Mechanism of earth pressure reduction using tire chips in sand backfill

It is known that the use of compressible material (e.g. tire chips) in the backfill can significantly reduce the load against retaining walls. The reduction of earth pressure is achieved through the mechanism of simulating the quasi-active or the intermediate active state in the backfill. If there exists a highly compressible material between soil and retaining wall, the backfill soil approaches the active state. In this paper, this mechanism has been numerically evaluated. In the numerical simulation, the modified Cam clay model with super-subloading yield surface and rotational hardening concept (SYS Cam Clay model) was used. The SYS Cam Clay model, an elasto-plastic model that takes into the account the soil structure, overconsolidation and anisotropy, can describe the typical response of sand of various densities. Numerical simulations reveal that it is easier to achieve the active state in the sandy backfill due mainly to light weight nature, and low young's modulus and poison's ratio values of tire chips. Also, the reduction effect depends on the density of backfill, which implies that the shear behavior of various densities will be different.