一种适用于饱和黏土循环动力分析边界面塑性模型的隐式积分算法

An implicit integration algorithm in the bounding-surface plasticity model for cyclic behaviors of saturated clay

修正了传统隐式回映算法,建立了适用于饱和黏土循环动力分析的边界面塑性模型的完全隐式积分格式。该模型基于无弹性域概念和临界状态理论,采用各向同性、运动硬化准则、旋转的边界面,并引入表征土体结构损伤和重塑程度的损伤变量以反映循环载荷作用下饱和黏土的各向异性、刚度、强度软化及塑性变形累积等特征。针对等压固结0K?1.0和偏压固结0K?0.67的饱和高岭黏土的不排水三轴试验进行模拟,采用不同的应变增量步长进行计算,并与试验数据对比,结果表明,修正隐式回映算法应用于该类边界面模型的合理性、积分格式的精确性和稳定性;另外,结合有限元软件自动时间步长的增量迭代解法,对饱和黏土应力控制的不排水动三轴试验进行预测,结果表明,修正的适用于该边界面的塑性模型隐式回映算法可以得到比较合理的数值分析结果,能够反映饱和黏土的循环刚度的退化和强度的弱化等动力特性。

A fully implicit integration scheme in the bounding-surface plasticity model for cyclic behaviors of saturated clay is presented by modifying the conventional implicit return mapping algorithm. Within the critical state framework, based on the concept of shrinking the elastic region to a point, combining isotropic with kinematic hardening rule and a rotated bounding surface, and introducing a damage parameter representing the remolding of the soil fabric, the model can reflect the initial anisotropy, the cyclic stiffness degradation and strength softening of saturated clay under cyclic loading. Firstly, the numerical simulations of the undrained triaxial tests both for isotropic （ K0 = 1.0 ） and anisotropic （ K0 = 0.67 ） consolidated kaolin clay are carried out with variable strain increments. By comparing with the test data, the rationality, robustness and the accuracy of the new fully implicit integration for the bounding surface plasticity model are verified. Furthermore, the prediction for an undrained cyclic triaxial test on a saturated clay is given, and the cyclic degradation of the stiffness and strength is obtained, which indicates the validity of the computational results.