Impact Dynamics of Flow-type Landslides on V-shaped Diversions: Combined Numerical and Experimental Approach

In sparsely populated and rural areas, government agencies propose the installation of V-shaped diversions to mitigate flow-type landslides. In contrast to rigid barriers, diversions are small, easy-to-construct, and cost-effective. Nonetheless, the impact dynamics of flow-type landslides against diversion structures remains unclear and hinders the development of scientific-based design guidelines. Diversion angles that are too large decelerates the flow and causes an overspill. In contrast, diversion angles that are too small results in long walls that are not feasible to construct. In this study, laboratory-scale flume experiments modelling the impact of dry sand against diversions are conducted. The diversion angles are changed from 15 to 60 degrees. The experimental data is used to calibrate a coupled Material Point Method (MPM) and Discrete Element Method (DEM) numerical model to back-analyze the experimental data. The numerical model is used to conduct a parametric study to investigate the effects of post-impact flow Froude numbers. It is proposed to design V-shaped diversions based on bow and oblique shock mechanisms. Design charts that consider the competing effects between deflected and accumulated debris are proposed. The newly proposed analytical model for predicting the deflection height to mitigate overspill shows close agreement with experimental results.