Dynamic shear modulus and damping of expanded polystyrene composite soils at low strains

Expanded polystyrene composite soil (EPSCS) has been used extensively in various engineering applications. However, the dynamic characteristics of EPSCS are not well understood. In order to understand the dynamic performance of EPSCS, a series of unconfined compression and resonant column tests were carried out to investigate its stiffness and damping characteristics at low strains, with particular focus on the role of expanded polystyrene (EPS) bead content, cement content and confining pressures. First, the unconfined compressive strength (q_ucs) was quantified using replicate specimens to form a basis for quantifying its static strength and correlation to dynamic properties. Then, the dynamic shear modulus and damping ratio for EPSCS were quantified. It is found that the effects of EPS bead and cement content on q_ucs and initial shear modulus (G₀) are similar. The q_ucs or G₀ of EPSCS increases approximately linearly with the increasing cement content or confining pressure, whereas it decreases with EPS bead content. Empirical models were proposed to predict G₀ using the more readily determined q_ucs. Models used to describe the degradation in normalized shear modulus and damping ratio were calibrated for EPSCS at low strains considering EPS bead content, cement content and confining pressure.