Numerical investigation on the evolution of landslide-induced river blocking using coupled DEM-CFD

Abstract

This paper presents a two-way coupled discrete element method (DEM) and computational fluid dynamics (CFD) scheme to quantitatively investigate the evolution of landslide-induced river blocking. The particle–fluid interaction is considered by exchanging interaction forces, such as drag force, buoyancy force, and lift force, which are essential for describing the evolution of river blocking. The coupled DEM-CFD scheme is first benchmarked by comparing the settling velocities of particles with different diameters with corresponding experiments. The scheme is then employed to investigate the effects of river flow velocity, river water depth, landslide velocity, and landslide volume on the evolution of river blocking. Based on the understanding of the river blocking mechanism, we propose a river blockage coefficient (Ic) to predict the river blocking. The results indicate that river water reduces the mean normal contact force of landslide particles, leading to river water quickly washing them away. The deposit velocity along the direction of the river valley is positively correlated with river water depth and river flow velocity but negatively correlated with the initial landslide velocity and landslide mass volume. The study indicates that when Ic > 1, a river is completely blocked. Otherwise, a river is unblocked or partially blocked.