From Static Response to Impact Loading in Soils: a Discrete Element Method Analysis

The design of protective structures against impacts loading, such as rockfall impacts, is a difficult task since their efficiency is not automatically related to their integrity. For high energy impacts, these structures often include a soil layer which is used to dissipate the kinetic energy of the impacting block. Studying the behavior of the soil material is of first importance to understand the response of the entire construction subjected to an impact loading. Given the mechanical properties of a typical soil layer, a discrete element model has been used to reproduce both its quasi-static and its dynamic behaviors. For the quasi-static behavior, simulations of tri-axial tests have been carried out to identify the local mechanical parameter contributions to reproduce and predict the strength, the deformation and the peak dilatancy, as well as residual strength for large deformations. The numerical model has then been used to simulate impact loadings due to a massive boulder falling on a soil medium. It was observed that the local constitutive law of the model had to be updated in order to take into account non linear viscosity and unloading irreversibility. The numerical model was subsequently capable of predicting the penetration depth recorded during experiments for energies ranging from 1 000 to 10 000 kJ.