Dissipative effects of baffles on the dynamics of debris flow and its impact on downstream structure

Debris flows triggered by heavy rainfall constitute a mixture of slurry and earthen aggregates. These flows travel downhill at a high speed, causing significant damage to downstream facilities. Baffles are among the common protective structures installed along debris flow paths to decelerate the flows, impeding their impact on downstream structures. Previous research mainly focused on the interactions between baffle systems and debris flows, while the flow impact responses, especially on downstream structures, were rarely examined. Based on a coupled VOF-DEM method, this study investigates the impeding effects of baffles on the dynamics of debris mixture flows and their impact on a downstream barrier. We found that baffles are more effective in decelerating the flows with low Froude numbers generally occurring on gentle slopes. However, debris flow with high Froude numbers run up and overflow through baffle arrays, reducing interactions between baffles and the flows. Increasing the number of baffle rows in a baffle system can further decelerate the flows, thereby transitioning flow run-up to stable pipe-up at the downstream barrier, reducing dynamic impact force on the barrier. Remarkably, regardless of flow inertial conditions, baffle systems with more baffle rows and shorter baffles alleviate the flow impact on the downstream barrier better than those with fewer rows and higher baffles. This finding provides a reference for baffle designers to prioritise baffle systems with more rows rather than higher baffles.