fredlund边坡稳定未来讲义（精品）

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1、WhatistheFutureforSlopeStabilityAnalysis?(AreWeApproachingtheLimitsofLimitEquilibriumAnalyses?)Dr.DelwynG.FredlundUniversityofSaskatchewan,CanadaSecondSymposiumandShortCourseonUnsaturatedSoilsandEnvironmentalGeotechnicsBudapest,HungaryNovember4-5,2003IntroductionLimitE

2、quilibriummethodsofsliceshavebeen“Good”forthegeotechnicalengineeringprofessionsincethemethodshaveproducedfinancialbenefitEngineersareoftensurprisedattheresultstheyareabletoobtainfromLimitEquilibriummethodsSoWhyChange?ThereareFundamentalLimitationswithLimitEquilibriumMe

3、thodsofSlices??TheboundariesforaFREEBODYDIAGRAMarenotknown-TheSHAPEfortheslipsurfacemustbeassumedTheLOCATIONofthecriticalslipsurfacemustbefoundbyTRIALandERRORSHAPEandLOCATIONarethedrivingforceforaparadigmshiftObjectivesofthisPresentation:Toshowthegradualchangethatiseme

4、rginginthewaythatslopestabilityanalysescanbeundertakenToillustratethebenefitsassociatedwithimprovedproceduresfortheassessmentofstressesinaslopeOutlineofPresentationProvideabriefSummaryofcommonLimitEquilibriummethodsalongwiththeirlimitations(2-D&3-D)TaketheFIRSTstepforw

5、ardthroughuseofanindependentstressanalysisTaketheSECONDstepforwardthroughuseofOptimizationTechniquesIsaLimitEquilibriumAnalysisanUpperBoundorLowerBoundSolution?LimitEquilibriumMethodsprimarilysatisfytherequirementsofanupperboundtypeofsolutionReason:theshapeofslipsurfac

6、eisselectedbytheanalystandtherebyadisplacementboundaryconditionisimposedLimitEquilibriumandFiniteElementBasedMethodsofAnalysesWWWWWWWWNLimitEquilibriumMethodofAnalysisSm=tadldlsndlFiniteElementBasedMethodofAnalysisldtadlQUESTION:HowcantheNormalStressatthebaseofaslicebe

7、mostaccuratelycomputed?ConsidertheFreeBodyDiagramsusedtocalculatetheNormalStress?AssumptionforallLimitEquilibriumAnalysisSoilsbehaveasMohr-Coulombmaterials(i.e.,friction,f',andcohesion,c')Factorofsafety,Fs,forthecohesivecomponentisequaltothefactorofsafetyforthefriction

8、alcomponentFactorofsafetyisthesameforallslices()[]msnsSFuFc=-+bfsb'tan'SummaryofAvailableEquationsAssociatedwithaLimi