高等土力学第10讲变形特性1

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1、土的力学特性Part1孙德安上海大学大学土木系2012-11-10土的变形特性•1.非线性和非弹性•2.塑性体积应变•3.塑性剪应变•4.硬化与软化•5.应力路径与应力历史的影响•6.中间主应力的影响•7.固结应力的影响•8.各向异性1.Non-linearandnon-elasticσσεεMetalSoilσPlasticstrain—irrecoverablestrain,duetoadjustmentofpositionofgrains.Oneparticlemayslipoveranotherparticle,maydr

2、opintoporespace,εpeandtherelativepositionbetweentheεεtwoparticlescannotberecovered.Deformationcannotberecovered2.PlasticvolumetricstrainMetal—noplasticvolumetricstrainp0ε=vSoil—obviousplasticvolumetricstrainp0ε≠v•pinducedbypεvMacroscopic—compressMicroscopic—slipbetwee

3、ngrainsppploadingunloadingεvpeεεvvp•εinducedbyshearstressv1()Triaxialtestwithp=constantp=σ+σ+σ3123σ1−σ3increase,butdecreaseσ3p--meannormalstresskeepsconstantσ−σ13σ−σ13p=constantp=constantεεvvShearcontractionSheardilation•SheardilationDilation——densesand,overconsolidat

4、edclayContraction——loosesand,normallyconsolidatedclay1−ε>εra2ε=ε+2ε<0varεrν=−>0.5Sheardilativeεaεrν=−<0.5εaShearcontraction3.ShearstraininducedbymeanstresspTriaxialtestτσ−σ13σ3σSimultaneouslyreduce,andkeepconstantσσ(σ−σ)1313q=constant,pdecreases.Mohr’stresscirclegoesl

5、eft.WhentheMohrcircletangenttothefailureline,thedeviatorstrainbecomesverylarge.Thedeviatorstrainisinducedbychangeinp.εaisduetoexistenceofinitialshearstress.•Effectofintersectioninstress-strainmatrix⎧Δε⎫⎡CCC⎤⎧Δσ⎫x111213x⎪⎪⎢⎥⎪⎪⎨Δεy⎬=⎢C21C22C23⎥⎨Δσy⎬⎪Δγ⎪⎢CCC⎥⎪Δτ⎪⎩xy⎭⎣313

6、233⎦⎩xy⎭CC—reflectsheardilation1323CC—reflectshearstraininducedbynormalstress3132Elasticmodel—CC=0=0CC13233132Plasticmodelcanreflecttheseeffects4.SofteningandhardeningττResidualstrengthγSimplesheartestγσ−σ13σ−σ13hardeningSofteningresidualstrengthεaεaTriaxialsheartest5

7、.Influenceofstresspath&stresshistoryStressspace—aspaceconsistsofstresscomponentaxesσq1q-pf·MFailurelineσ3pσ2Principalstressspacep-qplaneApointinstressspacerepresentsastressstateatapointinsoilbody•Stresspath—thelocusofmovingpointinthestressspace.Pointrepresentsstressst

8、ate.Stresspathrepresentsvariationinstressstate,thatistheloadingmannerσ1σ1N·Mσ3·σ2σ3σ2Astresspathconsistsofseveralsections.Ea