中文摘要：

基于散体介质理论，利用PFC^2D内置FISH语言定义的流固之间的作用力方程和压力梯度方程，求解不可压缩流体中两相介质的连续方程和Navier-Stoke方程。并尝试用该理论模拟不同水压下渗流引起砂土特性变化的全过程，数值试验得NT流速、渗透系数、孔隙率和砂的流失量等参量的定性变化规律，表明水土相互作用贯穿于渗流的全过程。模拟结果与试验结果相符，且流速与压力梯度满足达西定律，表明应用该理论来模拟复杂的水土相互作用是可行的，它具有一定的理论意义，为进一步研究多孔介质中考虑流固耦合的渗透破坏研究如流土、管涌等奠定了一定的理论基础。

英文摘要：

The interaction and pressure gradient equation of fluid-solid was defined on the basis of particle flow theory using FISH language embedded in PFC^2D, and the continuity equation and N-S equation for fluid-solid two-phase flow model in incompressible fluid were solved. It attempts to get insight into the changes in the mechanical properties of soil subjected to seepage erosion under various pressure differences. The variations of fluid velocity, permeability, porosity and the percentage of eroded particles, etc. were obtained qualitatively in the test. The simulated results were consistent with the experimental results, and the obtained fluid velocity and hydraulic gradient satisfied the Daycy＇s law. So it was of practical and theoretical significance to simulate the complex interaction between the fluid and soil, and it provided the theoretical basis for the further study of more complicated seepage failure problems in porous media such as flowing soil, piping, etc.