Numerical simulation of debris-flow impact on multiple check dams using the material point method

It is essential to capture the transient impact forces of debris flows on check dam barriers for accurate hazard mitigation and structural design, yet traditional depth-averaged or mesh-based numerical approaches often fail to resolve the complicated local flow–structure interaction subject to large deformation. This study employs the material point method (MPM) to simulate the impact-force evolution during a well-documented disaster—the 2010 Wenjia Gully debris flow—and investigates its interaction with a series of check dams. The MPM framework naturally handles the extreme deformation, contact between different materials, and multiphase mixing without mesh distortion. Validation against flume experiments and field measurements confirms its predictive accuracy for both the runout distance and impact loading. Results reveal a staged force attenuation mechanism—where upstream dams dissipate momentum and reduce downstream peak loads—and an intermittent load recovery phase due to flow front re-acceleration between dams. Parametric analyses highlight that the internal friction angle predominantly controls runout extent, while cohesion and density nonlinearly influence the impact magnitude. The study elucidates underlying physical mechanisms in the interaction between debris flows and barriers and demonstrates the unique suitability of the MPM in resolving localized, time-dependent impact phenomena. The findings provide insight into the optimization of the multi-dam configuration and enhance understanding of flow–structure coupling in debris-laden geophysical flows.