The effects of particle size and surface roughness on the small-strain shear modulus of sands

Inconsistent experimental findings in the literature regarding the influence of particle size on small-strain shear modulus (Gmax) highlight the need for deeper mechanical insights. A series of resonant column tests was conducted on glass beads and silica sands to investigate the effects of particle size on Gmax considering various particle surface roughness. Results indicate that Gmax decreases with increasing particle surface roughness (Sq) and decreasing mean particle size (d50) under otherwise similar conditions. There is a unified correlation between Gmax and Sq/d50 when the effects of gradation and particle shape are properly considered, showing that Gmax initially decreases with increasing Sq/d50, but then stabilises for a given confining pressure and void ratio. This study further confirmed the combined effects of particle size and surface roughness on Gmax through a semi-analytical analysis. These results suggest that the inconsistent findings regarding the effects of particle size on Gmax may be related to the neglect of particle surface roughness.