Energy transfer mechanisms in flow-like landslide processes in deep valleys

Abstract

A large-scale landslide in a deep valley often travels a long distance. The moving landslide debris impacts into the valley and interacts with the river and the opposite side of the valley. In the landslide movement process, energy, mass and momentum transfers inevitably take place. An in-depth study of energy and mass transfer mechanisms in various types of flow-like landslides will provide a scientific basis for developing energy criteria for evaluating landslide hazard chains and mitigation measures. In this study, a coupled DEM-ALE method is used to systematically evaluate the energy transfer mechanisms in landslides of various solid concentrations. The landslide dynamics involving river damming can be divided into three stages: the travel stage, the interaction stage, and the deposition stage. Kinetic energy is dominant in the travel stage but the frictional energy dissipation increases rapidly in the interaction stage. In the deposition stage, the kinetic energy changes to other energy components. The energy transfer mechanisms differ in different types of landslides. The kinetic energy of the fluid phase is mainly dissipated by viscosity shearing and turbulence, which is less efficient than internal and boundary frictional dissipations in the solid phase. The fraction of friction-dissipated energy increases with the solid concentration of the landslide mixture. Most of the remaining energy is dissipated by turbulence. Kinetic energy is the main energy transfer component during the landslide-river interaction. Flows of lower solid concentrations, e.g., debris flows, impact larger areas but are less likely to block a river.