Development of a Modeling Method and Parametric Study of Seepage-Induced Erosion in Clayey Gravel

The aim of this study is to develop a method to simulate the behaviors of clayey gravel during water erosion by using computational fluid dynamics–discrete element method. The fluid phase was solved using the "fixed coarse-grid" scheme based on Navier–Stokes equations, and the solid phase was described by an assemblage of discontinuous particles in the Particle Flow Code in three dimensions (PFC3D) modeling framework. A fictitious clay method was introduced, in which the suffosion of clay matrix was translated to the strength degradation of bond according to a degradation law. The degradation law was embedded into PFC3D by the development of additional code in the Python language. The method was first validated by comparing with experimental results. Then, a parametric study was carried out to investigate the influence of three different factors, particle-size distribution (PSD), soil porosity, and pressure gradient, on the erosion behavior of soil. Results show that the proposed model offers a promising method to predict the erosion behavior of clay soil at the particle level. The numerical results generally match the empirical criteria, for example, it demonstrates that the initiation of the erosion process is significantly influenced by material properties (PSD, porosity) and loading condition (hydraulic gradient), and also reveals clearly defined critical levels for the three parameters, below which through-piping cannot be expected.