Abstract: As a novel and inexpensive material, rubber-sand mixture is commonly utilized as filler in road base and retaining wall. However, limited research has been conducted on its dynamic mechanical properties under bi-directional cyclic loading. A series of direct shear tests was conducted on rubber-sand mixture with different rubber-sand particle size ratios using a large dynamic direct shear instrument to investigate the effects of particle size ratio, normal cyclic load amplitude and horizontal shear load frequency on the shear properties of rubber-sand mixture. The findings indicate that the cyclic peak shear stress of rubber-sand mixture under normal cyclic loading increases with increasing particle size ratio, while the final shear shrinkage decreases with a higher particle size ratio. In terms of shear stress, rubber-sand mixture with large particle size ratio exhibit greater sensitivity to the change of normal cyclic loading amplitude compared to those with small particle size ratio. Moreover, the shear swelling of rubber-sand mixture with large particle size ratio becomes more pronounced with increasing normal cyclic loading amplitude. Additionally, at different horizontal shear frequencies, the shear stress of the specimens display different forms of cyclic changes over shear time, with the maximum cyclic shear stress decreasing as horizontal shear frequency increases. The shear stiffness and damping ratio of the rubber-sand mixture are positively correlated with the particle size ratio, indicating that the rubber-sand mixture with a higher particle size ratio is more capable of improving the stability of roadbed under cyclic loading.

Key words: rubber-sand mixture, cyclic direct shear test, damping ratio, shear stiffness