Contact-scale insights into the shear stiffness of non-spherical granular materials

Small-strain shear stiffness (G 0 ) is an essential parameter to predict deformation characteristics and dynamic properties of granular materials. It is empirically known that G 0 increases with decreasing a void ratio (e 0 ) and increasing isotropic stress level (p0′). Recently, the effect of particle shape on G 0 has been studied; however, the mechanism underlying the evolution of G 0 is not fully understood. Using the discrete element method (DEM), this contribution quantifies the G 0 of granular materials by performing small-strain probing where multi-sphere clumped particles are used to vary particle shape and surface topology systematically. The Hertzian contact theory is applied for each sphere-element contact to capture the stress-dependent contact stiffness. The results reveal that G 0 is well correlated with e 0 or mean coordination number for a given particle shape; however, G 0 is measurably reduced when finer sphere-elements dominate inter-particle contact responses. The present study proposes two contact-scale expressions of G 0 for non-spherical particles based on contact area (CA) and micromechanical effective medium theory (EMT) by extending the EMT expression for spherical particles; both can capture the effects of particle shape and p0′ on G 0 under given conditions where particle breakage does not occur.