Measuring and Modeling Proportion-Dependent Stress-Strain Behavior of EPS-Sand Mixture

A geofoam was produced by blending expanded polystyrene (EPS) beads and sands in proportions. The formed mixtures, known as EPS-sands, were 26–63% lighter than general earth fills (e.g., sand). Consolidated-drained (CD) triaxial compression tests were conducted on EPS-sand mixture specimens to observe their stress-strain characteristics, specifically, the stress-strain responses in relation to the EPS contents (0.5, 1.5, and 2.5% by weight) used in the mixtures and confining pressures (100, 200, 300 to 400 kPa) loaded on the specimens. The EPS content and confining pressure were found to influence the stress-strain and volumetric strain behavior of the mixtures. Increasing EPS content led to decreased shear strength and increased volumetric strain. Increasing confining pressures enhanced the strength of the mixture. EPS-sand mixtures underwent a shear contraction throughout the CD tests. The optimum EPS bead content (i.e., the one reasonably balancing the unit weight, strength, and deformation) was in the order of 0.5% by weight. EPS content dependent strain increment equations were derived by compromising Cam-clay and modified Cam-clay, and used to model the stress-strain characteristics of EPS-sand mixtures. The established equations were verified being able to depict the stress-strain observations of EPS-sand specimens, at least for the ranges of EPS contents and confinements considered in this study.