Coarse-fine mixtures subjected to repetitive Ko loading: Effects of fines fraction, particle shape, and size ratio

This study explores the effects of fines fraction, particle shape, and size ratio on the long-term response of sand-silt mixtures with fines fraction FF = 0-to-100% during Ko-loading cycles i = 104. The void ratio for all specimens evolves toward the asymptotic terminal void ratio eT that captures the transition from coarse-to-fine controlled behavior. Shear wave velocity versus intergranular eC and equivalent intergranular (eC)eq void ratios estimates the participation rate of fines-in-sand for the force chain. More fine particles contribute to the load-carrying skeleton as the particle shape becomes rounder and the size ratio decreases. In contrast, shear wave velocity against interfine eF and equivalent interfine (eF)eq void ratios reflects the reinforcing effect of coarse grains floating in the load-carrying fines matrix. The rounder sand in the fine-dominant matrix leads to more significant fabric changes. Clearly, there is a transition from coarse-to-fine controlled repetitive load-deformation response that promotes the reassessment of current soil classification systems.