Impact effects of debris avalanches based on centrifuge modeling and DEM simulation

The complexity of the material composition of debris avalanches results in the impact effects on engineering structures not being completely understood. In particular, how the particle size and distribution characteristics affect the impact force and its composition and how to consider the influences of characteristics of particle size in the design of barrier structures still lack in-depth researches. To answer these questions, a series of centrifuge modeling tests and DEM simulation tests are conducted. The results indicate that the particle size dominates the fluctuation behaviors of the impact force of the debris avalanche, and with the increasing particle size, the peaks become increasingly obvious, accompanied by a significant discrete impact force. The smaller particles show an obvious cushion-effect to larger particles, and they more easily enter into the void formed by larger particles and interact with the barrier, thus contributing to the total impact force. Therefore, both the particle size and the distribution characteristics control the absolute value of the impact force. The particle characteristics determine the momentum transfer mechanism at the particle scale and thus the impact effects. For this reason, it is found that the dynamic impact pressure coefficient$\alpha$shows an increasing trend with the increasing Savage number of debris avalanches. Thus, it is suggested that the Froude number and Savage number should be jointly used to select appropriate$\alpha$. In addition, based on the analysis of the acting point of the resultant impact force, we suggest that in engineering design, the total impact force combined with the rectangular distribution mode can be adopted for safety.