饱和黏土振动弱化性态的边界面模型分析

Cyclic Degradation of Saturated Clay Based on a Bounding Surface Model

基于增量弹塑性边界面理论,构建一种可以描述振动应力作用下饱和黏土弱化的边界面应力应变关系。该关系利用具有严谨理论基础的旋转硬化法则描述振动应力作用过程中边界面大小与位置的变化,并将塑性累积偏应变长度作为反映振动应力历史对饱和黏土应力应变响应影响的状态参数,通过建立包含状态参数的塑性模量插值关系描述饱和黏土振动弱化应力应变响应,进一步按照正交流动法则形成增量应力应变关系。该关系包含9个参数,其中5个是剑桥模型参数,其余4个参数有相对明确的物理意义。利用所构建的边界面应力应变关系,对两种黏土的等压固结不排水静三轴试验和动三轴试验进行预测,并与试验结果进行比较,结果表明这一关系能够较好描述振动应力作用下饱和黏土刚度与强度弱化特性。

An incremental stress-strain relationship was developed based on the incremental elastoplastic bounding surface theory.This relationship could describe the degradation of saturated clay subjected to cyclic loads.In the relationship,a rotational hardening rule based on a rigorous theory was used to describe the change in size and location of the bounding surface during the action of vibrational stress.The plastic accumulative deviatoric strain length was used as a state parameter to reflect the effect of vibration stress history on the stress-strain response of saturated clay.An interpolated relationship of plastic modulus associated with the state parameter was formulated to describe the cyclic degradation of soft clay subjected to cyclic loads.Finally,the incremental stress-strain relationship was established using the associative flow rule.The relationship included nine parameters,five of which were modified Cambridge model parameters,while four had relatively clear physical meanings.Monotonic and cyclic undrained triaxial test results of two kinds of saturated clay were predicted using the relationship to verify its validity.Comparison of predicted and test results showed that the relationship can skillfully describe the cyclic degradation behavior of saturated soft clay subjected to cyclic loading.