Performance Characteristics of Tunnel Boring Machine in Basalt and Pyroclastic Rocks of Deccan Traps-A Case Study

Journal of Rock Mechanics and Geotechnical Engineering 6 (2014) 3647

Journal of Rock Mechanics and Geotechnical Engineering

Journal of Rock Mechanics andEngineering

j ourna l ho mepage: www.rockge

Perform acrocks o

Prasnna a National Instib Indian Institu

a r t i c l

Article history:Received 6 MaReceived in reAccepted 28 N

Keywords:TunnelingOpen-type tunnel boring machine (TBM)Rock mass classicationGround supportingDeccan trap

hi anystemtweeuctiohe Mork

are npyroclastic rocks with layers of red boles and intertrappean beds consisting of various types of shales.Relations between rock mass properties, physico-mechanical properties, TBM specications and the cor-responding TBM performance were established. A number of support systems installed in the tunnelduring excavation were also discussed. The aim of this paper is to establish, with appropriate accuracy,the nature of subsurface rock mass condition and to study how it will react to or behave during under-

1. Introdu

The Brihchange all sby constructional loss asupply systbuilt for moand need resurized andmaintenancpass belowburst it wil

CorresponE-mail add

Peer review uAcademy of Sc

ELSEVIER

1674-7755 2Sciences. Prodhttp://dx.doi.oground excavation by TBM. The experiences gained from this project will increase the ability to cope withunexpected ground conditions during tunneling using TBM.

2013 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

ction

anmumbai Municipal Corporation (BMC) has decided tourface water pipelines and to create subsurface systemsting tunnels to avoid problems of leakage, unconven-nd also to protect water from contamination. The waterems through surface pipelines in Mumbai are age-old,re than 70 years. These supply systems leak frequentlypeated maintenance. All these pipes are highly pres-

badly encroached by the population, which makese difcult. In Maroshi and Vakola sections, these pipes

the runways of Mumbai Airport and in case of strongl affect the ground below the runways. The decision

ding author. Tel.: +91 22 2576 7271; fax: +91 22 2576 7253.ress: [email protected] (T.N. Singh).nder responsibility of Institute of Rock and Soil Mechanics, Chineseiences.

Production and hosting by Elsevier

013 Institute of Rock and Soil Mechanics, Chinese Academy ofuction and hosting by Elsevier B.V. All rights reserved.rg/10.1016/j.jrmge.2013.11.003

for the construction of tunnels was made because tunnels haveadvantages of low maintenance and less security accident. Withthe development of tunneling technology, it is possible to exca-vate tunnels with tunnel boring machine (TBM) under favorableground conditions instead of adopting conventional methods likedrill-and-blast method. For the Mumbai water supply scheme, ahard rock TBM was deployed earlier in 1984 and a tunnel of 3.87 kmwas driven with 3.5 m diameter gripper type TBM (Tribune no-ITA-AITES). The tunnel was reported successfully excavated in 450 dayswith a best monthly advance of 376 m. Construction of the tunnelshas improved substantially the distribution of water supply systemin Mumbai, which is an effective manner. Prior to these projects,worldwide experiences in driving tunnel through basalts and pyro-clastics rocks with full-face were limited. The present scheme is acontinuation to those successful efforts.

To improve the water supply to Vakola, Mahim, Dadar andMalbar Hill of Greater Mumbai, a 12.24 km long tunnel betweenMaroshi and Ruparel College is being excavated by TBM. The tun-nel is divided into three sections, i.e. MaroshiVakola (5.834 kmlong), VakolaMahim (4.549 km long) and MahimRuparel Col-lege (1.859 km long) (Fig. 1). The longest tunnel between Maroshiand Vakola has been completed. A vent hole of 30 cm diameter atChainage 3230 m at MaroshiVakola section was drilled for releas-ing pressure. For constructing tunnels from Maroshi to the venthole and from Vakola to the vent hole, vertical shafts were con-structed at either end. The inlet shafts of 82.0 m and 68.0 m in depthance characteristics of tunnel boring mf Deccan traps A case study

Jaina, A.K. Naithania, T.N. Singhb,

tute of Rock Mechanics (NIRM), Kolar Gold Fields, Karnataka, Indiate of Technology, Mumbai, India

e i n f o

y 2013vised form 16 October 2013ovember 2013

a b s t r a c t

A 12.24 km long tunnel between Maros(TBM) to improve the water supply smade to establish the relationship beTBM performances during the constrMaroshiVakola tunnel passes under tcover of around 70 m. The tunneling wtypes encountered during excavation Geotechnical

otech.org

hine in basalt and pyroclastic

d Ruparel College is being excavated by tunnel boring machine of Greater Mumbai, India. In this paper, attempt has been

n various litho-units of Deccan traps, stability of tunnel andn of 5.83 km long tunnel between Maroshi and Vakola. Theumbai Airport and crosses both runways with an overburdenwas carried out without disturbance to the ground. The rocke compacted basalt, porphyritic basalt, amygdaloidal basalt,

P. Jain et al. / Journal of Rock Mechanics and Geotechnical Engineering 6 (2014) 3647 37

Maro

from grounand Vakolaassembly tufor assembltwo 50 m locar movemand tail tunmethod.

The inve35.50 m bit is 30.633.6 m with E S30 W between Mage, varyinzones. In thtionship beperformancships betwcorrespondrock mass cward probiindicate thatacts, rock sweak zonesstability of

The rockand the disditions certrecognized TBM perforGong and Zhage, becausthe existingstudies, Bruspacing, the

The inuwidely obseAeberli andincreases wplanes of scphenomenaphyllite and

rizede sing athane mual tt spases. En ratect o009)

logy

logicc owCretaa, 19

you geond acffs. Tocks Fig. 1. Longitudinal section and plan of tunnel from

d level, 9.0 m in diameter, were constructed at Maroshi respectively to lower the TBMs parts. 5.4 m D-shapednnels of 90.0 m and 60.0 m length were constructedy of TBMs. On the opposite side along the tunnel axis,ng tail tunnels were also excavated to facilitate muckent while unloading. Vertical shafts, assembly tunnelsnels were excavated by conventional drill-and-blast

rt level of tunnels at Maroshi and Vakola shafts iselow the mean sea level (m.s.l.) while at the vent hole

m below m.s.l. The excavated diameter of a tunnel wasa designed gradient of 1:600 and its alignment is N30

(Table 1). The tunnel boring was extremely challengingaroshi and Vakola section due to heavy water seep-g rock strata condition and presence of various weakis paper, an attempt has been made to establish the rela-tween various litho-units, stability of tunnel and TBMe during the construction of these tunnels. Relation-een rock mass properties, TBM specications and theing TBM performances have also been established. Theonditions were assessed by precise judgment using for-ng and 3D geological logging of tunnel walls. Studiest in Deccan traps, variations in rock types, ow con-

summaand maincreasis less ever, thwas eqof joindecreaetratiothe effZhao, 2

2. Geo

GeobasaltiUpper (Sethnbe theall, thebasic aand tuAcid rtrength, and volumetric joint amount with presence of have predominantly affected the penetration rate andtunnels (Jain et al., 2011).

mass has the characteristics of both the intact rockcontinuities, therefore the existing discontinuity con-ainly affect the rock breakage process. It has been wellthat joints or fractures have an important effect on themance (Howarth, 1981; Bruland, 1998; Cheema, 1999;ao, 2009). The discontinuities can facilitate rock break-e cracks induced by TBM cutters easily develop with

discontinuities. On the basis of a large number of caseland (1998) concluded that with the decrease of joint

TBM penetration increases distinctly.ence of joint orientation on TBM penetration rate wasrved in the tunneling projects (Gong and Zhao, 2009).

Wanner (1978) observed that the advance rate of TBMith the increase of the angle between TBM axis and thehistosity in a homogeneous schistose phyllite. Similar

were also observed by Thuro and Plinninger (2003) in phyllitecarbonate-schist interbedding. Bruland (1998)

include rewas well as by columnatypes encouphyritic bastuff and tubeds consisand structubasalt, and on propertiat the timeor unsuitabincrease towthe bole at strata of thgas cavitiessecondary msilica, i.e. agare massivejointed.shi to Ruparel College.

d the effects of joint orientation of different classesimilar observation. The penetration rate increases withngle between tunnel axis and joint plane as the angle

60, and then decreases with increasing angle. How-aximum penetration rate was recorded when the angleo 60. Bruland (1998) also noted that with the increasecing, the effect of joint orientation on TBM penetrationach joint set may have different effects on the TBM pen-e. The higher the joint density or frequency is, the largerf the joint set on the TBM penetration rate is (Gong and.

of the study area

ally, the entire Mumbai area is occupied by the Deccan and the associated pyroclastic and plutonic rocks ofceous to Palaeogene age classied as Sahyadri Group99). Deccan basalt of Mumbai Island is considered tongest basalt of Eocene age (Subbarao, 1988). Over-logy around Mumbai indicates presence of ultrabasic,id differentions with intertrappean beds, agglomerateshe ultrabasic differentiates are of limited occurrence.include quartz trachyte. The agglomerate and tuff

orked materials as indicated by the current bedding

graded bedding. The lava pile of Mumbai is intrudedr jointed, medium grained doleritic dykes. The rockntered during tunneling are ne compacted basalt, por-alt, amygdaloidal basalt and pyroclastic rocks, namelyff breccia with layers of red boles and intertrappeanting of different types of shales. The thickness, presenceral characteristic of ne compacted basalt, porphyriticamygdaloidal basalt vary in different ows, dependinges of magma, cooling history and geological conditions

of formation, which make these rock types suitablele for engineering structures. Vesicles and amygdalesard the top of a ow unit which in turn merges into

some places. The red bole is overlain by the massivee next younger ow unit. Vesicular basalt with empty

and amygdaloidal basalt with gas cavities lled withinerals like zeolites, carbonate minerals and secondaryate, etc., do not have a regular pattern of jointing and, while compacted basalt with no gas cavities is usually

38 P. Jain et al. / Journal of Rock Mechanics and Geotechnical Engineering 6 (2014) 3647

Table 1Salient features of Maroshivent hole and Vakolavent hole tunnels.

Tunnels Tunnel boring Shape Excavated diameter Finished Excavationy (m3/

Volume (total Lining (reinforced Concrete quantity

Maroshiven

Vakolavent

Tunnels ss

Mp(

Maroshivenhole

5

Vakolaventhole

4

The lavafractures, vewith differeary. Due to of the earlieobserved. Tin N020Nwere open,some wereprovide pasor soft matbetween twcontact wasadvance ratwas high in

The sequtunnel indicimentary rotops and boextent, suchas a fault. Itows do noeral extent in thicknessent parts. Itconstant diable that the investigdoes not indlar structurfault betweow sequenoutcome of

Traps share paralleljoints werethey were gchoidal fracamygdaloidphyritic basne grainedGenerally, basalt than ture that wzeolites of dtabular or rability and

ck. Id. Abola swered coned du

minck trphy%), g), anass. Teccia%), a

s, chl waslly h.52

is cof 5

spe

TH T of Mtivelyshmactur

boriousBM t worlength (m) (bore section) (m) diameter (m) quantit

t hole 3086.34 Circular 3.6 3.0 10.18

hole 2590.4 Circular 3.6 3.0 10.18

Boring startdate

Boring completiondate

Tunnel boringduration (month)

Monthly averagetunnel boring progre(m)

t 27 Dec. 2008 26 Sep. 2009 9 339.16

7 Nov. 2008 10 Aug. 2009 9 281.57

ows show various types of structures such as joints,sicles, veins, breccias clasts, mac-dykes and amygdulent shapes like circular, elliptical and irregular bound-the emplacement of the traps upon the eroded surfacesr rock strata, minor undulations in the ow were alsohe general ows contact dip varies between 30 and 45

040 and N200N220 directions. Some ow contacts lled with weathered, altered or soft materials while

tight and commonly coalescent. Open ow contactssage for water and weathered materials. Weatherederials are generally deposited during the time internalo ows. The angle between the tunnel axis and the ow

80 and penetration rate was less at ow contact. Thee was low in case of open ow contact zones while it

tight ow contact zones.ences of ows are different in different chainages ofating they do not have regular structure like ideal sed-cks. In sedimentary rocks, beds having plane surfacesttoms, constant dip, uniform thickness and wide lateral

a disparity in sequences could validly be interpreted has now been well established that Deccan trap basaltt have such regular structure, and have limited the lat-and stretch out over short distances. There is variationes, i.e. ows usually have different thickness in differ-s tops and bottoms are not regular plane surfaces withp but irregular surfaces. As a result, it is almost invari-ow sequence in boreholes, which were drilled duringation does not normally match. This disparity howevericate faulting as it would be in case of beds with regu-

al behavior. Hence, the possibility of the occurrence of aen boreholes need not be apprehended merely becausece in boreholes does not match, as this disparity is the

wall romappethe Vakwhich ing anobserv

Theeach roand po(1520(710%and gltuff brene (20of glasbrecciageneraTiO2 (0of CaOrange o

3. TBM

WIRvationrespecrefurbimanufsimilarat prev360H Tlying a the structural irregularity of the basalt ows.ow two or more sets of vertical joints. Horizontal joints

to the top or bottom surfaces. Two sets of columnar observed in thicker ows. Fractures were identied andenerally parallel to the prominent joint directions. Con-turing of rock mass was a common feature. Generally,al basalt and tuff breccia were massive while in por-alt the spacing of joint sets was more than 2 m and in

jointed compacted basalt it varied from 10 cm to 30 cm.TBM penetration rate was greater in ne compactedthat in the porphyritic basalt. Veins are extension frac-as lled with mineral deposits of quartz, calcite andifferent dimensions. They were generally sheet like oregular in shape. Veins have major inuences on cav-fragmentation and may be weaker or stronger than the

specicatioufacturer arthrust forceare importaon the macment.

4. Physico

The rocTBM. Uniaxstrength terecommendto evaluate results of com) excavation) (m3) cement concrete,RCC)-grade andthickness

(m3/m)

31,419 Total lined: M-20 and300 mm

3.11

26,370 Total lined: M-20 and300 mm

3.11

aximum progresser monthm/month)

Daily average tunnelboring progress (m/d)

Maximum boringprogress in one day(m/d)

42.6 13.57 29.5

74.4 11.26 39.9

n the tunnels, generally, calcite and zeolite veins wereout 32 cm to 3.5 m thick mac dykes were mapped inhaft area. The dyke exhibits prominent columnar joints,

formed due to differential volume changes in cool-tracting magma. No curviplanar (fold) structure wasring the geological 3D logging of the tunnel wall.eralogical content of basaltic rocks was analyzed forype. Major mineral composition of ne grained basaltritic basalt constitutes plagioclase (4045%), pyroxenelass (1015%), iron oxide (810%), and secondary calcited groundmass was composed of plagioclase, pyroxenehe mineral contents of the amygdaloidal basalt and

are plagioclase (35%), devitried glass (30%), pyrox-nd oxide phase (15%), and groundmass was composedorite, calcite and zeolite. Cutter abrasion in basalts and

less due to less quartz and low silica percentage. Basaltas a composition of SiO2 (4555%), total alkalis (26%),%), FeO (514%) and Al2O3 (14% or more). The contentmmonly about 10% and that of MgO is usually in the12%.

cications

B-II-320H and TB-II-360H TBMs were used for the exca-aroshivent hole and Vakolavent hole tunnel sections. These are refurbished full face hard rock TBMs andent was carried out under supervision of equipmenter. TBMs were previously used in earlier projects withe diameter. TB-II-320H TBM has done 4.5 km boring

project and was idle at workshop for 3 years. TB-II-has done 7.5 km boring at earlier project and was alsokshop for 3 years before used at this project site. TBMs

ns collected from the documents provided by the man-e given in Table 2. The operating parameters including, torque and rotation per minute (RPM) of the machinent for understanding the effect of geological conditionshine performance and for penetration rate measure-

-mechanical properties of rocks

k strength is directly related to the performance ofial compressive strength (UCS) and Brazilian tensilests were performed in accordance with the procedureed by ISRM (Brown, 1981). These are the parametersthe rock mass boreability. Laboratory rock strength testre samples are given in Table 3.


Table 2Principal specications of TBMs employed in MaroshiVakola sections.

Tunnel sections TBM model Type Input supply Cutter head Cutter numbers Cutter disk Cutter spacing No. of buckets

Maroshiven (centee cuttgaugege cu

Vakolavent (centee cuttgaugege cu

Tunnel secti ad thm) (b

Maroshiven

Vakolavent

Table 3Laboratory roc

Rock type 0, MP

Avera

Fine compac Porphyritic b Amygdaloid Tuff breccia 2.38 Tuff 0.87 Flow contac Intertrappea

UCS is orock mass crock mass bter indents strength. Thpression. Dis distribute12 mm/rev adopted. Sothe penetra1976; FarmORourke etincreases, f25 MPa of tthe penetra

Brittleneformance oof rock combrittleness iand Zhao (2tleness indindentationthen generaGenerally, ttleness indeother rock m

5. Assessm

A detailein the tunnei.e. rock detion, ground

s rocnd 3ass c(kV) diameter (m)

t hole WIRTHTB-II-320H

Hard rock,open type

11 3.6 31 facpregau

hole WIRTHTB-II-360H

Hard rock,open type

6.6 3.6 31 facpregau

ons No. of scrapers Cutter headspeed (rpm)

Cutter head torque(maximum) (bar)

Cutter he(maximu

t hole 2 5 sets = 10scraper plates

014 225 220

hole 3 5 sets = 15scraper plates

012 185 220

k strength results of core samples.

RQD (%) UCS (MPa) Point load test (Is5

Range Average Range

t basalt 3090 33.35115.90 78.20 asalt 90100 115.87143.33 130.60 al basalt 95100 54.1065.70 59.80

95100 26.4350.20 34.46 1.333.44 95100 15.6824.28 18.40 0.51.25

t zone 4060 12.4031.87 14.60 ns (shale) 4575 28.3034.35 31.32

ne of the most important rock strength parameters forondition evaluation and is commonly used to assessoreability. It has been proved that when the rolling cut-

VariouFigs. 2 arock mthe rock, the stress exerted must be higher than the rocke rock strength affects the rock behavior under com-uring the excavation of tunnels, the penetration rated in a large range from about 2 mm/rev to more thandue to the effect of UCS. A loading rate of 200 N/s wasme models for predicting penetration rate show thattion rate is directly associated with rock UCS (Graham,er and Glossop, 1980; Rostami and Ozdemir, 1993;

al., 1994). The penetration rate decreases as the UCSor example, the penetration rate is about 6.3 m/h athe rock UCS, and 1.9 m/h at 105 MPa of UCS. Generally,tion rate and UCS show a linear relationship.ss index is another parameter to understand the per-f TBM. The rock brittleness index is dened as the ratiopressive strength to tensile strength. The effect of rockndex on TBM penetration process was studied by Gong007). The result shows that with increasing rock brit-ex, the cutter indentation process gets easier. Cutter

means the rolling cutter intrudes into the rock, andtes small and large fragments as well as internal cracks.he penetration rate increases with increasing rock brit-x but there is not a linear relation due to the effects ofass parameters like jointing pattern in the rock mass.

ent of rock mass

d engineering geological investigation was carried outls to acquire the geological and/or geotechnical details,scription, rock discontinuity orientation and descrip-water condition, etc., for rock mass quality assessment.

RMR (rock tem) (InnauSundaram eIn this projsications (geological mmass classigiven in Figlength fell i375 m lengtrespectivelyof good rocwere of fairGenerally, tthe ow coobserved. Fmaximum Twere achievrock masse

Based ontheir enginwere classidaloidal ba(tuff/tuff brtheir behavnostic engiporphyriticthis area, cotypes. Abouin basalts (diameter (mm) (mm)

r cutters-6;ers-17;

cutters-5;tters-3)

432 62 5

r cutters-6;ers-17;

cutters-5;tters-3)

432 62 5

rustar)

Stroke (mm) Muck handlingcapacity (m/h)

Estimated weight (t)

1100 5 107

1100 5 107

a) Brazilian tensilestrength (MPa)

Brittleness index

ge Range Average Range Average

2.5713.31 9.46 8.2615.12 8.268.7615.26 13.28 8.3115.78 9.83

1.53.2 2.35 4.6011.5 14.481.63.8 2.7 4.1215.17 6.8

4.906.10 5.50 4.637.10 5.70

k types encountered during tunneling are illustrated in. Some researchers have correlated TBM performance tolassication systems using RSR (rock structure rating),

mass rating), Q-system and IMS (integrated mass sys-rato et al., 1991; McFeat-Smith and Broomeld, 1997;t al., 1998; Sapigni et al., 2002; Hamidi et al., 2010).ect, the rock mass was characterized using RMR clas-Bieniawski, 1989). RMR values were calculated afterapping and measurements of discontinuity data. Rock

cation for different litho-units of tunnel sections ares. 4 and 5. In the Maroshivent hole section, 1160 mn good rock mass category, while 1098.5 m, 453 m andhs fell in fair, very good and poor rock mass categories. In the Vakolavent hole section, 1510.5 m length wask mass category, while 998 m, 60 m and 22 m lengths, very good and poor rock mass categories respectively.he rock conditions were fair to good except at or nearntacts where poor to fair rock mass conditions wereor medium quality rock masses (RMR of 4075), theBM performances (penetration rate and advance rate)ed while lower penetration was for poor and very goods.

petrographic, textural and structural characteristics,eering properties and RMR, the tunneling rock mediaed into three main categories, i.e. basalts (amyg-salt/compacted basalt/porphyritic basalt), pyroclasticseccia) and intertrappeans (shaly material), to assessiors and the performances of TBM. The different diag-neering properties of amygdaloidal, compacted and

basalts lie in the degree and pattern of jointing. Inmmonly basalts were transitional between these threet 62.25%, i.e. 3534 m length, of the tunnel was excavatedcompacted basalt-3341 m, porphyritic basalt-193 m).

40 P. Jain et al. / Journal of Rock Mechanics and Geotechnical Engineering 6 (2014) 3647Fig. 2. Lithological mapping along tunnel from Maroshi to v

Fig. 3. Lithological mapping along tunnel from Vakola to ve

-20

0

20

40

60

80

100

90 to

93

93 to

94

94 to

148

148

to 1

5715

7 to

163

163

to 1

7517

5 to

185

185

to 1

9519

5 to

208

208

to 2

0920

9 to

535

535

to 5

6556

5 to

582

582

to 5

9759

7 to

720

720

to 7

2872

8 to

759

759

to 7

6076

0 to

777

777

to 7

8278

2 to

849

849

to 8

5185

1 to

865

865

to 8

6786

7 to

975

975

to 9

8098

0 to

101

210

12 to

101

310

13 to

101

910

19 to

102

010

20 to

115

711

57 to

116

011

60 to

118

011

80 to

118

911

89 to

119

111

91 to

121

012

10 to

128

912

20 to

122

412

24 to

124

912

49 to

128

912

89 to

129

512

95 to

136

013

60 to

136

913

69 to

178

717

87 to

181

618

16 to

193

8

RM

R R

atin

g s &

Val

ue

Chainage in metres

UCS RQD Spacing Discontinuity Conditions Gr

Fig. 4. RMR rating at different chainages along Marosent hole (Ch. 903180 m).

nt hole (Ch. 572645 m).

1938

to 1

941

1941

to 1

949

1949

to 1

952

1952

to 1

994

1994

to 2

003

2003

to 2

036

2036

to 2

066

2066

to 2

105

2105

to 2

150

2150

to 2

210

2210

to 2

294

2294

to 2

302

2302

to 2

316

2316

to 2

320

2320

to 2

326

2326

to 2

337

2337

to 2

345

2345

to 2

415

2415

to 2

448

2448

to 2

471

2471

to 2

529

2529

to 2

536

2536

to 2

555

2555

to 2

610

2610

to 2

659

2659

to 2

672

2664

to 2

667

2667

to 2

782

2782

to 3

151

3151

to 3

162

3162

to 3

177

ound water Orientation RMR

hvent hole tunnel.


Vakola

The ne coJoints provibearing. In the compacjoints werecrown and them. Porpground conthere werewidely joinof the intacrock mass f

A total ovated in thejoints and qsional planexcavationsto be a veryworks in it camygdaloidrock mass f

A total olength) (tubreccias andunjointed. Uthe UCS of medium forbility and hwas not verand affectedthus taking system.

There wassociated nantly madgrained varto 34.35 MPto its softetunnel lengwas about entire lengtbution of diTable 4.

per

dictioationting uousand cludand ts on

TBMion a

of d for su

of ecle dspecTBMies aanc

n Tae advtivelyenetFig. 5. RMR rating at different chainages along

mpacted basalt showed a higher degree of jointing.ded access to water, thus, the compacted basalt is wateraddition, the fragmentation brought by jointing madeted basalt unstable during excavation especially when

closely spaced. Rock falls were reported at tunnelssides, and rock bolts were implemented to preventhyritic basalt was widely jointed and provided stabledition for TBM tunneling. Even in a single basaltic ow,

some portions with close jointing and others wereted. Due to its structural and textural variation, the UCSt basalt varied from 33.35 MPa to 143.33 MPa and theell in fair to good rock mass categories.f 35.0 m, i.e. less than 1% of the tunnel length, was exca-

amygdaloidal basalt. Amygdaloidal basalt was free ofuite impervious when fresh. Due to the absence of divi-es, the rock mass was stable in all kinds of cuts and. Therefore, the amygdaloidal basalt was considered

suitable medium for tunneling, and all undergroundan be expected to be trouble free. The UCS of the intactal basalt varied from 54.10 MPa to 65.70 MPa and theell in good to very good rock mass categories.f 1617 m of tunnel length (about 28.48% of the totalff breccia-1257 m, tuff-360 m) was excavated in tuff

tuff. Tuff breccia and tuff were generally less jointed or

6. TBM

Prepenetrexcavacontinvating also indown dependon theutilizatportiondelaysvarietytime cywith re1990). capacitperformgiven iaveragrespectime. PCS of the fresh tuff breccia was up to 50.20 MPa, whiletuff was up to 24.28 MPa. Tuff breccia was a suitable

the tunneling by TBM due to its impermeability, sta-igh penetration rate, but excavation in tuff with TBMy much favorable because it led to cutter jam problem

the production cycle due to sticky property of muck,longer discharge time at every transfer point of mucking

ere sedimentary beds known as intertrappean bedswith the Deccan trap lava ows. They were predomi-e up of argillaceous and carbonaceous shales. The neiety of shale had good compressive strength, i.e. upa, but it was thinly bedded. Rock fall occurred duening when contacting water. Approximately 90 m ofth was excavated in the intertrappean shales, which2% of total length. Due to its swelling behavior, theh was supported by steel ribs. The percentage distri-fferent rock types mapped in tunnel sections is given in

its mediumegory, whicPenetrationits very higthose chainground concontacts ening in a lowTBMs couldworking facous litho-unare given in

Cutter aaverage cuttion was 54The average73.48 m/cutcutter chanstretch. Thevent hole tunnel.

formances

n of TBM performances requires estimation of both rate and advance rate. Penetration rate is dened asthe distance divided by the operating time during a

excavation phase, while advance rate is the actual exca-supporting distance divided by the total time and ites downtime for TBM maintenance, machine break-unnel failure (Alber, 1996). The performance of TBM

the intact rock and rock mass properties as well as specications and TBM operation parameters. TBMschieved in these tunnels varied according to the pro-ifferent litho-units, capacity of muck disposal system,pport installation, management of water inows and a

lectrical/mechanical backup and service delays. Boringetails from Maroshi to vent hole and Vakola to vent holet to international norms are given in Fig. 6 (Robbins,s deployed at those two sections were of different inputnd because of this, in similar geological conditions thee characteristics were different for both stretches asble 5. Because these were the refurbished TBMs, theance rate for both tunnels was 1.86 m/h and 1.34 m/h,, and was low due to breakdown and contractors down-ration rate was higher in case of tuff breccia because of strength (Brown, 1981) and fell in good rock mass cat-h was considered as a suitable medium for tunneling.

rate was low in case of porphyritic basalt because ofh strength and fell in very good rock mass category. Inages, where breccia was mapped, seepage and unstabledition were also insignicant. The large number of owcountered were unfavorable for TBM operations, result-

advance rate. In the mixed face ground (ow contacts), not operate efciently due to cutter head vibration ande instability. Graphical view of penetration rate in vari-its of Maroshivent hole and Vakolavent hole sections

Figs. 7 and 8, respectively.brasion is of obviously economic importance. Overallter consumption for the MaroshiVakola tunnel sec-.58 m per cutter change or 556 m3 per cutter change.

cutter consumption for Maroshivent hole stretch waster change or 748 m3 per cutter change, and 41 m perge or 425 m3 per cutter change for Vakolavent hole

highest cutter wear, i.e. 20 m per cutter change, was


Table 4Percentage distribution of different rock types in the tunnel sections.

Rock types

Fine compacPorphyritic bAmygdaloidTuff breccia Tuff Flow contacIntertrappea

Table 5Summary of T

Tunnel secti

Maroshiven

Vakolavent

Table 6Summary of cu

Description

Center cutteGeneral cuttPregauge cuGauge cutteTotal cutter Length of boExcavation/cMaroshivent hole section

Total length (m) Percentage of length (%)

t basalt 1439.5 46.64 asalt 193.0 6.25 al basalt

1131.0 36.64

t zone 323.0 10.47 ns

Fig. 6. Boring time cycle details with respect to international norms Maro

BM performance characteristics for different litho-units of tunnel sections.

ons Rock types UCS (MPa) Turning movement (bar)

Min. Max. Ave.

t hole Compacted basalt 33116 85 130 115 Porphyritic basalt 115143 90 140 123 Tuff breccia 2650 91 125 108 Flow contact zone 85 125 110 Total length 85 130 109

hole Compacted basalt 33116 74 142 110 Amygdaloidal basalt 5466 70 130 90 Tuff breccia 2650 55 115 78 Tuff 1624 62 63 61 Flow contact zone 65140 70 125 98 Intertrappeans 3065 30 70 53 Total length 30 142 95

tter abrasion in Maroshivent hole and Vakolavent hole sections.

Number alongMaroshivent hole

NumVako

Fitted Changed Fitted

r 6 No change 6 er 17 No change 17 tter 5 4 5 r 3 7 3

31 + 11 = 42 ring/cutter 73.48 m/cutter utter 748 m3/cutter Vakola-vent hole section

Total length (m) Percentage of length (%)

1901.5 73.40

35.0 1.35126.0 4.9360.0 13.978.0 390.0 3.47

shi to vent hole and Vakola to vent hole.

Thrust (bar) Penetration rate (m/h)

Min. Max. Ave. Min. Max. Ave.

90 139 113 1.49 3.66 2.3180 150 139 0.66 3.74 1.4965 100 80 1.38 4.11 3.1169 120 95 2.18 3.28 2.6665 139 96 1.38 4.11 2.66

53 115 90 1.61 2.55 2.050 110 75 1.47 2.91 2.0740 106 60 1.71 2.88 2.335 56 45 1.79 1.89 1.856 115 87 1.53 2.01 1.835 61 48 2.36 2.85 2.635 115 78 1.53 2.88 2.1

ber alonglavent hole

Total number alongMaroshiVakola

Changed

4 1615 496 206 19

31 + 31 = 62 10441 m/cutter 54.58 m/cutter

425 m3/cutter 556 m3/cutter


6.00

Lithology Vs Penetration Rate -Maroshi -Vent hole tunnel

PR- Min PR-AVE PR- MaxPe

netr

atio

n R

ate

(m/h

r)

recorded frnel section.and basaltsby blockingsion in bassilica percevery high cand Zhao, 2SiO2. The pand the proof abrasion0.501.001.502.002.503.003.504.004.505.005.50

Pene

trat

ion

rate

(m/h

r)0.00

Bre

ccia

90-

148

Bas

alt (

blac

k) 1

48- 1

57

Bas

alt a

nd b

recc

ia (

CZ)

157

- 163

Bas

alt (

blac

k) 1

63- 1

75

Bas

alt a

nd B

recc

ia (

CZ)

175

-185

Bre

ccia

185

-195

Br e

ccia

and

Bas

alt (

CZ)

195

-208

Gra

y B

asal

t 20

8-53

5

Bas

alt a

nd B

recc

ia (

CZ)

535

-565

Bre

ccia

565

- 582

Bre

ccia

and

Bas

alt (

CZ)

582

-597

Gra

y B

asal

t 59

7-72

0

Bas

alt a

nd B

recc

ia (

CZ)

720

-728

Br e

ccia

728

-777

Bre

ccia

and

Bas

alt (

CZ)

777

- 782

Porp

hyrit

ic B

asal

t (gr

ay)

782-

975

Bas

alt a

nd B

recc

ia (

CZ)

975

-980

Bre

ccia

980

-116

0

Gra

y B

asa l

t 11

60-1

180

Bas

a lt a

nd B

recc

ia (

CZ)

118

0-12

10

Bre

ccia

121

0-12

89

Bre

ccia

and

Bas

alt (

CZ)

128

9-12

95

Gra

y B

asal

t 12

95-1

360

Chainage in metres and rock

Fig. 7. Lithology vs. penetration rate along different chainages

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

Chainage in metres and rock

Lithology Vs Penetration Rate -Vakola to V

PR-Min PR-Ave PR

Fig. 8. Lithology vs. penetration rate along different chainages

om chainage 57 m to 330 m in Vakolavent hole tun- At this stretch, tuff with patches of carbonaceous shale

was encountered and highest cutter wear was induced of cutters rotation due to sticky muck. Cutters abra-alts and breccia was low due to less quartz and lowntage, compared to granitic and quartzitic rocks whereutter consumption was reported (Goel, 2008; Gong009). Basalts generally have a composition of 4555%osition of the cutters on cutter head is shown in Fig. 9le created after cutting is illustrated in Fig. 10. Types

and corresponding details of cutters for TBMs used

in MaroshiTable 6.

A grippethan a shierequired (Faby increasiground supwith suppodrills and wassisted insPenetrationBas

alt a

nd B

recc

ia (

CZ)

136

0-13

69

Bre

ccia

136

9-17

87

Bre

ccia

and

Bas

alt (

CZ)

178

7-18

16

Gra

y B

asal

t 18

16-1

994

Bas

alt a

nd B

recc

ia (

CZ)

199

4-20

03

Bre

ccia

200

3-20

36

Bre

ccia

and

Bas

alt (

CZ)

203

6-20

66

Gra

y B

asa l

t 20

66- 2

105

Bre

ccia

210

5-21

50

Bre

ccia

and

Bas

alt (

CZ)

215

0-22

10

Gra

y B

asal

t 22

10-2

320

Bre

ccia

and

Bas

alt (

CZ)

232

0-23

45

Bre

ccia

with

Bas

alt p

atch

234

5-24

15

Bre

ccia

and

Bas

alt (

CZ)

241

5-24

48

Gra

y B

asal

t 24

48- 2

610

Bre

ccia

261

0-27

82

Bas

alt

2782

-317

6.5

types

of Maroshivent hole tunnel.

types

ent hole tunnel

-Max

of Vakolavent hole tunnel.

vent hole and Vakolavent hole tunnels are given in

r TBM (open TBM) can achieve higher advance ratesld TBM only, if a small amount of ground support isrrokh et al., 2011). TBM performance can be improvedng the penetration rate and decreasing the time forport installation. Open-type machines can be equippedrt installation equipments like ring erectors, anchorire mesh erectors, etc., to enable the mechanically

tallation of rock support measures behind cutter head. rate improvement is limited by the ground material


F

Fig. 10. View o

and equipmter loads anTBM modeland cutter respectivelysure of thrrotation prin case of oimproved aing the timthe performtransportatto overall dgenerally, gmaintenancoverall progAverage utifor the Mar

f strok

e

Avg

. strok

elengt

h

(m)

Avg

.pen

etra

tion

rate

(m/h

)

Avg

. adva

nce

rate

(m/h

)

0.56

1.55

1.19

0.9

1.88

1.45

0.96

1.71

1.36

1.06

2.34

1.84

1.06

3.38

2.6

1.06

2.86

2.16

1.08

3.24

2.46

1.07

2.63

2.15

1.06

1.82

1.57

0.98

2.38

1.86ig. 9. Cutters position on cutter head of 3.6 m diameter.

f excavated tunnel face using TBM (Vakolavent hole tunnel section).

ent capacity, such as the maximum permissible cut-d the installed torque and thrust. In WIRTH TB-II-360H, the maximum pressure of thrust cylinders was 220 bar,head RPM and rotation pressure were 12 and 185 bar. In WIRTH TB-II-320H TBM model, the maximum pres-ust cylinders was 220 bar, and cutter head RPM andessure were 14 and 225 bar respectively. Especiallypen-type TBM operation, machine utilization can bend thus TBM advance rate can be increased by reduc-e for ground support. The other components affectingance of the TBM are maintenance, utility installation,ion, surveying, ventilation, etc., but their contributionowntime is generally small (Martin, 1988). In this case,round support installation was carried out during TBMe and other downtimes. Details of month-wise andress/utilization of TBMs are shown in Tables 7 and 8.lization coefcient (U = advance rate/penetration rate)oshiVakola tunnel was 76%, which was much higher Ta

ble

7Det

ails

of

over

all a

nd

mon

th-w

ise

TBM

pro

gres

s/utiliza

tion

in

Mar

oshive

nt

hole

tunnel.

Des

crip

tion

Mon

th

Bor

ing

lengt

h

(m)

Bor

ing

tim

e

(h)

Ave

. res

etting

tim

e

(min

)To

tal r

eset

ting

tim

e

(h)

Num

ber

o

Actual

pro

gres

s/utiliza

tion

(fro

m

Januar

y

toSe

pte

mbe

r

in

2009

)

Januar

y

116.5

75.08

6.57

22.67

207

Febr

uar

y

284.9

151.42

8.54

44.83

315

Mar

ch

355.6

207.42

8.71

53.58

369

April

421.5

179.83

7.41

49

397

May

491.9

145.33

5.68

44

465

June

542.6

189.50

7.22

61.75

513

July

410.5

126.67

6.31

40.083

381

Augu

st

179.5

68.33

5.48

15.33

168

Septe

mbe

r

281.8

155.17

5.45

24.25

267

Total

3084

.8

1298

.75

6.82

355.50

3082


Table

8Det

ails

of

over

all a

nd

mon

th-w

ise

TBM

pro

gres

s/utiliza

tion

in

Vak

ola

vent

hole

tunnel.

Des

crip

tion

Tim

e

Bor

ing

lengt

h

(m)

Bor

ing

tim

e

(h)

Ave

. res

etting

tim

e

(min

)To

tal r

eset

ting

tim

e

(h)

Num

ber

of

stro

ke

Avg

. strok

elengt

h

(m)

Avg

.pen

etra

tion

rate

(m/h

)

Avg

. adva

nce

rate

(m/h

)

Actual

pro

gres

s/utiliza

tion

(fro

m

Nov

embe

r20

08

to

July

2009

)

Nov

. 200

8

52.9

33.34

4.03

13.24

197

0.27

1.59

1.14

Dec

. 200

826

1.6

159.58

5.90

41.92

426

0.61

1.64

1.30

Jan. 2

009

271.3

193.75

11.22

59.08

316

0.86

1.40

1.07

Feb.

2009

474.4

228.17

10.10

77.58

461

1.03

2.08

1.55

Mar

. 200

9

381.0

189.17

10.74

67.83

379

1.01

2.01

1.48

Apr.

2009

352.1

174.75

10.00

62

372

0.95

2.01

1.49

May

2009

412.8

199.00

10.06

70.75

422

0.98

2.07

1.53

June

2009

257.7

138.67

12.61

55.92

266

0.97

1.86

1.32

July

2009

113.7

69.67

13.17

26.33

120

0.95

1.63

1.18

Total

2577

.513

86.09

9.76

474.66

2959

0.85

1.81

1.34

because of less ground support requirements, i.e. 10.25% of tunnellength only and less cutter consumption (556 m3 per cutter).

7. Support

For the sin order to included byoverburdento 80 m whfor each rocof Barton (for Norweg1993). RMRing to the (1989):

Q = e(RMR4

Since TBrequiremenexcavation modifying twas used foto 1.5 accorTBM suppoapplied by ESR and it w

The rockwidth (B) an

L = 2 + 0.1ES

By applyculated to proposed is2.02.5 m, aconditions.

Tunnel stions from wand rock reimesh, steelrocks met wbolt is the ftunnel. Rocstrength of was used.

The shotwhat was prthe backup shotcrete whead. Steel in the problrock masse

The rstto 6 m fromhead shieldpassage of ttotal 399.88to vent holwere suppoTable 9. Finaroller comp16 months.wire mesh w system

upport, economic reinforcement system was selectedeffectively cope with the stress change of the site rock

excavation and to ensure the safety. The maximum cover above the crown of the tunnel varied from 65 mich was not very high. The reinforcement pattern usedk mass class was based on the reinforcement standard2000) which was modied from Q-system standardian Method of Tunneling (NMT) (Grimstad and Barton,

values were assessed and then converted to Q accord-correlation between RMR and Q given by Bieniawski

4)/9 (1)

M tunnels have a multiple of purposes, a range of safetyts exists as in the case of drill-and-blast tunnels. Thesupport ratio (ESR) concept used in the Q-system forhe effective tunnel dimension, when selecting support,r support design in TBM tunnel. The ESR was appliedding to the ESR values that Barton (2000) suggested forrt/liner selection. The equivalent dimension (De) wasdividing the span of the tunnel by the fore-mentionedas 2.4 m.

bolt length (L) can be estimated from the excavationd the ESR (Barton et al., 1974):

5BR

(2)

ing the above formula, the length of rock bolt was cal-be 2.36 m. The value of Barton TBM Q-system chart

2.22.6 m. The proposed value of basic design wasccordingly rock bolt was applied according to the site

upport measures were applied at several specic loca-ork platforms behind the cutter head. Tunnel support

nforcement methods, such as rock bolts, shotcrete, wire rib and steel liner panel were used in TBM tunnels. Theithin the tunnels were generally self-supported. Rockastest ground support method in the open-type TBMk bolts of 25 mm diameter, with corresponding yieldapproximately 200 kN, and steel quality of 500 N/mm2

crete of 50100 mm thickness was applied consideringoposed by Q-system. Shotcrete was normally applied inarea; however, under difcult conditions, 100 mm thickith wire mesh was applied immediately behind cutterrib with 3.15 mm MS lagging plates was also installedematic areas. Steel liner panels were used in very poors where rock bearing capacity was very low.

support was installed at a distance ranging from 4 m the working face, i.e. immediately behind the cutter

while other supports were generally installed afterhe main body of the TBM. From Maroshi to vent hole,

m out of 3086.34 m length of tunnel and from Vakolae, total 180.40 m out of 2590.40 m length of tunnelrted and various types of supports are summarized inlly, the tunnels were lined by M-20 grade 300 mm thickacted concrete (RCC) lining, which was completed in

Perforated drainage pipes of 2 in. diameter, attached toere provided.


Table 9Summary of supported length of MaroshiVakola tunnel.

Support type Rib support (m) Steel liner panels (m) Spot rock bolts (m) Rock bolt withwir

50/100 mm thick Total supporting

Maroshiven 91.9Vakolavent 0.0

Due to tcreeks, Powsalt and swemeasured. Tmaximum wincreased today. Heavy for reductioboring wereof cutter heof this was nal RCC liing were do32 mm diam420 m leningredientswater (70 L(naphthalention groutialso. 20,19chemical anquantity excarried out quality andadvance ratvided betw

To arresboring activrying groutwere used t

8. Discussi

The Decseparated francient burThe rock typacted basatuff and inbasalt and tThey were the compabecause of ties lled wTBM tunnelpattern of jowhereas ottight. Over-when it wabasalt, heavsected joinbolting, shoried out inwas also dowere widelbreak occur

cted ritichyriygde ad

suitapendare eva m

Wellnneln ratd tuhe p

disc chaid, wltingles w

aggpervprob

advath wppor

conifferelity fess anctie patthe cas w

ifcu cutIn thnel tion wated thelso. Bwhe

of lquenel prts we

slig bolaverly prt hole 84.33 14.10 95.00 hole 66.00 5.00 10.00

he vicinity of this project to the Arabian Sea and itsai Lake and upsteam Mithi River, high ingress of bothet water from the jointed basalts and ow contacts washe minimum seepage recorded was 3 L/min while theas 250 L/min. During monsoon, the tunnel seepage had

about 25,000 m3/d and in average it was 7850 m3 peringress of water during boring was one of the reasonsn in advance rate because ne particles generated by

separated from muck and deposited in the invert areaad due to the heavy ingress of water. Manual cleaningtime-consuming. To tackle the seepage areas, prior toning, chemical (solution) grouting and cement grout-ne. Chemical grouting was done through 2 m deep andeter holes while cement grouting was done through

gth and 32 mm diameter holes. For cement grouting, used were portland cement (140 kg), y ash (15 kg),), pre-hydrated diluted gum (8 L) and super plasticizere based) (1.40 L). Polyurethane grout was used for solu-

ng because it was injectable into very ne aperture0 kg chemical and 6527 cement bags were used ford cement grouting. During the probing, when waterceeded 25 L/min, pre-excavation cement grouting wasto prevent seepage which also improved the rock mass

stabilized ahead the working face thus increasing thee. Post grouting was done through sleeve pipes, pro-een the drainage pipes.t the heavy seepage by chemical or cement grouting,ity was stopped because arrangements made for car-ing did not allow the movement of locomotives whicho transport the detritus (muck) into mine cars.

on and conclusions

can traps of the study area consist of a number of owsom each other at some places by inert-trap ash beds andied soils (red bole) and behave as a multiaquifer system.pes encountered during excavation were ne com-lt, porphyritic basalt, amygdaloidal basalt, tuff breccia,tertrappeans shales. Amygdaloidal basalt, porphyriticuff breccia which are impervious and generally massive.very suitable media for tunneling using TBM, whereascted basalt at some places was proved troublesomeits jointing nature. Amygdaloidal basalt, with gas cavi-ith secondary minerals was unjointed, impervious anding was trouble free. There was a wide variation in theinting of compacted basalts. Some were closely jointedhers were broadly jointed and joints were generallybreak was recorded during TBM tunneling, especiallys imperfectly interlocked. In the zone of compacted

compaporphyin porpand amwhy th

Thetuff dements with labasalt.TBM tuetratio(tuff anaffect tlongerAt fewmapperock bo

Shafurtherwas imposed duringtact wiwas su

Flowwith dsuitabithicknow juprovidity of joints wvery dof TBMzones. the tunuctuaage of affectement ainvert motorsfell frein tunncontactight toby rock

An monthy seepage was recorded along many mutually inter-

t sets. Rock support system like closely spaced rocktcrete with wire mesh and cement grouting was car-

those locations. At few locations chemical groutingne. In ne to medium grained porphyritic basalt, jointsy spaced and tight, and during TBM tunneling no over-red. The average penetration rate in the ne-grained

achieved. Thother parts ing projectstransportatexist in Dethis reason e mesh (m) shotcrete with wiremesh and spot rockbolting (m)

length (m)

0 114.55 399.88 99.40 180.40

basalt was 2.15 m/h which was more than those of the basalt and amygdaloidal basalt, but the advance ratetic and amygdaloidal basalts was higher. Porphyriticaloidal basalts TBM tunnels were unsupported, thatsvance rate was higher.bility of excavation and stability in volcanic breccia and

on the nature of the matrix, in which the explosion frag-mbedded, and degree of consolidation. Volcanic brecciaatrix is usually suitable as it behaves like amygdaloidal

cemented tuff breccia and tuff offer suitable media foring due to their impermeability, stability and high pen-e. However, clay minerals available in the pyroclasticsff breccia) rocks make cutter jam problem as well asroduction cycle due to sticky property of muck, takingharge time at every transfer point of mucking system.nages, softened and decomposed volcanic breccia washich was supported by shotcrete with wire mesh, spot

and rib.ere unstable due to their inherent softness which wasravated by their closely spaced laminations. Shale itselfious, but along bedding planes water was present. Shalelems with respect to driving side support for the TBMncing, as shale softened and slacked when it was in con-ater. Whole stretch of the tunnel, where shale occurringted by steel rib.tact zones show break in the continuity of rock massnt lithologies and/or engineering properties. Degree ofor tunneling at ow junctions depends on tightness,nd weathering state of lling materials. Tight and fusedons were suitable for tunneling. Open ow junctionsh for water inow. Usually the rock mass in the vicin-ontact zones was weathered and the interlocking ofeak, which posed problems on ground stability. It was

lt for gripping of jacks and maintaining the alignmentter heads in highly weathered and clay lled contactse event of such type of soft ground when gripper pads,invert level was difcult to maintain, with the resultin the tunnel invert, causing water ponds due to seep-r in the tunnel. This uctuation of tunnel invert also

main rail track and thus the train speed and train derail-ecause of water ponds formation due to uneven tunneln the locomotives passed through the water ponds,ocomotives mounted under the chassis of locomotivetly which also contributed at large to low productivityogress. Highly weathered and soft material lled owre supported by steel liner panels and steel rib whereashtly open, unweathered contact zones were supportedt and shotcrete with wire mesh.age penetration rate of 2.10 m/h and a maximumogress of 542.6 m, ensuring tunneling safety, were

e study provided better understanding of using TBM in

of Deccan traps region, and of various upcoming tunnel- for hydropower, sewerage, water supply, irrigation andion, etc. Suitable geological and geotechnical conditionsccan traps for the underground construction, and forunderground space should be regarded as an important


natural resource to be utilized wisely to reduce the populationpressure on surface.

Acknowledgements

First two authors are thankful to Director of NIRM for the per-mission to send the manuscript for publication. Authors are gratefulto the Managements of Municipal Corporation of Greater Mumbai,Hindustan Construction Company Limited, Mumbai and Noble GeoStructs, Mumbai for providing the valuable data and helping renderduring the visit of the site.

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Performance characteristics of tunnel boring machine in basalt and pyroclastic rocks of Deccan traps A case study1 Introduction2 Geology of the study area3 TBM specifications4 Physico-mechanical properties of rocks5 Assessment of rock mass6 TBM performances7 Support system8 Discussion and conclusionsAcknowledgementsReferences

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Performance Characteristics of Tunnel Boring Machine in Basalt and Pyroclastic Rocks of Deccan Traps-A Case Study