Influence of submerged sill on the deposition and energy dissipation of granular flow

The large-volume and high-speed channelized granular flows transformed from energetic rockslides and rockfalls are serious geological disasters. The submerged sills embedded in the bedrock and immersed in a granular flow are widely used as a prevention measure in the midstream and downstream of the gullies due to their advantages of high shear resistance, good energy dissipation, and easy cleaning. However, the influence of the geometric characteristics of the submerged sill on the energy dissipation of the granular flow is still not elucidated. Herein, the volume-, velocity-, and runout-reduction effects of the granular flow by the different geometric submerged sill (rectangular, triangular, and cambered) and the geomorphic characteristics of the deposit were studied through physical modeling tests and numerical simulation tests. The results show that: (1) the rank of energy dissipation capacity of submerged sills with different shapes follows the order of cambered > rectangular > triangular; (2) the height of the submerged sill can facilitate the energy dissipation and velocity reduction, especially when the height increases to nearly the depth of the flow; (3) the energy consumption in the interaction process can be attributed to the friction between the particles and sill, the friction between the subsequent mobile particle and stagnant one on the dead zone, and the enhanced collision of the particles during the overflow. The research could provide helpful guidance for disaster prevention and mitigation of channelized granular flow in mountainous areas.