Dynamic properties of high-density polyethylene-sand by large-scale direct shear experiments

Recycling and reuse of plastic waste in civil projects is one way to reduce its negative impacts on the environment. High-density polyethylene (HDPE) is a highly abundant plastic waste found widely and in high volumes worldwide. Although sand has a relatively high frictional resistance, if its dynamic parameters are improved, it can be used in geotechnical projects that require higher dynamic parameters than those of pure sand. This study aimed to investigate the dynamic properties of sand mixed with crushed HDPE waste and its application to mitigate its negative environmental impacts. Crushed HDPE was added to sand at 0, 4 and 8% by weight. Under three vertical stresses and two shear amplitudes, the dynamic parameters of the mixture, including damping and shear stiffness, were investigated by conducting a large-scale cyclic direct shear test under ten cycles and are discussed. The results showed that with increasing HDPE percentage, the damping ratio rose and the shear stiffness decreased compared with those of pure sand due to the elasticity, deformation, tensile properties and high potential of HDPE for energy absorption. Furthermore, the rise in shear amplitude decreased the dynamic shear stiffness and raised the damping ratio of the mixtures.