Earth Pressures on Retaining Walls Backfilled with Sand Admixed with Building Derived Materials: Laboratory Scale Study

Abstract

Earth retaining structures are constructed to withstand lateral pressure from backfill soil and surcharge pressures from the foundations of adjacent structures. Although sands are considered as the most suitable backfill material for retaining walls due to their high permeability, currently the scarcity of this natural material has raised serious environmental concerns. This study will propose the usage of building derived materials (BDM) as a partial replacement for sand as backfill material for the retaining walls. The utilization of this waste material will help to reduce the cost related to the disposal of waste materials, as well as reducing the carbon footprint, therefore making the process eco-friendly and sustainable. Experimental studies will be conducted on a laboratory scale prototype rigid, nonyielding retaining wall, which can rotate about its base to simulate rotational failure conditions. The width of the backfill was 0.35, 0.5, and 0.65H to assess its effect on the variation of earth pressures (H = height of the retaining wall). The experimental results indicate that the earth pressures were not significantly enhanced by the addition of BDM to sand, which suggests that BDM could be used as an effective lightweight backfill. The optimum pressure was obtained by mixing 20% of BDM with red soil. For backfills that had sufficient widths, the failure surfaces had adequate space to fully develop, whereas it had a limited extension in a narrow backfill. An increase in backfill width (b) decreased the rotation of the wall, therefore reducing the probability of rotational failure. Numerical simulations using finite element software PLAXIS 2D are conducted with the experiments to validate the observations. The numerical results suggest good agreement with that of experimental results.