Title
Numerical study on the mechanical behavior of progressive
failure of slope by 2D and 3D FEM( 内容の要旨(Summary) )
Author(s)
叶, 冠林
Report No.(Doctoral
Degree)
博士(工学) 甲第214号
Issue Date
2004-03-25
Type
博士論文
Version
URL
http://hdl.handle.net/20.500.12099/1935
※この資料の著作権は、各資料の著者・学協会・出版社等に帰属します。
氏 名(本籍) 学 位 の 種 類 学位授与番号 学位授与日付 専 攻 学位論文題目 叶 冠 林(中国) 博 士(工学) 甲第 214 号 平成16 年 3 月 25 日 生産開発システム工学専攻 Numericalstudyonthemechanicalbehaviorl Slope by2D and3D FEM
(2次元,3次元FEMによる斜面の進行性破壊メ 究) 学位論文審査委員 (主査) (副査) 教 授 厚 太 鋒 真 嶋 戸 八 杉 張 授 授 授 教 教 教 助
論文内容の要旨
SlopefailureduetoheavyrainaIwaysdrawmuchattentionofgeobecauseit maylead to tremendous disaster to human being andl dimculties to predict when and where the slope failurewi1loccI COnductedinthepaperareaimedtopredictwhenandwherearockslo]
The failure ofa soft-rOCk slopeis thoughtto belinkedwiths] excavation,CyClicdrylng-Wettingprocess,decreaseofe飽ctivestrez
negativeexcessiveporewaterpressure(negativeE.RWRinexcavatio】
E.RW巳).
Progressive Lhilure,Whichis a typICaltime-dependentbehavior;
fhilureofso氏rock・Indealingwithlong-termStabilityofaslope,tl behaviorsinso氏一rOCkgroundcanbeconsidered,thatis,theonecaus
determination ofmaterialparameters,and above aIl,the time consumption ofcalcuJation・ Especiallyinthecaseconsideringthee能ctofthemovementofundergroundwater・Carefu1ground
surveylSneCeSSarytOaCqulreaSatisfhctoryaccuracyoftheanalysis・Furthermore,the2Dnnite elementanalysishasbeenusedtoevaluatethegeotechnicalproblemsforalongtimeandmany
experiences havebeenaccumulated・Therefore,nOrmalIyenglneerSPrefer2D analysisto3D analysistoevaluatethestabilityofaslope・
Tbevaluate the stability ofa slopein overconsolidated clay,Clay shale and soRrockby numericalsimu)ation,theconstitutivtmodelplaysamuchimportantrole・Someresearcheshave
beingdoneonso食sedimentaryrocks,bothinexperimentandnumericalmodeling・Itiscommonly
known that the mechanicalbehavior ofso氏sedimentary rockis elastoplastic,dilatant,Strain hardening-Strainso鮎ningatlowerconnningstresslevel,andtime-dependent・Thecementation
deteriorates because ofthe breakdown ofthe structure,Whichis usually caused by various processes,SuChaslargeshearlngdeformation,CyClicdrying-Wettingorstressrelaxation・The mechanicaIbehaviorofso氏rockduringshearlngislargelydependentonthecon坑ningstress,and alsothepore-WaterpreSSureWithintherock・
InChapter2,anelastoplasticstrain-SOfteningconstitutivemodelproposedbyOkaandAdachi
forso氏rockismodinedbyintroducingtheSMPfailurecriterionandthetijconceptinorderto
preciselytakeintoconsiderationthein飢1enCeOfin蔽hediateprlnCIPalstress・Themodelis
veri丘edbycomparlngthetheoreticalpredictionwiththeexperimentalresultsonanarti丘cialso氏rock under plane-Strain condition・Itisfound that the modelcan describe not only the strain-SOtteningbehaviqrandstress-dilatancyrelationofso氏rockthatcouldbepredictedbythe originalmodel,butalsotheinnuenceoftheintermediateprlnCIPalstresstoasatisfhctoryaccuracy・ Itisalsoknown丘omthetheoreticaIpredictionconductedinthepaperthatdi飴rentfailurecriteria mayglVeatOtaldi飴rentstrain-hardeningandstrain-SO鮎ningbehaviorofageologlCmaterial・The materialparametersinvoIvedintheorlglnalmodelarealmostremainedthesameandonlyone parameterrelatedtostress-dilatancylSrePlacedbyadditionaltwoparameters,Whicharemuch easiertobedeterminedinconventionaltriaxialcompressiontests.Themodelcanalsobeappliedto
cohesivesoilsorsandysoilbychooslngaSuitablevalueoftheparameterみFurtherstudyshould
bedoneforthever描cationofthemodelundermoregeneralizedloadingconditions,forinstance,a truetriaxialsheartest. InChapter3,themathematicalfbrmulationsof2D,3D soil-WaterCOuPlingnniteelementanalysisareinducedbasedonBiot'stheory・Inthisformulation,nniteelementmethod(FEM)is
usedforthespatialdiscretizationortheequilibriumequation,Whilethennitedit粘rencemethod(FDM)wasusedforthespatialdiscretizationofthepore-WaterPreSSureinthecontinuityequation・
TheninChapter4,basedonthemodinedelastoplasticmodel,2Dand3Dsoil-WaterCOuPled nniteelementanalysesareconductedtoinvestigateanactualprogressivefhilureofaslope,Which locatesatrrbkai-HokurikuExpressway,Japan・Theobservedhilureisatypicalprogressivehilure andtheheavyrainfhIlisthemainreasonforthehilure・Thecharacteristicsofslopefhilure,SuChasthedevelopmentofshearstrain,thedeformationofground,thepropagationofshearbandandthe progressivefhilureal・ediscussedil-detai1with2Dand3Danalyses・Thedifrbrencesbetween2D and3DanalysesarecareAJIIy)nVeStigated・ttisfbundthatboth2Dand3Dsoiトwatercoupled analysesbasedonthemodinedeJastoplasticmodelcansimulatetheprogressivefailureofas]ope・
InChapter5,amOdinedelasto-Viscoplasticmodelisproposedbyintroducingthe旬concept
andSMPfailurecriterionintothemodelprQPOSedbyAdachietaJ・・Thismodinedmodelcannot
onlydescribethestrainsoReningandtime-dependencybehaviorofsoftrockasorlglnalmbdel,butalsotakeintoconsiderationtheinnuenceofintermediateprlnCipleitress.Basedonthemodined
and orlglnalelasto-Viscoplastic model,numericalanalyses are carried outtoinvestigate the
mechanicalbehaviorofaslopefailurelgnitedbytunnelexcavation・Ttisfoundthatbothmodels
can be adopted to simulate the progressive failure due to the time dependent property of geomaterial,althoughthereareslightlydi脆rencesbetweentwoanalyses・Furtherstudyshouldbe focusonthee飴ctoftheconstruCtionofretainingreclaimedsoiltothestabilityoftheslope・
論文審査結果の要旨
InthePhDcahdidate,sdissertation,nrStly;P3mOdinedelastoplasticmodelandamodi鮎d
elasto-Viscoplasticmodelwereproposed・Secondly,basedon theeIastoplasticmodels,2Dand3D soil-WaterCOuPled丘niteelementanalyseswereconductedtoinvestigatethemechanicalbehaviors ofaslopethilureduetoheavyrain・Atlast,2DFEAwasperformedtoanalyzeaslopefailuredue tothedeteriorationofsoilskeleton.Thenecessityofaccuratemodelsandthedi飴rencesbetween 2Dand3Danalysesare・Clarinedclearlyinthedissertation・Themainconclusions丘omthe candidate,sstudyarelistedbelow・ InChapter2,anelastoplasticstrain-SOReningconstitutivemodelproposedbyOkaandAdachiforso氏rockwasmodinedbyintroducingtheSMPfailurecriterionandthe旬COnCePtinorderto
preciselytakeintoconsiderationtheinnuenceofintermediateprlnCIPalstress・Themodelwas verinedbycomparlngthetheoreticalpredictionwiththeexperimentalresultsonanartincialso氏rock under plane-Strain condition・Itisfound that the modelcan describe not only the strain-SOfteningbehaviorandstress-dilatancyrelationofso氏rockthatcouldbepredictedbythe
orlglnalmodel,butalsotheinfluenceoftheintermediateprlnCIPalstresstoasatisfhctoryaccuracy・
ThematerialparametersinvoIvedintheorlglnalmodelarealmostremainedthesameandonlyone parameterrelatedtostress-dilatancylSrePlacedbyadditionaltwoparameters,Whicharemuch easiertobedeterminedinconventionaltriaxialcompressiontests・Asaconsequence,itispossibletoclarifythed騰rencebetween2Dand3Dnniteelementanalysesbasedonthemodel・
Tbsimulateaslope払ilureduetoheavyrainhIlorseverechangeofundergroundwater, soil-WaterCOuP]edana]ysISisnecessary・Therefore,inChapter3,fh・Stly,thefbrmulationsof2D& 3Dsoil-WaterCOuPlednnitee]ementmethodswerepresentrespective]y・Secondly・foraspecinedboundal・yValueproblemconcernlngSOiI-Waterintel・aCtion,thetreatmentsofboundarycondition wereintroduced.Furthennore,tOaVOidtheinstabilityduringcalculationwhichadoptsthemodined model,SeVeralspecialtreatmentswereconductedinthe伽iteelementana]ys)S・ InChapter4,basedonasuitableelastoplasticmodeI,both2Dand3Dsoil-WaterCOuPled伽ite elementmethodswereconductedtorecoveraslopefailureduetoheavyrain・Itisfoundtheboth methodsareabletosimulatethetimedependentbehaViorofso氏rockduetosoilskeleton-POre waterinteraction,andtheprogressivefailureofarealslopeduetoheavyrainfhll・Thedetailed conclusionsobtained什omthecomparisonsof2Dand3DanalysescanbeglVenaSfo1lowlng‥
(1)Byadoptingasuitablee)astoplasticmodelforso代rock,both2D,and3Dsoil-WaterCOuPled
finiteelementmethodsareabletosimulatethetimedependentbehaviorofso氏rockduetosoil skeleton-POreWaterinteraction・AstheresuIt,theprogressivefailureofarealslopeduetoheavyrainfa11canbesimulatedtoanengineeringacceptableaccuracy.(2)Fromthestress-Strainrelations
andthetimechangesofstrainrateinsoilelementsalongtheshearband,itisfoundthatthe formationandthepropagationoftheshearbandweredirectlycausedbythestrain-SOftening behavioroftheground・Comparedto2DanalysISlnWhichthepropagationoftheshearbandcanonlydevelopln One Verticalplane,3D analysISis able to describethe propagationintwo orthogonalverticalplanes,beingmuchmorerealisticthan2Danalysisifcomparedwiththeneld
observation.In other words,3D analysiS Can glVe卑⊥甲Ore COmPrehensive description ofthe
progressivefailureofaslope.(3)An、overall鮎1ureofaslopewasignitedbythepropagationof
shearbandwithinthegroundofslope・Thisconclusioncanbeobtained-bothin2Dand3Danalyses・(4)ThevolumetricexpansionofthesoiIwithinshearband,Obtainedftom2Danalysis,ismuch
sma11erthanthoseof3Danalysis・Consideringthefactorthatunderthesmallertheexpansionis, thesmaIlerthee能ctivecon伽ingstresswillbe,itisnotdifnculttounderstandtheresultthatthe groundat2Danalysisiseasiertofhilcomparedwith3Danalysis・Thatis,2DanalysISmayglVeaconservative estimation ofthe failure riskofaslope compared to3D
analysis・(5)Accurate
predictionofstress-dilatancyrelationwillplayaverylmPOrtantru1eindescribingtheprogressivefhilureofasloperelatedtosoil-WaterCOupledproblem・(6)Presentanalysiscannotsimulatethe
processofmulti-StagePrOgreSSivefailureobservedintherealfhilureevent,thefailuresurfhce predictedby2Dand3Danalysescoihcidesonlywiththeobservedfailuresurfaceat伽alstage・InChapter5,amOdinedelasto-Viscoplasticmodelwasproposedbyintroducingthetuconcept
andSMPfhilurecriterionintothemodelproposedbyAdachietal‥Theanalyticalresultsindicated thatthemodinedmodelnotonlycandescribethestrainsoReningandtime-dependencybehavior ofso氏rockasorlglnalmodel,butaIsocantakeintoconsiderationtheinnuenceofintermediate prlnCiplestress・Thenthemodelwasemployedinanumericalstudyonaslopefhilureduetothe deteriorationofground・Andtheresultswerecomparedwiththeonespredictedbyanalysisbased onorlglnalelasto-Viscoplasticmodel・Itiffbundthatbothmodelscanbeusedtosirnulatethe progressivefhilureduetotheinherentvisco-Plasticityofground,althoughtherewereslightly di脆rencesbetweentwoanalyses. Slopehiluremayleadtotremendousdisastertohtlmanbeingandcivlifhcilities,andhasbeenoneofthemostimportantanddi爪culttopicsingcotechincalresearch・Inthisstudy,thePhD candidateprovidedsomeusefu1methodstoanalyzetheprogressivehilureofslope,andobtained someveryexce11entconclusionsn・Omthenniteelementanalyses・Accordjngtothat,thecommittee approvedthatthisdissertationsatisneda11therequll・ementSfbrthePhDdegree・ ●