Stress-strain responses of EPS geofoam upon cyclic simple shearing: Experimental investigations and constitutive modeling

Abstract

This paper investigates the cyclic simple shearing behaviors of Expanded Polystyrene (EPS) geofoams considering influences of the shear strain amplitude (γa), number of shear cycles, shear rate, vertical stress (σn), and EPS density (ρEPS). The experimental results demonstrate that the cyclic shear stress (τ)-shear strain (γ) relationships of EPS are not sensitive to the shear rate. As the γ exceeds 2%, the EPS yields and its τ-γ relationships and backbone curve become nonlinear. There are linear relationships between the elastic modulus E, elastic shear modulus Ge, and plastic shear modulus Gp. They increase linearly with an increase in the ρEPS. The Ge and Gp are not sensitive to the γa. The cyclic shear stiffness G increases while the equivalent damping ratio D of EPS decreases with an increase in the σn and ρEPS. The G decreases while the D increases nonlinearly as the γa increases. Empirical models were developed to describe the variations of the Ge, Gp, G, and D with σn, ρEPS, and γa. A modified Hardin-Drnevich model was proposed to describe the backbone curves and τ-γ loops upon cyclic simple shearing, which has achieved good agreement with the experimental measurements and the testing results from the literature.