中文摘要：

引入Newton-PCG算法，编制了算法程序，建立了流-固耦合砂土模型，实现了饱和砂土边坡液化问题的有限元数值模拟。采用一次牛顿步，和多步预条件共轭梯度子迭代的Newton—PCG复合算法，编制了算法的FORTRAN语言程序。基于临界状态塑性模型框架，给出了饱和状态下砂土固-液耦合模型的本构关系，再现了某饱和砂土边坡液化的力学状态，探讨了水压力分布与流动特性。结果表明：Newton—PCG算法能更有效地进行大规模非线性求解；建立的模型能较好地反映砂土-流体耦合状态下的力学行为；多孔介质中由于流体的流动，孔隙水压力对砂土液化的力学行为影响较大，在局部剪切带即将形成的区域，水压力值明显增大，而且方向指向剪切带的外法线方向；根据液化发生准则，画出了边坡发生液化的滑动面，对于预测边坡的发生具有重要的现实意义。

英文摘要：

A recently proposed model coupled with the solid-fluid of the saturated sand is utilized by introducing the Newton-PCG algorithm. A Newton-PCG composite algorithm is established, with a Newtonian step and p steps of preconditioned conjugate gradient, which is coded by FORTRAN program. Based on the critical state plasticity model, a model coupled with the solid-fluid of the saturated sand is derived by considering the function of the fluid flow. FEM numerical simulation of a saturated sand slope is performed to study the onset and development of the liquefaction, and the mechanism of the pore pressure and the liquefaction are discussed at last. The results show that the Newton-PCG algorithm can solve the multidimensional nonlinear problems efficiently. The proposed constitutive model works well, and can reflect the mechanical behaviors of the coupling of the sand-fluid. It is also found that the pore pressure will affect the development of the shear band greatly. What is more, the pore pressure increases around the shear band region obviously with the direction toward the outer side of the normal of the shear band. The slip surface of the slope liquefaction is obtained according to the criteria for the onset of liquefaction, which will be important to predict the onset of the liquefaction.