Assessment of EPS-geofoam as light weight backfilling in the construction of underground metro station: a case study

Abstract

Underground metro stations play a crucial role in urban transportation systems, which necessitating the need for effective structural design and maintenance. The use of lightweight materials such as backfill above underground metro station roofs has gained significant attention due to their potential in reducing internal forces on the structure. This study aims to investigate the effect of using geofoam as a backfilling material on reducing the internal forces within underground metro stations elements. EPS Geofoam, a lightweight and cellular plastic material, offers various advantages, such as low density, high compressive strength, and excellent insulating properties. These properties make it a prominent candidate for mitigating the internal forces induced by the applied loads on underground metro station roofs. By replacing traditional backfilling materials with geofoam, the overall weight of the fill above the roof is significantly reduced, leading to a reduction in the applied loads and subsequently minimizing the internal forces experienced by the structure. To assess the effect of geofoam, a comprehensive numerical analysis was conducted by using finite element modeling through PLAXIS2D package software. Various scenarios of loading and stag of construction were considered, simulating different types of live loads. The study encompassed a comparison of internal forces, encompassing bending moments, shear forces, and axial forces, between the conventional backfill and the backfill utilizing EPS geofoam. The primary focus of this research is to emphasize the advantages associated with integrating geofoam as a material for backfilling. In addition to the potential of geofoam in reducing internal forces and optimizing the structural behavior of underground metro stations. The implementation of geofoam-based backfilling can lead to enhance the safety, increase cost-effectiveness, and improve sustainability of underground metro station structures. The results of the study demonstrated that the incorporation of geofoam as a backfilling material above the roof of underground metro stations leads to a substantial reduction in internal forces. The lightweight nature of geofoam significantly decreases the bending moments, shear forces, and axial forces acting on the roof structure, improving its overall performance and extending its service life.