Discrete Element Modeling of Boulder Energy Distribution in Rock Avalanches on Irregular Terrain

Abstract

The destructive potential of a rock avalanche can come from any single boulder. Rock avalanches across irregular terrain were simulated using the discrete element method (DEM) with high-performance computing to model particle quantities from one to millions. Simulations were validated against published miniature flume experiments and varied in terms of particle shape, rolling friction between particles, rolling friction on the flume, and restitution coefficient to quantify how various mechanisms of energy dissipation affect the avalanche runout sequence. Non-spherical particle shapes idealized as superquadrics demonstrated superior capability in representing the motion of angular particles and capturing physically observed runout sequences and inundation thicknesses when compared with equivalent simulations performed with spherical particles. Rheological rolling friction at the interparticle contacts had a significant effect on the runout sequence but proved to be an inferior substitute for geometric non-sphericity. Higher quantities of particles in rock avalanches produced lower average kinetic energies per particle due to the greater amount of energy dissipated through more frequent contact damping; however, the maximum single-particle kinetic energy still increased with particle quantity. The simulation results provide insight into how kinetic energies are distributed temporally and spatially across irregular terrain during rock avalanches, facilitating visualization of the locations of the highest impact energy for individual particles and for the entire avalanche. The locations of highest kinetic energy associated with individual particles do not always overlap with those associated with the whole avalanche, which signifies the importance of considering the destructive potential of individual boulders at multiple locations along runout paths.