On the Time-Dependent Behavior of EPS Geofoam: Experimental and Numerical Investigations

Expanded polystyrene geofoam (EPS) is used as a lightweight fill material in a wide range of geotechnical engineering applications, including, embankments, retaining walls, and buried structures. Under high compressive loads, EPS may experience long-term compression that needs to be taken into consideration during design. This study presents the results of an experimental investigation that has been conducted to evaluate the creep response of two different EPS geofoam materials (EPS15 and EPS22) under uniaxial compression loading. Four identical setups have been designed and built to allow for multiple geofoam samples to be simultaneously tested under different applied pressures. The effect of stress level on the creep strain is investigated. Results showed that, for the two investigated EPS materials, creep strains started to develop when the applied pressure exceeded 50% of the uniaxial compressive strength of the material and became significant at applied pressure of about 70% of the material strength. A three-dimensional numerical model that is capable of capturing the creep response of soft soils is adapted and calibrated using the available experimental data. The suitability of the model to investigate the effect of lateral confinement on the creep deformation of the geofoam samples is also examined. It is concluded that, although soft soil creep models are able to capture the uniaxial creep response of geofoam, it is not suitable to model the effect of lateral confinement, particularly for low density EPS material.