Multiscale modeling of seepage-induced suffusion and slope failure using a coupled FEM–DEM approach

Suffusion refers to the detachment and migration of fine particles through voids among coarse particles and is one of the major causes of slope failure. This study investigates the seepage-induced suffusion and slope instability using a hierarchical multiscale finite–discrete element method (FEM–DEM). An erosion law with the critical hydraulic gradient for the onset of suffusion is proposed. Two examples, including one-dimensional suffusion and biaxial compression tests, are performed to verify the proposed scheme. Emphases are placed on reproducing suffusion and progressive slope failure process under seepage flow. The results indicate that a shear band is initiated from the slope toe and gradually extends to the crest. The increase of erosion rate accelerates the process of suffusion and slope failure, whereas a higher critical hydraulic gradient plays an opposite role. In addition, fines loss caused by suffusion occurs mainly on the slope surface, especially near the slope toe. Microscopic analyses on locally embedded representative volume elements (RVEs) indicate that RVEs inside the shear band experience severe deformation and microstructural changes, manifested by the rearrangement of soil skeletons and variation of contact force chains.