Inclined Block Impacts on Granular Strata: Coupled DEM-FDM Numerical Investigation and Rheological Modelling

In mountain regions, rockfall is a very widespread natural hazard, difficult to be numerically simulated, from the initial detachment of the block to its impact on natural/artificial strata. When a rock block impacts on a granular stratum, the interaction is dominated by inertial effects and is severely affected by block mass, shape, velocity magnitude/direction, and soil geomechanical properties. The kinematic description of the response of the block during the impact requires complex and time-consuming numerical modeling approaches. Moreover, these numerical approaches cannot be easily coupled with classical mass-lumped rockfall analysis tools employed to simulate blocks trajectory. To overcome this problem, a dynamic upscaled visco-plastic rheological model (BIMPAM), suitable for simulating inclined impacts on generally inclined deformable strata, has been conceived in the past by one of the authors. Up to now, due to the absence of suitable numerical and experimental data, BIMPAM has been only validated on experimental large-scale vertical impacts on horizontal strata. In this paper, the impact problem is analyzed, by performing numerical analyses by means of a coupled Discrete Element and Finite Difference numerical model (DEM-FDM), calibrated on available experimental data, to provide (i) a novel numerical dataset highlighting the crucial role played by the impacting velocity inclination on the dynamic interaction between soil stratum and penetrating rigid object and (ii) a detailed micromechanical description identifying the processes responsible for the complex macroscopic behavior. The obtained numerical results have allowed to both validate BIMPAM model, even in case of inclined velocities, and provide a micromechanical interpretation of its constitutive assumptions.

Automated summary

Rockfall, a common natural hazard in mountain regions, is difficult to simulate numerically due to the complex interaction between rock blocks and soil strata. In this study, a dynamic upscaled visco-plastic rheological model (BIMPAM) was validated using numerical analyses based on experimental data. The results highlighted the importance of impacting velocity inclination on the dynamic interaction and provided a detailed micromechanical description.