Experimental validation of a discrete impact model of the rebound of a boulder on a coarse granular soil

International audienceThe impact of a block on a coarse granular soil corresponding to rockfall events is investigated using the Discrete Element Method (DEM). The soil is considered as a noncohesive granular medium and the DEM impact model is calibrated compared to results from half-scale experiments. The effects of scale changes are also explored by comparing real-scale simulations using the DEM impact model and the half-scale experimental results. This comparison shows that using simple similitude criteria limits scale changes effects. Finally, the DEM model is used to perform a numerical analysis of the bouncing phenomenon. Different impacting particle and medium characteristics are considered. An impacting particle bouncing occurrence diagram is defined for various impacting particle radius Rb*/Rm, sample heights H*/Rm, and incident kinematic parameters. The bouncing occurrence diagram brings out three impact regimes. For a small impacting particle (Rb*/Rm < Rcrit*/Rm), the impact is mainly determined by the first interaction between the impacting particle and the soil, whereas for an intermediate-sized impacting particle (Rcrit*/Rm ≤ Rb*/Rm < Rmin*/Rm), the compression wave propagation through the sample is the leading phenomenon. For large impacting particles (Rb*/Rm ≥ Rmin*/Rm), bouncing is associated with the formation of a compact layer below the impacting particle