Population growth has resulted in industrialization, massive construction, and significant mining to supply the population's ever-increasing needs. The study deals with waste material utilization for soil properties enhancement, reducing construction costs and benefiting the environment. Bottom ash, one such effluent released from thermal power plants, was used in percentages 0, 20, 50, 70, and 100% by weight. Laboratory tests were conducted, including the sand replacement method, unconfined compression test, and shear test, to study the enhanced mechanical properties of the soil, adding bottom ash to it. Initially, the property of backfill material is enhanced and further it is used behind the wall along with the geofoam placed strategically to significantly reduce lateral stresses exerted on the retaining wall further optimizing the overall structural efficiency. Geofoam of three different densities, 11 kg/m3 (11EPS), 16 kg/m3 (16EPS), and 34 kg/m3 (34EPS), has been tested to understand how the compressive strength and corresponding modulus values change with the unit weight and strain rate. It was observed that with an elevating density of geofoam, unit weight, compressive strength, shear strength, and shear strength parameters increased, whereas water absorption capacity decreased. The results of this study can be used as a reference for the quality control of geofoam. The effective use of geofoam placed behind a stiff retaining wall in reducing lateral stresses brought on by a combination of backfill material and loading conditions was evaluated using a finite element model. The results obtained through the numerical investigations were validated with the differential element method developed. Results obtained through numerical and calculated models were in good accord with a percentage error of less than 20%. The impact of geofoam density, relative thickness, and friction angle of backfill on the efficiency of geofoam in reducing lateral stresses was then investigated using a parametric analysis. Earth pressure reduction obtained for different backfill types and lower density geofoam (11 EPS) of thickness 10 cm was between 23.27 and 62.72% obtained numerically. The highest earth pressure reduction, i.e., 64.17%, was obtained for 11EPS geofoam of thickness 15 cm laid behind the bottom-ash-backfilled retaining wall. Parametric charts prepared with the obtained results can help determine the required thickness of geofoam for any desired earth pressure reduction efficiency.

来源平台：INDIAN GEOTECHNICAL JOURNAL