Experimental investigation into the compression characteristics and lateral earth pressure coefficient of Bandar-e Anzali sand in Caspian Sea shore mixed with HDPE

In the last decades, considerable attempts in geotechnical study have been made to reduce plastic waste by recycling and reusing. This study aimed to reuse waste plastic mixed with sand for geotechnical application. To this end, large-scale oedometer experiments were carried out to examine the compressibility of Bandar-e Anzali sands stabilized with plastic waste-originated high-density polyethylene (HDPE). Bandar-e Anzali is a populated coastal city in the vicinity of the Caspian Sea (Northern Iran). Large-scale oedometer and direct shear tests were performed to study the applicability of HDPE chips mixed with sand at various HDPE contents (0, 2, 4, 6, and 8%). Based on the experimental tests, the addition of plastic waste to the soil improved the soil's strength, significantly raised its compressibility, and decreased the undrained elasticity modulus. By adding 8% HDPE, the constrained compression modulus decreased to 50% at a pressure of 300 kPa due to the elastic deformability of HDPEs. However, at higher relative density, adding HDPE by more than 4% did not affect the coefficient of lateral earth pressure at rest.