土木地质岩土工程专业毕业英文翻译原文和译文.docx
- 文档编号:24942981
- 上传时间:2023-06-03
- 格式:DOCX
- 页数:21
- 大小:759.25KB
土木地质岩土工程专业毕业英文翻译原文和译文.docx
《土木地质岩土工程专业毕业英文翻译原文和译文.docx》由会员分享,可在线阅读,更多相关《土木地质岩土工程专业毕业英文翻译原文和译文.docx(21页珍藏版)》请在冰豆网上搜索。
土木地质岩土工程专业毕业英文翻译原文和译文
FailurePropertiesofFracturedRockMassesasAnisotropic
HomogenizedMedia
Introduction
Itiscommonlyacknowledgedthatrockmassesalwaysdisplaydiscontinuoussurfacesofvarioussizesandorientations,usuallyreferredtoasfracturesorjoints.Sineethelatterhavemuchpoorermechanicalcharacteristicsthantherockmaterial,theyplayadecisiveroleintheoverallbehaviorofrockstructures,whosedeformationaswellasfailurepatternsaremainlygovernedbythoseofthejoints.Itfollowsthat,fromageomechanicalengineeringstandpoint,designmethodsofstructuresinvolvingjointedrockmasses,mustabsolutelyaccountforsuch
‘‘weakness''surfaeesahalysis.
Themoststraightforwardwayofdealingwiththissituationistotreatthejointedrockmassasanassemblageofpiecesofintactrockmaterialinmutualinteractionthroughtheseparatingjointinterfaces.Manydesign-orientedmethodsrelatingtothiskindofapproachhavebeendevelopedinthepastdecades,amongthem,thewedlnown‘‘blocktheory,''whichattemptstoidentifypoten-
tiallyunstablelumpsofrockfromgeometricalandkinematicalconsiderations(GoodmanandShi1985;Warburton1987;Goodman1995).Oneshouldalsoquotethewidelyuseddistinetelementmethod,originatingfromtheworksofCundallandcoauthors(CundallandStrack1979;Cundall1988),whichmakesuseofanexplicit?
nite-differencenumericalschemeforcomputingthedisplacementsoftheblocksconsideredasrigidordeformablebodies.Inthiscontext,attentionisprimarilyfocusedontheformulationofrealisticmodelsfordescribingthejointbehavior.
Sincethepreviouslymentioneddirectapproachisbecominghighlycomplex,andthennumericallyuntractable,assoonasaverylargenumberofblocksisinvolved,itseemsadvisabletolookforalternativemethodssuchasthosederivedfromtheconceptofhomogenization.Actually,suchaconceptisalreadypartiallyconveyedinanempiricalfashionbythefamousHoekandBrown'scriterion(HoekandBrown1980;Hoek1983).Itstemsfromtheintuitiveideathatfromamacroscopicpointofview,arockmassintersectedbyaregularnetworkofjointsurfaces,maybeperceivedasahomogeneouscontinuum.Furthermore,owingtotheexistenceofjointpreferentialorientations,oneshouldexpectsuchahomogenizedmaterialtoexhibitanisotropicproperties.
Theobjectiveofthepresentpaperistoderivearigorousformulationforthefailurecriterionofajointedrockmassasahomogenizedmedium,fromtheknowledgeofthejointsandrockmaterialrespectivecriteria.Intheparticularsituationwheretwomutuallyorthogonaljointsetsareconsidered,aclosed-formexpressionisobtained,givingclearevidenceoftherelatedstrengthanisotropy.Acomparisonisperformedonanillustrativeexamplebetweentheresultsproducedbythehomogenizationmethod,makinguseofthepreviouslydeterminedcriterion,andthoseobtainedbymeansofacomputercodebasedonthedistinctelementmethod.Itisshownthat,whilebothmethodsleadtoalmostidenticalresultsforadenselyfracturedrockmass,a‘‘size''or‘‘scaleeffect''isobservedinthecaseofa
joints.Thesecondpartofthepaperisthendevotedtoproposingamethodwhichattemptsto
capturesuchascaleeffect,whilestilltakingadvantageofahomogenizationtechnique.ThisisachievedbyresortingtoamicropolarorCosseratcontinuumdescriptionofthefracturedrockmass,throughthederivationofageneralizedmacroscopicfailureconditionexpressedintermsofstressesandcouplestresses.Theimplementationofthismodelis?
nallyillustratedonasimpleexample,showinghowitmayactuallyaccountforsuchascaleeffect.
ProblemStatementandPrincipleofHomogenizationApproach
Theproblemunderconsiderationisthatofafoundation(bridgepierorabutment)restinguponafracturedbedrock(Fig.1),whosebearing
Fig,1,Bearingcapacit>poffoundationonfracturedrockmass
capacityneedstobeevaluatedfromtheknowledgeofthestrengthcapacitiesoftherockmatrixandthejointinterfaces.ThefailureconditionoftheformerwillbeexpressedthroughtheclassicalMohr-CoulombconditionexpressedbymeansofthecohesionCmandthefrictionanglem.Notethattensilestresseswillbecountedpositivethroughoutthepaper.
Likewise,thejointswillbemodeledasplaneinterfaces(representedbylinesinthe?
gure'splane).Theirstrengthpropertieiseadescribedbymeansofaconditioninvolvingthestressvectorofcomponents(c,t)actingatanypointofthoseinterfaces
F7(o-,t)=|t|+ Accordingtotheyielddesign(orlimitanalysis)reasoning,theabovestructurewillremainsafeunderagivenverticalloadQ(forceperunitlengthalongtheOzaxis),ifonecanexhibitthroughouttherockmassastressdistributionwhichsatis? estheequilibriumequationsalongwiththestressboundaryconditions,whilecomplyingwiththestrengthrequirementexpressedatanypointofthestructure. + ThisproblemamountstoevaluatingtheultimateloadQbeyondwhichfailurewilloccur,orequivalentlywithinwhichitsstabilityisensured.Duetothestrongheterogeneityofthejointedrockmass,insurmountabledif? cultiesareilkelytoarisewhentryingtoimplementtheabovereasoningdirectly.Asregards,forinstanee,thecasewherethestrengthpropertiesofthejointsareconsiderablylowerthanthoseoftherockmatrix,theimplementationofa kinematicapproachwouldrequiretheuseoffailuremechanismsinvolvingvelocityjumpsacrossthejoints,sincethelatterwouldconstitutepreferentialzonesfortheoccurreneeof failure.Indeed,suchadirectapproachwhichisappliedinmostclassicaldesignmethods,isbecomingrapidlycomplexasthedensityofjointsincreases,thatisasthetypicaljointspacinglisbecomingsmallincomparisonwithacharacteristiclengthofthestructuresuchasthefoundationwidthB. Insuchasituation,theuseofanalternativeapproachbasedontheideaofhomogenizationandrelatedconceptofmacroscopicequivalentcontinuumforthejointedrockmass,maybeappropriatefordealingwithsuchaproblem.Moredetailsaboutthistheory,appliedinthecontextofreinforcedsoilandrockmechanics,willbefoundin(deBuhanetal.1989;deBuhanandSalenc,on1990;Bernaudetal.1995). MacroscopicFailureConditionforJointedRockMass Theformulationofthemacroscopicfailureconditionofajointedrockmassmaybeobtainedfromthesolutionofanauxiliaryyielddesignboundary-valueproblemattachedtoaunitrepresentativecellofjointedrock(BekaertandMaghous1996;Maghousetal.1998).Itwillnowbeexplicitlyformulatedintheparticularsituationoftwomutuallyorthogonalsetsofjointsunderplanestrainconditions.ReferringtoanorthonormalframeO12whoseaxesareplacedalongthejointsdirections,andintroducingthefollowingchangeofstressvariables: p=((T]|+(T22)/\2,i? =((T22-O,i1)/\2,1=\2(T|2 (2) (如 suchamacroscopicfailureconditionsimplybecomes m whereitwillbeassumedthat 15=5tan Aconvenientrepresentationofthemacroscopiccriterionistodrawthestrengthenveloperelatingtoanorientedfacetofthehomogenizedmaterial,whoseunitnormalnIisinclinedbyanangleawithrespecttothejointdirection.Denotingby-nandnthenormalandshearcomponentsofthestressvectoractinguponsuchafacet,itispossibletodetermineforanyvalueofathesetofadmissiblestresses,n)deducedfromconditions(3)expressedintermsof(J,、,-12).ThecorrespondingdomainhasbeendrawninFig.2intheparticularcasewhere乞m Fig.2.Strengthenvelopeattachedcofaceiofhomogenizedmaterial Twocommentsareworthbeingmade: 1.ThedecreaseinstrengthofarockmaterialduetothepresenceofjointsisclearlyillustratedbyFig.2.Theusualstrengthenvelopecorrespondingtotherockmatrixfailureconditionis‘‘truncatedytwoorthogonalsemilinesassoonasconditionHj: Hmisful? lled. 2.Themacroscopicanisotropyisalsoquiteapparent,sinceforinstancethestrengthenvelopedrawninFig.2isdependentonthefacetorientationa.Theusualnotionofintrinsiccurveshouldthereforebediscarded,butalsotheconceptsofanisotropiccohesionandfrictionangleastentativelyintroducedbyJaeger(1960),orMcLamoreandGray(1967). NorcansuchananisotropybeproperlydescribedbymeansofcriteriabasedonanextensionoftheclassicalMohr-Coulombconditionusingtheconceptofanisotropytensor(BoehlerandSawczuk1977;Nova1980;AllirotandBochler1981). ApplicationtoStabilityofJointedRockExcavation Theclosed-formexpression(3)obtainedforthemacroscopicfailurecondition,makesitthenpossibletoperformthefailuredesignofanystructurebuiltinsuchamaterial,suchastheexcavationshowninFig.3, Fig.3.Stabilityanalysisofjointedrockexcavation wherehandBdenotetheexcavationheightandtheslopeangle,respectively.Sinceno surchargeisappliedtothestructure,thespeci? cweightyoftheconstituentmaterialwillobviouslyconstitutethesoleloadingparameterofthesystem.AssessingthestabilityofthisstructurewillamounttoevaluatingthemaximumpossibleheightFbeyondwhichfailurewilloccur.Astandarddimensionalanalysisofthisproblemshowsthatthiscriticalheightmaybeputintheform where0=jointorientationandK+=nondimensionalfactorgoverningthestabilityoftheexcavation.Upper-boundestimatesofthisfactorwillnowbedeterminedbymeansoftheyielddesignkinemati
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 土木 地质 岩土 工程 专业 毕业 英文翻译 原文 译文