Influence of debris flow solid fraction on rigid barrier impact

The dynamics of debris flows are fundamentally governed by the interaction between the solid and fluid phases. However, current approaches used to estimate impact load treat debris flow as an equivalent fluid without considering solid-fluid interaction separately from other factors. In this study, a series of centrifuge tests was carried out to investigate the influence of interaction between solid and fluid phases on single-surge debris flow impact on a rigid barrier. The effect of solid-fluid interaction was studied by varying the solid fraction of the flows. A model rigid barrier was instrumented to capture induced bending moment and impact pressure. Test results demonstrate that the transition from a pile-up mechanism to a run-up mechanism is governed by the solid fraction and thus the grain contact stresses. The rigid barrier design for the impact with a pile-up mechanism is mainly dominated by the static load. Contrary to the hydrodynamic approach, which assumes that the frontal impact is the most critical, the frontal impact of a run-up mechanism contributes less than 25% of the total force impulse. The consideration of static loading leads to the development of a new impact model with a triangular distribution of the impact pressure.