Effects of EPS bead inclusions on stress–strain behaviour of sand

ABSTRACT: Lightweight fill solutions have been used in many civil engineering projects throughout the world. At locations with poor soil conditions, alternative lightweight construction fill materials such as expanded polystyrene (EPS) geofoam, wood chips, and tyre wastes may be used instead of conventional fill materials. These materials are used as an additive for the soil. It is known that the type, aspect ratio and content of the admixtures have an important role in the mechanical properties of the mixtures. The main objective of this study was to assess the feasibility of the potential use of EPS beads in geotechnical applications. The effect of EPS bead gradation on the stress–strain behaviour of lightweight composite materials composed of EPS bead–sand mixtures (EPS–sand) was investigated through a series of triaxial compression tests under three different confining pressures. Three different types of spherical EPS beads with different unit weights (EPS-1, EPS-2, and EPS-3) were mixed with sand with varying EPS bead content. This study has shown that the deviatoric stress of a EPS–sand mixture is not only a function of volumetric EPS bead content but it also depends on EPS bead grain size distribution (EPS bead type). Whereas volumetric EPS bead content increases when all other variables are constant (EPS bead type in EPS–sand), the initial modulus of elasticity decreases linearly. Consequently, EPS bead inclusion did not enhance the maximum deviatoric stress of EPS–sand when compared with that of the sand-only specimen. However, bead addition provides a lightweight aspect to the mixture which can be attractive to use in many geotechnical engineering projects. EPS bead content, confining pressure and EPS bead type-dependent multiple linear regression (MLR) equations were proposed to estimate the initial undrained elastic modulus of EPS–sand to reduce the cost and time involved in conventional laboratory testing of EPS–sand mixtures. Based on the stress–strain behaviour of EPS–sand, these mixtures may be utilised in geotechnical applications as a lightweight fill material.