A comprehensive numerical investigation of multi-scale particle shape effects on small-strain stiffness of sands

The effects of multi-scale particle shape characteristics on the small-strain stiffness of granular soils remain controversial. This study revisits this topic using well-calibrated three-dimensional discrete-element simulations incorporating a particle roughness–embedded contact model and particles of realistic shape. Based on the numerical simulation results, the multi-scale particle shape effects on the small-strain stiffness of sands and the magnitude of Hardin's equation parameters are systematically investigated, and the underlying micro-mechanisms are also thoroughly explored. Results indicate that the small-strain stiffness increases with the increase of particles’ overall irregularity due to the increased mechanical coordination number, but decreases with the increase of particle surface roughness because of the decreased contact normal stiffness. In addition, the constant term parameter and void ratio term parameter of Hardin's equation increases and decreases linearly, respectively, with the particles’ overall regularity, but reduces and grows with the particle surface roughness, respectively. Furthermore, the stress exponent is almost unchanged with the particles’ overall regularity, but increases with the particle surface roughness, which determines the relative proportions of contacts under asperity-dominated, transitional and Hertzian stages. The study helps to advance the cross-scale understanding of multi-scale particle shape information in relation to small-strain stiffness of sands.