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1、4.Elasto-plasticmodel——recoverablestrain,elastic——irrecoverablestrain,plasticPlasticstrain。failurecriterion,yieldcriterion。hardeninglaw。flueruleFailurecriterionelasticfailureFailuresurface——locusofthepointsinstressspacewhichrepresentfailure(1)failurecriterion——failurefunction
2、variablesarestresscomponentssimplestressstatecomplicatestressstateTrascacriterionHexagonalcolumnSaturatedsoil,undrainedMisescriterionCircularcolumnsurfaceExtensiveMisescriterionDrucker-PragerGeotecnicalmaterial——firststressinvariant——seconddeviatorstressinvariantCircularcones
3、urfaceCambridgeuniversityMohr-CoulombcriterionHexagonalconewithequaledgesbutunequalanglesMisesMohr-CoulunbTrascaLade-Duncancriterion(2)yieldcriterionsimplestresselasticplastic,yieldcomplicatestresselasticplastic,yieldtheoreticalmaterial,yield=failuregeotechnicalmaterial,yield
4、failureConceptofyield—yieldfunction,correspondingtoyieldsurfaceinstressspaceyieldsurface—locusofthepointsinstressspacewhichreachyieldifkchanges,yieldsurfacemovesYieldsurfaceVariationofyieldsurfaceLoadingandunloadingCurrentstressstate—onyieldsurface,Anewstressincrementisapplie
5、d.*unloading*loading*neutralloadinglimitofelasticplasticelastic2vectorsmultiplyYieldsurfaceforgeo-materialIndependentofdirectionofcoordinatesystemx,y,zConetypeCaptype2yieldsurfacekincreases—hardeningkdecreases—softeningkconstant—theoretical(3)hardeninglawAfteryield,kchanges,H
6、—hardeningparameter,aphysicalvariantwhichcauseskchangeForagivenvalueofH,yieldsurfaceisdefined.Howdoeskchange?Whichfactorcauseskchange?hardeningsofteningtheoretical(4)flueruleHowtheplasticstraindevelopsamongthestraincomponents?Howtodeterminetheproportionofthestraincomponents?—
7、plasticstrainincrementDirectionofdetermineseachcomponentoftheplasticstrainincrement.FluerulegivesdirectionofConceiveaplasticpotentialfunctionStrainspaceisoverlappedwithstressspace.PlasticstrainincrementisperpendiculartoplasticpotentialsurfaceAssociatedflueruleDrucker’spostula
8、tion—anelementexitsinitialstressstate,loadingslowly,andthenunloading