Experimental study on waste foundry sand as partial replacement of retaining wall backfill

Waste foundry sand (WFS) is a sustainable backfill geomaterial with potential to be used in retaining structures. In the present study, 28 distinct laboratory-scale physical model experiments are performed on a 0.5 m high retaining wall. The backfill sand is replaced with WFS at different replacement concentrations. The retaining wall model is reinforced with biaxial polyester geogrid to quantify the effect of reinforcement. The interaction properties of soil with soil, wall and geogrid are measured by a series of drained direct shear tests using a shear box of 300 mm × 300 mm × 150 mm is used. The model retaining wall study includes both at-rest and active cases of walls. The effect of WFS content, the relative density of backfill, static surcharge and reinforcement on earth pressure and lateral displacement of the wall is quantified. Backfill with 40% of WFS is observed to provide maximum values of interaction properties. The results of interaction studies are consistent with model tests. The earth pressure reduces by 22% with 40% WFS backfill compared to the control case of 100% sand. The lateral displacement reduces by 30% and 50% corresponding to single and double geogrid layers, respectively.