考虑剪切和压缩损伤的多面模型

A MULTI-SURFACE MODEL CONSIDERING SHEAR AND COMPRESSION DAMAGES

基于土结构损伤和多面模型的基本理论,将弹塑性混合应变硬化与各向同性剪切损伤和压缩损伤结合起来,推导循环荷载作用下饱和软黏土不排水弹塑性本构模型。采用剪切损伤和压缩损伤两个变量分别描述土的结构损伤,并基于累积塑性偏应变建立损伤演化方程。分析结果表明,分别考虑土的剪切损伤和压缩损伤可描述饱和软黏土在不排水动荷载作用下泊松比的变化过程。通过对饱和软黏土地基的地震响应的模拟来检验模型的有效性。研究结果表明,考虑模量损伤可引起加载和卸载过程中塑性模量的差异,使得卸载塑性模量大于加载塑性模量,从而导致加载塑性应变响应大于卸载塑性应变响应,由此产生塑性偏变形的累积。

Based on the theories of structural damage and multi-surface model,a new elastoplastic model for saturated clay subjected to cyclic loading is deduced by combining the mixed strain hardening with the isotropic shear and compression damage.The structural damage of clay is depicted by the shear and compression damage variables,and the damage evolution equations are presented on the basis of accumulated plastic deviatoric strain.It is shown that considering the shear and compression damages can describe the changing process of Poisson's ratio under undrained condition.The model is verified by simulating the seismic response of saturated clay subsoil.Results show that considering the modulus damage may cause the difference between the plastic moduli of the loading and unloading,making the latter greater than the former.Further,this difference makes the plastic strain response during the loading greater than that during the unloading and as a result,the plastic deviatoric deformation accumulates with the continuation of cyclic loading.