Numerical analysis of dynamic behavior of falling rock block impact against soil-rock mixture by coupling DEM-FDM...

Rockfall, as a common geological hazard, exhibits extremely complex impact dynamic behaviors that are significantly influenced by factors like the impact falling height and the composition of soil layers. To this end, this paper initially establishes a three-dimensional impact model of falling rock based on the DEM-FDM, which takes into account the near-field impact effect. In this model, the near-field DEM of the soil-rock mixture considers the spatial configuration of rock blocks, while the far-field FDM is employed to analyze the mechanical response of impact. On this basis, numerical analyses are conducted on the impact dynamic response of falling rock and the failure mechanism of soil-rock mixture at different falling heights, followed by series of parametric sensitivity analyses. The results indicate that the impact dynamic response of falling rock and the failure degree of soil-rock mixture increase significantly with the falling height, yet the failure mode remains consistent. The increase in particle stiffness reduces the dynamic amplification factor, exacerbating the failure degree of the model along with the energy dissipation through friction and damping. The increase in particle strength elevates the dynamic amplification factor and mitigates the degree of failure of the model as well as energy dissipation through friction and damping. Moreover, there is a threshold effect for the influence of the proportion of rock block on the dynamic behavior of the soil-rock mixture, but the variation of all three parameters exerts no effect on the failure mode resulting from rockfall impact against the soil-rock mixture. These findings contribute to a better understanding and prediction of the impact-collision of rockfall on soil-rock mixture.