Abstract: In recent years, lightweight soil composed of scrap tire crumbs and plain soil is applied as the backfill soil for geotechnical structures, subgrades and retaining walls, lawn engineering and other fields. The shear strength and deformation characteristics of rubber-clay mixtures were investigated with ShearTrac-Ⅱ apparatus, with varying shear rate, consolidation pressure and tire crumbs content into account. Moreover, the consolidation characteristics of mixtures were analyzed via one-dimensional consolidation test. Test results indicated that the shear strength of mixtures can be improved by increasing rubber content and consolidation pressure. However, increasing the shear rate would result in the deterioration of shear strength, the larger the shear rate, the lower the consolidation pressure, the more likely of shear dilatancy. As the shearing proceeds, the shear strength of rubber-clay mixture reached peak, displaying strain softening feature, and then declined until reaching a stable residual strength. Compared with those of clay, the peak strength and residual strength of rubber-clay mixture improved by 20% and 10%, respectively; residual internal friction angle reduced by 10% compared with peak internal friction angle; and residual cohesion by 60%. The cumulative shear displacement which is required for reaching residual strength augmented gradually with the increasing of rubber content. In addition, under the same vertical pressure, the consolidation time of rubber-clay mixture shortens by four times compared with that of clay.

Key words: scrap tire crumbs, content of tire crumb, clay, shear strength, coefficient of consolidation