Dry Granular Flows Impacts on Rigid Obstacles: DEM Evaluation of a Design Formula for the Impact Force

In the design of sheltering structures or embankments for the mitigation of the risk due to rapid and long spreading landslides, a crucial role is played by the evaluation of the impact force exerted by the flowing mass on the artificial obstacle. This paper is focused on this issue and in particular on the evaluation of the maximum impact force on the basis of the results obtained by performing an extensive numerical campaign by means of a 3D discrete element code (PFC3D), in which a dry granular mass is represented as a random distribution of rigid spherical particles. The analyses regard the impact process only, while triggering and the propagation phase of the flow are not considered. For this reason, in the model the granular mass is generated just in front of the obstacle; its initial volume, velocity distribution, height, length and porosity are assigned as initial conditions. The initial conditions are varied to take into consideration a large variety of geometrical/mechanical factors, such as the initial front inclination, its height, the initial void ratio, the length of the impacting mass and the inter-particle friction angle. A design formula is also proposed on the base of the obtained results and critically compared with the literature data and previous formulations based on hydrodynamic models.