Study of sediment transport in granular avalanches

Abstract

AbstractUnderstanding the characteristics and mechanics of granular avalanches along sloping channels is fundamental and vital for the study of different geophysical flows in the field. By using the discrete element method (DEM), three‐dimensional (3D) granular (mass) flows along a sloping channel are numerically modelled to study the contact behaviour between solid particles. The evolution of 3D unsteady granular flows from a quasi‐static state to an inertial flow is systematically investigated through numerical simulations. Captured velocity profiles along the flow height show variation in the flow regimes, while utilisation of the definition of the Savage number allows study of the vibration of solids inside a granular body along the sloping channels. These numerical results are compared with field measurements to observe the effect of channel confinement on the solids discharge per unit width of granular flows. This particulate study illustrates that, for unsteady granular flows, solid particles in the front head are more collision dominated, with shear rates and Savage numbers greatly enhanced. Also, the solids discharge inside a granular body is not uniformly distributed. Finally, channel width acts as a confinement to the granular debris flow, which can significantly affect sediment transport.