Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2013 Article ID 916069 9 pageshttpdxdoiorg1011552013916069

Research ArticleInvestigation of Rock Failure Pattern in Creepby Digital Speckle Correlation Method

Yunliang Tan Yanchun Yin and Tongbin Zhao

State Key Laboratory of Mine Disaster Prevention and Control Shandong University of Science and TechnologyQingdao Shandong 266590 China

Correspondence should be addressed to Yunliang Tan tylllp163169net

Received 9 January 2013 Accepted 11 March 2013

Academic Editor Z Barber

Copyright copy 2013 Yunliang Tan et al This 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

In order to study the mechanical characteristics from creep deformation to failure of rock the tests of uniaxial compressionand pushing steel-plate anchored in rock were performed by using RLJW-2000 servo test synchronizing with Digital SpeckleCorrelation Method (DSCM) The investigations showed that for a uniaxial compressive specimen when load arrived at 05120590

119888

displacement clusters orderly formed which was ahead of themacrocreep strain occurring in a slight jumpmodewhen load arrivedat 07120590

119888 When the load level arrived at 08120590

119888 displacement clusters gathered to be a narrow band After that the specimen abruptly

fractured in a shear mode In the creep pushing steel-plate test when pushing force arrived at 25 kN crack began to occur thehorizontal displacement field as well as shear strain field concentrated continuously along the interface between steel-plate androck and a new narrow concentrating band gathered in the upper layer When pushing force arrived at 275 kN another newnarrow shear deformation band formed in the lower layerThen the steel-plate was pushed out quickly accompanying strong creepdeformation

1 Introduction

Rock is a typical inhomogeneous and rheologic materialMany investigations showed that the rheological mechanicalbehaviours of deep rock mass are stronger than those ofshallow ones [1ndash4] Both rheologic deformation and dilatantrheologic deformation are getting larger and larger as thedepth increases [5 6] However some analytical rheologicmodels were invalid for many cases because variety ofmicrostructure exists in rocks So laboratory experimentsare receiving attention Since the first creep experiment onlimestone shale and sandstonewas finished byGriggs in 1939[7] many rheologic experiments were finished The mainachievements were as follows (a) it is found that rock creeprate had three types steady increase constant and steady[8] (b) some rock creep empirical formulas were obtained inlaboratory [9ndash11] (c) rock creep damage evolvingmechanismwas understood [12ndash14]

The rock complexity attributes to random heterogeneouscomponents defects or fissures and so forth This causescreep deformation and stress distributing nonuniformly in

rock mass and failure localization is inevitable Generallya localized failure originates from location of larger creepdeformation Thus to monitor the creep deformation dif-ference of each region interior rock is a valid approach forforecasting rock creep failure

Bearing this in mind we firstly used author-developedRLJW-2000 servo compression test machine synchronizingwith Digital Speckle Correlation Method (DSCM) [15ndash17]to learn the difference of creep deformation and failurezone in rock under the uniaxial compressive load pushingload to steel-plate anchored in rock We then analysedthe relations between the failure pattern and the differenceof creep deformation so as to make better understandingof heterogeneous rock rheologic failure mechanism withdifferent load conditions

2 Methodology

21 Digital Speckle Correlation Method Digital Speckle Cor-relation Method (DSCM) is employed in this research for

2 Advances in Materials Science and Engineering

Speckle surface

Computer

Rock specimen

Cell

Load device

Illuminates

Camera

Figure 1 DSCM used in rock compression test

real-time capturing and accurate processing of the speckleimages on the specimen surface It is a noncontact andfull-field detection The basis of DSCM is the matchingof points (pixels in an image) between two digital images[18] In DSCM the digital speckle images (images withrandom speckle grains on them) are firstly captured fromspecimen surface on two deformation states during loadingThen one reference image (before deformation) and onedeformed image (after deformation) are processed to obtainthe displacement field between these two statesThematchingis quantitatively accomplished by correlating the pixel graylevel values (intensity) that compose the digital images TheDSCM used for rock mechanics experiments is composed ofa CCD Camera white illuminates and computers (Figure 1)

Before the test a target zone rock specimen surface mustbe sprayed using white paint to a thickness of 1mm andthen sprayed evenly with black paint to prepare the specklesThe speckles are stable and unchanged in colour duringthe whole experimental process The maximum diameterof a black speckle is less than 1mm The white and blackpaints must be dried before being illuminated by one opticilluminator A digital camera connected to a computer is usedto record speckle images in the target zone Furthermorein order to control the speckle quality a speckle image iscaptured and its grey level is evaluated As the quality ofthese speckles is critical for the final accuracy of the DSCMresults the statistical distribution of gray level was employedto evaluate it Generally DSCM is accomplished by matchingsquare subsets of pixels rather than individual pixel becausesubsets comprise a wide variation in gray level The fullfield displacements are obtained by overlapping thematchingsubsets

For the original state (before deformation) the grayscalefunction is expressed as

119865119887 = 119865

119887(119909 119910) 119909 = 1 119872 119910 = 1 119873 (1)

the grayscale function of deformed state (after deformation)or shift copy of 119865

119887 is expressed as

119865119886 = 119865

119886(119909 119910) 119909 = 1 119872 119910 = 1 119873 (2)

where119872times119873 is the intensity with pixel

Assume that 119865119886(119909 119910) is the shift copy of the original

subset 119865119887(119909 119910) after a deformation 119906

119909and 119906

119910 which can be

considered as constant locally in mesoscale The relationshipbetween the original and deformed subset is as follow

119865119886(119909 + 119906

119909 119910 + 119906

119910) = 119865119887(119909 119910) + 120585 (119909 119910) (3)

where 120585(119909 119910) is random noise which induced by camerailluminates and so forth

To evaluate displacement 119906119909and 119906

119910 we may minimize

the difference between 119865119886(119909 119910) and 119865

119887(119909 119910) with respect to

a trial displacement 119906lowast119909and 119906lowast

119910 this problem is equivalent to

evaluate the similarity of two pixel subsets [15 18ndash20] whichcan be expressed by correlation coefficient as

119862(119906lowast

119909 119906lowast

119910)

=

sum119898

119894=1sum119898

119895=1[119865119887(119909119894 119910119895) minus 119865119887] times [119865

119886(1199091015840

119894 1199101015840

119895) minus 119865119886]

radicsum119898

119894=1sum119898

119895=1[119865119887(119909119894 119910119895) minus 119865119887]

2

times radicsum119898

119894=1sum119898

119895=1[119865119886(119909119894 119910119895) minus 119865119886]

2

(4)

where 1199091015840119894= 119909119894+ 119906119894119909 1199101015840

119895= 119910119895+ 119906119895119910

119865119887=

1

1198982

119898

sum

119894=1

119898

sum

119895=1

119865119887(119909119894 119910119895)

119865119886=

1

1198982

119898

sum

119894=1

119898

sum

119895=1

119865119886(1199091015840

119894 1199101015840

119895)

(5)

is the average of intensity of119898 times 119898 pixel subsetIf the grey level of black speckles in the target zone is not

a normal distribution the specimen should be abandonedNote that the speed of image collection depends on themoving conditions of a specimen and the expected comput-ing precision It must be pointed out that a subpixel levelsearch must be completed to obtain a 001 pixel displacementmeasurement precision Displacement of the object can bemeasured through comparing all the point pairs in these twospeckle images The full-field displacements are obtained byoverlapping the matching subsets finally

22 Creep Experimental Test

221 Uniaxial Compressive Creep Test Uniaxial compressivetest is a conventional approach for observing rock failure pat-tern Gathering uniaxial creep compressive test and DSCM isa valid approach to observe rock failure evolution in creepThis kind of test should be strict in accordance with theprocedures Primarily the conventionally uniaxial compres-sive test was carried out to obtain the rock basic mechanicalparameters uniaxial compressive strength 120590

119888(Mpa) Youngrsquos

modulus 119864 (Mpa) Poissonrsquos ratio 120583 Extensometers with50mm in diameter were adopted tomeasure the longitudinaldisplacement Then the specimens of rock were cut intocuboids with 40mm long 40mm wide and 80mm highso as to be convenient for DSCM test After that on onesurface of specimen speckle paint with 1mm thick was

Advances in Materials Science and Engineering 3

100 mm

1 mm

4 mm

40 m

m

Red sandstoneSpeckle field

Steel-plate

Epoxy resin

Figure 2 Section of steel-plate anchored rock specimen

Pushing device

Camera

Steel-plateRock

Vertical load device

Figure 3 Creep pushing test of steel-plate anchored in rock

sprayed At last the uniaxial creep compressive test wascarried out by RLJW-2000 servo compression test machine(developed by authors) synchronizing with DSCM In orderto responsibly determine the creep loading stage the averageuniaxial compressive strength of three specimens was neededto obtain firstly

The creep test loadingwas in themanner of stage by stageAt first the displacement control mode was kept unchangedtill the load is stableThen the pressure loadmodewith 50NSin loading rate was adopted The first stage load is about 20percent of 120590

119888 After that 10 percent of 120590

119888was enhanced for

each stage until the ultimate strength 120590119888 reached In each

loading stage the constant time was kept for 8 hours longThe time interval for load and displacement data collectionwas 1 minute At the same time digital speckle correlationmethod was adopted to obtain the displacement field duringthe rock rheologic process (Figure 1) Before photographingthe load-host computer and image collection-host computerwere accurately kept in the same pace In the period of loadincreasing the speckle image was collected at the rate of5 frames During the constant load stage the speckle imagewas collected at the rate of 5minframe

222 Creep Test on Pushing Steel-Plate Anchored in RockIn deep underground engineering anchored rock failurein creep often occurs accompanying anchors being pushedout This kind failure pattern should be learned by specialcreep test on pushing steel anchored in rock It is somedifferent from the uniaxial compressive creep test mentioned

0 2 4 6 8

Slight creep

Failure

02

03

04

05

06

07

08

09

Time (hr)

07120590119888

06120590119888

0512059011988804120590119888

03120590119888

02120590119888

08120590119888

Stra

in (times

10minus2)

Figure 4 Creep strain-time curve of uniaxial compressive test

CrackLoad device

Bearing plate

Figure 5 Breaking state of uniaxial compressive rock specimen

earlier At first steel-plate anchored rock specimens weremanufactured In a specimen a steel-plate with 4mm thick25mm wide and 150mm long was anchored in the centreThe upper layer and lower layer were sandstones whichwere cut into cuboids with 40mm thick 25mm wide and100mm long The interface between rock and steel-platewas adhered by epoxy resin Then on the specimen surfacespeckle paint with 1mm thick was sprayed (Figure 2) Afterthen pushing test synchronizingwithDSCMwas carried outThe detail procedures were as follows Firstly a specimenwas placed on the bearing platform of RLJW-2000 servocompression test machine and steel-plate was ordered in thehorizontal direction Secondly a vertical pressure with 5Mpawas applied and was kept constantly Thirdly a pushing loaddevice was applied to the out end of steel-plate horizontally(Figure 3)The creep pushing loadwas in themanner stage bystage The pushing load first of stage was applied to 10 kN ata rate 20Ns gradually and then was kept constantly within 6hours From the second stage the load increment was alwayskept on 5 kN until the steel-plate was pushed out During theload increasing period the load and displacement samplinginterval was 1 minute and the speckle image was collectedat the rate of 5 frames correspondingly During the periodof load kept constantly the speckle image was collected at

4 Advances in Materials Science and Engineering

60 70 80

10

20

30

40

50

60

70

80

0

001

minus004

minus003

minus002

minus001

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

1

2

3

4

5

6

7

8times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

minus0095

minus009

minus0085

minus008

minus0075

minus007

(c) Shear strain

Figure 6 Deformation field under the load level of 1265Mpa 02120590119888

60 70 80

10

20

30

40

50

60

70

0

2

4

minus4

minus2

times10minus3

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

minus003

minus0028

minus0026

minus0024

minus0022

minus002

minus0018

minus0016

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 2

4

6

8

10

12times10minus4

(c) Shear strain

Figure 7 Deformation field under the load level of 37965Mpa 05120590119888

the rate of 5minframe At last the failure pattern as wellas displacement field evolution of a steel-plate anchored rockspecimen was obtained

3 Results and Discussion

31 Uniaxial Creep Compressive Test Results Threemudstonerock specimenswere sampled from theKouzidongMine situ-ated at Huainan city Anhui province China By conventional

uniaxial compressive test we obtained their average uniaxialcompressive strength 120590

119888 being 6326Mpa Other new three

specimens were used to do the uniaxial creep compressivetest The loading stages were 02120590

119888 03120590119888 04120590119888 06120590119888 07120590119888

and 08120590119888 correspondingly The total creep test time went

through 481 hoursThe typical curve of axial strain-time wasshown in Figure 4 It was found that when the compressiveload was lower than 06120590

119888 the creep strain was less when

the load level arrived at 07120590119888 the creep strain began to

Advances in Materials Science and Engineering 5

60 70 80

10

20

30

40

50

60

70

0

0005

001

0015

minus002

minus0015

minus001

minus0005

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70minus15

minus10

minus5

0

5

times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 1

2

3

4

5

6

7

times10minus3

(c) Shear strain

Figure 8 Deformation field under the load level of 5694Mpa 08120590119888

increase slightly in a jump mode when the load level arrivedat 08120590

119888 the creep strain increased rapidly After 01 hour

the specimen abruptly fractured in a shear mode (Figure 5)Thus mudstone rock was in the elastic deformation at thelow loading level When the load reached its limit valuestrong creep deformation happened and leaded to the rockfracturing rapidlyThe creep deformation durationwas short

At the same time we obtained the horizontal and verticaldisplacement fields and shear strain field We selected thethree states while load arriving at 02120590

119888 05120590

119888and 08120590

119888to

analyse the creep deformation distribution When load wasat the lower level 02120590

119888 the deformation in the specimen

was less in magnitude and distributed inhomogeneously andrandomly and deformation concentrated locally due to theheterogeneity of rock in mesoscale (Figure 6) When loadlevel arrived at 05120590

119888 the deformation field became ordering

(Figure 7) compared with the lower load level 02120590119888 At

this load level two horizontal displacement clusters formedin the left-up and right-down regions separately The shearstrain cluster gathered more and more prominently Thisphenomenon can not be indicated by creep strain-time curveWhen load level arrived at 08120590

119888 as the displacement clusters

became more ordering a narrow deformation concentratingband formed (Figure 8) which led to the specimen fracturedafter 01 hour Both displacement field and shear strain fieldwere in keeping with the creep strain-time curve (Figure 4)

Just as mentioned earlier rock is a kind of naturalheterogeneous material in mesoscale A lot of detects ordisordered mini-fissures existed in it due to the long timegeological movement For a rock sample when compressiveload is in a low level the fissures are easy to close andthe displacement field within rock is disordered so rockis dominated by elastic deformation in macro-scale at thisstage As the load level increases gradually some damages

originating from defects or fissures occur which cause thedisplacement or strain field concentrating locally severaldeformation clusters gather But themacrocreep deformationis still not distinct in displacement-time curve This is theperiod of creep damage accumulation before rock beginsmacrofailure In this period the creep deformation fieldevolves to gather some ordered clusters This behaviour maybe considered as a useful indication for forecasting the rockfailure in a long term Thus DSCM is valid to remedy theimperfection that conventional creep test cannot reflect thedeformation field within rock in laboratory which extendsthe function of conventional rock creep test indeed Howeverin macrorock engineering how to adopt such techniquesas DSCM to monitor local creep damage evolution withinrock is a challenge work It must be pointed out that such asituation as rock filled with water or rock chemical reactionwith other medium was not considered

As for the rationale of failure bands formation it can beexplained by Mohr-Coulomb criterion [21] as

120591 = 120590119899tan120593 + 119862 (6)

where 120591 and 120590119899are the shear stress and normal at failure

plane which can be easily obtained under a compressive loadcondition 119862 is cohesion and 120593 is angle of internal frictionThe Mohr envelope represents the true shape of the failurecurve (Figure 9) Mohrrsquos stress circle can be determined bymaximum and minimum principal stresses 120590

1and 120590

3 For

the case of uniaxial compressive test 1205903= 0

One easily finds from this theory that the failure planeforms the angle (45∘ + 1205932) to the plane against which themajor principal stress operates and this does not agree withthe axial splitting Let us start by examining the simpleapproach that the strength of rock can be expressed in terms

6 Advances in Materials Science and Engineering

Coulombrsquos relation

119862

120593

12059012

1205901 2

1205901 120590

120591

119862tan 120593

120591 = 120590119899tan 120593 + 119862

Figure 9 Stress failure at Coulomb-Mohr criterion

0 5 10 15 20 250

5

10

15

20

25

30Pushing force

Displacement

0

02

04

06

08

1

12

14

16

Time (h)

Disp

lace

men

t (m

m)

Failured3

d2d1

c1

b1

a2a1

c2

b2Push

ing

forc

e (kN

)

Figure 10 Pushing force-displacement-time curve

of a cohesion term and a friction term from amesomechani-cal point of view Assume that the former represents the crys-tal matrix of the smallest rock units and the latter to mirrorthe influence of discrete discontinuities of different extensionMobilization of the two strength components requires verydifferent amounts of strain Naturally if continuous planeweaknesses extend across a rock volume separating blocksshearing by relative movement of the blocks may take placewithout bringing the rockmaterial in the blocks into a criticalstate This case leads to shear failure Not surprisingly rockis a kind of inhomogeneous material and many fissures arecontained in it randomly This causes cohesion decreasingand shear failure happening easily at last Coulomb-Mohrcriterion is satisfied

32 Creep Test on Pushing Steel-Plate Anchored in Rock In thecreep pushing test five stages of pushing load 10 15 20 25and 30 kNwere applied and the corresponding displacementduring each stage was named after a1-a2 b1-b2 c1-c2 and d1-d2-d3 (Figure 10) Before pushing force was less than 20 kNcreep deformation was little and the composite specimenwas in an elastic deformation state When pushing forcearrived at 20 kN creep displacement occurred and increasedas the pushing force level was enhanced When pushingforce arrived at 25 kN crack began to occur and creepdisplacement increased rapidly After pushing force arrived at

Failure band

Failure band

Steel-plate

Figure 11 Creep failure pattern of pushing steel-plate anchored inrock

275 kN the steel-plate was pushed out quickly accompanyingstrong creep deformation and two win-shape macrocracksformed (Figure 11) at last

At the same time we obtained the horizontal displace-ment field and shear strain field by DSCM Five stagesof pushing force 10 15 20 25 and 275 kN were adoptedto analyse the evolution of creep deformation field Beforepushing force arrived at 15 KN the creep deformationwas lessinmagnitude and distributed inhomogenously and randomlyand concentrated locally because of the heterogeneity of rockin mesoscale (Figures 12-13) When pushing force arrivedat 20 kN the displacement field tended to be ordering andshear strain concentrated discontinuously along the interfacebetween steel-plate and rock (Figure 14)While pushing forcearrived at 25 kN the horizontal displacement and shear strainconcentrated continuously along the interface between steel-plate and rock and a new narrow shear strain band formed inthe upper layer (Figure 15) which indicated the first narrowshear band occurred Unfortunately when pushing forcearrived at 275 kN the another new narrow shear strain bandformed in the lower layer was not recorded because of thesudden failure of switch to illuminators The duration fromstrong creep deformation to shear band formed till to steel-plated was pushed out is short which is consistent with thatobtained by conventional creep test

In order to verify the correctness of two win-shapefailure bands formed (Figure 11) numerical simulations wereperformed by using Particle Flow Code (PFC2d) [22] Theresults showed that the formation of shear bandwent throughthe process crack initiation from original defect rarr clustergeneration rarr cluster increasing rarr cluster interfusion rarrcore or continuous zone At last the two win-shape failurebands formed (Figure 16) which is similar with laboratorytest result

The test process of pushing steel-plate anchored in rockshowed that when pushing force was at a low level thedisplacement field was disordered and rock was in elasticdeformation As pushing force increased some damagesoriginated from some defects which caused the displacementor strain concentrating locally and several deformationclusters gathered although macrocreep deformation was notdistinct Similarly because the duration from strong creepdeformation to failure zone formed is short only through

Advances in Materials Science and Engineering 7

20 40 60 80 100

20

30

40

50

60

70

80

0018 002 0022 0024 0026 0028 003

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

60

50

70

80

0 05minus15 minus1 minus05 times10119890minus3

el-plate

Steel-plate

(b) Shear strain

Figure 12 DSCM results at pushing force 10 kN

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0045 005 0055 006 0065 007 0075

Steel-plate

(a) Horizontal displacement (mm)

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0 1minus3 minus2 minus1

Steel-plate

times10119890minus3

(b) Shear strain

Figure 13 DSCM results at pushing force 15 kN

observing the shortly strong creep deformation to forecast therock failure is too hasty

Fortunately DSCM can be easily used to monitor all theevolution progress of creep deformation field which providesa wealth of information for forecasting rock failure indeedThus such techniques as DSCM may bring about some newmonitoring approaches in anchored rock engineering

4 Conclusions

Theaimof the approach of RLJW-2000 servo test synchroniz-ing with DSCM was adopted to investigate the rock failurepattern and creep deformation By comparing with the pastinvestigation this research contains at least three originalaspects

(1) The RLJW-2000 servo test synchronizing with DSCMon creep failure of uniaxial compression and ofpushing steel-plate contained in rock was performedfirstly

(2) The deformation field evolution from creep damageaccumulation to macrofailure under the uniaxialcreep compression load condition was obtained

(3) Thedisplacement field evolution in rock and rock fail-ure pattern during creep pushing steel-plate anchoredin rock were obtained

The investigations showed the following

(1) For a uniaxial compressive specimen when loadarrives at 05120590

119888 ordered displacement clusters form

which is ahead of the macrocreep strain occurringin a slight jump mode when load arrives at 07120590

119888

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

2 Advances in Materials Science and Engineering

Speckle surface

Computer

Rock specimen

Cell

Load device

Illuminates

Camera

Figure 1 DSCM used in rock compression test

real-time capturing and accurate processing of the speckleimages on the specimen surface It is a noncontact andfull-field detection The basis of DSCM is the matchingof points (pixels in an image) between two digital images[18] In DSCM the digital speckle images (images withrandom speckle grains on them) are firstly captured fromspecimen surface on two deformation states during loadingThen one reference image (before deformation) and onedeformed image (after deformation) are processed to obtainthe displacement field between these two statesThematchingis quantitatively accomplished by correlating the pixel graylevel values (intensity) that compose the digital images TheDSCM used for rock mechanics experiments is composed ofa CCD Camera white illuminates and computers (Figure 1)

Before the test a target zone rock specimen surface mustbe sprayed using white paint to a thickness of 1mm andthen sprayed evenly with black paint to prepare the specklesThe speckles are stable and unchanged in colour duringthe whole experimental process The maximum diameterof a black speckle is less than 1mm The white and blackpaints must be dried before being illuminated by one opticilluminator A digital camera connected to a computer is usedto record speckle images in the target zone Furthermorein order to control the speckle quality a speckle image iscaptured and its grey level is evaluated As the quality ofthese speckles is critical for the final accuracy of the DSCMresults the statistical distribution of gray level was employedto evaluate it Generally DSCM is accomplished by matchingsquare subsets of pixels rather than individual pixel becausesubsets comprise a wide variation in gray level The fullfield displacements are obtained by overlapping thematchingsubsets

For the original state (before deformation) the grayscalefunction is expressed as

119865119887 = 119865

119887(119909 119910) 119909 = 1 119872 119910 = 1 119873 (1)

the grayscale function of deformed state (after deformation)or shift copy of 119865

119887 is expressed as

119865119886 = 119865

119886(119909 119910) 119909 = 1 119872 119910 = 1 119873 (2)

where119872times119873 is the intensity with pixel

Assume that 119865119886(119909 119910) is the shift copy of the original

subset 119865119887(119909 119910) after a deformation 119906

119909and 119906

119910 which can be

considered as constant locally in mesoscale The relationshipbetween the original and deformed subset is as follow

119865119886(119909 + 119906

119909 119910 + 119906

119910) = 119865119887(119909 119910) + 120585 (119909 119910) (3)

where 120585(119909 119910) is random noise which induced by camerailluminates and so forth

To evaluate displacement 119906119909and 119906

119910 we may minimize

the difference between 119865119886(119909 119910) and 119865

119887(119909 119910) with respect to

a trial displacement 119906lowast119909and 119906lowast

119910 this problem is equivalent to

evaluate the similarity of two pixel subsets [15 18ndash20] whichcan be expressed by correlation coefficient as

119862(119906lowast

119909 119906lowast

119910)

=

sum119898

119894=1sum119898

119895=1[119865119887(119909119894 119910119895) minus 119865119887] times [119865

119886(1199091015840

119894 1199101015840

119895) minus 119865119886]

radicsum119898

119894=1sum119898

119895=1[119865119887(119909119894 119910119895) minus 119865119887]

2

times radicsum119898

119894=1sum119898

119895=1[119865119886(119909119894 119910119895) minus 119865119886]

2

(4)

where 1199091015840119894= 119909119894+ 119906119894119909 1199101015840

119895= 119910119895+ 119906119895119910

119865119887=

1

1198982

119898

sum

119894=1

119898

sum

119895=1

119865119887(119909119894 119910119895)

119865119886=

1

1198982

119898

sum

119894=1

119898

sum

119895=1

119865119886(1199091015840

119894 1199101015840

119895)

(5)

is the average of intensity of119898 times 119898 pixel subsetIf the grey level of black speckles in the target zone is not

a normal distribution the specimen should be abandonedNote that the speed of image collection depends on themoving conditions of a specimen and the expected comput-ing precision It must be pointed out that a subpixel levelsearch must be completed to obtain a 001 pixel displacementmeasurement precision Displacement of the object can bemeasured through comparing all the point pairs in these twospeckle images The full-field displacements are obtained byoverlapping the matching subsets finally

22 Creep Experimental Test

221 Uniaxial Compressive Creep Test Uniaxial compressivetest is a conventional approach for observing rock failure pat-tern Gathering uniaxial creep compressive test and DSCM isa valid approach to observe rock failure evolution in creepThis kind of test should be strict in accordance with theprocedures Primarily the conventionally uniaxial compres-sive test was carried out to obtain the rock basic mechanicalparameters uniaxial compressive strength 120590

119888(Mpa) Youngrsquos

modulus 119864 (Mpa) Poissonrsquos ratio 120583 Extensometers with50mm in diameter were adopted tomeasure the longitudinaldisplacement Then the specimens of rock were cut intocuboids with 40mm long 40mm wide and 80mm highso as to be convenient for DSCM test After that on onesurface of specimen speckle paint with 1mm thick was

Advances in Materials Science and Engineering 3

100 mm

1 mm

4 mm

40 m

m

Red sandstoneSpeckle field

Steel-plate

Epoxy resin

Figure 2 Section of steel-plate anchored rock specimen

Pushing device

Camera

Steel-plateRock

Vertical load device

Figure 3 Creep pushing test of steel-plate anchored in rock

sprayed At last the uniaxial creep compressive test wascarried out by RLJW-2000 servo compression test machine(developed by authors) synchronizing with DSCM In orderto responsibly determine the creep loading stage the averageuniaxial compressive strength of three specimens was neededto obtain firstly

The creep test loadingwas in themanner of stage by stageAt first the displacement control mode was kept unchangedtill the load is stableThen the pressure loadmodewith 50NSin loading rate was adopted The first stage load is about 20percent of 120590

119888 After that 10 percent of 120590

119888was enhanced for

each stage until the ultimate strength 120590119888 reached In each

loading stage the constant time was kept for 8 hours longThe time interval for load and displacement data collectionwas 1 minute At the same time digital speckle correlationmethod was adopted to obtain the displacement field duringthe rock rheologic process (Figure 1) Before photographingthe load-host computer and image collection-host computerwere accurately kept in the same pace In the period of loadincreasing the speckle image was collected at the rate of5 frames During the constant load stage the speckle imagewas collected at the rate of 5minframe

222 Creep Test on Pushing Steel-Plate Anchored in RockIn deep underground engineering anchored rock failurein creep often occurs accompanying anchors being pushedout This kind failure pattern should be learned by specialcreep test on pushing steel anchored in rock It is somedifferent from the uniaxial compressive creep test mentioned

0 2 4 6 8

Slight creep

Failure

02

03

04

05

06

07

08

09

Time (hr)

07120590119888

06120590119888

0512059011988804120590119888

03120590119888

02120590119888

08120590119888

Stra

in (times

10minus2)

Figure 4 Creep strain-time curve of uniaxial compressive test

CrackLoad device

Bearing plate

Figure 5 Breaking state of uniaxial compressive rock specimen

earlier At first steel-plate anchored rock specimens weremanufactured In a specimen a steel-plate with 4mm thick25mm wide and 150mm long was anchored in the centreThe upper layer and lower layer were sandstones whichwere cut into cuboids with 40mm thick 25mm wide and100mm long The interface between rock and steel-platewas adhered by epoxy resin Then on the specimen surfacespeckle paint with 1mm thick was sprayed (Figure 2) Afterthen pushing test synchronizingwithDSCMwas carried outThe detail procedures were as follows Firstly a specimenwas placed on the bearing platform of RLJW-2000 servocompression test machine and steel-plate was ordered in thehorizontal direction Secondly a vertical pressure with 5Mpawas applied and was kept constantly Thirdly a pushing loaddevice was applied to the out end of steel-plate horizontally(Figure 3)The creep pushing loadwas in themanner stage bystage The pushing load first of stage was applied to 10 kN ata rate 20Ns gradually and then was kept constantly within 6hours From the second stage the load increment was alwayskept on 5 kN until the steel-plate was pushed out During theload increasing period the load and displacement samplinginterval was 1 minute and the speckle image was collectedat the rate of 5 frames correspondingly During the periodof load kept constantly the speckle image was collected at

4 Advances in Materials Science and Engineering

60 70 80

10

20

30

40

50

60

70

80

0

001

minus004

minus003

minus002

minus001

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

1

2

3

4

5

6

7

8times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

minus0095

minus009

minus0085

minus008

minus0075

minus007

(c) Shear strain

Figure 6 Deformation field under the load level of 1265Mpa 02120590119888

60 70 80

10

20

30

40

50

60

70

0

2

4

minus4

minus2

times10minus3

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

minus003

minus0028

minus0026

minus0024

minus0022

minus002

minus0018

minus0016

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 2

4

6

8

10

12times10minus4

(c) Shear strain

Figure 7 Deformation field under the load level of 37965Mpa 05120590119888

the rate of 5minframe At last the failure pattern as wellas displacement field evolution of a steel-plate anchored rockspecimen was obtained

3 Results and Discussion

31 Uniaxial Creep Compressive Test Results Threemudstonerock specimenswere sampled from theKouzidongMine situ-ated at Huainan city Anhui province China By conventional

uniaxial compressive test we obtained their average uniaxialcompressive strength 120590

119888 being 6326Mpa Other new three

specimens were used to do the uniaxial creep compressivetest The loading stages were 02120590

119888 03120590119888 04120590119888 06120590119888 07120590119888

and 08120590119888 correspondingly The total creep test time went

through 481 hoursThe typical curve of axial strain-time wasshown in Figure 4 It was found that when the compressiveload was lower than 06120590

119888 the creep strain was less when

the load level arrived at 07120590119888 the creep strain began to

Advances in Materials Science and Engineering 5

60 70 80

10

20

30

40

50

60

70

0

0005

001

0015

minus002

minus0015

minus001

minus0005

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70minus15

minus10

minus5

0

5

times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 1

2

3

4

5

6

7

times10minus3

(c) Shear strain

Figure 8 Deformation field under the load level of 5694Mpa 08120590119888

increase slightly in a jump mode when the load level arrivedat 08120590

119888 the creep strain increased rapidly After 01 hour

the specimen abruptly fractured in a shear mode (Figure 5)Thus mudstone rock was in the elastic deformation at thelow loading level When the load reached its limit valuestrong creep deformation happened and leaded to the rockfracturing rapidlyThe creep deformation durationwas short

At the same time we obtained the horizontal and verticaldisplacement fields and shear strain field We selected thethree states while load arriving at 02120590

119888 05120590

119888and 08120590

119888to

analyse the creep deformation distribution When load wasat the lower level 02120590

119888 the deformation in the specimen

was less in magnitude and distributed inhomogeneously andrandomly and deformation concentrated locally due to theheterogeneity of rock in mesoscale (Figure 6) When loadlevel arrived at 05120590

119888 the deformation field became ordering

(Figure 7) compared with the lower load level 02120590119888 At

this load level two horizontal displacement clusters formedin the left-up and right-down regions separately The shearstrain cluster gathered more and more prominently Thisphenomenon can not be indicated by creep strain-time curveWhen load level arrived at 08120590

119888 as the displacement clusters

became more ordering a narrow deformation concentratingband formed (Figure 8) which led to the specimen fracturedafter 01 hour Both displacement field and shear strain fieldwere in keeping with the creep strain-time curve (Figure 4)

Just as mentioned earlier rock is a kind of naturalheterogeneous material in mesoscale A lot of detects ordisordered mini-fissures existed in it due to the long timegeological movement For a rock sample when compressiveload is in a low level the fissures are easy to close andthe displacement field within rock is disordered so rockis dominated by elastic deformation in macro-scale at thisstage As the load level increases gradually some damages

originating from defects or fissures occur which cause thedisplacement or strain field concentrating locally severaldeformation clusters gather But themacrocreep deformationis still not distinct in displacement-time curve This is theperiod of creep damage accumulation before rock beginsmacrofailure In this period the creep deformation fieldevolves to gather some ordered clusters This behaviour maybe considered as a useful indication for forecasting the rockfailure in a long term Thus DSCM is valid to remedy theimperfection that conventional creep test cannot reflect thedeformation field within rock in laboratory which extendsthe function of conventional rock creep test indeed Howeverin macrorock engineering how to adopt such techniquesas DSCM to monitor local creep damage evolution withinrock is a challenge work It must be pointed out that such asituation as rock filled with water or rock chemical reactionwith other medium was not considered

As for the rationale of failure bands formation it can beexplained by Mohr-Coulomb criterion [21] as

120591 = 120590119899tan120593 + 119862 (6)

where 120591 and 120590119899are the shear stress and normal at failure

plane which can be easily obtained under a compressive loadcondition 119862 is cohesion and 120593 is angle of internal frictionThe Mohr envelope represents the true shape of the failurecurve (Figure 9) Mohrrsquos stress circle can be determined bymaximum and minimum principal stresses 120590

1and 120590

3 For

the case of uniaxial compressive test 1205903= 0

One easily finds from this theory that the failure planeforms the angle (45∘ + 1205932) to the plane against which themajor principal stress operates and this does not agree withthe axial splitting Let us start by examining the simpleapproach that the strength of rock can be expressed in terms

6 Advances in Materials Science and Engineering

Coulombrsquos relation

119862

120593

12059012

1205901 2

1205901 120590

120591

119862tan 120593

120591 = 120590119899tan 120593 + 119862

Figure 9 Stress failure at Coulomb-Mohr criterion

0 5 10 15 20 250

5

10

15

20

25

30Pushing force

Displacement

0

02

04

06

08

1

12

14

16

Time (h)

Disp

lace

men

t (m

m)

Failured3

d2d1

c1

b1

a2a1

c2

b2Push

ing

forc

e (kN

)

Figure 10 Pushing force-displacement-time curve

of a cohesion term and a friction term from amesomechani-cal point of view Assume that the former represents the crys-tal matrix of the smallest rock units and the latter to mirrorthe influence of discrete discontinuities of different extensionMobilization of the two strength components requires verydifferent amounts of strain Naturally if continuous planeweaknesses extend across a rock volume separating blocksshearing by relative movement of the blocks may take placewithout bringing the rockmaterial in the blocks into a criticalstate This case leads to shear failure Not surprisingly rockis a kind of inhomogeneous material and many fissures arecontained in it randomly This causes cohesion decreasingand shear failure happening easily at last Coulomb-Mohrcriterion is satisfied

32 Creep Test on Pushing Steel-Plate Anchored in Rock In thecreep pushing test five stages of pushing load 10 15 20 25and 30 kNwere applied and the corresponding displacementduring each stage was named after a1-a2 b1-b2 c1-c2 and d1-d2-d3 (Figure 10) Before pushing force was less than 20 kNcreep deformation was little and the composite specimenwas in an elastic deformation state When pushing forcearrived at 20 kN creep displacement occurred and increasedas the pushing force level was enhanced When pushingforce arrived at 25 kN crack began to occur and creepdisplacement increased rapidly After pushing force arrived at

Failure band

Failure band

Steel-plate

Figure 11 Creep failure pattern of pushing steel-plate anchored inrock

275 kN the steel-plate was pushed out quickly accompanyingstrong creep deformation and two win-shape macrocracksformed (Figure 11) at last

At the same time we obtained the horizontal displace-ment field and shear strain field by DSCM Five stagesof pushing force 10 15 20 25 and 275 kN were adoptedto analyse the evolution of creep deformation field Beforepushing force arrived at 15 KN the creep deformationwas lessinmagnitude and distributed inhomogenously and randomlyand concentrated locally because of the heterogeneity of rockin mesoscale (Figures 12-13) When pushing force arrivedat 20 kN the displacement field tended to be ordering andshear strain concentrated discontinuously along the interfacebetween steel-plate and rock (Figure 14)While pushing forcearrived at 25 kN the horizontal displacement and shear strainconcentrated continuously along the interface between steel-plate and rock and a new narrow shear strain band formed inthe upper layer (Figure 15) which indicated the first narrowshear band occurred Unfortunately when pushing forcearrived at 275 kN the another new narrow shear strain bandformed in the lower layer was not recorded because of thesudden failure of switch to illuminators The duration fromstrong creep deformation to shear band formed till to steel-plated was pushed out is short which is consistent with thatobtained by conventional creep test

In order to verify the correctness of two win-shapefailure bands formed (Figure 11) numerical simulations wereperformed by using Particle Flow Code (PFC2d) [22] Theresults showed that the formation of shear bandwent throughthe process crack initiation from original defect rarr clustergeneration rarr cluster increasing rarr cluster interfusion rarrcore or continuous zone At last the two win-shape failurebands formed (Figure 16) which is similar with laboratorytest result

The test process of pushing steel-plate anchored in rockshowed that when pushing force was at a low level thedisplacement field was disordered and rock was in elasticdeformation As pushing force increased some damagesoriginated from some defects which caused the displacementor strain concentrating locally and several deformationclusters gathered although macrocreep deformation was notdistinct Similarly because the duration from strong creepdeformation to failure zone formed is short only through

Advances in Materials Science and Engineering 7

20 40 60 80 100

20

30

40

50

60

70

80

0018 002 0022 0024 0026 0028 003

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

60

50

70

80

0 05minus15 minus1 minus05 times10119890minus3

el-plate

Steel-plate

(b) Shear strain

Figure 12 DSCM results at pushing force 10 kN

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0045 005 0055 006 0065 007 0075

Steel-plate

(a) Horizontal displacement (mm)

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0 1minus3 minus2 minus1

Steel-plate

times10119890minus3

(b) Shear strain

Figure 13 DSCM results at pushing force 15 kN

observing the shortly strong creep deformation to forecast therock failure is too hasty

Fortunately DSCM can be easily used to monitor all theevolution progress of creep deformation field which providesa wealth of information for forecasting rock failure indeedThus such techniques as DSCM may bring about some newmonitoring approaches in anchored rock engineering

4 Conclusions

Theaimof the approach of RLJW-2000 servo test synchroniz-ing with DSCM was adopted to investigate the rock failurepattern and creep deformation By comparing with the pastinvestigation this research contains at least three originalaspects

(1) The RLJW-2000 servo test synchronizing with DSCMon creep failure of uniaxial compression and ofpushing steel-plate contained in rock was performedfirstly

(2) The deformation field evolution from creep damageaccumulation to macrofailure under the uniaxialcreep compression load condition was obtained

(3) Thedisplacement field evolution in rock and rock fail-ure pattern during creep pushing steel-plate anchoredin rock were obtained

The investigations showed the following

(1) For a uniaxial compressive specimen when loadarrives at 05120590

119888 ordered displacement clusters form

which is ahead of the macrocreep strain occurringin a slight jump mode when load arrives at 07120590

119888

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 3

100 mm

1 mm

4 mm

40 m

m

Red sandstoneSpeckle field

Steel-plate

Epoxy resin

Figure 2 Section of steel-plate anchored rock specimen

Pushing device

Camera

Steel-plateRock

Vertical load device

Figure 3 Creep pushing test of steel-plate anchored in rock

sprayed At last the uniaxial creep compressive test wascarried out by RLJW-2000 servo compression test machine(developed by authors) synchronizing with DSCM In orderto responsibly determine the creep loading stage the averageuniaxial compressive strength of three specimens was neededto obtain firstly

The creep test loadingwas in themanner of stage by stageAt first the displacement control mode was kept unchangedtill the load is stableThen the pressure loadmodewith 50NSin loading rate was adopted The first stage load is about 20percent of 120590

119888 After that 10 percent of 120590

119888was enhanced for

each stage until the ultimate strength 120590119888 reached In each

loading stage the constant time was kept for 8 hours longThe time interval for load and displacement data collectionwas 1 minute At the same time digital speckle correlationmethod was adopted to obtain the displacement field duringthe rock rheologic process (Figure 1) Before photographingthe load-host computer and image collection-host computerwere accurately kept in the same pace In the period of loadincreasing the speckle image was collected at the rate of5 frames During the constant load stage the speckle imagewas collected at the rate of 5minframe

222 Creep Test on Pushing Steel-Plate Anchored in RockIn deep underground engineering anchored rock failurein creep often occurs accompanying anchors being pushedout This kind failure pattern should be learned by specialcreep test on pushing steel anchored in rock It is somedifferent from the uniaxial compressive creep test mentioned

0 2 4 6 8

Slight creep

Failure

02

03

04

05

06

07

08

09

Time (hr)

07120590119888

06120590119888

0512059011988804120590119888

03120590119888

02120590119888

08120590119888

Stra

in (times

10minus2)

Figure 4 Creep strain-time curve of uniaxial compressive test

CrackLoad device

Bearing plate

Figure 5 Breaking state of uniaxial compressive rock specimen

earlier At first steel-plate anchored rock specimens weremanufactured In a specimen a steel-plate with 4mm thick25mm wide and 150mm long was anchored in the centreThe upper layer and lower layer were sandstones whichwere cut into cuboids with 40mm thick 25mm wide and100mm long The interface between rock and steel-platewas adhered by epoxy resin Then on the specimen surfacespeckle paint with 1mm thick was sprayed (Figure 2) Afterthen pushing test synchronizingwithDSCMwas carried outThe detail procedures were as follows Firstly a specimenwas placed on the bearing platform of RLJW-2000 servocompression test machine and steel-plate was ordered in thehorizontal direction Secondly a vertical pressure with 5Mpawas applied and was kept constantly Thirdly a pushing loaddevice was applied to the out end of steel-plate horizontally(Figure 3)The creep pushing loadwas in themanner stage bystage The pushing load first of stage was applied to 10 kN ata rate 20Ns gradually and then was kept constantly within 6hours From the second stage the load increment was alwayskept on 5 kN until the steel-plate was pushed out During theload increasing period the load and displacement samplinginterval was 1 minute and the speckle image was collectedat the rate of 5 frames correspondingly During the periodof load kept constantly the speckle image was collected at

4 Advances in Materials Science and Engineering

60 70 80

10

20

30

40

50

60

70

80

0

001

minus004

minus003

minus002

minus001

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

1

2

3

4

5

6

7

8times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

minus0095

minus009

minus0085

minus008

minus0075

minus007

(c) Shear strain

Figure 6 Deformation field under the load level of 1265Mpa 02120590119888

60 70 80

10

20

30

40

50

60

70

0

2

4

minus4

minus2

times10minus3

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

minus003

minus0028

minus0026

minus0024

minus0022

minus002

minus0018

minus0016

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 2

4

6

8

10

12times10minus4

(c) Shear strain

Figure 7 Deformation field under the load level of 37965Mpa 05120590119888

the rate of 5minframe At last the failure pattern as wellas displacement field evolution of a steel-plate anchored rockspecimen was obtained

3 Results and Discussion

31 Uniaxial Creep Compressive Test Results Threemudstonerock specimenswere sampled from theKouzidongMine situ-ated at Huainan city Anhui province China By conventional

uniaxial compressive test we obtained their average uniaxialcompressive strength 120590

119888 being 6326Mpa Other new three

specimens were used to do the uniaxial creep compressivetest The loading stages were 02120590

119888 03120590119888 04120590119888 06120590119888 07120590119888

and 08120590119888 correspondingly The total creep test time went

through 481 hoursThe typical curve of axial strain-time wasshown in Figure 4 It was found that when the compressiveload was lower than 06120590

119888 the creep strain was less when

the load level arrived at 07120590119888 the creep strain began to

Advances in Materials Science and Engineering 5

60 70 80

10

20

30

40

50

60

70

0

0005

001

0015

minus002

minus0015

minus001

minus0005

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70minus15

minus10

minus5

0

5

times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 1

2

3

4

5

6

7

times10minus3

(c) Shear strain

Figure 8 Deformation field under the load level of 5694Mpa 08120590119888

increase slightly in a jump mode when the load level arrivedat 08120590

119888 the creep strain increased rapidly After 01 hour

the specimen abruptly fractured in a shear mode (Figure 5)Thus mudstone rock was in the elastic deformation at thelow loading level When the load reached its limit valuestrong creep deformation happened and leaded to the rockfracturing rapidlyThe creep deformation durationwas short

At the same time we obtained the horizontal and verticaldisplacement fields and shear strain field We selected thethree states while load arriving at 02120590

119888 05120590

119888and 08120590

119888to

analyse the creep deformation distribution When load wasat the lower level 02120590

119888 the deformation in the specimen

was less in magnitude and distributed inhomogeneously andrandomly and deformation concentrated locally due to theheterogeneity of rock in mesoscale (Figure 6) When loadlevel arrived at 05120590

119888 the deformation field became ordering

(Figure 7) compared with the lower load level 02120590119888 At

this load level two horizontal displacement clusters formedin the left-up and right-down regions separately The shearstrain cluster gathered more and more prominently Thisphenomenon can not be indicated by creep strain-time curveWhen load level arrived at 08120590

119888 as the displacement clusters

became more ordering a narrow deformation concentratingband formed (Figure 8) which led to the specimen fracturedafter 01 hour Both displacement field and shear strain fieldwere in keeping with the creep strain-time curve (Figure 4)

Just as mentioned earlier rock is a kind of naturalheterogeneous material in mesoscale A lot of detects ordisordered mini-fissures existed in it due to the long timegeological movement For a rock sample when compressiveload is in a low level the fissures are easy to close andthe displacement field within rock is disordered so rockis dominated by elastic deformation in macro-scale at thisstage As the load level increases gradually some damages

originating from defects or fissures occur which cause thedisplacement or strain field concentrating locally severaldeformation clusters gather But themacrocreep deformationis still not distinct in displacement-time curve This is theperiod of creep damage accumulation before rock beginsmacrofailure In this period the creep deformation fieldevolves to gather some ordered clusters This behaviour maybe considered as a useful indication for forecasting the rockfailure in a long term Thus DSCM is valid to remedy theimperfection that conventional creep test cannot reflect thedeformation field within rock in laboratory which extendsthe function of conventional rock creep test indeed Howeverin macrorock engineering how to adopt such techniquesas DSCM to monitor local creep damage evolution withinrock is a challenge work It must be pointed out that such asituation as rock filled with water or rock chemical reactionwith other medium was not considered

As for the rationale of failure bands formation it can beexplained by Mohr-Coulomb criterion [21] as

120591 = 120590119899tan120593 + 119862 (6)

where 120591 and 120590119899are the shear stress and normal at failure

plane which can be easily obtained under a compressive loadcondition 119862 is cohesion and 120593 is angle of internal frictionThe Mohr envelope represents the true shape of the failurecurve (Figure 9) Mohrrsquos stress circle can be determined bymaximum and minimum principal stresses 120590

1and 120590

3 For

the case of uniaxial compressive test 1205903= 0

One easily finds from this theory that the failure planeforms the angle (45∘ + 1205932) to the plane against which themajor principal stress operates and this does not agree withthe axial splitting Let us start by examining the simpleapproach that the strength of rock can be expressed in terms

6 Advances in Materials Science and Engineering

Coulombrsquos relation

119862

120593

12059012

1205901 2

1205901 120590

120591

119862tan 120593

120591 = 120590119899tan 120593 + 119862

Figure 9 Stress failure at Coulomb-Mohr criterion

0 5 10 15 20 250

5

10

15

20

25

30Pushing force

Displacement

0

02

04

06

08

1

12

14

16

Time (h)

Disp

lace

men

t (m

m)

Failured3

d2d1

c1

b1

a2a1

c2

b2Push

ing

forc

e (kN

)

Figure 10 Pushing force-displacement-time curve

of a cohesion term and a friction term from amesomechani-cal point of view Assume that the former represents the crys-tal matrix of the smallest rock units and the latter to mirrorthe influence of discrete discontinuities of different extensionMobilization of the two strength components requires verydifferent amounts of strain Naturally if continuous planeweaknesses extend across a rock volume separating blocksshearing by relative movement of the blocks may take placewithout bringing the rockmaterial in the blocks into a criticalstate This case leads to shear failure Not surprisingly rockis a kind of inhomogeneous material and many fissures arecontained in it randomly This causes cohesion decreasingand shear failure happening easily at last Coulomb-Mohrcriterion is satisfied

32 Creep Test on Pushing Steel-Plate Anchored in Rock In thecreep pushing test five stages of pushing load 10 15 20 25and 30 kNwere applied and the corresponding displacementduring each stage was named after a1-a2 b1-b2 c1-c2 and d1-d2-d3 (Figure 10) Before pushing force was less than 20 kNcreep deformation was little and the composite specimenwas in an elastic deformation state When pushing forcearrived at 20 kN creep displacement occurred and increasedas the pushing force level was enhanced When pushingforce arrived at 25 kN crack began to occur and creepdisplacement increased rapidly After pushing force arrived at

Failure band

Failure band

Steel-plate

Figure 11 Creep failure pattern of pushing steel-plate anchored inrock

275 kN the steel-plate was pushed out quickly accompanyingstrong creep deformation and two win-shape macrocracksformed (Figure 11) at last

At the same time we obtained the horizontal displace-ment field and shear strain field by DSCM Five stagesof pushing force 10 15 20 25 and 275 kN were adoptedto analyse the evolution of creep deformation field Beforepushing force arrived at 15 KN the creep deformationwas lessinmagnitude and distributed inhomogenously and randomlyand concentrated locally because of the heterogeneity of rockin mesoscale (Figures 12-13) When pushing force arrivedat 20 kN the displacement field tended to be ordering andshear strain concentrated discontinuously along the interfacebetween steel-plate and rock (Figure 14)While pushing forcearrived at 25 kN the horizontal displacement and shear strainconcentrated continuously along the interface between steel-plate and rock and a new narrow shear strain band formed inthe upper layer (Figure 15) which indicated the first narrowshear band occurred Unfortunately when pushing forcearrived at 275 kN the another new narrow shear strain bandformed in the lower layer was not recorded because of thesudden failure of switch to illuminators The duration fromstrong creep deformation to shear band formed till to steel-plated was pushed out is short which is consistent with thatobtained by conventional creep test

In order to verify the correctness of two win-shapefailure bands formed (Figure 11) numerical simulations wereperformed by using Particle Flow Code (PFC2d) [22] Theresults showed that the formation of shear bandwent throughthe process crack initiation from original defect rarr clustergeneration rarr cluster increasing rarr cluster interfusion rarrcore or continuous zone At last the two win-shape failurebands formed (Figure 16) which is similar with laboratorytest result

The test process of pushing steel-plate anchored in rockshowed that when pushing force was at a low level thedisplacement field was disordered and rock was in elasticdeformation As pushing force increased some damagesoriginated from some defects which caused the displacementor strain concentrating locally and several deformationclusters gathered although macrocreep deformation was notdistinct Similarly because the duration from strong creepdeformation to failure zone formed is short only through

Advances in Materials Science and Engineering 7

20 40 60 80 100

20

30

40

50

60

70

80

0018 002 0022 0024 0026 0028 003

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

60

50

70

80

0 05minus15 minus1 minus05 times10119890minus3

el-plate

Steel-plate

(b) Shear strain

Figure 12 DSCM results at pushing force 10 kN

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0045 005 0055 006 0065 007 0075

Steel-plate

(a) Horizontal displacement (mm)

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0 1minus3 minus2 minus1

Steel-plate

times10119890minus3

(b) Shear strain

Figure 13 DSCM results at pushing force 15 kN

observing the shortly strong creep deformation to forecast therock failure is too hasty

Fortunately DSCM can be easily used to monitor all theevolution progress of creep deformation field which providesa wealth of information for forecasting rock failure indeedThus such techniques as DSCM may bring about some newmonitoring approaches in anchored rock engineering

4 Conclusions

Theaimof the approach of RLJW-2000 servo test synchroniz-ing with DSCM was adopted to investigate the rock failurepattern and creep deformation By comparing with the pastinvestigation this research contains at least three originalaspects

(1) The RLJW-2000 servo test synchronizing with DSCMon creep failure of uniaxial compression and ofpushing steel-plate contained in rock was performedfirstly

(2) The deformation field evolution from creep damageaccumulation to macrofailure under the uniaxialcreep compression load condition was obtained

(3) Thedisplacement field evolution in rock and rock fail-ure pattern during creep pushing steel-plate anchoredin rock were obtained

The investigations showed the following

(1) For a uniaxial compressive specimen when loadarrives at 05120590

119888 ordered displacement clusters form

which is ahead of the macrocreep strain occurringin a slight jump mode when load arrives at 07120590

119888

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

4 Advances in Materials Science and Engineering

60 70 80

10

20

30

40

50

60

70

80

0

001

minus004

minus003

minus002

minus001

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

1

2

3

4

5

6

7

8times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70

80

minus0095

minus009

minus0085

minus008

minus0075

minus007

(c) Shear strain

Figure 6 Deformation field under the load level of 1265Mpa 02120590119888

60 70 80

10

20

30

40

50

60

70

0

2

4

minus4

minus2

times10minus3

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70

minus003

minus0028

minus0026

minus0024

minus0022

minus002

minus0018

minus0016

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 2

4

6

8

10

12times10minus4

(c) Shear strain

Figure 7 Deformation field under the load level of 37965Mpa 05120590119888

the rate of 5minframe At last the failure pattern as wellas displacement field evolution of a steel-plate anchored rockspecimen was obtained

3 Results and Discussion

31 Uniaxial Creep Compressive Test Results Threemudstonerock specimenswere sampled from theKouzidongMine situ-ated at Huainan city Anhui province China By conventional

uniaxial compressive test we obtained their average uniaxialcompressive strength 120590

119888 being 6326Mpa Other new three

specimens were used to do the uniaxial creep compressivetest The loading stages were 02120590

119888 03120590119888 04120590119888 06120590119888 07120590119888

and 08120590119888 correspondingly The total creep test time went

through 481 hoursThe typical curve of axial strain-time wasshown in Figure 4 It was found that when the compressiveload was lower than 06120590

119888 the creep strain was less when

the load level arrived at 07120590119888 the creep strain began to

Advances in Materials Science and Engineering 5

60 70 80

10

20

30

40

50

60

70

0

0005

001

0015

minus002

minus0015

minus001

minus0005

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70minus15

minus10

minus5

0

5

times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 1

2

3

4

5

6

7

times10minus3

(c) Shear strain

Figure 8 Deformation field under the load level of 5694Mpa 08120590119888

increase slightly in a jump mode when the load level arrivedat 08120590

119888 the creep strain increased rapidly After 01 hour

the specimen abruptly fractured in a shear mode (Figure 5)Thus mudstone rock was in the elastic deformation at thelow loading level When the load reached its limit valuestrong creep deformation happened and leaded to the rockfracturing rapidlyThe creep deformation durationwas short

At the same time we obtained the horizontal and verticaldisplacement fields and shear strain field We selected thethree states while load arriving at 02120590

119888 05120590

119888and 08120590

119888to

analyse the creep deformation distribution When load wasat the lower level 02120590

119888 the deformation in the specimen

was less in magnitude and distributed inhomogeneously andrandomly and deformation concentrated locally due to theheterogeneity of rock in mesoscale (Figure 6) When loadlevel arrived at 05120590

119888 the deformation field became ordering

(Figure 7) compared with the lower load level 02120590119888 At

this load level two horizontal displacement clusters formedin the left-up and right-down regions separately The shearstrain cluster gathered more and more prominently Thisphenomenon can not be indicated by creep strain-time curveWhen load level arrived at 08120590

119888 as the displacement clusters

became more ordering a narrow deformation concentratingband formed (Figure 8) which led to the specimen fracturedafter 01 hour Both displacement field and shear strain fieldwere in keeping with the creep strain-time curve (Figure 4)

Just as mentioned earlier rock is a kind of naturalheterogeneous material in mesoscale A lot of detects ordisordered mini-fissures existed in it due to the long timegeological movement For a rock sample when compressiveload is in a low level the fissures are easy to close andthe displacement field within rock is disordered so rockis dominated by elastic deformation in macro-scale at thisstage As the load level increases gradually some damages

originating from defects or fissures occur which cause thedisplacement or strain field concentrating locally severaldeformation clusters gather But themacrocreep deformationis still not distinct in displacement-time curve This is theperiod of creep damage accumulation before rock beginsmacrofailure In this period the creep deformation fieldevolves to gather some ordered clusters This behaviour maybe considered as a useful indication for forecasting the rockfailure in a long term Thus DSCM is valid to remedy theimperfection that conventional creep test cannot reflect thedeformation field within rock in laboratory which extendsthe function of conventional rock creep test indeed Howeverin macrorock engineering how to adopt such techniquesas DSCM to monitor local creep damage evolution withinrock is a challenge work It must be pointed out that such asituation as rock filled with water or rock chemical reactionwith other medium was not considered

As for the rationale of failure bands formation it can beexplained by Mohr-Coulomb criterion [21] as

120591 = 120590119899tan120593 + 119862 (6)

where 120591 and 120590119899are the shear stress and normal at failure

plane which can be easily obtained under a compressive loadcondition 119862 is cohesion and 120593 is angle of internal frictionThe Mohr envelope represents the true shape of the failurecurve (Figure 9) Mohrrsquos stress circle can be determined bymaximum and minimum principal stresses 120590

1and 120590

3 For

the case of uniaxial compressive test 1205903= 0

One easily finds from this theory that the failure planeforms the angle (45∘ + 1205932) to the plane against which themajor principal stress operates and this does not agree withthe axial splitting Let us start by examining the simpleapproach that the strength of rock can be expressed in terms

6 Advances in Materials Science and Engineering

Coulombrsquos relation

119862

120593

12059012

1205901 2

1205901 120590

120591

119862tan 120593

120591 = 120590119899tan 120593 + 119862

Figure 9 Stress failure at Coulomb-Mohr criterion

0 5 10 15 20 250

5

10

15

20

25

30Pushing force

Displacement

0

02

04

06

08

1

12

14

16

Time (h)

Disp

lace

men

t (m

m)

Failured3

d2d1

c1

b1

a2a1

c2

b2Push

ing

forc

e (kN

)

Figure 10 Pushing force-displacement-time curve

of a cohesion term and a friction term from amesomechani-cal point of view Assume that the former represents the crys-tal matrix of the smallest rock units and the latter to mirrorthe influence of discrete discontinuities of different extensionMobilization of the two strength components requires verydifferent amounts of strain Naturally if continuous planeweaknesses extend across a rock volume separating blocksshearing by relative movement of the blocks may take placewithout bringing the rockmaterial in the blocks into a criticalstate This case leads to shear failure Not surprisingly rockis a kind of inhomogeneous material and many fissures arecontained in it randomly This causes cohesion decreasingand shear failure happening easily at last Coulomb-Mohrcriterion is satisfied

32 Creep Test on Pushing Steel-Plate Anchored in Rock In thecreep pushing test five stages of pushing load 10 15 20 25and 30 kNwere applied and the corresponding displacementduring each stage was named after a1-a2 b1-b2 c1-c2 and d1-d2-d3 (Figure 10) Before pushing force was less than 20 kNcreep deformation was little and the composite specimenwas in an elastic deformation state When pushing forcearrived at 20 kN creep displacement occurred and increasedas the pushing force level was enhanced When pushingforce arrived at 25 kN crack began to occur and creepdisplacement increased rapidly After pushing force arrived at

Failure band

Failure band

Steel-plate

Figure 11 Creep failure pattern of pushing steel-plate anchored inrock

275 kN the steel-plate was pushed out quickly accompanyingstrong creep deformation and two win-shape macrocracksformed (Figure 11) at last

At the same time we obtained the horizontal displace-ment field and shear strain field by DSCM Five stagesof pushing force 10 15 20 25 and 275 kN were adoptedto analyse the evolution of creep deformation field Beforepushing force arrived at 15 KN the creep deformationwas lessinmagnitude and distributed inhomogenously and randomlyand concentrated locally because of the heterogeneity of rockin mesoscale (Figures 12-13) When pushing force arrivedat 20 kN the displacement field tended to be ordering andshear strain concentrated discontinuously along the interfacebetween steel-plate and rock (Figure 14)While pushing forcearrived at 25 kN the horizontal displacement and shear strainconcentrated continuously along the interface between steel-plate and rock and a new narrow shear strain band formed inthe upper layer (Figure 15) which indicated the first narrowshear band occurred Unfortunately when pushing forcearrived at 275 kN the another new narrow shear strain bandformed in the lower layer was not recorded because of thesudden failure of switch to illuminators The duration fromstrong creep deformation to shear band formed till to steel-plated was pushed out is short which is consistent with thatobtained by conventional creep test

In order to verify the correctness of two win-shapefailure bands formed (Figure 11) numerical simulations wereperformed by using Particle Flow Code (PFC2d) [22] Theresults showed that the formation of shear bandwent throughthe process crack initiation from original defect rarr clustergeneration rarr cluster increasing rarr cluster interfusion rarrcore or continuous zone At last the two win-shape failurebands formed (Figure 16) which is similar with laboratorytest result

The test process of pushing steel-plate anchored in rockshowed that when pushing force was at a low level thedisplacement field was disordered and rock was in elasticdeformation As pushing force increased some damagesoriginated from some defects which caused the displacementor strain concentrating locally and several deformationclusters gathered although macrocreep deformation was notdistinct Similarly because the duration from strong creepdeformation to failure zone formed is short only through

Advances in Materials Science and Engineering 7

20 40 60 80 100

20

30

40

50

60

70

80

0018 002 0022 0024 0026 0028 003

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

60

50

70

80

0 05minus15 minus1 minus05 times10119890minus3

el-plate

Steel-plate

(b) Shear strain

Figure 12 DSCM results at pushing force 10 kN

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0045 005 0055 006 0065 007 0075

Steel-plate

(a) Horizontal displacement (mm)

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0 1minus3 minus2 minus1

Steel-plate

times10119890minus3

(b) Shear strain

Figure 13 DSCM results at pushing force 15 kN

observing the shortly strong creep deformation to forecast therock failure is too hasty

Fortunately DSCM can be easily used to monitor all theevolution progress of creep deformation field which providesa wealth of information for forecasting rock failure indeedThus such techniques as DSCM may bring about some newmonitoring approaches in anchored rock engineering

4 Conclusions

Theaimof the approach of RLJW-2000 servo test synchroniz-ing with DSCM was adopted to investigate the rock failurepattern and creep deformation By comparing with the pastinvestigation this research contains at least three originalaspects

(1) The RLJW-2000 servo test synchronizing with DSCMon creep failure of uniaxial compression and ofpushing steel-plate contained in rock was performedfirstly

(2) The deformation field evolution from creep damageaccumulation to macrofailure under the uniaxialcreep compression load condition was obtained

(3) Thedisplacement field evolution in rock and rock fail-ure pattern during creep pushing steel-plate anchoredin rock were obtained

The investigations showed the following

(1) For a uniaxial compressive specimen when loadarrives at 05120590

119888 ordered displacement clusters form

which is ahead of the macrocreep strain occurringin a slight jump mode when load arrives at 07120590

119888

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 5

60 70 80

10

20

30

40

50

60

70

0

0005

001

0015

minus002

minus0015

minus001

minus0005

(a) Horizontal displacement (mm)

60 70 80

10

20

30

40

50

60

70minus15

minus10

minus5

0

5

times10minus3

(b) Vertical displacement (mm)

60 70 80

10

20

30

40

50

60

70 1

2

3

4

5

6

7

times10minus3

(c) Shear strain

Figure 8 Deformation field under the load level of 5694Mpa 08120590119888

increase slightly in a jump mode when the load level arrivedat 08120590

119888 the creep strain increased rapidly After 01 hour

the specimen abruptly fractured in a shear mode (Figure 5)Thus mudstone rock was in the elastic deformation at thelow loading level When the load reached its limit valuestrong creep deformation happened and leaded to the rockfracturing rapidlyThe creep deformation durationwas short

At the same time we obtained the horizontal and verticaldisplacement fields and shear strain field We selected thethree states while load arriving at 02120590

119888 05120590

119888and 08120590

119888to

analyse the creep deformation distribution When load wasat the lower level 02120590

119888 the deformation in the specimen

was less in magnitude and distributed inhomogeneously andrandomly and deformation concentrated locally due to theheterogeneity of rock in mesoscale (Figure 6) When loadlevel arrived at 05120590

119888 the deformation field became ordering

(Figure 7) compared with the lower load level 02120590119888 At

this load level two horizontal displacement clusters formedin the left-up and right-down regions separately The shearstrain cluster gathered more and more prominently Thisphenomenon can not be indicated by creep strain-time curveWhen load level arrived at 08120590

119888 as the displacement clusters

became more ordering a narrow deformation concentratingband formed (Figure 8) which led to the specimen fracturedafter 01 hour Both displacement field and shear strain fieldwere in keeping with the creep strain-time curve (Figure 4)

Just as mentioned earlier rock is a kind of naturalheterogeneous material in mesoscale A lot of detects ordisordered mini-fissures existed in it due to the long timegeological movement For a rock sample when compressiveload is in a low level the fissures are easy to close andthe displacement field within rock is disordered so rockis dominated by elastic deformation in macro-scale at thisstage As the load level increases gradually some damages

originating from defects or fissures occur which cause thedisplacement or strain field concentrating locally severaldeformation clusters gather But themacrocreep deformationis still not distinct in displacement-time curve This is theperiod of creep damage accumulation before rock beginsmacrofailure In this period the creep deformation fieldevolves to gather some ordered clusters This behaviour maybe considered as a useful indication for forecasting the rockfailure in a long term Thus DSCM is valid to remedy theimperfection that conventional creep test cannot reflect thedeformation field within rock in laboratory which extendsthe function of conventional rock creep test indeed Howeverin macrorock engineering how to adopt such techniquesas DSCM to monitor local creep damage evolution withinrock is a challenge work It must be pointed out that such asituation as rock filled with water or rock chemical reactionwith other medium was not considered

As for the rationale of failure bands formation it can beexplained by Mohr-Coulomb criterion [21] as

120591 = 120590119899tan120593 + 119862 (6)

where 120591 and 120590119899are the shear stress and normal at failure

plane which can be easily obtained under a compressive loadcondition 119862 is cohesion and 120593 is angle of internal frictionThe Mohr envelope represents the true shape of the failurecurve (Figure 9) Mohrrsquos stress circle can be determined bymaximum and minimum principal stresses 120590

1and 120590

3 For

the case of uniaxial compressive test 1205903= 0

One easily finds from this theory that the failure planeforms the angle (45∘ + 1205932) to the plane against which themajor principal stress operates and this does not agree withthe axial splitting Let us start by examining the simpleapproach that the strength of rock can be expressed in terms

6 Advances in Materials Science and Engineering

Coulombrsquos relation

119862

120593

12059012

1205901 2

1205901 120590

120591

119862tan 120593

120591 = 120590119899tan 120593 + 119862

Figure 9 Stress failure at Coulomb-Mohr criterion

0 5 10 15 20 250

5

10

15

20

25

30Pushing force

Displacement

0

02

04

06

08

1

12

14

16

Time (h)

Disp

lace

men

t (m

m)

Failured3

d2d1

c1

b1

a2a1

c2

b2Push

ing

forc

e (kN

)

Figure 10 Pushing force-displacement-time curve

of a cohesion term and a friction term from amesomechani-cal point of view Assume that the former represents the crys-tal matrix of the smallest rock units and the latter to mirrorthe influence of discrete discontinuities of different extensionMobilization of the two strength components requires verydifferent amounts of strain Naturally if continuous planeweaknesses extend across a rock volume separating blocksshearing by relative movement of the blocks may take placewithout bringing the rockmaterial in the blocks into a criticalstate This case leads to shear failure Not surprisingly rockis a kind of inhomogeneous material and many fissures arecontained in it randomly This causes cohesion decreasingand shear failure happening easily at last Coulomb-Mohrcriterion is satisfied

32 Creep Test on Pushing Steel-Plate Anchored in Rock In thecreep pushing test five stages of pushing load 10 15 20 25and 30 kNwere applied and the corresponding displacementduring each stage was named after a1-a2 b1-b2 c1-c2 and d1-d2-d3 (Figure 10) Before pushing force was less than 20 kNcreep deformation was little and the composite specimenwas in an elastic deformation state When pushing forcearrived at 20 kN creep displacement occurred and increasedas the pushing force level was enhanced When pushingforce arrived at 25 kN crack began to occur and creepdisplacement increased rapidly After pushing force arrived at

Failure band

Failure band

Steel-plate

Figure 11 Creep failure pattern of pushing steel-plate anchored inrock

275 kN the steel-plate was pushed out quickly accompanyingstrong creep deformation and two win-shape macrocracksformed (Figure 11) at last

At the same time we obtained the horizontal displace-ment field and shear strain field by DSCM Five stagesof pushing force 10 15 20 25 and 275 kN were adoptedto analyse the evolution of creep deformation field Beforepushing force arrived at 15 KN the creep deformationwas lessinmagnitude and distributed inhomogenously and randomlyand concentrated locally because of the heterogeneity of rockin mesoscale (Figures 12-13) When pushing force arrivedat 20 kN the displacement field tended to be ordering andshear strain concentrated discontinuously along the interfacebetween steel-plate and rock (Figure 14)While pushing forcearrived at 25 kN the horizontal displacement and shear strainconcentrated continuously along the interface between steel-plate and rock and a new narrow shear strain band formed inthe upper layer (Figure 15) which indicated the first narrowshear band occurred Unfortunately when pushing forcearrived at 275 kN the another new narrow shear strain bandformed in the lower layer was not recorded because of thesudden failure of switch to illuminators The duration fromstrong creep deformation to shear band formed till to steel-plated was pushed out is short which is consistent with thatobtained by conventional creep test

In order to verify the correctness of two win-shapefailure bands formed (Figure 11) numerical simulations wereperformed by using Particle Flow Code (PFC2d) [22] Theresults showed that the formation of shear bandwent throughthe process crack initiation from original defect rarr clustergeneration rarr cluster increasing rarr cluster interfusion rarrcore or continuous zone At last the two win-shape failurebands formed (Figure 16) which is similar with laboratorytest result

The test process of pushing steel-plate anchored in rockshowed that when pushing force was at a low level thedisplacement field was disordered and rock was in elasticdeformation As pushing force increased some damagesoriginated from some defects which caused the displacementor strain concentrating locally and several deformationclusters gathered although macrocreep deformation was notdistinct Similarly because the duration from strong creepdeformation to failure zone formed is short only through

Advances in Materials Science and Engineering 7

20 40 60 80 100

20

30

40

50

60

70

80

0018 002 0022 0024 0026 0028 003

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

60

50

70

80

0 05minus15 minus1 minus05 times10119890minus3

el-plate

Steel-plate

(b) Shear strain

Figure 12 DSCM results at pushing force 10 kN

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0045 005 0055 006 0065 007 0075

Steel-plate

(a) Horizontal displacement (mm)

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0 1minus3 minus2 minus1

Steel-plate

times10119890minus3

(b) Shear strain

Figure 13 DSCM results at pushing force 15 kN

observing the shortly strong creep deformation to forecast therock failure is too hasty

Fortunately DSCM can be easily used to monitor all theevolution progress of creep deformation field which providesa wealth of information for forecasting rock failure indeedThus such techniques as DSCM may bring about some newmonitoring approaches in anchored rock engineering

4 Conclusions

Theaimof the approach of RLJW-2000 servo test synchroniz-ing with DSCM was adopted to investigate the rock failurepattern and creep deformation By comparing with the pastinvestigation this research contains at least three originalaspects

(1) The RLJW-2000 servo test synchronizing with DSCMon creep failure of uniaxial compression and ofpushing steel-plate contained in rock was performedfirstly

(2) The deformation field evolution from creep damageaccumulation to macrofailure under the uniaxialcreep compression load condition was obtained

(3) Thedisplacement field evolution in rock and rock fail-ure pattern during creep pushing steel-plate anchoredin rock were obtained

The investigations showed the following

(1) For a uniaxial compressive specimen when loadarrives at 05120590

119888 ordered displacement clusters form

which is ahead of the macrocreep strain occurringin a slight jump mode when load arrives at 07120590

119888

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

6 Advances in Materials Science and Engineering

Coulombrsquos relation

119862

120593

12059012

1205901 2

1205901 120590

120591

119862tan 120593

120591 = 120590119899tan 120593 + 119862

Figure 9 Stress failure at Coulomb-Mohr criterion

0 5 10 15 20 250

5

10

15

20

25

30Pushing force

Displacement

0

02

04

06

08

1

12

14

16

Time (h)

Disp

lace

men

t (m

m)

Failured3

d2d1

c1

b1

a2a1

c2

b2Push

ing

forc

e (kN

)

Figure 10 Pushing force-displacement-time curve

of a cohesion term and a friction term from amesomechani-cal point of view Assume that the former represents the crys-tal matrix of the smallest rock units and the latter to mirrorthe influence of discrete discontinuities of different extensionMobilization of the two strength components requires verydifferent amounts of strain Naturally if continuous planeweaknesses extend across a rock volume separating blocksshearing by relative movement of the blocks may take placewithout bringing the rockmaterial in the blocks into a criticalstate This case leads to shear failure Not surprisingly rockis a kind of inhomogeneous material and many fissures arecontained in it randomly This causes cohesion decreasingand shear failure happening easily at last Coulomb-Mohrcriterion is satisfied

32 Creep Test on Pushing Steel-Plate Anchored in Rock In thecreep pushing test five stages of pushing load 10 15 20 25and 30 kNwere applied and the corresponding displacementduring each stage was named after a1-a2 b1-b2 c1-c2 and d1-d2-d3 (Figure 10) Before pushing force was less than 20 kNcreep deformation was little and the composite specimenwas in an elastic deformation state When pushing forcearrived at 20 kN creep displacement occurred and increasedas the pushing force level was enhanced When pushingforce arrived at 25 kN crack began to occur and creepdisplacement increased rapidly After pushing force arrived at

Failure band

Failure band

Steel-plate

Figure 11 Creep failure pattern of pushing steel-plate anchored inrock

275 kN the steel-plate was pushed out quickly accompanyingstrong creep deformation and two win-shape macrocracksformed (Figure 11) at last

At the same time we obtained the horizontal displace-ment field and shear strain field by DSCM Five stagesof pushing force 10 15 20 25 and 275 kN were adoptedto analyse the evolution of creep deformation field Beforepushing force arrived at 15 KN the creep deformationwas lessinmagnitude and distributed inhomogenously and randomlyand concentrated locally because of the heterogeneity of rockin mesoscale (Figures 12-13) When pushing force arrivedat 20 kN the displacement field tended to be ordering andshear strain concentrated discontinuously along the interfacebetween steel-plate and rock (Figure 14)While pushing forcearrived at 25 kN the horizontal displacement and shear strainconcentrated continuously along the interface between steel-plate and rock and a new narrow shear strain band formed inthe upper layer (Figure 15) which indicated the first narrowshear band occurred Unfortunately when pushing forcearrived at 275 kN the another new narrow shear strain bandformed in the lower layer was not recorded because of thesudden failure of switch to illuminators The duration fromstrong creep deformation to shear band formed till to steel-plated was pushed out is short which is consistent with thatobtained by conventional creep test

In order to verify the correctness of two win-shapefailure bands formed (Figure 11) numerical simulations wereperformed by using Particle Flow Code (PFC2d) [22] Theresults showed that the formation of shear bandwent throughthe process crack initiation from original defect rarr clustergeneration rarr cluster increasing rarr cluster interfusion rarrcore or continuous zone At last the two win-shape failurebands formed (Figure 16) which is similar with laboratorytest result

The test process of pushing steel-plate anchored in rockshowed that when pushing force was at a low level thedisplacement field was disordered and rock was in elasticdeformation As pushing force increased some damagesoriginated from some defects which caused the displacementor strain concentrating locally and several deformationclusters gathered although macrocreep deformation was notdistinct Similarly because the duration from strong creepdeformation to failure zone formed is short only through

Advances in Materials Science and Engineering 7

20 40 60 80 100

20

30

40

50

60

70

80

0018 002 0022 0024 0026 0028 003

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

60

50

70

80

0 05minus15 minus1 minus05 times10119890minus3

el-plate

Steel-plate

(b) Shear strain

Figure 12 DSCM results at pushing force 10 kN

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0045 005 0055 006 0065 007 0075

Steel-plate

(a) Horizontal displacement (mm)

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0 1minus3 minus2 minus1

Steel-plate

times10119890minus3

(b) Shear strain

Figure 13 DSCM results at pushing force 15 kN

observing the shortly strong creep deformation to forecast therock failure is too hasty

Fortunately DSCM can be easily used to monitor all theevolution progress of creep deformation field which providesa wealth of information for forecasting rock failure indeedThus such techniques as DSCM may bring about some newmonitoring approaches in anchored rock engineering

4 Conclusions

Theaimof the approach of RLJW-2000 servo test synchroniz-ing with DSCM was adopted to investigate the rock failurepattern and creep deformation By comparing with the pastinvestigation this research contains at least three originalaspects

(1) The RLJW-2000 servo test synchronizing with DSCMon creep failure of uniaxial compression and ofpushing steel-plate contained in rock was performedfirstly

(2) The deformation field evolution from creep damageaccumulation to macrofailure under the uniaxialcreep compression load condition was obtained

(3) Thedisplacement field evolution in rock and rock fail-ure pattern during creep pushing steel-plate anchoredin rock were obtained

The investigations showed the following

(1) For a uniaxial compressive specimen when loadarrives at 05120590

119888 ordered displacement clusters form

which is ahead of the macrocreep strain occurringin a slight jump mode when load arrives at 07120590

119888

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 7

20 40 60 80 100

20

30

40

50

60

70

80

0018 002 0022 0024 0026 0028 003

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

60

50

70

80

0 05minus15 minus1 minus05 times10119890minus3

el-plate

Steel-plate

(b) Shear strain

Figure 12 DSCM results at pushing force 10 kN

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0045 005 0055 006 0065 007 0075

Steel-plate

(a) Horizontal displacement (mm)

30 40 50 60 70 80 90 100 110

20

30

40

50

60

70

80

0 1minus3 minus2 minus1

Steel-plate

times10119890minus3

(b) Shear strain

Figure 13 DSCM results at pushing force 15 kN

observing the shortly strong creep deformation to forecast therock failure is too hasty

Fortunately DSCM can be easily used to monitor all theevolution progress of creep deformation field which providesa wealth of information for forecasting rock failure indeedThus such techniques as DSCM may bring about some newmonitoring approaches in anchored rock engineering

4 Conclusions

Theaimof the approach of RLJW-2000 servo test synchroniz-ing with DSCM was adopted to investigate the rock failurepattern and creep deformation By comparing with the pastinvestigation this research contains at least three originalaspects

(1) The RLJW-2000 servo test synchronizing with DSCMon creep failure of uniaxial compression and ofpushing steel-plate contained in rock was performedfirstly

(2) The deformation field evolution from creep damageaccumulation to macrofailure under the uniaxialcreep compression load condition was obtained

(3) Thedisplacement field evolution in rock and rock fail-ure pattern during creep pushing steel-plate anchoredin rock were obtained

The investigations showed the following

(1) For a uniaxial compressive specimen when loadarrives at 05120590

119888 ordered displacement clusters form

which is ahead of the macrocreep strain occurringin a slight jump mode when load arrives at 07120590

119888

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

8 Advances in Materials Science and Engineering

20 40 60 80 100

20

30

40

50

60

70

80

006 0065 007 0075 008 0085 009 0095

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 14 DSCM results at pushing force 20 kN

20 40 60 80 100

20

30

40

50

60

70

80

004 006 008 01 012

Steel-plate

(a) Horizontal displacement (mm)

20 40 60 80 100

20

30

40

50

60

70

80

0 1minus3minus4 minus2 minus1 times10119890minus3

Steel-plate

(b) Shear strain

Figure 15 DSCM results at pushing force 25 kN

Crack

Crack

Pushingforce

Steel-plate

(a) Before being pushed out

Crack band

Crack band

Pushingforce

Steel-plate

(b) After being pushed out

Figure 16 Simulations on failure pattern of steel-plate being pushed out

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 9

When the load level arrives at its threshold 08120590119888 the

creep strain increased rapidly and the displacementclusters shape a narrow band After that the specimenabruptly fractures in a shear mode

(2) In the creep pushing steel-plate test before pushingforce arrives at 20 kN the creep deformation is littleand the composite specimen is in an elastic defor-mation state When pushing force arrives at 25 kNcrack begins to occur creep displacement increasesrapidly the horizontal displacement field as well asshear strain field not only concentrates continuouslyalong the interface between steel-plate and rock butalso a new narrow band concentrates in the upperlayer When pushing force arrives at 275 kN anothernew narrow shear deformation band forms in thelower layer After that the steel-plate is pushed outquickly accompanying strong creep deformation

(3) The deformation field cluster is ahead of the macro-creep deformation and so the variation of deforma-tion field can be used to predicate the macrocreepdeformation occurring of rock

(4) Theduration from strong creep deformation to failureof rock is short Such a technique as DSCM maymake some new contributions on how tomonitor andforecast rock failure in engineering

Acknowledgments

This work was supported in part the National Basic ResearchProgram of China (973 Program) Grant no 2010CB226805China Natural Science Fund (nos 51074099 51274133 and51174129) Doctoral Scientific Fund Project of the Ministry ofEducation of China (no 20123718110013) Shandong ProvinceNatural Science Fund (no ZR2012EEZ002) and SDUSTResearch Fund (no 2010KYTD105)

References

[1] M S Paterson ldquoExperimental deformation and faulting inWombeyan marblerdquo Geological Society of America Bulletin vol69 pp 465ndash467 1958

[2] K Mogi ldquoDeformation and fracture of rocks under confiningpressure elasticity and plasticity of some rocksrdquo Bulletin of theEarthquake Research Institute vol 43 pp 349ndash379 1965

[3] K Mogi ldquoPressure dependence of rock strength and transitionfrom brittle fracture to ductile flowrdquo Bulletin of the EarthquakeResearch Institute vol 44 pp 215ndash232 1966

[4] H C Heard ldquoTransition from brittle fracture to ductile flow inSolenhofen limestone as a function of temperature confiningpressure and interstitial fluid pressurerdquo Geological Society ofAmerica Bulletin vol 79 pp 193ndash226 1960

[5] J A Hudson Comprehensive Rock Engineering PergamonPress Oxford UK 1993

[6] D F Malan ldquoManuel Rocha medal recipient simulating thetime-dependent behaviour of excavations in hard rockrdquo RockMechanics and Rock Engineering vol 35 no 4 pp 225ndash2542002

[7] D T Griggs ldquoCreep of rocksrdquo Journal of Geology vol 37 pp225ndash251 1939

[8] Y Li and C Xia ldquoTime-dependent tests on intact rocks inuniaxial compressionrdquo International Journal of Rock Mechanicsand Mining Sciences vol 37 no 3 pp 467ndash475 2000

[9] P Xu and X L Xia ldquoExperimental test on granite in ThreeGeorge Projectrdquo Chinese Journal of Geotechnical Engineeringvol 18 no 4 pp 63ndash67 1996

[10] X L Xia P Xu and X L Ding ldquoRheological characteristics ofrock and stability rheological analysis for high sloperdquo ChineseJournal of Rock Mechanics and Engineering vol 15 no 4 pp312ndash322 1996

[11] T B Zhao Y L Tan S S Liu and Y X Xiao ldquoAnalysisof rheological properties and control mechanism of anchoredrockrdquo Rock and Soil Mechanics vol 33 no 6 pp 1730ndash17342012

[12] XGe J Ren Y PuWMa andY Zhu ldquoReal-in-timeCT triaxialtesting study of meso-damage evolution law of coalrdquo ChineseJournal of Rock Mechanics and Engineering vol 18 no 5 pp497ndash502 1999

[13] X R Ge and J X Ren ldquoStudy on the real in time CT test of therock meso-damage propagation lawrdquo Science in China Series Evol 30 no 2 pp 104ndash111 2000

[14] J Ren and X Ge ldquoStudy of rock meso-damage evolution lawand its constitutivemodel under uniaxial compression loadingrdquoChinese Journal of Rock Mechanics and Engineering vol 20 no4 pp 425ndash431 2001

[15] W H Peters and W F Ranson ldquoDigital imaging techniques inexperimental stress analysisrdquo Optical Engineering vol 21 no 3pp 427ndash431 1982

[16] I Yamaguchi ldquoA laser-speckle strain gaugerdquo Journal of PhysicsE vol 14 no 11 article 012 pp 1270ndash1273 1981

[17] Y M Song S P Ma X B Wang and X Wang ldquoExperimentalinvestigation on failure of rock by digital speckle correlationmethodrdquo Chinese Journal of Rock Mechanics and Engineeringvol 30 no 1 pp 1701ndash1176 2011

[18] Y H Zhao and S P Ma ldquoDeformation field around thestress induced crack area in sandstone by the digital specklecorrelation methodrdquo Acta Geologica Sinica vol 83 no 3 pp661ndash672 2009

[19] M A Sutton S R Meneill and J Jang ldquoEffects of sub-Pixelimages to ration on digital correlation error estimationrdquoOpticalEngineering vol 27 no 10 pp 870ndash877 1988

[20] J Zhang G Jin S Ma and L Meng ldquoApplication of animproved subpixel registration algorithm on digital specklecorrelation measurementrdquoOptics and Laser Technology vol 35no 7 pp 533ndash542 2003

[21] J C Jaeger ldquoShear failure of anisotropic rocksrdquo GeologicalMagazine vol 97 pp 65ndash72 1960

[22] P A Cundall and O D L Strack ldquoDiscrete numerical modelfor granular assembliesrdquo Geotechnique vol 29 no 1 pp 47ndash651979

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials