基于改进CM模型的土石坝三维弹塑性地震反应分析

3D elasto-plastic seismic response analysis of embankment dam based on improved CM model

基于交变移动性(CM)模型,引入饱和度作为状态变量,给出了改进的土体塑性势面方程、屈服方程和协调方程,推导了新的硬化参量计算公式,发展了可连续描述非饱和与饱和土体静动力学特性的弹塑性本构模型。通过转换应力法,将模型从试验应力状态拓展到一般应力状态,使得本构模型可用于复杂三维河谷场地上修建的土石坝的弹塑性地震反应分析。数值模拟了汶川地震中典型震损土石坝的震害过程,模拟结果与实际震害吻合较好。对比研究了输入地震动强度对土石坝弹塑性地震反应分析结果的影响,结果表明土体的弹塑性特性对坝-基动力相互作用有着较大影响。

Based on the Cyclic Mobility( CM) model,a modified elasto-plastic model with rotation hardening which could systematically describe the monotonic and cyclic mechanical behaviors of soils combining the subloading,normal and superloading yield surfaces,is employed in the static and seismic stability analysis of embankment dam. By using the degree of saturation as independent state variable,this model could uniformly describe the behavior of unsaturated soil and saturated soil. By the transform stress method,this model could uniquely describe the overall mechanical properties of soils under general stress states,without changing the values of parameters. This model is suitable for threedimensional static-dynamic analysis for complex embankment dam and foundation. Simulation reappears the disaster process of typical embankment dam in Wenchuan earthquake,and the results agree well with the phenomena of field survey,which indicates that the proposed method is sufficient for simulating seismic disaster process of embankment dam. Furthermore,the influence of PGA of input ground motion on the elasto-plastic seismic response analysis of embankment dam is studied.