双层堤基条件下管涌逸出的颗粒流模拟

基于颗粒离散元理论,结合实际工程中的双层堤基管涌对管涌口颗粒逸出问题进行仿真模拟。基于颗粒流程序平台PFC2D(Particle Flow Code in Two Dimension)建立了管涌口附近地层的数值模型,通过模拟实验确定了颗粒参数,分别采用线性接触刚度和平行粘结本构模型定义黏土层和砂性土层的接触模型。通过与水的耦合作用,得到管涌口从发生到扩展的管涌演化全过程。采用FISH语言开发程序,分别得到其流失量、孔隙率、流速等参数并进行分析。宏观方面的研究结果表明,采用颗粒流模拟的结果与实际管涌的宏观现象基本吻合;细观方面,管涌颗粒在管涌发生发展过程中沿着实际水流速度最大的通道溢出,流速的分布情况存在从相等的平均流速状态向局部流速集中并逐渐增大的改变过程,局部细小通道逐的流速集中,引起周边颗粒的加速流失,最终导致管涌通道的形成。这些结果为PFC2D在渗透破坏方面的深入研究应用提供了一定的实用依据,同时也为在细观尺度上解释和分析管涌现象提供了一条新的途径。

Piping Outlet Pfc Simulation of Double Layer Embankment Foundation

Based on double layer embankment foundation, the piping outlet particles’ transgression process is simulated using particle discrete element theory. A stratum model around piping outlet is set up by PFC2D(Particle Flow Code in Two Dimension) software, parameters are confirmed with small scale simulate test, linear contact model and parallel bond model are adopted to simulate the contact relationship of clay and sandy soil respectively. Via soil water coupling, the whole process of piping evolution is presented. Programs based on FISH language are compiled to acquire the loss mass, porosity factor and velocity of flow. Analysis to the results shows that: the simulation phenomena correspond with the macro phenomena of real piping process. As to mesomechanical results, piping particles run out along a zone which has the maximum velocity of flow, the values scatter of velocity follows the tendency of average to local concentration, the separated tiny channels’ occurrence, caused higher velocity and particles around the zone run out rapidly, thus result in the piping zones formation. These results provide practical warranty for the farther research using PFC2D on seepage failure, and thus provide a new approach to analyze piping problem at mesomechanical scale.