Numerical investigation of the mechanism of granular flow impact on rigid control structures

Abstract

Baffles and check-dam systems are often used as granular flow (rock avalanches, debris flows, etc.) control structures in regions prone to dangerous geological hazards leading to massive landslides. This paper explores the use of numerical modelling to simulate large volume granular flow and the effect of the presence of baffles and check dam systems on granular flow. In particular, the paper offers a solution based on the smoothed particle hydrodynamics numerical method, combined with a modified Bingham model with Mohr–Coulomb yield stress for granular flows. This method is parallelised at a large scale to perform high-resolution simulations of sand flowing down an inclined flume, obstructed by rigid control structures. We found that to maximise the flow deceleration ability of baffle arrays, the design of baffle height ought to reach a minimum critical value, which can be quantified from the flow depth without baffles (e.g. 2.7 times for frictional flows with friction angle of 27.5°). Also, the check-dam system was found to minimise run-out distances more effectively but experiences substantially higher forces compared to baffles. Finally, flow-control structures that resulted in lower run-out distances were associated with lower total energy dissipation, but faster kinetic energy dissipation in the granular flows; as well as lower downstream peak flow rates.