Effects of inclusion of granulated rubber tires on the mechanical behaviour of a compressive sand

Drained triaxial shearing tests were performed on a well-graded compressive sand (completely decomposed granite, CDG) and its mixtures with granulated rubber tires to investigate the effects of rubber size and content on their mechanical behaviour. Three sizes of rubber particles, GR1, GR2, and GR3, were used with size ratios to CDG ([D.sub.50,rubber]: [D.sub.50,CDG]) of 0.9, 3.5, and 7.2, respectively, and the rubber content ranged from 0% to 30%. The results show that for CDG-GR1 mixtures, the strength decreases with increasing rubber content, while for CDG-GR2 and CDG-GR3 mixtures, the strength decreases only at 10% rubber content and then increases markedly with increasing rubber content. The increase of strength is mainly because the inclusion of large rubber particles widens the particle size distributions of the mixtures, resulting in denser packings. The denser packings also lead to a decrease in compressibility. At larger size ratio and higher rubber content, the CDG-rubber mixtures show higher shear strength and lower compressibility than pure CDG, which indicates the CDG-rubber mixtures are very suitable to be used as filling materials.