Leili Kouhneshin - M.Sc Student in Geotechnics, School of Civil Engineering, The University of Guilan
E Ebrahimi - M.Sc Student in Geotechnics, School of Civil Engineering, The University of Guilan
R Jamshidi Chenari - Assistant Professor, School of Civil Engineering, The University of Guilan

Lightweight fill materials have been used in many civil engineering applications throughout the world. A lightweight fill was produced by blending expanded polystyrene (EPS) beads and sands. Such formed granular geomaterials , known as sand-EPS lightweight fills, have potential of being lightweight compared to traditional fills, thus are suitable for many infrastructure works where less overburdens are expected, e.g., utilities trench backfills. This paper examines the static and cyclic behavior of sand-EPS mixtures under direct shear test conditions. Large direct shear tests were conducted on the lightweight fills to observe materials’ stress-strain relationships, specifically, the stress-strain variations associated with the mixing ratios of EPS beads. The behaviors of mixtures under cyclic loading are worth to pay much attention on, though there are few relative studies about this at present. Cyclic stress–strain relationships and stiffness degradation curves for sand-EPS mixtures with different mix ratios are also discussed. EPS beads were incorporated into the mixtures based on their mass ratios over sands, i.e., 0.15% and 0.35%. Monotonic Direct shear tests were conducted under 3 different vertical stresses (40, 80, 160kPa) and the cyclic shear behaviors of the sands was tested by considering the normal stress of 50 kPa. The results showed that the inclusion of EPS bead in sand will lead to a decreased shear modulus and damping ratio.

EPS-sand mixture ، Dynamic properties ، cyclic direct shear ، Shear modulus ، damping ratio ،