Numerical simulation of the entrainment effect during mass movement in high-speed debris avalanches

Abstract

Due to the actions from upper motion masses with high speed, impacting, scouring and shear failures may occur in the substrate materials, which can change the motion properties and increase the volume of the moving masses. How to simulate the entrainment effect during the mass movement process in a high-speed debris avalanche is an important topic in the research of landslide dynamics. A set of three-dimensional simulation models have been established to study the entrainment effect during the mass movement process. The RNG k-e turbulence model is used to simulate the motion of avalanche flow, and a substrate entrainment model is adopted to estimate the entrainment of substrate materials, which is an improved method to display the entrainment effect in high-speed debris avalanches. Sensitive analysis is applied to evaluate the mechanism parameters, and the velocity magnitude, entrainment, and deposition depth net change have all been discussed in detail. The computational results show that the gravitational energy is translated into kinetic energy with a variable velocity for the sliding masses after landslide initiated, and three stages occur in the sliding process: fragmentation, entrainment, and deposition. In addition, the parameters of viscosity, angle of repose, and entrainment coefficient play important roles in simulations of the entrainment process; the entrainment effect in a debris avalanche depends on not only the mechanical parameters but also the topographical conditions.