Static and Cyclic Properties of EPS Geofoam

Abstract

This paper presents static and cyclic behavior of geofoam specimens of 100 mm cube and 15 kg/m3 density (D). To understand cyclic behavior of Geofoam, a factor “R”, defined as ratio of combined axial static and cyclic stress component to the yield strength of geofoam, is used in cyclic uniaxial compression (CUC) tests. CUC tests are conducted at three frequencies (f) of 0.5, 1 and 3 Hz, R values of 0.4, 0.6, 0.8, 1 and 1.2, and for 5000 cycles. Static tests on geofoam exhibited a bi-linear axial stress–strain response. From CUC tests, it is noted that effect of number of cycles is insignificant on cyclic modulus, and effect of testing frequency on cyclic modulus is found marginal, for lower values of R. As the value of R increases, the cyclic axial strain increases, which decreases cyclic modulus of geofoam, irrespective loading frequency and number of cycles. Previous studies, while modeling Geofoam behavior, assumed positive values of Poisson’s ratio and linear regression models relating Poisson’s ratio and density of geofoam. In contrary, the present study revealed that Poisson’s ratio of geofoam not only depends on its density, but also strongly influenced by number cycles and axial strain of geofoam, and can also take negative values.