Effect of rubber-sand particle size ratio on shear properties of rubber-sand mixtures under normal cyclic loading

Abstract

The mechanical properties of rubber-sand mixtures are influenced by the ratio of rubber-sand particle sizes and the rubber content. Rubber-sand mixtures used as roadbed fillers are primarily subjected to normal cyclic traffic loading. Therefore, a series of direct shear tests on rubber-sand mixtures under normal cyclic loading were conducted using a large-scale direct shear apparatus. The effects of the rubber-sand particle size ratio, rubber content, initial stress, and amplitude of normal cyclic loading on the shear strength of rubber-sand mixtures were evaluated. Based on the indoor tests, discrete element models of rubber-sand mixtures with different particle size ratios were established to explore the meso-mechanical mechanism of the mixed soil during the direct shear process. The results indicate that rubber-sand mixtures with low rubber content and a particle size ratio >1 have a positive effect on the shear strength of the mixed soil. The impact of initial stress on the shear stress of the mixed soil is greater than that of the normal cyclic load amplitude. As the particle size ratio increases, the inter-particle contact force becomes larger, resulting in more noticeable group anisotropy. Additionally, the main direction of the normal contact force anisotropy in the mixture consistently aligns with the deflection direction of the force chain. Rubber particles in rubber-sand mixtures with a large particle size ratio actively participate in the contact force chain network system, facilitating load transfer and positively influencing shear strength.