Experimental Investigation of the Reduction of Lateral Pressures on Retaining Walls Using Expanded Polystyrene Granules

Expanded Polystyrene (EPS) is commonly used in construction, especially in geotechnical projects, due to its super lightweight and high compressibility. One of the applications of this material is to use it behind the retaining walls to reduce the lateral earth pressures exerted on the wall by the embankment. In this research, two types of EPS in the form of granules and sheets of EPS are used as interface between the embankment and the wall. In order to carry out this research, an instrumented laboratory model of retaining wall has been used and the effect of using these materials as buffer behind retaining wall has been investigated. The assembly includes a 105 28.5 70 cm sand box, a retaining wall model with 28.3 54.2 cm front dimension, a wall-displacement system for driving the wall, and a data acquisition system (data logger). The lateral pressures are measured by eight load cells attached to 8 equally spaced wall sections. The approximate relative density of the backfill sand was 70%. Experiments included cases in which a sheet of EPS-block or stack of small bags filled with granular EPS was used as a buffer between soil and wall. The results of these two cases were compared with the case in which the backfill was the sand alone. After measuring the lateral forces in the at-rest state, the active and passive states were created by displacing the wall away or toward the backfill. The lateral stresses could be measured in any state of displacement. The results showed that the use of EPS behind the retaining wall as an interface material resulted in a significant reduction in lateral pressures. This was due to the very low stiffness of EPS compared to the soil. It was also observed that the use of bags filled with EPS-granules had a greater effect on the reduction of lateral pressures on the retaining wall compared to using sheets of EPS-block.