适用于饱和粘土循环动力分析的新型边界面塑性模型

为了合理评估嵌入式海洋工程结构在海洋环境中的动力响应和工作性能，建立一种形式简单且能真实模拟饱和土体复杂动力特性的本构模型显得极为必要。本文基于广义各向同性硬化准则提出了适用于描述循环荷载作用下饱和粘土复杂动力特性的新型边界面塑性模型。模型引入广义各向同性硬化中心，实现边界面的等向硬化和运动硬化，以反映循环荷载作用下饱和粘土各向异性的演化；同时，土体的连续循环加载过程被分为三类加载事件：初始加载，卸载和再加载事件，采用不同的插值公式计算其塑性模量，以模拟循环塑性应变和孔压的累积；以该硬化中心作为映射中心，从而体现土体在卸载过程中产生的塑性变形，合理地模拟循环荷载作用下土体应力应变关系的滞回特性。应用该模型对饱和粘土在短期较高应力水平下和长期低应力水平下的循环动力特性进行预测，并与相关文献中的试验数据比较，证明了该模型的合理性。

A new type of bounding surface plasticity model for cyclic behavior of saturated clay

In order to precisely evaluate the response of embedded offshore structures in a complicated ocean environment, it is essential to develop simpler and more accurate soil models under cyclic loading. Based on the generalized isotropic hardening rule, a new type of bounding surface plasticity model is herein proposed which is capable of modeling the undrained saturated clay behavior under cyclic loading. According to the movement of the hardening center, the new bounding surface plasticity model for predicting the evolvement of clay anisotropy can not only harden isotropically but also kinematically. Meanwhile, virgin loading, unloading and reloading processes are treated differently when calculating the hardening modulus to predict the accumulation of permanent strain and pore pressure. The hardening center is taken as the mapping origin in the radial mapping rule to simulate the hysteresis property of clay under cyclic loading. The results of model simulations show an encouraging agreement with the experimental data from triaxial tests subjected to both short-term high stress level and long-term low stress level cyclic loading conditions.