Use of Waste Tire Chips and PET Plastic Flakes in Backfill Behind Retaining Walls

The use of waste in the field of civil engineering is one of the solutions to reduce the harmful impact of waste on the environment on the one hand and preserve natural resources on the other. This study aims to investigate the effect of using waste materials such as plastic and tire chips that can be used as backfill in retaining walls. A numerical study has been carried out by using PLAXIS 2D software version 8.6 to model three types of rigid retaining walls, namely: scale wall test, cantilever wall, and gravity wall. In addition, the backfills of those retaining walls are composed of two mixtures. The first is a mixture of sand and tire chips (TC) with different percentages (10%, 30%, 50%, and 70%). The second is a mixture of sand and PET plastic flakes at different percentages (12.5%, 22.5%, and 32.5%). The results obtained from this study confirmed that the use of PET plastic waste and tire chips waste mixed with sand in the backfills of rigid retaining walls contributes effectively to the reduction of horizontal and vertical displacements as well as the earth pressures behind the retaining walls, therefore improving the stability of the retaining walls.