Numerical study on seepage-induced instability of soil-rock mixture slopes using CFD-DEM coupling method

Abstract

Soil-rock mixtures (S-RM) are prevalent in both nature and practice, and stability of S-RM slopes is one of the focuses for engineers. In addition to soil strength, seepage erosion is one of the main factors affecting the stability of S-RM slopes. As water infiltration complicates the multi-field coupling effects and micro-scale mechanical behaviors of S-RM, it is essential to investigate seepage-induced S-RM landslides from both macro and micro perspectives. This study proposed a CFD-DEM fluid–solid coupling method, and the method was validated with Darcy experiments and lab slope stability experiments. The method was then applied to analyze seepage-induced slope instability, focusing on the impact of rock content and rock shape. The results indicate that slope failure under seepage showed the same characteristics as debris flow, with instability features such as sliding surfaces, damage range, and particle motions varying according to rock content and shape. As rock content increased, the accumulation of slope transitions through three distinct modes. Slope was prone to failure along the soil-rock interface, and low rock content further impaired the stability. The slope deformation was primarily driven by changes in particles contact. Once slope instability occurred, the system tended to adjust particle contacts to achieve new state of equilibrium.