Modeling the behavior of a hybrid interactive system involving soil, structure and EPS geofoam

In recent years, EPS (Expanded Polystyrene) geofoam is gaining worldwide recognition in the construction industry either as lightweight substitution or as compressible inclusion, in reducing the earth pressures against retaining structures. When EPS geofoam is used behind a structure, the structure interacts with the soil via the EPS blocks giving birth to a hybrid interactive system. In this paper, a numerical model is described for the analysis of such a soil-geofoam-structure interaction system. The development of the model focused mainly on the material constitutive law and the interface modeling. Recognizing the fact that there is always a thin layer of interface that participates in the interaction process, a hybrid type interface model was developed. The interface was assumed to be elasto-plastic in its behavior. A constitutive law of geofoam was formulated using an elasto-plastic hardening law. The soil backfill was modeled assuming it as the elasto-plastic hardening and softening material. The developed model was validated through a numerical experiment on a rigid retaining structure. The model offers an improved performance of the normal and shear deformation at the interfaces, which in turn results in a better prediction of the reduced pressure on a retaining structure.