Influence of size gradation on particle separation and the motion behaviors of debris avalanches

Abstract

Debris avalanches have complex structures due to the internal discreteness of fragmentation events. From a meso perspective, a debris avalanche is essentially a collection of debris particles of various sizes. Friction and collision events are directly influenced by the gradation of debris particles, restricting the movement process of debris avalanches. Accordingly, a series of numerical simulations have been conducted to research the influence of motion behavior based on experimental tests. The results indicate that the inhomogeneous character of a debris avalanche creates a conducive particle structure for the movement of the debris avalanche, in which the fine particles can play a role in the conversion of sliding to rolling at the bottom, causing the reduction of friction dissipation and the differentiation of particle friction resistance along the vertical direction, which continues until deposition. Sudden decreases in friction resistance occurring on high-speed, fluid-like debris avalanches are primarily correlated to the particular particle structure due to the significant inhomogeneity of particle gradation.