Expanded polystyrene inclusion behind yielding wall: numerical study and cost analysis

The standard Expanded Polystyrene (EPS) effectiveness as compressible inclusion behind rigid non-yielding walls is verified by previous studies, but limited literature addresses its performance with rigid yielding walls, such as a cantilever retaining wall. The present study uses numerical modeling to examine the behavior of the yielding wall-inclusion system. The effects of inclusion thickness, density, placement height, and wall height are investigated. Among these, the EPS thickness is a governing parameter in the pressure reduction. The study further examines the mechanism of pressure reduction, and it is observed that major pressure reduction occurs at the bottom one-third of the wall. A cost analysis correlating the efficiency and cost of inclusion is presented, providing guidelines for practitioners to select inclusion thickness and estimate the associated costs to achieve a desired reduction in lateral pressure. Additionally, the cost analysis reveals that although the standard EPS reduces lateral pressure, it can cost up to 7% of the project cost, which is substantial. Alternatively, the use of elasticized EPS instead of standard EPS as an inclusion can reduce the thickness of the inclusion by 9% to 38% compared to standard EPS without compromising the inclusion efficiency, making it a more economical and effective solution.