Channelized free-surface flow of cohesionless granular avalanches in a chute with shallow lateral curvature

A series of laboratory experiments and numerical simulations have been performed to investigate the rapid fluid-like flow of a finite mass of granular material down a chute with partial lateral confinement. The chute consists of a section inclined at 40° to the horizontal, which is connected to a plane run-out zone by a smooth transition. The flow is confined on the inclined section by a shallow parabolic cross-slope profile. Photogrammetric techniques have been used to determine the position of the evolving boundary during the flow, and the free-surface height of the stationary granular deposit in the run-out zone. The results of three experiments with different granular materials are presented and shown to be in very good agreement with numerical simulations based on the Savage-Hutter theory for granular avalanches. The basal topography over which the avalanche flows has a strong channelizing effect on the inclined section of the chute. As the avalanche reaches the run-out zone, where the lateral confinement ceases, the head spreads out to give the avalanche a characteristic 'tadpole' shape. Sharp gradients in the avalanche thickness and velocity began to develop at the interface between the nose and tail of the avalanche as it came to rest, indicating that a shock wave develops close to the end of the experiments.