Experimental Preliminary  Analysis of the Fluid Drag Effect in Rapid and Long-runout Flowlike Landslides

Abstract During a landslide, the multi-phase nature of landslide debris defines its mobility. Eventually, frictional forces cause the slide energy to dissipate, and contact forces transmit the energy into nearby material. To analyze the dynamic characteristics of high-velocity long-runout landslides, we conducted flume model tests to empirically determine the mobility characteristics of flow-like landslides with various slide materials. Our conclusions are as follows: (1) Liquid-phase flow-like landslides are highly mobility and have long runout; solid-phase flow-like landslides are highly destructive because of their higher kinetic energy; and two-phase flow-like landslides are both highly mobility. (2) During a two-phase flow-like landslide, the mobility ability of the liquid-phase material is stronger than that of the solid-phase material; when the liquid slide volume fraction is sufficiently large, the liquid phase exerts a drag force on the solid phase. (3) Various liquids exert different drag effects on the solid; the solid-liquid velocity difference and the liquid viscosity determine the drag intensity and the mobility and depositional characteristics of the landslide.