砂土液化变形的数值模拟

Numerical modeling of liquefaction-induced deformation in sand

基于模拟饱和砂土液化后大应变响应的弹塑性循环本构模型及相应的数值算法,采用完全耦合的饱和土动力反应分析程序SWANDYNE II,对VELACS项目中的三个动力离心模型试验(饱和松砂水平地基、饱和松砂倾斜地基、松砂和密砂的水平组合地基)进行了数值模拟。数值模拟较好地再现了离心模型试验测得的加速度响应、超静孔压响应及变形累积过程,给出了典型土单元的应力应变曲线和有效应力路径,从土的应力应变响应的角度较好地解释了模型中超静孔压的产生、扩散、消散过程以及液化大变形的发展过程。

A cyclic elasto-plasticity model developed by the authors, which could be used to simulate the large strain development during an entire pre- and post-liquefaction process, had been implemented in an effective stress based and fully coupled finite element program - SWANDYNE Ⅱ. Three dynamic centrifuge model tests performed in the VELACS project were simulated in this paper using the program. The macroscopic phenomena observed in the physical model tests, such as acceleration series, the generation, diffusion and dissipation of excess pore water pressure, and permanent deformation accumulation, were well reproduced in the numerical models. The calculated stress-strain curves and effective stress paths of typical soil elements in the models were also given by the numerical models, through which the whole liquefaction process of the models could be well understood.