双孔岩石破碎过程的数值模拟(英文)

ORIGINALPAPERNumericalsimulationoftherockfragmentationprocessinducedbytwodrillbitssubjectedtostaticanddynamic(impact)loadingS.Y.Wang•S.W.Sloan•H.Y.Liu•C.A.TangReceived:22June2010/Accepted:19October2010/Publishedonline:4November2010Springer-Verlag2010AbstractRockfragmentationprocessesinducedbydoubledrillbitssubjectedtostaticanddynamicloadingareexaminedbyanumericalmethod.Micro-heterogeneitiesoftherockaretakenintoaccountinthisnumericalmodel.Forthestaticcase,thesimulatedresultsreproducetheprogressiveprocessofbrittlerockfragmentationduringindentation.Forthedynamiccase,numericalsimulationsrepresentradialcracks,incipientchips,pulverizedzones,andshellcracks.Comparingthestaticanddynamiccases,thedynamicloadingcanleadtorockfragmentationmoreefficiently.Inaddition,numericalresultsindicatethatthedynamicpressure(Pmax)playsanimportantroleinthefailureprocessofspecimenswithtwoindenters.Further-more,theheterogeneityoftherockcanalsoaffectthefailuremodesoftherockwhentwoindentersareused.Finally,thenumericalresultsdemonstratetheeffectofthespacingbetweentheindentersontherock.KeywordsRockfragmentationNumericalsimulationIndentationFractureprocess1IntroductionRockfragmentationwithadrillbitisaneffectivetech-niqueinminingengineering.Usually,thekineticenergyistransferredbymeansofastresswavethroughthedrillbit,untilitreachestheendincontactwiththemediumtoproducefailureandfracturesofrocks(Chiang2004).Manyexperimentaltestshavebeencarriedoutinthepastdecadestoinvestigatethemechanismofrockfragmentation(WagnerandSchumann1971;HustrulidandFairhurst1972;Lindqvist1982;Cooketal.1984;PangandGoldsmith1990;Lindqvistetal.1994;MishnaevskyJr1995;Kou1995).Theseexperimentshavebeenessentialforobserv-ingrockfragmentationphenomenaandthentoestablishmodelstostudyfailuremechanismsofrockduetomechanicaltools.Forexample,researchershaveperformedindentationtestsondifferentrockssubjectedtoindentersofvariousshapesandsizes,withtheforce-penetrationbehaviorbeingrecordedandtheformationofcratersandfracturesbeinginvestigated(Lindqvist1982;Cooketal.1984;PangandGoldsmith1990).Basedonexperimen-talresults,therearebasicallythreesystemsofcracksaccordingtotheirpositionsrelatedtotheindenter,i.e.,sidecracks,radialcracks,andmediancracks(Kou1995;PaulandGangal1969;Liuetal.2008).Fullydevelopedsidecracksoneachsideoftheindentedareacanconnectwiththoseinducedbyneighboringindenterstoformchips.Thisformstheso-calledconceptualmodelforfracturepatternsinducedbyindenters(Kou1995).Inaddition,PaulandGangal(1969)reportedthatatthepointofcontactwiththerocksurfaceabulbofveryhighhydrostaticpressureisS.Y.Wang(&)S.W.SloanCentreforGeotechnicalandMaterialsModelling,Civil,SurveyingandEnvironmentalEngineering,TheUniversityofNewcastle,Callaghan,NSW2308,Australiae-mail:[e-mail]-mail:[e-mail],UniversityofTasmania,Tasmania7001,Australiae-mail:[e-mail]aulicEngineering,DalianUniversityofTechnology,Dalian116024,People’sRepublicofChinae-mail:[e-mail]123RockMechRockEng(2011)44:317–332DOI10.1007/s00603-010-0123-4generatedbythehighbearingstresses.ThegeneralpictureoffracturesinrocksunderindentationissummarizedinFig.1.Manydetailscanbeaddedintothissimpledescription(Lindqvist1982;Kou1995;HoodandAlehossein2000;Detournayetal.2008).However,duetotheanisotropyandheterogeneityofrock,theprocessoffractureinitiation,propagation,andcoalescenceundermechanicalindentationisrarelyobserveddirectlyinstandardlaboratorytests.Moreover,itisalsodifficultforempiricalandpurelyanalyticalmodelstostudythecomplexproblemsofrockfragmentationwithadrillbitduetotheirsimplifiedassumptions.Forexample,thecavityexpansionmodelwasextendedbyJohnson(1985)forwedgeorconeindentationinaTrescamaterial.Alehosseinetal.(2000)usedthismodeltopredicttheindentationofrockbyblunttools.However,thismodelisusuallyassumedthatthematerialishomogeneous.Accordingly,theprocessoffracturepropagationandinteractionduetodrillbitactioninheterogeneousrockisdifficulttounderstandwiththismodel.Althoughfracturemechanicshasbeenusedtoderiveasimpleanalyticalformulatoevaluatethecuttingorpenetratingforces(Zhaoetal.1994),theheterogeneityoftherockisgenerallyneglectedinfracturemechanicsmodels.Numericaltechniquesbasedonthefiniteelementmethod(FEM)havebeendevelopedtosimulatetheimpactprobleminrockdrilling.Kumano(1980)proposedamodeltostudytherockresponseduetoimpactloadsandsimu-latedtheimpactofprojectilesongranularandporousrock.Inthismodel,itisassumedthatallthekineticenergyoftheprojectileisusedincrushingandplasticdeformation,withtheeffectofwavepropagationbeingneglected.WangandLehnhoff(1976)usedaFEMmodeltosimulatethechipformationduetopenetrationintotherock.Unfortunately,thedynamicinteractionbetweenthehammerandrockwasnotconsidered.Followingthisstudy,Hanetal.(2005)proposedanumericalmodeltosimulatemultipleimpacts,withthefailureoftherockbeingbasedonaMohr–Cou-lombmodelwithstrain-softeningbehavior.Intheirstudy,therockdampingeffectonthestresswavepropagationwasconsidered.Asrocksareheterogeneousmat