Impact dynamics of debris flow with entrained material on frame structure

To evaluate the dynamic interactions between debris flows, entrained material sources, and infrastructure in the Naojiao Gully watershed of Beijing, and to develop a predictive framework for mitigating geohazard risks through energy-based strategies, debris flow dynamics are investigated, a coupled SPH-DEM-FEM multiscale model integrating fluid dynamics (SPH), granular mechanics (DEM), and structural mechanics (FEM) is developed to simulate debris flow propagation, material source behavior, and frame structure responses, and to capture cross-scale failure mechanisms. Key findings include the identification of a critical flow velocity threshold of 12 m/s, beyond which solid-phase kinetic energy dominates, inducing 60%-75% capacity loss in central columns via through-cracking. Furthermore, a novel compound failure criterion is proposed based on the solid-liquid energy proportion. The model achieves a boulder impact force prediction error of only 5.47%, significantly outperforming empirical methods in cross-scale accuracy. An optimized 0.3 m layered configuration experimentally reduces impact pulse peaks by 57% through directed energy redistribution, thereby shifting mitigation strategies from structural reinforcement to media modulation. These results establish a robust framework for quantifying failure thresholds, enhancing predictive precision, and innovating energy-based mitigation. By bridging multiscale modeling gaps in geohazard analysis, this study provides actionable insights for infrastructure resilience in debris flow-prone regions through energy-centric design principles.