Damage Caused by Underground MiningDeformation Calculation Analysis and Reinforcement

Peixian Li 1 Lili Yan 2 and Dehua Yao 3

1China University of Mining and Technology (Beijing) Beijing China2China Center for Resources Satellite Data and Application Beijing China3China Railway Fifth Survey and Design Institute Group COLTD Beijing China

Correspondence should be addressed to Peixian Li pxlicumt126com

Received 11 September 2018 Revised 30 November 2018 Accepted 5 December 2018 Published 18 February 2019

Academic Editor Patrick W C Tang

Copyright copy 2019 Peixian Li et al is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Bayueshan tunnel (BYS) is an important construction crossing over coal mine goaf e underground mining subsidence hasled the tunnel cracked seriously in three years after it was built In order to evaluate the coal mine influence and future stabilityof the tunnels probability integral method (PIM) was used to calculate the tunnel deformation PIM is an experience functionmethod based on randommedium theory which is used widely in ChinaWith the parameters analyzed the tunnelsrsquo subsidencewas calculated e results show that it can interpret the tunnel damage well and the maximum normal strain positions fit thedamaged tunnel positions well It proved that PIM can be used to evaluate the tunnelrsquos radial deformation caused by un-derground coal excavation In order to maintain tunnels to keep a long-term stability the future deformation was calculated incase the coal excavation continues It shows that the tunnel would be cracked again if the excavation continued Other reasonssuch as the old goaf deformation and water and vehicle dynamic load are also important reasons for the tunnelsrsquo deformationIn order to keep traffic safety it needs to reinforce the cracked foundation under the tunnel en grouting injection wasproposed to reduce the old goaf deformation under the tunnels If the fracture zone under the tunnels disturbed by the dynamictraffic load the old goaf will face a risk of sudden collapse So to ensure the grouting effect the grouting depth should be deeperthan the sum of traffic load influence depth and height of coal mine caved fissure zone e grouting scope should keep all thecrack rock area under the tunnel from being disturbed by the dynamic traffic load is design can reduce the sudden collapserisk of the goaf and reduces the vehiclesrsquo load disturbance on the cracked rock e researched technology provides anengineering guidance to tunnel subsidence calculation stability evaluation and maintenance in complex geological andengineering situations

1 Introduction

Underground coal mining plays an important role inChinarsquos economic development Chinarsquos coal production isabout 36 billion tonnes per year Underground miningsubsidence could cause damage to houses land and otherconstructions e lands damaged by underground coalmine in China are more than 150 million hectares [1] andincreases by 70 thousand hectares every year For the widearea of goaf and subsidence a lot of roads have changed theiralignment or faced the problem of old goaf deformation Forthe safety evaluation numerical simulation is often usedto get the stress and normal strain [2 3] and probability

integral method is used to calculate the residual deformationof old goaf [4 5] According to different positions betweenroad tunnel and goaf Tong classified three typical condi-tions the tunnels below mine level the tunnels intersectingwith the coal seam and the tunnels above mine level andgave protection measures for those conditions [6] Simu-lation can be used to assess the tunnel convergence in cavedzones [7 8] Fang et al have simulated the tunnel de-formation under the caved zone e scale model experi-ments show that the tunnel settlement has a relation with thedistance of caved zone to the tunnel and dip angle of cavedzones [9 10] the conclusions have guiding significance totunnel design under caved areas Numerical simulation such

HindawiAdvances in Civil EngineeringVolume 2019 Article ID 4865161 18 pageshttpsdoiorg10115520194865161

as FLAC (Fast Lagrangian Analysis of Continua) UDEC(Universal Distinct Element Code) and FEM (Finite Ele-ment Method) method also have been used widely to cal-culate or assess the tunnel deformation in mined area[7 8 11 12] Most of those research studies were just in-terested in the deformation of the tunnel cross sectioncaused by the old goaf But BYS tunnel cracks were mainlycaused by the coal mining after the construction wascompleted e tunnel was damaged by the undergroundcoal mine tunnels were cracked mainly by the differentialmovement along or perpendicular to the tunnels Tunnellining and surrounding rock are secondary reasons PIM isan appropriate method to calculate the tunnel deformationcaused by rock redistribution after underground coalmining

Grouting is a widely used method on reinforcement intunnel engineering [13 14] Grouting in caved zone can beused to reinforce the goaf and reduce the goaf deformationIt can increase the strength of surrounding rock effectively[15 16] A suitable grouting scheme should keep balancebetween effect and grouting cost [16 17] So grouting depthand scope were designed based on dynamic traffic influenceand height of coal excavation cracked zone

Highway tunnels over the goaf are a complicatedproblem that has a relationship with geological goafcondition water and tunnel supporting method Tunneldeformation of coal mine subsidence is a complex problemthat has no unified solution Chongqing BYS tunnel islocated in western China Two tunnels were damaged byboth old goaf and underground coal mining Tunnel de-formation was calculated first and a fix measurement isproposed in order to maintain the tunnel e researchgives a reliable way of tunnel deformation evaluation andold goaf reinforcement

2 Geological

21 Engineering Introduction e BYS tunnel is an im-portant construction in the highway from Chongqing toChengdu e tunnels are double-separate-hole highwaytunnels which have 188sim446 m separation e tunnelconstruction is 1625 m wide and 820 m high e lefthole is 3270 m long starting from LK32 + 065 (elevation is34211 m) to LK35 + 335 (elevation is 30457 m) eright hole is 3302 m long from RK32 + 06615 (elevationis 34212 m) to RK35 + 36815 (elevation is 30392 m) einvestigated area of the tunnels was built from December31 2010 to April 23 2011

CR and XS are two collieries in the investigated areaBoth collieries had mining activities under the tunnel from2012 to 2015e tunnels were damaged by the undergroundmine deformation from 2014e first crack was LK35 + 168on September 4 2014 e crack was 1 cm wide and 4m inheight from the tunnel foot as shown in Figure 1 enRK35+ 268 tunnel lining structure cracked on November 152014 (Figure 2(b)) the crack was 3 cm wide and 6m inheight from the foot e crack extended to the top of thetunnel on June 9 2015(Figure 2(b)) ZK35 + 220 cracked onJuly 7 2016 (Figure 3) In order to ensure the traffic safety and

keep the stability of the tunnels a major repair is necessaryis paper calculated and predicted the mining subsidenceand tunnel deformation which can be used as guidance fortunnel maintenance

22CoalMineunder theBYSTunnel ere are two collieriesin the investigated area CR and XS CR coal mine is3375Km long from south to north and 055Km long fromeast to west It has two adits and two air shafts production is9 tonnes per year Mine method is inclined wall type blastingmining method wooden support and all caving roofmanagemente coal dip angle is 47deg on average CRminedK5 K7 K9 and K10 coal seams

e K5 coal seam is located on the floor of Triassicsystem upper series of third member of XJ formation(T3XJ3) 40m above the second member (T3XJ2) and 45mlower than the K7 coal seam ickness of this layer is022sim026m average 024m Under the K5 floor aremudstones and sandy mudstones

e K7 coal seam is located on the Triassic systemmiddle series third member of XJ formation (T3XJ3) 34mlower than the K7 coal seam ickness of this layer is020sim025m average 023m Under the floor are mudstonesand sandy mudstones

e K9 coal seam is located on the Triassic system upperseries of third member of XJ formation (T3XJ3) 8sim9m lowerthan the K10 coal seam ickness of this layer is031sim035m average 033m Under the floor are mudstonesand sandy mudstones

e K10 coal seam is located on the Triassic systemupper series of third member of XJ formation (T3XJ3) 28mlower than the fourth member of XJ formation (T3XJ4) coalseamickness of this layer is 044sim050m average 048mUnder the floor are mudstones and sandy mudstones

e XS coal mine covers an area of 16078Km2 e coalmine has one adit It is mined by the strike long wall methodand all caving roof management method e XS coal minemined the K11 and K12 coal seam and production was 9tonnes per year

(a) (b)

Figure 1 Crack of LK35 + 168 (September 4 2014)

2 Advances in Civil Engineering

e K11 coal seam is located on the fifth member of XJformation (T3XJ5minus1) 5sim7m lower than K12 coal seamickness is 034sim055m average 047m is coal seam isstability occurrence

e K12 coal seam is located on the fifth member of XJformation (T3XJ5minus1) and mine thickness is 040sim051maverage 049m

e geological section of the tunnel is shown in Figures 4and 5 And the mine plan and its mine times are shown inFigures 6ndash11

As shown in the figures the coal mine did not stopexcavation during and after the construction of the tunnelso the damage has great relation with mining activities afterthe tunnel construction complete So the deformation wascalculated and compared with damage positions

3 Tunnel Deformation Calculation

31Probability IntegralMethod ere are various methodsof mine subsidence calculation e most used in China isa profile function based on statistic medium algorithm[18] e method was introduced to China by Baochen

Liu and Guohua Liao in 1960s [19 20] and was devel-oped into a more reliable and easy used model namedPIM is method has just eight parameters based ongeological data and reliable surface deformation can beobtained

In order to calculate the surface deformation caused bycoal mining the rock was simplified as statistic mediumand formed with small statistic movement elements Asshown in Figure 12 after the small element in the firstlayer was excavated there are same chances for the twoelements in the second layer to fill it So as shown in thefigure the surface subsidence is similar to the Gaussianbell function when one element was excavated in the firstlayer

e PIM is based on this statistical theory and canobtain the subsidence with geometry integral of all exca-vation space

is model is easily accepted by engineers and technicalpersonnel and selected as a government recommendedmethod for mine subsidence prediction and damage esti-mation [21]

e PIM calculates deformation of underground miningby equations (2)ndash(6) [20]

We(x) 1r

eminusπ x2r2( ) (1)

W(x y) 1113944n

j1B

Dj

W0We(x y) ds dt

1113944n

j1B

Dj

W0

r2jeminusπ (xminuss)2+(yminust)2r2

j ds dt

(2)

i(x yφ) zW(x y)

zxcosφ +

zW(x y)

zysinφ

1113944n

j1B

Dj

minus2πW0

r4j11138961113858(xminus s)cosφ

+(yminus t)sinφ1113859eminusπ (xminuss)2+(yminust)2( )r2j1113872 1113873

1113897 ds dt

(3)

(a) (b)

Figure 2 Crack of RK35 + 268 (a) First cracked (November 15 2014) (b) Cracked after mended (June 9 2015)

Figure 3 Crack of LK35 + 220 (July 4 2014)

Advances in Civil Engineering 3

K(x yφ) zi(x yφ)

zxcosφ +

zi(x yφ)zy

sinφ

sumn

j1B

Dj

minus2πW0

r4j

1minus

2πr2j[(xminus s)cosφ

+(yminus t)sinφ]2eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(4)

U(x yφ) sumn

j1B

Dj

minus2πbW0

r3j

[(xminus s)cosφ

+(yminus t)sinφ]eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(5)

ε(x y φ) sumn

j1B

Dj

minus2πbW0

r3j

1minus

2πr2j[(xminus s)cosφ

+(yminus t)sinφ]2eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(6)

where (x y) are coordinates of the surface point φ is directionangle of surface movement W0 is the maximum groundsubsidence given by W0 mq cos α We(x y) is the sub-sidence of a small unit mining r is the major inuence radiusgiven by r Htan β H is mining depth q is the subsidencefactor b is the displacement factorm is the mining thicknesstan β is tangent of major inuence angle D is the calculationof mining area that deviation of inection point (S) removedfrom actual mining area n is the total number of miningpanels and α is the dip angle of the coal seam [19]

For inclined coal seam as shown in Figure 13 [20] theinection point of subsidence curve is not located directlyabove the boundary of the goaf but moved to the dip sidepointO the angle between OC and horizontal line is anotherprobability integration parameter θ0 called propagationangle of extraction S is the parameter of the point ofsubsidence inection [22] It is a distance of roof over-hanging in the goaf boundary e subsidence inection isshifting because of the roof overhanging

erefore parameters of the PIM are q b tan β θ0 andS S is dierent in dip direction (S1) rise direction (S2) andstrikes (S3) and (S4) ose eight parameters are all requiredin a mining subsidence calculatione parameters are oftenobtained from back analysis of eld survey results of sub-sidence in the nearby area

380

K36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

Le tunnel

Elev

atio

n 30

457

End

tunn

el Z

K35

+33

5

287deg

K5K7 K9

K10

K12K11

Mined before Oct 2008Mined from Oct 2008 to Oct 2010Mined from Nov 2010 to end of 2012Mined in 2013

Mined in 2014Mined in 2015Unmined coal seam

Figure 4 Section of left tunnel

4 Advances in Civil Engineering

And the results of subsidence tilt curvature horizontaldisplacement normal strain are marked asW i K U and ε

e PIM method is a semiempirical physical modele parameters can be obtained from site survey data InChina there are a lot of coal mines that have parametersthat are closely linked with their own geological andmining conditions en reliable mine subsidence anddeformation can be obtained from parameters based oneld measurement

32 ParametersUsed in BYSTunnel DeformationCalculatione XS and CR coal mines are located between Sichuan andChongqing in western China e coal seam dip angle isnearly 45∘ A lot of research work in nearby area of Sichuanhas been done According to geological and mining methodthe XS and CR are steep seam medium overlaying hard rockcoal mines According to reference [21] the conditions aresimilar to those of Nantong Coal Mine of Sichuan area eobserved parameters can be found in [21 23 24] as shownin Table 1

ere are also empirical equations that can be refer-enced According to the rock classication table in reference[21] the investigated area is medium hard rock overlaying

and the parameters of medium rock are q 055sim085tan β 192sim24 and S (008sim03)H

θ0 is a parameter to locate the subsidence position for dipcoal seams e CR and XS coal mines are both dip anglecoal seams so the θ0 can be obtained from the followingexperience equation

θ0 90∘ minus 068α αle 45∘ (7)

33 Inuence of Old Goaf e mining history of the in-vestigated area extends long before the tunnel was built etunnel crossed over old goaf According to related researchnearly 998 of mine subsidence occurred within 2sim3 yearsof coal excavation [25ndash28] And some observations showthat the residue subsidence of old goaf is often smaller than5sim10 maximum subsidence [29]

BYS tunnel is located at a mine colliery with long historybut the tunnel was only built in October 2010 In order tocalculate the subsidence caused by underground mining theproblem was simplied to three stages

First ignore the subsidence inuence of old goaf ex-cavated before October 2008 which was 2 years before thetunnel was built

380

420

460

500

YK36

YK35

YK34

+8 9 1 2 3 4 5 6 7 8 9 1

340

300

260

220

180

140

100

60

20

ndash20

ndash60

ndash100

ndash140

ndash180

ndash220

Mileage

Right tunnel Elev

atio

n 30

392

End

tunn

el Y

K35

+36

815

0

283deg

K5 K7K9

K10

K12K11

Mined before Oct 2008Mined from Oct 2008 to Oct 2010Mined from Nov 2010 to end of 2012Mined in 2013

Mined in 2014Mined in 2015Original coal seam

Figure 5 Section of right tunnel

Advances in Civil Engineering 5

Second the inuence between November 2008 andOctober 2010 seems as residuesrsquo subsidence use 10 of theinitial mining subsidence factor

In the third stage deformation caused by mining afterthe tunnel construction is completed (October 2010) shoulduse the initial subsidence factor

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92500 93000

Left tunnel

Right tunnel

3

4

5

7

4

5

6

7

ZK35 + 168ZK35 + 220

Ls-350

YK35 + 268

YK351

23

4578K36

YK368 7 5

43 2

1

8

8

1

1

ZK35

9350092000

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

+50m

+80m

+100m

+150m

6

6

69

96

9

9

23

HZ

plusmn0m

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 6 Coal mined area of K5 seam

2010

11-20

126

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

6

7

4

3

5

6

7

ZK35 + 168ZK35 + 220

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

plusmn0m

+50m

+80m

+100m

+150m

+200m

+250m

+300m

+350m

2010

11-20

12 0

620

14

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 7 Coal mined area of K7 seam

6 Advances in Civil Engineering

34 InuenceofMulti-Seam ere are four coal seams in theinvestigated area e inuence of repeated mining shouldalso be considered e factor K is a parameter to evaluate

repeated mining inuence on the subsidence For a repeatmining the factor can be obtained from the followingequation [20 21 30]

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008-2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

3

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

R-4000

2012

JD2

2011

2014

2010 20

07

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

OLD GOAF

ndash150m

ndash120m

ndash100m

ndash50m

0m

+50m

+80m

+100m

+150m

+200m

+250m+300m

+350mEn

d of

the r

ight

tunn

el 32

35m

End

YK35

+36

815

0

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

Figure 8 Coal mined area of K9 seam

3

3

Mine area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mine area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

9

7

4

5

6

7

ZK35 + 168

ZK35 + 220

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

2320

1320

12

2011

Rndash4000

JD2

2014

3ndash4

2010

2009

2014

520

146ndash

10

2014

10ndash1

1

2014

7ndash9

2010

11ndash2

0120

6

2014

2008

2009

2015

2015

456789K36

YK369 8 7 6 5

43 2

1

6

68

8

123

HZ

1

ZK35

93500

OLD GOAF

XS coal mine

ndash120m

ndash100m

ndash50m

0m

+50m

+80m+10

0m

+150m

+200m +25

0m+30

0m

+350m

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

CR coal mine

Figure 9 Coal mined area of K10 seam

Advances in Civil Engineering 7

qr (1 +K)q (8)

where the repeat mining factor qr always depends on theporosity of the failure rock for this area K 01 [31]

As shown in Figures 4 and 5 the K5 coal seam has notbeen mined after October 2008 e mining of K7 seam hasinuenced K9 and K10 and will disturbed by K5 so the K7coal seam is a repeat mining inuence subsidence K9 and

ndash400

ndash300

ndash200

ndash100

+0

+100

+150

+200

Ls-350

4

4 JD2

Rndash4000567899 20

15 2014

K36

YK368 7 6 5123

HZ

1

XS coal mine

2013

03ndash20

1312

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

Left tunnel

Right tunnel

CR coal mine

201208ndash201209

201203ndash201206

201210ndash20132

2015

2500

2000

150091500 92000 92500 93000 93500

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

Figure 10 Coal mined area of K11 seam

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

ndash400

ndash300

ndash200

ndash100

2015

2015

2012

2

2012

10ndash20

132

2010

11ndash20

112

2013

03ndash20

1312

2014

2014

2011

3ndash20

116

2010

11ndash20

112

+0+10

0

+150

+200

2500

2000

150091500 92000 92500 93000 93500

OLD GOAF

OLD GOAF

Ls-350

4

4 JD2

Rndash4000567899

K36

YK368 7 6 5123

HZ

1

Left tunnel

Right tunnel

CR coal mine

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

2011

10ndash20

1111

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

XS coal mine

Figure 11 Coal mined area of K12 seam

8 Advances in Civil Engineering

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

e K11 coal seam is located on the fifth member of XJformation (T3XJ5minus1) 5sim7m lower than K12 coal seamickness is 034sim055m average 047m is coal seam isstability occurrence

e K12 coal seam is located on the fifth member of XJformation (T3XJ5minus1) and mine thickness is 040sim051maverage 049m

e geological section of the tunnel is shown in Figures 4and 5 And the mine plan and its mine times are shown inFigures 6ndash11

As shown in the figures the coal mine did not stopexcavation during and after the construction of the tunnelso the damage has great relation with mining activities afterthe tunnel construction complete So the deformation wascalculated and compared with damage positions

3 Tunnel Deformation Calculation

31Probability IntegralMethod ere are various methodsof mine subsidence calculation e most used in China isa profile function based on statistic medium algorithm[18] e method was introduced to China by Baochen

Liu and Guohua Liao in 1960s [19 20] and was devel-oped into a more reliable and easy used model namedPIM is method has just eight parameters based ongeological data and reliable surface deformation can beobtained

In order to calculate the surface deformation caused bycoal mining the rock was simplified as statistic mediumand formed with small statistic movement elements Asshown in Figure 12 after the small element in the firstlayer was excavated there are same chances for the twoelements in the second layer to fill it So as shown in thefigure the surface subsidence is similar to the Gaussianbell function when one element was excavated in the firstlayer

e PIM is based on this statistical theory and canobtain the subsidence with geometry integral of all exca-vation space

is model is easily accepted by engineers and technicalpersonnel and selected as a government recommendedmethod for mine subsidence prediction and damage esti-mation [21]

e PIM calculates deformation of underground miningby equations (2)ndash(6) [20]

We(x) 1r

eminusπ x2r2( ) (1)

W(x y) 1113944n

j1B

Dj

W0We(x y) ds dt

1113944n

j1B

Dj

W0

r2jeminusπ (xminuss)2+(yminust)2r2

j ds dt

(2)

i(x yφ) zW(x y)

zxcosφ +

zW(x y)

zysinφ

1113944n

j1B

Dj

minus2πW0

r4j11138961113858(xminus s)cosφ

+(yminus t)sinφ1113859eminusπ (xminuss)2+(yminust)2( )r2j1113872 1113873

1113897 ds dt

(3)

(a) (b)

Figure 2 Crack of RK35 + 268 (a) First cracked (November 15 2014) (b) Cracked after mended (June 9 2015)

Figure 3 Crack of LK35 + 220 (July 4 2014)

Advances in Civil Engineering 3

K(x yφ) zi(x yφ)

zxcosφ +

zi(x yφ)zy

sinφ

sumn

j1B

Dj

minus2πW0

r4j

1minus

2πr2j[(xminus s)cosφ

+(yminus t)sinφ]2eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(4)

U(x yφ) sumn

j1B

Dj

minus2πbW0

r3j

[(xminus s)cosφ

+(yminus t)sinφ]eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(5)

ε(x y φ) sumn

j1B

Dj

minus2πbW0

r3j

1minus

2πr2j[(xminus s)cosφ

+(yminus t)sinφ]2eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(6)

where (x y) are coordinates of the surface point φ is directionangle of surface movement W0 is the maximum groundsubsidence given by W0 mq cos α We(x y) is the sub-sidence of a small unit mining r is the major inuence radiusgiven by r Htan β H is mining depth q is the subsidencefactor b is the displacement factorm is the mining thicknesstan β is tangent of major inuence angle D is the calculationof mining area that deviation of inection point (S) removedfrom actual mining area n is the total number of miningpanels and α is the dip angle of the coal seam [19]

For inclined coal seam as shown in Figure 13 [20] theinection point of subsidence curve is not located directlyabove the boundary of the goaf but moved to the dip sidepointO the angle between OC and horizontal line is anotherprobability integration parameter θ0 called propagationangle of extraction S is the parameter of the point ofsubsidence inection [22] It is a distance of roof over-hanging in the goaf boundary e subsidence inection isshifting because of the roof overhanging

erefore parameters of the PIM are q b tan β θ0 andS S is dierent in dip direction (S1) rise direction (S2) andstrikes (S3) and (S4) ose eight parameters are all requiredin a mining subsidence calculatione parameters are oftenobtained from back analysis of eld survey results of sub-sidence in the nearby area

380

K36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

Le tunnel

Elev

atio

n 30

457

End

tunn

el Z

K35

+33

5

287deg

K5K7 K9

K10

K12K11

Mined before Oct 2008Mined from Oct 2008 to Oct 2010Mined from Nov 2010 to end of 2012Mined in 2013

Mined in 2014Mined in 2015Unmined coal seam

Figure 4 Section of left tunnel

4 Advances in Civil Engineering

And the results of subsidence tilt curvature horizontaldisplacement normal strain are marked asW i K U and ε

e PIM method is a semiempirical physical modele parameters can be obtained from site survey data InChina there are a lot of coal mines that have parametersthat are closely linked with their own geological andmining conditions en reliable mine subsidence anddeformation can be obtained from parameters based oneld measurement

32 ParametersUsed in BYSTunnel DeformationCalculatione XS and CR coal mines are located between Sichuan andChongqing in western China e coal seam dip angle isnearly 45∘ A lot of research work in nearby area of Sichuanhas been done According to geological and mining methodthe XS and CR are steep seam medium overlaying hard rockcoal mines According to reference [21] the conditions aresimilar to those of Nantong Coal Mine of Sichuan area eobserved parameters can be found in [21 23 24] as shownin Table 1

ere are also empirical equations that can be refer-enced According to the rock classication table in reference[21] the investigated area is medium hard rock overlaying

and the parameters of medium rock are q 055sim085tan β 192sim24 and S (008sim03)H

θ0 is a parameter to locate the subsidence position for dipcoal seams e CR and XS coal mines are both dip anglecoal seams so the θ0 can be obtained from the followingexperience equation

θ0 90∘ minus 068α αle 45∘ (7)

33 Inuence of Old Goaf e mining history of the in-vestigated area extends long before the tunnel was built etunnel crossed over old goaf According to related researchnearly 998 of mine subsidence occurred within 2sim3 yearsof coal excavation [25ndash28] And some observations showthat the residue subsidence of old goaf is often smaller than5sim10 maximum subsidence [29]

BYS tunnel is located at a mine colliery with long historybut the tunnel was only built in October 2010 In order tocalculate the subsidence caused by underground mining theproblem was simplied to three stages

First ignore the subsidence inuence of old goaf ex-cavated before October 2008 which was 2 years before thetunnel was built

380

420

460

500

YK36

YK35

YK34

+8 9 1 2 3 4 5 6 7 8 9 1

340

300

260

220

180

140

100

60

20

ndash20

ndash60

ndash100

ndash140

ndash180

ndash220

Mileage

Right tunnel Elev

atio

n 30

392

End

tunn

el Y

K35

+36

815

0

283deg

K5 K7K9

K10

K12K11

Mined before Oct 2008Mined from Oct 2008 to Oct 2010Mined from Nov 2010 to end of 2012Mined in 2013

Mined in 2014Mined in 2015Original coal seam

Figure 5 Section of right tunnel

Advances in Civil Engineering 5

Second the inuence between November 2008 andOctober 2010 seems as residuesrsquo subsidence use 10 of theinitial mining subsidence factor

In the third stage deformation caused by mining afterthe tunnel construction is completed (October 2010) shoulduse the initial subsidence factor

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92500 93000

Left tunnel

Right tunnel

3

4

5

7

4

5

6

7

ZK35 + 168ZK35 + 220

Ls-350

YK35 + 268

YK351

23

4578K36

YK368 7 5

43 2

1

8

8

1

1

ZK35

9350092000

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

+50m

+80m

+100m

+150m

6

6

69

96

9

9

23

HZ

plusmn0m

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 6 Coal mined area of K5 seam

2010

11-20

126

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

6

7

4

3

5

6

7

ZK35 + 168ZK35 + 220

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

plusmn0m

+50m

+80m

+100m

+150m

+200m

+250m

+300m

+350m

2010

11-20

12 0

620

14

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 7 Coal mined area of K7 seam

6 Advances in Civil Engineering

34 InuenceofMulti-Seam ere are four coal seams in theinvestigated area e inuence of repeated mining shouldalso be considered e factor K is a parameter to evaluate

repeated mining inuence on the subsidence For a repeatmining the factor can be obtained from the followingequation [20 21 30]

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008-2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

3

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

R-4000

2012

JD2

2011

2014

2010 20

07

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

OLD GOAF

ndash150m

ndash120m

ndash100m

ndash50m

0m

+50m

+80m

+100m

+150m

+200m

+250m+300m

+350mEn

d of

the r

ight

tunn

el 32

35m

End

YK35

+36

815

0

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

Figure 8 Coal mined area of K9 seam

3

3

Mine area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mine area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

9

7

4

5

6

7

ZK35 + 168

ZK35 + 220

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

2320

1320

12

2011

Rndash4000

JD2

2014

3ndash4

2010

2009

2014

520

146ndash

10

2014

10ndash1

1

2014

7ndash9

2010

11ndash2

0120

6

2014

2008

2009

2015

2015

456789K36

YK369 8 7 6 5

43 2

1

6

68

8

123

HZ

1

ZK35

93500

OLD GOAF

XS coal mine

ndash120m

ndash100m

ndash50m

0m

+50m

+80m+10

0m

+150m

+200m +25

0m+30

0m

+350m

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

CR coal mine

Figure 9 Coal mined area of K10 seam

Advances in Civil Engineering 7

qr (1 +K)q (8)

where the repeat mining factor qr always depends on theporosity of the failure rock for this area K 01 [31]

As shown in Figures 4 and 5 the K5 coal seam has notbeen mined after October 2008 e mining of K7 seam hasinuenced K9 and K10 and will disturbed by K5 so the K7coal seam is a repeat mining inuence subsidence K9 and

ndash400

ndash300

ndash200

ndash100

+0

+100

+150

+200

Ls-350

4

4 JD2

Rndash4000567899 20

15 2014

K36

YK368 7 6 5123

HZ

1

XS coal mine

2013

03ndash20

1312

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

Left tunnel

Right tunnel

CR coal mine

201208ndash201209

201203ndash201206

201210ndash20132

2015

2500

2000

150091500 92000 92500 93000 93500

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

Figure 10 Coal mined area of K11 seam

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

ndash400

ndash300

ndash200

ndash100

2015

2015

2012

2

2012

10ndash20

132

2010

11ndash20

112

2013

03ndash20

1312

2014

2014

2011

3ndash20

116

2010

11ndash20

112

+0+10

0

+150

+200

2500

2000

150091500 92000 92500 93000 93500

OLD GOAF

OLD GOAF

Ls-350

4

4 JD2

Rndash4000567899

K36

YK368 7 6 5123

HZ

1

Left tunnel

Right tunnel

CR coal mine

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

2011

10ndash20

1111

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

XS coal mine

Figure 11 Coal mined area of K12 seam

8 Advances in Civil Engineering

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

K(x yφ) zi(x yφ)

zxcosφ +

zi(x yφ)zy

sinφ

sumn

j1B

Dj

minus2πW0

r4j

1minus

2πr2j[(xminus s)cosφ

+(yminus t)sinφ]2eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(4)

U(x yφ) sumn

j1B

Dj

minus2πbW0

r3j

[(xminus s)cosφ

+(yminus t)sinφ]eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(5)

ε(x y φ) sumn

j1B

Dj

minus2πbW0

r3j

1minus

2πr2j[(xminus s)cosφ

+(yminus t)sinφ]2eminusπ (xminuss)2+(yminust)2( )r2j( ) ds dt

(6)

where (x y) are coordinates of the surface point φ is directionangle of surface movement W0 is the maximum groundsubsidence given by W0 mq cos α We(x y) is the sub-sidence of a small unit mining r is the major inuence radiusgiven by r Htan β H is mining depth q is the subsidencefactor b is the displacement factorm is the mining thicknesstan β is tangent of major inuence angle D is the calculationof mining area that deviation of inection point (S) removedfrom actual mining area n is the total number of miningpanels and α is the dip angle of the coal seam [19]

For inclined coal seam as shown in Figure 13 [20] theinection point of subsidence curve is not located directlyabove the boundary of the goaf but moved to the dip sidepointO the angle between OC and horizontal line is anotherprobability integration parameter θ0 called propagationangle of extraction S is the parameter of the point ofsubsidence inection [22] It is a distance of roof over-hanging in the goaf boundary e subsidence inection isshifting because of the roof overhanging

erefore parameters of the PIM are q b tan β θ0 andS S is dierent in dip direction (S1) rise direction (S2) andstrikes (S3) and (S4) ose eight parameters are all requiredin a mining subsidence calculatione parameters are oftenobtained from back analysis of eld survey results of sub-sidence in the nearby area

380

K36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

Le tunnel

Elev

atio

n 30

457

End

tunn

el Z

K35

+33

5

287deg

K5K7 K9

K10

K12K11

Mined before Oct 2008Mined from Oct 2008 to Oct 2010Mined from Nov 2010 to end of 2012Mined in 2013

Mined in 2014Mined in 2015Unmined coal seam

Figure 4 Section of left tunnel

4 Advances in Civil Engineering

And the results of subsidence tilt curvature horizontaldisplacement normal strain are marked asW i K U and ε

e PIM method is a semiempirical physical modele parameters can be obtained from site survey data InChina there are a lot of coal mines that have parametersthat are closely linked with their own geological andmining conditions en reliable mine subsidence anddeformation can be obtained from parameters based oneld measurement

32 ParametersUsed in BYSTunnel DeformationCalculatione XS and CR coal mines are located between Sichuan andChongqing in western China e coal seam dip angle isnearly 45∘ A lot of research work in nearby area of Sichuanhas been done According to geological and mining methodthe XS and CR are steep seam medium overlaying hard rockcoal mines According to reference [21] the conditions aresimilar to those of Nantong Coal Mine of Sichuan area eobserved parameters can be found in [21 23 24] as shownin Table 1

ere are also empirical equations that can be refer-enced According to the rock classication table in reference[21] the investigated area is medium hard rock overlaying

and the parameters of medium rock are q 055sim085tan β 192sim24 and S (008sim03)H

θ0 is a parameter to locate the subsidence position for dipcoal seams e CR and XS coal mines are both dip anglecoal seams so the θ0 can be obtained from the followingexperience equation

θ0 90∘ minus 068α αle 45∘ (7)

33 Inuence of Old Goaf e mining history of the in-vestigated area extends long before the tunnel was built etunnel crossed over old goaf According to related researchnearly 998 of mine subsidence occurred within 2sim3 yearsof coal excavation [25ndash28] And some observations showthat the residue subsidence of old goaf is often smaller than5sim10 maximum subsidence [29]

BYS tunnel is located at a mine colliery with long historybut the tunnel was only built in October 2010 In order tocalculate the subsidence caused by underground mining theproblem was simplied to three stages

First ignore the subsidence inuence of old goaf ex-cavated before October 2008 which was 2 years before thetunnel was built

380

420

460

500

YK36

YK35

YK34

+8 9 1 2 3 4 5 6 7 8 9 1

340

300

260

220

180

140

100

60

20

ndash20

ndash60

ndash100

ndash140

ndash180

ndash220

Mileage

Right tunnel Elev

atio

n 30

392

End

tunn

el Y

K35

+36

815

0

283deg

K5 K7K9

K10

K12K11

Mined before Oct 2008Mined from Oct 2008 to Oct 2010Mined from Nov 2010 to end of 2012Mined in 2013

Mined in 2014Mined in 2015Original coal seam

Figure 5 Section of right tunnel

Advances in Civil Engineering 5

Second the inuence between November 2008 andOctober 2010 seems as residuesrsquo subsidence use 10 of theinitial mining subsidence factor

In the third stage deformation caused by mining afterthe tunnel construction is completed (October 2010) shoulduse the initial subsidence factor

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92500 93000

Left tunnel

Right tunnel

3

4

5

7

4

5

6

7

ZK35 + 168ZK35 + 220

Ls-350

YK35 + 268

YK351

23

4578K36

YK368 7 5

43 2

1

8

8

1

1

ZK35

9350092000

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

+50m

+80m

+100m

+150m

6

6

69

96

9

9

23

HZ

plusmn0m

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 6 Coal mined area of K5 seam

2010

11-20

126

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

6

7

4

3

5

6

7

ZK35 + 168ZK35 + 220

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

plusmn0m

+50m

+80m

+100m

+150m

+200m

+250m

+300m

+350m

2010

11-20

12 0

620

14

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 7 Coal mined area of K7 seam

6 Advances in Civil Engineering

34 InuenceofMulti-Seam ere are four coal seams in theinvestigated area e inuence of repeated mining shouldalso be considered e factor K is a parameter to evaluate

repeated mining inuence on the subsidence For a repeatmining the factor can be obtained from the followingequation [20 21 30]

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008-2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

3

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

R-4000

2012

JD2

2011

2014

2010 20

07

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

OLD GOAF

ndash150m

ndash120m

ndash100m

ndash50m

0m

+50m

+80m

+100m

+150m

+200m

+250m+300m

+350mEn

d of

the r

ight

tunn

el 32

35m

End

YK35

+36

815

0

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

Figure 8 Coal mined area of K9 seam

3

3

Mine area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mine area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

9

7

4

5

6

7

ZK35 + 168

ZK35 + 220

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

2320

1320

12

2011

Rndash4000

JD2

2014

3ndash4

2010

2009

2014

520

146ndash

10

2014

10ndash1

1

2014

7ndash9

2010

11ndash2

0120

6

2014

2008

2009

2015

2015

456789K36

YK369 8 7 6 5

43 2

1

6

68

8

123

HZ

1

ZK35

93500

OLD GOAF

XS coal mine

ndash120m

ndash100m

ndash50m

0m

+50m

+80m+10

0m

+150m

+200m +25

0m+30

0m

+350m

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

CR coal mine

Figure 9 Coal mined area of K10 seam

Advances in Civil Engineering 7

qr (1 +K)q (8)

where the repeat mining factor qr always depends on theporosity of the failure rock for this area K 01 [31]

As shown in Figures 4 and 5 the K5 coal seam has notbeen mined after October 2008 e mining of K7 seam hasinuenced K9 and K10 and will disturbed by K5 so the K7coal seam is a repeat mining inuence subsidence K9 and

ndash400

ndash300

ndash200

ndash100

+0

+100

+150

+200

Ls-350

4

4 JD2

Rndash4000567899 20

15 2014

K36

YK368 7 6 5123

HZ

1

XS coal mine

2013

03ndash20

1312

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

Left tunnel

Right tunnel

CR coal mine

201208ndash201209

201203ndash201206

201210ndash20132

2015

2500

2000

150091500 92000 92500 93000 93500

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

Figure 10 Coal mined area of K11 seam

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

ndash400

ndash300

ndash200

ndash100

2015

2015

2012

2

2012

10ndash20

132

2010

11ndash20

112

2013

03ndash20

1312

2014

2014

2011

3ndash20

116

2010

11ndash20

112

+0+10

0

+150

+200

2500

2000

150091500 92000 92500 93000 93500

OLD GOAF

OLD GOAF

Ls-350

4

4 JD2

Rndash4000567899

K36

YK368 7 6 5123

HZ

1

Left tunnel

Right tunnel

CR coal mine

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

2011

10ndash20

1111

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

XS coal mine

Figure 11 Coal mined area of K12 seam

8 Advances in Civil Engineering

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

And the results of subsidence tilt curvature horizontaldisplacement normal strain are marked asW i K U and ε

e PIM method is a semiempirical physical modele parameters can be obtained from site survey data InChina there are a lot of coal mines that have parametersthat are closely linked with their own geological andmining conditions en reliable mine subsidence anddeformation can be obtained from parameters based oneld measurement

32 ParametersUsed in BYSTunnel DeformationCalculatione XS and CR coal mines are located between Sichuan andChongqing in western China e coal seam dip angle isnearly 45∘ A lot of research work in nearby area of Sichuanhas been done According to geological and mining methodthe XS and CR are steep seam medium overlaying hard rockcoal mines According to reference [21] the conditions aresimilar to those of Nantong Coal Mine of Sichuan area eobserved parameters can be found in [21 23 24] as shownin Table 1

ere are also empirical equations that can be refer-enced According to the rock classication table in reference[21] the investigated area is medium hard rock overlaying

and the parameters of medium rock are q 055sim085tan β 192sim24 and S (008sim03)H

θ0 is a parameter to locate the subsidence position for dipcoal seams e CR and XS coal mines are both dip anglecoal seams so the θ0 can be obtained from the followingexperience equation

θ0 90∘ minus 068α αle 45∘ (7)

33 Inuence of Old Goaf e mining history of the in-vestigated area extends long before the tunnel was built etunnel crossed over old goaf According to related researchnearly 998 of mine subsidence occurred within 2sim3 yearsof coal excavation [25ndash28] And some observations showthat the residue subsidence of old goaf is often smaller than5sim10 maximum subsidence [29]

BYS tunnel is located at a mine colliery with long historybut the tunnel was only built in October 2010 In order tocalculate the subsidence caused by underground mining theproblem was simplied to three stages

First ignore the subsidence inuence of old goaf ex-cavated before October 2008 which was 2 years before thetunnel was built

380

420

460

500

YK36

YK35

YK34

+8 9 1 2 3 4 5 6 7 8 9 1

340

300

260

220

180

140

100

60

20

ndash20

ndash60

ndash100

ndash140

ndash180

ndash220

Mileage

Right tunnel Elev

atio

n 30

392

End

tunn

el Y

K35

+36

815

0

283deg

K5 K7K9

K10

K12K11

Mined before Oct 2008Mined from Oct 2008 to Oct 2010Mined from Nov 2010 to end of 2012Mined in 2013

Mined in 2014Mined in 2015Original coal seam

Figure 5 Section of right tunnel

Advances in Civil Engineering 5

Second the inuence between November 2008 andOctober 2010 seems as residuesrsquo subsidence use 10 of theinitial mining subsidence factor

In the third stage deformation caused by mining afterthe tunnel construction is completed (October 2010) shoulduse the initial subsidence factor

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92500 93000

Left tunnel

Right tunnel

3

4

5

7

4

5

6

7

ZK35 + 168ZK35 + 220

Ls-350

YK35 + 268

YK351

23

4578K36

YK368 7 5

43 2

1

8

8

1

1

ZK35

9350092000

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

+50m

+80m

+100m

+150m

6

6

69

96

9

9

23

HZ

plusmn0m

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 6 Coal mined area of K5 seam

2010

11-20

126

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

6

7

4

3

5

6

7

ZK35 + 168ZK35 + 220

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

plusmn0m

+50m

+80m

+100m

+150m

+200m

+250m

+300m

+350m

2010

11-20

12 0

620

14

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 7 Coal mined area of K7 seam

6 Advances in Civil Engineering

34 InuenceofMulti-Seam ere are four coal seams in theinvestigated area e inuence of repeated mining shouldalso be considered e factor K is a parameter to evaluate

repeated mining inuence on the subsidence For a repeatmining the factor can be obtained from the followingequation [20 21 30]

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008-2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

3

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

R-4000

2012

JD2

2011

2014

2010 20

07

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

OLD GOAF

ndash150m

ndash120m

ndash100m

ndash50m

0m

+50m

+80m

+100m

+150m

+200m

+250m+300m

+350mEn

d of

the r

ight

tunn

el 32

35m

End

YK35

+36

815

0

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

Figure 8 Coal mined area of K9 seam

3

3

Mine area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mine area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

9

7

4

5

6

7

ZK35 + 168

ZK35 + 220

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

2320

1320

12

2011

Rndash4000

JD2

2014

3ndash4

2010

2009

2014

520

146ndash

10

2014

10ndash1

1

2014

7ndash9

2010

11ndash2

0120

6

2014

2008

2009

2015

2015

456789K36

YK369 8 7 6 5

43 2

1

6

68

8

123

HZ

1

ZK35

93500

OLD GOAF

XS coal mine

ndash120m

ndash100m

ndash50m

0m

+50m

+80m+10

0m

+150m

+200m +25

0m+30

0m

+350m

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

CR coal mine

Figure 9 Coal mined area of K10 seam

Advances in Civil Engineering 7

qr (1 +K)q (8)

where the repeat mining factor qr always depends on theporosity of the failure rock for this area K 01 [31]

As shown in Figures 4 and 5 the K5 coal seam has notbeen mined after October 2008 e mining of K7 seam hasinuenced K9 and K10 and will disturbed by K5 so the K7coal seam is a repeat mining inuence subsidence K9 and

ndash400

ndash300

ndash200

ndash100

+0

+100

+150

+200

Ls-350

4

4 JD2

Rndash4000567899 20

15 2014

K36

YK368 7 6 5123

HZ

1

XS coal mine

2013

03ndash20

1312

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

Left tunnel

Right tunnel

CR coal mine

201208ndash201209

201203ndash201206

201210ndash20132

2015

2500

2000

150091500 92000 92500 93000 93500

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

Figure 10 Coal mined area of K11 seam

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

ndash400

ndash300

ndash200

ndash100

2015

2015

2012

2

2012

10ndash20

132

2010

11ndash20

112

2013

03ndash20

1312

2014

2014

2011

3ndash20

116

2010

11ndash20

112

+0+10

0

+150

+200

2500

2000

150091500 92000 92500 93000 93500

OLD GOAF

OLD GOAF

Ls-350

4

4 JD2

Rndash4000567899

K36

YK368 7 6 5123

HZ

1

Left tunnel

Right tunnel

CR coal mine

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

2011

10ndash20

1111

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

XS coal mine

Figure 11 Coal mined area of K12 seam

8 Advances in Civil Engineering

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

Second the inuence between November 2008 andOctober 2010 seems as residuesrsquo subsidence use 10 of theinitial mining subsidence factor

In the third stage deformation caused by mining afterthe tunnel construction is completed (October 2010) shoulduse the initial subsidence factor

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92500 93000

Left tunnel

Right tunnel

3

4

5

7

4

5

6

7

ZK35 + 168ZK35 + 220

Ls-350

YK35 + 268

YK351

23

4578K36

YK368 7 5

43 2

1

8

8

1

1

ZK35

9350092000

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

+50m

+80m

+100m

+150m

6

6

69

96

9

9

23

HZ

plusmn0m

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 6 Coal mined area of K5 seam

2010

11-20

126

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008ndash2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

6

7

4

3

5

6

7

ZK35 + 168ZK35 + 220

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

ndash150m

ndash120m

ndash100m

ndash50m

plusmn0m

+50m

+80m

+100m

+150m

+200m

+250m

+300m

+350m

2010

11-20

12 0

620

14

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

JD2

Rndash4000

Figure 7 Coal mined area of K7 seam

6 Advances in Civil Engineering

34 InuenceofMulti-Seam ere are four coal seams in theinvestigated area e inuence of repeated mining shouldalso be considered e factor K is a parameter to evaluate

repeated mining inuence on the subsidence For a repeatmining the factor can be obtained from the followingequation [20 21 30]

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008-2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

3

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

R-4000

2012

JD2

2011

2014

2010 20

07

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

OLD GOAF

ndash150m

ndash120m

ndash100m

ndash50m

0m

+50m

+80m

+100m

+150m

+200m

+250m+300m

+350mEn

d of

the r

ight

tunn

el 32

35m

End

YK35

+36

815

0

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

Figure 8 Coal mined area of K9 seam

3

3

Mine area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mine area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

9

7

4

5

6

7

ZK35 + 168

ZK35 + 220

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

2320

1320

12

2011

Rndash4000

JD2

2014

3ndash4

2010

2009

2014

520

146ndash

10

2014

10ndash1

1

2014

7ndash9

2010

11ndash2

0120

6

2014

2008

2009

2015

2015

456789K36

YK369 8 7 6 5

43 2

1

6

68

8

123

HZ

1

ZK35

93500

OLD GOAF

XS coal mine

ndash120m

ndash100m

ndash50m

0m

+50m

+80m+10

0m

+150m

+200m +25

0m+30

0m

+350m

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

CR coal mine

Figure 9 Coal mined area of K10 seam

Advances in Civil Engineering 7

qr (1 +K)q (8)

where the repeat mining factor qr always depends on theporosity of the failure rock for this area K 01 [31]

As shown in Figures 4 and 5 the K5 coal seam has notbeen mined after October 2008 e mining of K7 seam hasinuenced K9 and K10 and will disturbed by K5 so the K7coal seam is a repeat mining inuence subsidence K9 and

ndash400

ndash300

ndash200

ndash100

+0

+100

+150

+200

Ls-350

4

4 JD2

Rndash4000567899 20

15 2014

K36

YK368 7 6 5123

HZ

1

XS coal mine

2013

03ndash20

1312

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

Left tunnel

Right tunnel

CR coal mine

201208ndash201209

201203ndash201206

201210ndash20132

2015

2500

2000

150091500 92000 92500 93000 93500

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

Figure 10 Coal mined area of K11 seam

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

ndash400

ndash300

ndash200

ndash100

2015

2015

2012

2

2012

10ndash20

132

2010

11ndash20

112

2013

03ndash20

1312

2014

2014

2011

3ndash20

116

2010

11ndash20

112

+0+10

0

+150

+200

2500

2000

150091500 92000 92500 93000 93500

OLD GOAF

OLD GOAF

Ls-350

4

4 JD2

Rndash4000567899

K36

YK368 7 6 5123

HZ

1

Left tunnel

Right tunnel

CR coal mine

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

2011

10ndash20

1111

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

XS coal mine

Figure 11 Coal mined area of K12 seam

8 Advances in Civil Engineering

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

34 InuenceofMulti-Seam ere are four coal seams in theinvestigated area e inuence of repeated mining shouldalso be considered e factor K is a parameter to evaluate

repeated mining inuence on the subsidence For a repeatmining the factor can be obtained from the followingequation [20 21 30]

Mined area of 2014

Mined area of 2015

Mined area of 2013

Mined area from Oct 2008 to Oct 20102008-2010

Mined area from Nov 2010 to end of 20122011~2012

Coal mine area

Coal floor elevation+300m

Mined area before Oct 2008History

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

3

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

R-4000

2012

JD2

2011

2014

2010 20

07

Ls-350

YK35 + 268

YK351

23

456789K36

YK369 8 7 6 5

43 2

1

9

98

8

123

HZ

1

ZK35

93500

CR coal mine

XS coal mine

OLD GOAF

ndash150m

ndash120m

ndash100m

ndash50m

0m

+50m

+80m

+100m

+150m

+200m

+250m+300m

+350mEn

d of

the r

ight

tunn

el 32

35m

End

YK35

+36

815

0

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

Figure 8 Coal mined area of K9 seam

3

3

Mine area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mine area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

2500

2000

150091500 92000 92500 93000

Left tunnel

Right tunnel

4

5

9

7

4

5

6

7

ZK35 + 168

ZK35 + 220

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

Ls-350

YK35 + 268

YK351

2320

1320

12

2011

Rndash4000

JD2

2014

3ndash4

2010

2009

2014

520

146ndash

10

2014

10ndash1

1

2014

7ndash9

2010

11ndash2

0120

6

2014

2008

2009

2015

2015

456789K36

YK369 8 7 6 5

43 2

1

6

68

8

123

HZ

1

ZK35

93500

OLD GOAF

XS coal mine

ndash120m

ndash100m

ndash50m

0m

+50m

+80m+10

0m

+150m

+200m +25

0m+30

0m

+350m

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

CR coal mine

Figure 9 Coal mined area of K10 seam

Advances in Civil Engineering 7

qr (1 +K)q (8)

where the repeat mining factor qr always depends on theporosity of the failure rock for this area K 01 [31]

As shown in Figures 4 and 5 the K5 coal seam has notbeen mined after October 2008 e mining of K7 seam hasinuenced K9 and K10 and will disturbed by K5 so the K7coal seam is a repeat mining inuence subsidence K9 and

ndash400

ndash300

ndash200

ndash100

+0

+100

+150

+200

Ls-350

4

4 JD2

Rndash4000567899 20

15 2014

K36

YK368 7 6 5123

HZ

1

XS coal mine

2013

03ndash20

1312

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

Left tunnel

Right tunnel

CR coal mine

201208ndash201209

201203ndash201206

201210ndash20132

2015

2500

2000

150091500 92000 92500 93000 93500

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

Figure 10 Coal mined area of K11 seam

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

ndash400

ndash300

ndash200

ndash100

2015

2015

2012

2

2012

10ndash20

132

2010

11ndash20

112

2013

03ndash20

1312

2014

2014

2011

3ndash20

116

2010

11ndash20

112

+0+10

0

+150

+200

2500

2000

150091500 92000 92500 93000 93500

OLD GOAF

OLD GOAF

Ls-350

4

4 JD2

Rndash4000567899

K36

YK368 7 6 5123

HZ

1

Left tunnel

Right tunnel

CR coal mine

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

2011

10ndash20

1111

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

XS coal mine

Figure 11 Coal mined area of K12 seam

8 Advances in Civil Engineering

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

qr (1 +K)q (8)

where the repeat mining factor qr always depends on theporosity of the failure rock for this area K 01 [31]

As shown in Figures 4 and 5 the K5 coal seam has notbeen mined after October 2008 e mining of K7 seam hasinuenced K9 and K10 and will disturbed by K5 so the K7coal seam is a repeat mining inuence subsidence K9 and

ndash400

ndash300

ndash200

ndash100

+0

+100

+150

+200

Ls-350

4

4 JD2

Rndash4000567899 20

15 2014

K36

YK368 7 6 5123

HZ

1

XS coal mine

2013

03ndash20

1312

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

Left tunnel

Right tunnel

CR coal mine

201208ndash201209

201203ndash201206

201210ndash20132

2015

2500

2000

150091500 92000 92500 93000 93500

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

Figure 10 Coal mined area of K11 seam

End

of th

e lef

t tun

nel 3

230m

End

ZK35

+33

5

ndash400

ndash300

ndash200

ndash100

2015

2015

2012

2

2012

10ndash20

132

2010

11ndash20

112

2013

03ndash20

1312

2014

2014

2011

3ndash20

116

2010

11ndash20

112

+0+10

0

+150

+200

2500

2000

150091500 92000 92500 93000 93500

OLD GOAF

OLD GOAF

Ls-350

4

4 JD2

Rndash4000567899

K36

YK368 7 6 5123

HZ

1

Left tunnel

Right tunnel

CR coal mine

End

of th

e rig

ht tu

nnel

3235

mEn

d YK

35+

368

150

3

3

4

5

6

7

4

5

6

7

ZK35 + 168ZK35 + 220

YK35 + 268

YK351

23

3 21

6

68

8

ZK35

2011

10ndash20

1111

Mined area of 2014

Mined area of 2015

Mined area from Oct 2008 to Oct 2010

Mined area of 2013

Mined area from Nov 2010 to end of 2012

2008ndash2010

2011~2012

Coal mine area

Coal floor elevation

Mined area before Oct 2008History

+300m

XS coal mine

Figure 11 Coal mined area of K12 seam

8 Advances in Civil Engineering

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

K10 were mined at almost the same time and do not in-uence the other coal seams so use the initial subsidencefactor K11 and K12 are very close and were mined at thesame time so the factor of K11 and K12 also uses the initialsubsidence factor

35 Parameters Used As in the analysis above the PIMparameters selected are shown in Table 2

36 Results Using the method and parameters above thetunnel deformation was calculated as shown in Figures 14and 15

e results show the following

(1) e Normal strain along the tunnel of ZK35 + 168caused by 2013 coal mine was 206mmm and261mmm by 2014 coal mine which is the biggesttensile strain of the investigated left tunnel etunnel lining was cracked in September 4 2014 after atorrential rain e crack was 4m high and 1 cmwide e tunnel was damaged by the horizontaldilation

(2) e normal strain of YK35+ 268 was minus112mmmwith 2013 coal mine and minus258mmm caused by 2014coal mine which means the strain was compression

Table 1 PIM parameters of Nantong Coal Mine

Station M (m) q b tan β θ0 (∘) S1 (m) S2 (m) S3 (m) S4 (m)

2309 25 06 011 14 minus018H minus031H4106 30 06 017 15 73 +005H minus002H4305 30 06 023 13 80 minus011H +005H0362_Up 12 06 115 78 minus016H minus019H0362_Down 25 06 145 78 minus016H minus019H

Fourth layer 18

14

12 12

1

1424

38 38 18

y

xo

ird layer

Second layer

First layer

Figure 12 eory of statistic model

S 2

0prime0

Cprime

C

θ0

θ0

S 1

Figure 13 Diagrammatic sketch for PIM parameters of inclined coal seam (copy reproduced from Li et al [22] under the Creative CommonsAttribution License (CC BY-NC-ND 40))

Advances in Civil Engineering 9

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

Table 2 PIM parameters used in calculation

Excavation time Coal seam q b tan β θ0 S1 S2 S3 S4

October 2008ndashOctober 2010 All 007 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K5 K9 K10 K11 K12 07 023 140 73∘ 005H 005H 005H 005HAfter October 2010 K7 077 023 140 73∘ 005H 005H 005H 005H

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

20122013

20142015

Left tunnel

K5K7 K9

K10

K12K11

287deg

Subs

iden

ce (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

500

400

300

200

100

0

2011

(a)

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Disp

lace

men

t (m

m)

End

tunn

elZK

35+

335

Elev

atio

n30

457

50

ndash500

ndash100ndash150ndash200ndash250

2011

(b)

Figure 14 Continued

10 Advances in Civil Engineering

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

20122013

20142015

380

ZK36

ZK35

ZK34

+7 8 9 1 2 3 4 5 6 7 8 9 1

340300260220180140100

6020

ndash20ndash60

ndash100ndash140ndash180ndash220

Mileage

K12K11

Left tunnel

K5K7 K9

K10

287deg

Stra

in (m

mm

)

End

tunn

elZK

35+

335

Elev

atio

n30

457

302520

15010

0500

ndash050ndash10ndash15ndash20ndash25ndash30

2011

(c)

Figure 14 e left tunnel deformation (a) Subsidence (b) Displacement (c) Horizontal strain along the tunnel

0

380340300260220180140100

60202060

100140180220

Mileage

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

50100150200250300350400450500

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK36

YK35

20122013

20142015

(a)

Figure 15 Continued

Advances in Civil Engineering 11

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

deformation e movement made the tunnel de-formation joints join together and caused the tunnelconcrete to collapse In fact the tunnel collapse on thesecond lining was 6m high and 3 cm wide

(3) e results show that the road of ZK35 + 350 toZK35 + 500 was stretching and it increased every

year With this correspondence the crevice of theroad area was ZK35 + 450 to ZK35 + 490

(4) At ends of the both tunnels the deformations werecompression And the damage of floor heave problemwas obvious the maximum heave value was 15 cmAnd it caused the vehicles to skip up and down

380340300260220180140100

60202060

100140180220

Right tunnel

K11K12

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

ndash50

500

ndash100ndash150ndash200ndash250

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Disp

lace

men

t (m

m)

20122013

20142015

K5 K7 K9K10

(b)

380340300260220180140100

60202060

100140180220

Right tunnel

Elev

atio

n 30

392

End

tunn

elYK

35+

368

150

K5K7 K9

K10

K11K12

Mileage

1 2 3 4 5 6 7 8 99 1

YK34

+8

YK35

YK36

Stra

in (m

mm

)

25201510

0ndash050

ndash10ndash15ndash20ndash25ndash30

20122013

20142015

(c)

Figure 15 e right tunnel deformation (a) Subsidence (b) Displacement (c) Normal strain along the tunnel

12 Advances in Civil Engineering

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

(5) In summary the calculated tunnel deformationmainly happened between ZK35 + 100 to ZK35 +300 of left tunnel and YK35 + 150 to YK35 + 300of right tunnel And the calculated results co-incide with the damage and deformation phe-nomenon of the tunnel It is a good proof for thecalculated result

37 Tunnel Deformation Prediction in Case of All Coal Re-source Excavated In order to evaluate the deformationinfluence of future mining it is proposed that all coal re-sources of both collieries be excavatede results are shownin Figure 16

As shown in Figure 16 the subsidence horizontal dis-placement and normal strain along the tunnel will increasewith the resource excavated for the futuree normal strainin this area has two forms

e stretching areas are ZK35 + 000 to ZK35 + 200YK35 + 000 to YK35 + 190 and YK35 + 340 to exit of righttunnel For the stretching area the tunnel lining will befractured and the cement will be cracked e road of thestretching area also will be damaged with some crevices

e compression area is ZK35 + 200 to exit of left tunneland YK35 + 190 to YK35 + 340 e damage forms ofcompression are deformation joints joined together thelining and the road lifted up

4 Multiple Reasons Influence theTunnel Stability

With the analysis the underground mining is the majorreason to cause the tunnel to be damaged and cracked Butthere are other reasons like old goaf underground waterand dynamic load of vehicles which also have importantinfluence on the safety of the road and tunnel

41 Old Goaf Influence e overlaying rock of the goaf canbe divided into three zones according its crack character-istics the all caved zone the fissure zone and the saggingzone as shown in Figure 17

e caved zone after the coal was excavated the roof willbreak crack and cave into the goaf e caved rock withdifferent size will heap up in the goaf ose rocks break upwith a lot of gaps and compressible space e borehole coreshows that the rock of old goaf is very shattered It shows thatthere are a lot of rock spaces in the old goafose spaces willbe the original source of surface deformation With thedisturbance of water and dynamic load of the vehicles theold goaf will be compressed and the rock deformation scopewill enlarge to the tunnel

e fissure zone the fissure zone is located up the cavedzone e rock is bent deformed and cracked but can keepin bedded structureere are a lot of fissures both along andperpendicular to the bed plane e cracked fissures aresmaller in the up seam than in the down seam

e sagging zone is located up the fissure zone and up tothe surface e sagging zonersquos deformation characteristic is

subsidence and bending e rock has fewer fissures Butthere is also abscission between different rock seams

e caved zone and the fissure zone can be describedtogether as the caved fissure zone which contains space forthe future rock redisplacement and deformation

42Water e BYS tunnel damage happened in the rainingseason or after a torrential rain Although the original de-formation comes from the underground mining the wateractivity is also an important induction factor e water canweaken the rock strength and damage the weak interpolatedlayer e water also causes additional stress on the tunnellining

43 Vehicle Dynamic Load e vehicles have dynamic loadwhen run on the road and can make shock waves ere is alot of research and surveys showing that the traffic load hasa limited depth of influence and tapers out at a certaindepth [32ndash35] For the tunnel that crosses over theK5K7K9 L10rsquos old goaf the long-term dynamic traffic loadcan change and redistribute the cracked rock So the ve-hicle activity load is another risk for tunnel damage andsudden collapse To keep tunnel stability the old goafshould be reinforced and the reinforced scope should bedeeper than the vehicle load

5 Grouting Injection Measure to Reinforcethe Goaf

e underground mining water and dynamic load cancause tunnel damage or a sudden collapse of the road Bothdamages occurred on the tunnels and roads have great riskinfluence on the traffic safety With the evaluation of tunneldeformation safety and economy the government decidedto close the two collieries and repair the tunnel in Sep-tember 2016 [36] ere is little research on ways to dealwith the highway crossing over the old goaf For the smallmine depth the goaf can be rammed with great powerstrength for the deep old goaf grouting injection filling isthe best way At the same time the surrounding rock can bereinforced by grouted materials [37] e BYS tunnelcrosses over the goaf with a small mine height and adipping coal seam ere is little space for constructionengineering in the tunnel So grouting to reinforce the rockunder the tunnel is the best way ere are two reasonswhich should be considered for the grout depth and scopeheight of caved and fissure zone in old goaf and the dy-namic load of the traffic e grout reinforcement shouldkeep the caved fissure zone from being disturbed by thedynamic load

51 Height of the Caved Fissure Zone e grout re-inforcement should be overlaying all the cracked rock di-rectly under the tunnel so the height of the caved fissurezone is very important ere are two experience equationsfor caved zone height as shown below [21 38]

Advances in Civil Engineering 13

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

Hc M

Kc minus 1( 1113857 lowast cos α (9)

Hc 1001113936 M

471113936 M + 19plusmn 22 (10)

whereHc is the height of caved zone of old goaf (m) M is themine height (m) α is the angle of the coal seam (∘) and Kc isthe direct roof rock volume expansion coefficient where Kchas a relationship with the rock uniaxial compressionstrength [39] Kc 1 + 005 σ l

radic where σl is the roof uniaxialcompression strength (MPa) e uniaxial compressionstrength of sand rock for coal seam roof is 41MPa thenKc 132 ere are also two empirical formulas for fissurezone height as shown below [20]

Hf 1001113936 M

161113936 M + 36plusmn 56 (11)

Hf 20

1113944 M

1113969

+ 10 (12)

where Hf is the fissure zone height (m) With those fourequations the caved zone height and fissure zone height canbe obtained as shown in Table 3

52 Dynamic Traffic Load Influence on Depth A lot ofmeasured research studies show that the dynamic traffic loadhas influence on the road and must be considered inhighway design [32 34 40] Liu et al have given a load ofdifferent sized cars as shown in Table 4 [33]

30 Strain (mmm)

Horizontal displacementStrain

287deg

End

Tunn

el Z

K35+

335

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1ZK35

ZK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(a)

Horizontal displacementStrain

30 Strain (mmm)

287deg

Mileage (m)

300

Hor

izon

tal d

ispla

cem

ent (

mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK36

250200150100

500

ndash50ndash100ndash150ndash200ndash250ndash300ndash350

2520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35

SubsidenceTileCurvature

Mileage (m)

Curv

atur

e (m

mm

)

Tile

(mm

m)Su

bsid

ence

(mm

)

1 2 3 4 5 6 7 8 9 1YK35

YK360

50100150200250300350400450500550600650700750800

5045

015

010

005

ndash005

ndash010

ndash015

4035302520151005

ndash05ndash10ndash15ndash20ndash25ndash30ndash35ndash40ndash45ndash50

(b)

Figure 16 Tunnel deformation in condition of all coal resource excavated (a) Left tunnel (b) Right tunnel

Sagging zone

Fissure zone

Caving zone

Figure 17 ree zones of overlaying rock deformation

14 Advances in Civil Engineering

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

e dynamic load can cause the road above the goaf tosuddenly collapse en the reinforcement should cover allthe dynamic load influence area of broken rock surroundingthe tunnel Liu et al [33] and Tang et alrsquos [35] research studiesindicate that the depth of the influence reduced fast and willtaper out in certain depth e stress of vehicle dynamic loadcan reduce more than 90 in 8 sim 10m depth and lose in10 sim 20m So in order to reduce the long-term dynamicinfluence the grouting depth should be more than 20m

Considering the rock stability safety and economicalcost the drill depth was designed to be 30m In order to keepsafety the reinforced scope starts from 30m prior K5 andends until 30m after K10 coal seamrsquos caved fissure zone evertical section cross section and ichnography plan ofgrouting drill are shown in Figure 18

6 Discussion

Construction on the old goaf is a difficult and high-riskproblem It is an interdisciplinary subject which involvescivil engineering underground coal mine rock mechanicaletc e tunnel crossing over the old goaf is even moredifficult than simple construction for it has severalcharacteristics

(1) e tunnels or highways are high safety requirementobjects e subsidence of coal mine or old goaf canchange the curve and also cause sudden collapse ofthe road surface and will put the traffic at high risk

(2) e tunnels or highways are linear objects ose aresensitive to normal strain deformation especiallytensile strain e road construction can be crackedby the subsidiary stress of underground mining

(3) Tunnels often are transport hubs but difficult tomaintain ey should be constructed in a narrowconstruction space and with high cost

(4) ere is no reliable theory or model to interpret thecooperative motion mechanism between tunnelrock and old goaf It is difficult to predict the tunneldeformation accurately

is paper provides a method to calculate the tunneldeformation using experience mine subsidence method andan ordinary engineering method to calculate the groutingscope and depth according to old goaf cracked zone anddynamic load influence of the road It can be used on anengineering-decision basis to deal with such problems butthere are more questions for further research ese ques-tions deal with the following issues

(1) e tunnel antideformation ability needs to be en-hanced If the tunnels are obliged to cross over the

old goaf area to construct an antideformation tunnelis the first choice e deformation calculationprotection is a complex problem that has a re-lationship with tunnel lining surrounding rockcaved zone and environment elements

(2) e long term deformation law of old goaf needsmore research e old goaf deformation has animportant relationship with the geological conditioncoal mining method geometry underground wateretc It is a difficult problem in tunnel engineering

(3) Health evaluation of tunnel deformation needs moreresearch e traffic safety and construction healthevaluation should consider the tunnel strengthdeformation surrounding rock changes in old goafand even weather conditions It is a challengingproblem

(4) e old goaf handling method also needs more re-search At present the most used method is groutinginjection to fill the goaf or to reinforce the crackedrock But the effect depends on the grouting methodarea quantity geological conditions coal miningmethod etc How to deal with the old goaf needs abreakthrough in thinking e question is a dynamicsystem of vehicle tunnel and its support sur-rounding rock and goaf condition

In order to keep the BYS tunnel safe the governmentdecided to close the collieries and grouting to reinforce thetunnel and its surrounding rock e project changed themechanical property of the surrounding rock and improvedthe safety conditions of the tunnel

7 Conclusion

(1) e probability integral method was used to evaluatethe deformation of the tunnel underground mininge calculated result shows that the damaged po-sitions are closely related to maximum normal strainof the tunnel Underground mining deformationinduced the tunnel damage chiefly e probabilityintegral method is a reliable choice to calculate theunderground mining tunnel deformation

(2) Tunnels cross over the goaf as in the BYS casee interrelationship between surrounding rock

Table 3 e caved and fissure zone height

Coal seam M (m) Hc equation (9) (m) Hc equation (10) (m) Hf equation (11) (m) Hf equation (12) (m) Maximum (m)

K5 024 106 339 1162 1980 2319K7 023 102 335 1140 1959 2294K9 033 146 381 1359 2149 2529K10 048 212 446 1659 2386 2831

Table 4 Vertical stress of roadbed of 5 different size vehicle loads

Size Micro Small Middle Bigger SuperLoad (t) 125 50 100 250 500Dynamic stress (KPa) 12 30 49 97 158

Advances in Civil Engineering 15

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

Mileage

+020

+980

1 2

+040

+060

+080

+120

+140

+160

+180

+220

+240

+260

+280

Grouting drills

Le tunnel

30m

K5 K7K10

K9

K35

(a)

Axi

s30

m

(b)

Axi

s

4m

25m

(c)

Figure 18 e grouting drill design drawing (a) Vertical section (b) Cross section (c) Ichnography

16 Advances in Civil Engineering

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

redistribution and long-term dynamic vehicle loadhas a high risk of sudden collapse In order to re-inforce the tunnel the height of the caved fissurezone and the influence depth of the dynamic trafficload should be considered together

(3) Closing the collieries and grouting to reinforce thegoaf and overlaying rock are two main measures tobe taken One measurement can stop the new in-creasing deformation from excavation And thegrouting injection can reinforce surrounding rock ofthe tunnel and reduce the long-term deformationfrom old goaf It can improve the safety condition ofthe tunnel but the dynamic and complex system oftunnels surrounding rock goaf and vehicle loadetc needs more research in the future

Data Availability

Raw data were generated at China University of Mining andTechnology (Beijing) Derived data supporting the findingsof this study are available from the corresponding author onrequest

Conflicts of Interest

e authors declare that they have no conflicts of interest

Authorsrsquo Contributions

Peixian Li and Lili Yan calculated and analyzed the tunneldeformation Peixian Li and Dehua Yao calculated anddesigned grouting Peixian Li and Dehua Yao worked on thetunnel damage analysis Peixian Li completed the writing ofthe paper All authors reviewed the manuscript

Acknowledgments

e work was supported by the Natural Science Foundationof China (Grant no 51404272) and China Scholarship Funde authors would like to thank China Railway Fifth Surveyand Design Institute Group Co Ltd e authors thank thecompany for allowing them to write this paper and pro-viding a lot of useful data e authors would also like toexpress their gratitude to Qichun Wang who gave themsome helpful references about coal mine geological condi-tions of Chongqing area

References

[1] G shang Sun and J zhong ldquoStudy on reclamation of coalmining subsidence in Chinardquo Contemporary Economicsvol 2014 no 21 pp 52-53 2014

[2] X Han X Meng X Zhang and Y Zhang ldquoe deformationstability analysis of the tunnels in mined-out areas based oncreator and FLAC3Drdquo Journal of Water Resources and Ar-chitectural Engineering vol 12 no 5 pp 93ndash97 2014

[3] X Li D Jiang C Liu and S Ren ldquoStudy on treatmenttechnology of highway tunnel through working out areardquoRock and Soil Mechanics vol 26 no 6 pp 10ndash14 2005

[4] X Chen J Zhang G Yang and G An ldquoA method for de-termining engineering treatment scope of goaf under

highwayrdquo Chinese Journal of rock mechanics and engineeringvol 26 no 1 pp 162ndash168 2007 httpwwwrockmechorgCNabstractabstract20994shtml

[5] C Ding Study on character and forecast model of residualdeformation in mining site PhD thesis China University ofMining and Technology Beijing China 2009

[6] L Tong L Liu Y Qiu and S Liu ldquoTunneling in abandonedcoal mine areas problems impacts and protection measuresrdquoTunnelling and Underground Space Technology vol 38pp 409ndash422 2013

[7] F Gao D Stead and H Kang ldquoNumerical simulation ofsqueezing failure in a coal mine roadway due to mining-induced stressesrdquo Rock Mechanics and Rock Engineeringvol 48 no 4 pp 1635ndash1645 2014

[8] S Maghous D Bernaud and E Couto ldquoree-dimensionalnumerical simulation of rock deformation in bolt-supportedtunnels a homogenization approachrdquo Tunnelling and Un-derground Space Technology vol 31 pp 68ndash79 2012

[9] Y Fang C Xu G Cui and B Kenneally ldquoScale model test ofhighway tunnel construction underlying mined-out thin coalseamrdquo Tunnelling and Underground Space Technology vol 56pp 105ndash116 2016

[10] Y Fang Z Yao G Walton and Y Fu ldquoLiner behavior of atunnel constructed below a caved zonerdquo KSCE Journal of CivilEngineering vol 22 no 10 pp 4163ndash4172 2018

[11] Z Li ldquoStability analysis and reinforcement technology ofmined out area in tieshan tunnelrdquo Chinese journal of RockMechanics and Engineering vol 21 no 8 pp 1168ndash11732002

[12] C Yan D Ding Z Cui and Z Bi ldquoApplication of flac in thestability analysis of tieshanping tunnel surrounding rockrdquoChinese Jounal of Underground Space and Engineering vol 2no 3 pp 499ndash503 2006

[13] S Li B Ma Y Ge F Xu and B Luo ldquo3D finite elementnumerical analysis of the stability of a tunnel over the minedareardquo Soil Engineer and Foundation vol 29 no 5 pp 42ndash452015

[14] L Huang Y Lu D Su and D Zhang ldquoTreatment technologyof highway tunnel through steep inclined goafrdquo Journal ofHighway and Transportation Research and Developmentvol 29 no 11 pp 80ndash85 2012

[15] Z Li S Li H Liu Q Zhang and Y Liu ldquoExperimental studyon the reinforcement mechanism of segmented split groutingin a soft fillingmediumrdquo Processes vol 6 no 8 pp 1ndash16 2018httpwwwmdpicom2227-971768131

[16] Q Wang L Qu H Guo and Q Wang ldquoGrouting re-inforcement technique of Qingdao Jiaozhou bay subseatunnelrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 4 pp 790ndash802 2011

[17] C Wang Y Lu B Cui G Hao and X Zhang ldquoStabilityevaluation of old goaf treated with grouting under buildingloadrdquo Geotechnical and Geological Engineering vol 36 no 4pp 2553ndash2564 2018

[18] J Litwiniszyn Stochastic Methods in Mechanics of GranularBodies vol 93 Springer-erlag GmbH Vienna Austria 1stedition 1974

[19] B Liu and G Liao Basic Regulars of Coal Mine SubsidenceChina Industry Press Beijing China 1965 httpsbooksgooglecabooksidJleAtgAACAAJ

[20] G He L Yang G Ling F Jia and D Hong Mine SubsidenceChina University of Mining and Technology Press XuzhouChina 1991 httpsbooksgooglecabooksidnqrYAAAACAAJ

[21] China Coal Industry Publishing House Coal Industry Bureauof Peoplersquos Republic of China Regulations of Buildings

Advances in Civil Engineering 17

Waterbody Railway Shaft and Tunnel Pillar Design and itsmining China Coal Industry Publishing House BeijingChina 2000

[22] P Li D Peng Z Tan and K Deng ldquoStudy of probabilityintegration method parameter inversion by the genetic al-gorithmrdquo International Journal of Mining Science and Tech-nology vol 27 no 6 pp 1073ndash1079 2017

[23] G Yin G Dai L Wan and D Zhang ldquoNumerical simulationof strata movement behavior in deep excavationrdquo Journal ofChongqing University (Natural and Science Edition) vol 24no 5 pp 62ndash67 2001

[24] S Wu and H Deng ldquoStudy on law of ground deformation inmining at steep seam in Nantong coal minerdquo Subgrade En-gineering vol 2014 no 2 pp 123ndash126 2014

[25] W A Kapp ldquoSubsidence at kemira colliery new south walesrdquoin Proceedings of Symposium Subsidence in MinesA J Hargraves Ed pp 1ndash9 Australasian Insitute of Miningand Metallurgy Illawarra NSW Australia 1973

[26] W A Kapp ldquoStudy of mine subsidence at two collieries in thesouthern coalfield New South Walesrdquo Australian Institute ofMining and Metallurgy vol 276 pp 1ndash11 1980

[27] H Kratzsch Mining Subsidence Engineering SpringerBerlin Germany 1983 httpsbooksgooglecabooksidhE-4AAAAIAAJ

[28] H Zhang Distribution law of the old goaf residual cavity andvoid PhD thesis China Universtity of Mining and Tech-nology Xuzhou China 2013

[29] O R J ldquoe effect of mining subsidence upon public healthengineering worksrdquo Journal of the institution of public healthengineers vol 56 p 188 1957

[30] J Wang ldquoStudy of the surface movement regularity ofmultiple miningrdquo MA thesis AnHui University of Scienceand Technology Huainan China 2011

[31] Z Chan ldquoe evaluation research on the subsidence ofground cause by mining multi-coal bedsrdquo MA thesis ChinaUniversity of Geosciences Beijing China 2007

[32] S Li Investigation on dynamics of heavy vehicle-pavement-foundation coupled system PhD thesis Beijing JiaotongUniversity Beijing China 2008

[33] W Liu L Tang and Q Zhang ldquoResearch on dynamic stress ofsubgrade soil under vehicle loads and its diffused rulerdquoJournal of Chongqing Jiaotong University(Natural Science)vol 31 no 4 pp 799ndash802 2012

[34] X Ma J Qian L Han J Cao and M Huang ldquoEquivalentfinite element method for long-term settlement of subgradeinduced by traffic loadrdquo Chinese Journal of GeotechnicalEngineering vol 35 no 2 pp 910ndash913 2013

[35] L Tang P Lin K Wu X Deng Q Ding and Z DengldquoAnalysis of dynamic stress state and effective working radiusin subgrade under concentrated loadrdquoChinese Journal of RockMechanics and Engineering vol 30 no 2 pp 4056ndash40632011

[36] Chongqing Coal Mine Safety Supervision Bureau No 1 orderinformation (coal mine safety production license cancellationlist for 105 coal mining enterprises) 2017 httpwwwcqmjgovcnmjgovhtmlgztz2017011248047html

[37] Q Guo Research on the safety evaluation and key technologiesfor the expressway construction on old goaf of coal mine PhDthesis China University of Mininig and Technology XuzhouChina 2017

[38] X Xia and Q Huang ldquoStudy on the dynamic height of cavedzone based on porosityrdquo Journal of Mining and Safety En-gineering vol 31 no 1 pp 102ndash107 2014

[39] T Chu J Chao M Yu and X Han ldquoBulking coefficientevolution characteristics and mechanism of compacted bro-ken coalrdquo Journal of China coal society vol 42 no 12pp 3182ndash3188 2017

[40] M Hyodo and K Yasuhara ldquoAnalytical procedure for eval-uating pore-water pressure and deformation of saturated clayground subjected to traffic loadsrdquo in Proceedings of SixthInternational Conference on Numerical Methods in Geo-mechanics vol 2 pp 653ndash658 Innsbruck Austria April 1988

18 Advances in Civil Engineering

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