Effect of the Rolling Friction on the Heap Formation of Dry and Wet Coarse Discs

We performed 2D numerical simulations to study the dynamic heap formation of coarse particles in different dry and wet conditions. Our results show that the dynamics of the particles depend not only on the amount of liquid contained in the bulk, but also on the initial particles packing, i.e., the arrangement of the grains. The wet particles cohesion model effect on coarse discs heap formation is minimal. This effect is mostly noticed in the particle arrangement and the energy variation rather than the heap formation. We found that the energy of the system varies with the liquid content up to a threshold value, equal to 219% in our study, where the influences of the parameters are minimal. At high liquid volume, the final pile height and radius tend towards an asymptotic value. The initial particles arrangement has a significant impact on the behavior of the bulk after the opening of the lateral walls. The number of particles in the triangle, formed by the initial width of the packing as a base and with a depth equal to N x D, with N representing the number of particles on a vertical line and D their diameter, influences the final shape of the pile. Indeed, the larger the number, the smaller the height of the pile. The simulations performed with the same initial packing show that the cohesion and capillary forces reduce the bulk kinetic energy and increase the potential energy when used with the elastic-plastic spring dashpot model. For the directional constant model, the dependance of the torque on the normal force and the particle size explains that there is almost no difference between the dry and wet model regarding energies. Finally, the elastic-plastic spring-dashpot model is more efficient in reducing the kinetic energy of the system and producing stable piles. Our simulation results using glass beads are in good agreement with the experiments.