砂土速率相关黏性特性的有限元分析

FEM Analyses on Ratedependent Behaviors of Sand Due to Its Viscous Properties

摘要:

根据复杂加载条件下饱和砂土排水平面应变压缩试验,分析了砂土的速率相关的黏性特性.试验发现砂土存在显著的加载速率效应、蠕变变形和应力松弛,并且在应变速率突变、蠕变或应力松弛之后,以新的应变速率重新加载时呈现出高刚度行为.针对砂土的变形强度特性提出了一种非线性有限元计算方法,砂土本构关系采用了三要素弹黏塑性本构模型.将有限元计算结果与试验结果进行比较,表明建议的有限元计算方法不仅可以较为精确地模拟砂土的平均应力应变关系,同时也可以模拟包含变应变速率加载、蠕变加载、应力松弛加载的全过程黏塑特性.

Abstract:

Based on the experimental results from drained plane strain compression(PSC)tests on saturated sand under complex loading histories,the ratedependent behaviors of sand due to its viscous properties were studied.It was found that sand exhibits obvious loading rate effects,creep deformation and stress relaxation.When monotonic loading was restarted immediately after a stepchange in the strain rate or following a creep loading or stress relaxation stage,the stressstrain relation showed a very high tangent stiffness.A nonlinear finite element method(FEM)analysis technique was developed.In the FEM analyses,the sand was described by the threecomponent elastoviscoplastic constitutive model.It was shown that the present FEM analyses can properly simulate the global stressstrain relationships obtained from the experiments.And the whole process including the variable strain rate loadings,the creep loading and stress relaxation stages were implemented in the FEM analyses.