中文摘要：

软土在循环荷载作用下，很小剪应变幅值发生时就会使土体产生塑性变形，因此采用粘塑性模型模拟软土在循环荷载作用下的动力特性更合理。本文针对软土在动荷载下的变形特点，采用等向硬化和随动硬化相结合的硬化模量场理论，基于土体的广义塑性理论，建立了一个总应力增量形式的土体粘塑性动力本构模型。该模型通过记忆任一时刻的加载反向面、破坏面和与加载反向面内切的初始加载面来确定屈服面变化规则，模型参数容易确定。在ABAQUS软件平台上实现了该模型的算法，通过土样动三轴试验的结果与模型预测结果的对比分析，验证了该模型的可行性。同时，对南京某含有较厚软土层的典型软弱地基的地震反应进行了分析，分析结果符合软弱地基非线性地震反应的一般规律。因此，该模型为软土非线性地震反应和土-结构非线性动力相互作用分析提供了一个较为实用的土体本构模型。

英文摘要：

Under cyclic loadings, the plastic strain of soft soil would be happened under very small shear strain. So the visco-plastic model was appropriate to be used to simu late the dynamic characteristics of soft soils. Based on the principles of geotechnical plastic mechanics, the incremental visco-plastic memorial nested yield surface model was developed using the nonlinear isotropic and kinematic hardening modulus field theory. At the end of any increment, the inverted loading surface, the failure surface and the initial loading surface witch was tangent with the inside of inverted loading surface were memorized, and dynamic behavior of yield surface was defined by these surfaces. The developed model was implemented in ABAQUS software successfully. The predicted stress-strain relationship of soil were compared with the test results given by cyclic triaxial tests. It was proved that the cyclic undrained stress-strain relation of soils could be fairly simulated by the model. At last, the nonlinear earthquake response of a representative soft site in Nanjing was calculated with the dynamic behavior of soils modeled by the developed model. The results coincided with the earthquake response of soft site given by others