Modelling rock fracturing and blast-induced rock mass failure via advanced

Modellingrockfracturingandblast-inducedrockmassfailureviaadvanceddiscretisationwithinthediscontinuousdeformationanalysisframework

YoujunNinga,b,JunYangb,XinmeiAna,GuoweiMaa,c,

a

SchoolofCivilandEnvironmentalEngineering,NanyangTechnologicalUniversity,Singapore639798,SingaporeStateKeyLaboratoryofExplosionScienceandTechnology,BeijingInstituteofTechnology,Beijing100081,Chinac

SchoolofCivilandResourceEngineering,UniversityofWesternAustralia,35StirlingHighway,CrawleyWA6009,Australia

b

articleinfoabstract

Rockmassfailureisaparticularlycomplexprocessthatinvolvestheopeningandslidingofexistingdis-continuitiesandthefracturingoftheintactrock.Thispaperadoptsanadvanceddiscretisationapproachtosimulaterockfailureproblemswithinthediscontinuousdeformationanalysis(DDA)framework.Theaccuracyofthisapproachincontinuumanalysisisveri ed rst.Then,theadvanceddiscretisationapproachforfracturingmodellingispresented,andthediscretisationstrategyisdiscussed.Samplerockstaticfailuresaresimulatedandtheresultsarecomparedwithexperimentalresults.Thereafter,withageneralisedde nitionofthearti cialjoints,thisapproachisfurtherextendedandappliedinthesimu-lationofblast-inducedrockmassfailuresinwhichtheinstantexplosiongaspressureobtainedbythedetonationpressureequationofstateisloadedonthemainblastchamberwallsandtheinducedsur-roundingconnectedfracturesurfaces.Inthesimulationinstanceofrockmasscastblasting,thewholeprocess,includingtheblastchamberexpansion,explosiongaspenetration,rockmassfailureandcast,andtheformationofthe nalblastingpile,iswhollyreproduced.

Ó2010ElsevierLtd.Allrightsreserved.

Articlehistory:

Received20May2010

Receivedinrevisedform21September2010

Accepted21September2010Availableonline16October2010Keywords:

AdvanceddiscretisationRockmassfailure

ExplosiongaspressureRockblasting

Discontinuousdeformationanalysis

1.Introduction

Unlikemostengineeringmaterials,rockmassisaninhomoge-neousandanisotropicgeologicalmaterialconsistingofbothcon-tinuousrockmediumanddiscontinuouscomponents,suchasjoints,faults,andbeddingplanes.Inrockmassfailureproblems,breaksoccurringinrelativelyintactrockmediumareknownascracksandfractures,andthoseoccurringalongdiscontinuousplanesareknownasdiscontinuityopeningsandslidings.Inarockmasscontainingasmallnumberofdiscontinuities,crackingandfracturingmayplayamajorroleinitsfailure[1,2],whileinarockmasswithalargeproportionofdiscontinuities,openingandslid-ingalongexistingdiscontinuitieswillbemoresigni cant.Mean-while,inrockfailuresassociatedwithrockslopes[3]andundergroundexcavations[4],breaksalwaysappearinlimitedplacesandisolatedrockblocksareproducedandbecomeunstable.However,insomeothercomplexrockfailureproblems,suchasrockblasting[5],agreatnumberofbreakswilloccur,andtherockmasswillbefracturedintopiecesandcastaway.

Correspondingauthorat:SchoolofCivilandResourceEngineering,UniversityofWesternAustralia,35StirlingHighway,CrawleyWA6009,Australia.Tel.:+61864883102;fax:+61864881018.

E-mailaddresses:yjning@ntu.edu.sg(Y.Ning),yangj@bit.edu.cn(J.Yang),xman@ntu.edu.sg(X.An),ma@civil.uwa.edu.au(G.Ma).

0266-352X/$-seefrontmatterÓ2010ElsevierLtd.Allrightsreserved.doi:10.1016/j.compgeo.2010.09.003

Tonumericallysimulateopeningandslidingalongdiscontinu-itiesinarockmass,discontinuousnumericalmethods,suchasthedistinctelementmethod(DEM)[6]anddiscontinuousdeforma-tionanalysis(DDA)[7],arealwaysused.Thesemethodswereoriginallyderivedfordiscontinuousmediumanalysisandareapplicableinmodellingthebehaviourofdiscontinuousblockysystems.Byassemblingdiscreteblockstogetherwithaspecialalgorithmtoidentifyandupdatethecontactsbetweentheblocks,thedetachmentbetweenblocks,blockrotations,andthelarge-scaledisplacementofindividualblockscanbeaccuratelypredicted.Tosimulatefracturinginintactrock,continuum-basednumer-icalmethodsaretheoreticallymoreapplicable.Inthesemethods,thestressdistributionandthedeformationofcontinuumcanbecalculatedaccurately.Then,byusingfracturemechanicsand/orotherfailurecriteria,theprocessfromcontinuumtodiscontinuumcanbesimulated;however,somedif cultiesmaylikelybeencountered.Inthepopularlyused niteelementmethod(FEM),becausetheelementedgesneedtocoincidewiththeexternalboundariesandinternaldiscontinuousplanesofthephysicalmodel,greateffortisrequiredforthemeshingandre-meshingprocess,whichmakestherealisationofthemodellingprocedureforcomplexfailureproblemscomplicatedandsometimeseveninfeasible.Alterna-tively,toovercometheunexpectedtediousmeshingandre-mesh-ingprocess,theconventionalFEMhasbeenmodi edusingthepartitionofunity.Theextended niteelementmethod(XFEM)