Modeling of rainfall-induced failure of unsaturated soil-rock mixture slopes: CFD-DEM coupling method

Due to the complex coupled hydro-mechanical processes and soil-rock interactions involved, accurate simulation of rainfall-induced failure of soil-rock mixture (SRM) slopes remains a considerable challenge. To address this issue, this paper develops a numerical framework for simulating the unsaturated SRM slope failure under rainfall using the computational fluid dynamics-discrete element method (CFD-DEM) coupling approach. Within the numerical framework, the unsaturated soil behavior, the transient evolution of seepage during rainfall infiltration, and the soil-rock interactions are explicitly considered. The conventional CFD-DEM coupling approach is further enhanced to better represent the hydro-mechanical coupling behavior during rainfall-induced slope failure. Specifically, an unstructured mesh is adopted for the flow domain to accommodate the irregular geometry of SRM slopes; rainfall boundary conditions are prescribed at the slope boundaries; and Richards’ equation is solved using the finite volume method (FVM) to simulate rainfall infiltration. Meanwhile, the Monte Carlo simulation (MCS)-based stochastic generation method is employed to build the SRM model based on the statistical information on the rock block’s geometries, after which the corresponding DEM model is established. To verify the developed framework, two slope problems are analyzed. Further, a comparative analysis is conducted to highlight the proposed framework’s advantages over conventional approaches for modeling the rainfall-induced failure of unsaturated slopes. To illustrate its practical applicability, the proposed framework is applied to an actual SRM slope in Baidian, China, to investigate its rainfall-induced failure behavior.