Performance of debris flow barriers: an energy perspective

Barrier systems are widely applied to impede or retain debris flows. Due to complex flow characteristics and the lack of accurate measurements, the performance of different types of debris flow barriers is difficult to quantify. In this study, a coupled DEM-ALE-FEM method is employed to offer an insight into energy dissipation mechanisms in flow-barrier interactions. Two energy criteria are proposed to evaluate the energy dissipation efficiencies and impact forces of three common types of barriers (rigid barriers, baffles and flexible barriers). The simulation results reveal that a large channel slope or a high solid concentration of debris flow enhances the energy transfer process for all barrier types. The overflow effect is a key factor for barrier type selection. Under significant overflow conditions, the baffle structure outperforms the other two barrier types in terms of both energy transfer and dissipation efficiency. The efficiency of a rigid barrier is sensitive to the barrier height, which is determined by the runup height. The rigid barrier performs better with the increase in barrier height. The flexible net barrier with a smaller net opening than the solid particle size is a good option that balances energy dissipation efficiency and construction cost, especially for flows of high solid concentrations. The rigid barrier outperforms the other two barrier types for debris flows of low solid concentrations. The in-depth study of the barrier energy dissipation efficiency as carried out here facilitates the selection and design of barriers in mitigating debris flow hazards.