Effect of the platy shape of the particles

M Boton, E Azéma, N Estrada, F Radjaï and A Lizcano

This is the first paper of a series devoted to the study of clayey soils from a micromechanical perspective. We specifically focus on the effect of the platy shape of particles, typical of clays, in the mechanical behavior and microstructure of dry assemblies by means of discrete element simulations. The particles are three-dimensional square plates, approximated as spheropolyhedra. Several samples composed of particles of different levels of platyness (ratio of length to thickness) were numerically prepared and sheared up to large deformations. We analyzed the shear strength, solid fraction, orientation of the particles, connectivity, fabric of the interactions network, and interaction forces as functions of the particles' platyness. We found that both the mechanical behavior and the microstructure were strongly dependent on the particles' platyness. In particular, we found that the principal phenomenon underlying these dependences is the alignment of the particles' faces along a particular direction. This ordering phenomenon, which emerges even for shapes that deviate only slightly from that of a sphere, enhances the ability of the packing to develop an anisotropic structure, developing large shear strengths, especially as a consequence of the interactions fabric and the mobilization of friction forces. Additionally, the connectivity of the packings and their solid fraction also evolve with the particles' platyness. In particular, the solid fraction evolves in a non-monotonic fashion, as is usual for granular materials made up of non spherical particles.