The traffic loading caused deformation of sand-rubber filler

Incorporating rubber into sand as a subgrade filler not only helps to effectively utilize waste materials but also mitigates the environmental hazards associated with rubber disposal. During the service period, the rubber-sand filler is subjected to long-term traffic loading with a heart-shaped stress path, leading to subgrade settling. Drained monotonic and heart-shaped cyclic torsional shear tests were conducted on a rubber-sand mixture. The strength and dilatancy of the mixture were investigated under varying rubber contents. The influence of the torsional stress component and rubber content on the long-term deformation, including strain accumulation, shakedown behaviour and resilient modulus, was examined and discussed under different cyclic stress conditions. The test results indicate that the cyclic torsional stress component of traffic loading significantly enlarges the deformation of the rubber-sand mixture. The reduction in strength as the proportion of rubber rises is the primary explanation affecting the overall vertical deformation experienced by the mixture. A method was proposed to determine the limit cyclic stress ratio (CSR) for plastic creep of the mixture under traffic loading, based on the distinct bilinear relationship between CSR and dissipated energy. As the minimum void ratio of the mixture declines with increasing rubber content, volumetric strain accumulation escalates correspondingly under similar cyclic stress conditions. The resilient modulus of the mixture does not vary significantly with cyclic stress but exhibits a notable decrease with rubber content, with this effect being more pronounced at lower RC levels.