Dynamic properties of EPS-sand mixtures using cyclic triaxial and bender element tests

In this study, a series of strain-controlled cyclic triaxial as well as bender element tests are carried out, so that the dynamic properties of mixtures of sand and expanded polystyrene (EPS) beads can be assessed under large and small-scale shear strains, respectively. The effect of various parameters such as shear strain amplitude, confining pressure (25 kPa, 50 kPa and 100 kPa) and EPS weight content (up to 2% by weight) on the small strain shear modulus, secant shear modulus and damping ratio is investigated. Laboratory results indicated that the values of shear velocity and shear modulus obtained from the bender element tests decrease with increasing EPS content. The results also revealed that the damping and shear modulus of the samples are highly dependent on the weight percentage of EPS, such that the increase in EPS content results in the increase of damping ratio up to 100% or even more under constant confining pressure. On the contrary, for all the values of confining pressure, the shear modulus of the mixture undergoes a significant reduction with increasing EPS content. Moreover, it is shown that the confining pressure has a important impact on both the soil damping ratio and shear modulus.