Geofoam, when substituting soil, reduces lateral static load due to its lightweight and compressible nature. The alignment and the orientation of the geofoam greatly affect the deflection of the wall. This paper investigates the influence of different geofoam orientations on the load-deformation characteristics of the reinforced retaining wall. Static load tests were performed when sand or geomaterial prepared from sand, bottom ash, and plastic strips were used as a backfill material. Different orientations were explored when geofoam of densities 11D, 16D, and 34D where D is the density of geofoam were laid in different directions. A layer of compressible inclusion with a thickness of 10 cm was laid either in the vertical direction alone or in both vertical and horizontal directions. Another option was to use a 10-cm-thick geofoam laid in the vertical direction and geofoam strips of thickness 2, 3, or 5 cm laid in layers. The reinforcement effect was analyzed using bearing capacity ratio, vertical displacement reduction, and wall deflection reduction. Results indicated that higher-density geofoam is more efficient in reducing settlement values and increasing bearing capacity. Lower-density geofoam excelled in wall deflection reduction. The most substantial improvements were observed for 10-cm-thick 16D geofoam laid in the vertical direction, accompanied by 5-cm-thick strips laid in three layers in the horizontal direction. This combination reduced the settlement and wall deflection to 78.23% and 98.81%, respectively.

Due to extensive sand mining, the depletion of traditional backfill materials is a significant concern globally. Unsustainable sand mining practices, driven by construction demand, result in environmental degradation and resource depletion. Alternative materials like coal-fired power plant bottom ash and plastic waste offer cost and eco-friendly advantages for backfilling. Reinforced soil walls, compared to traditional structures, accommodate more settlement and load, providing flexibility, resistance to static and dynamic stresses, and improved aesthetics. To mitigate lateral earth pressure on retaining walls, incorporating compressible inclusions between the backfill and the wall reduces stress, ensuring long-term stability. The current investigation examines the effectiveness of sand or geomaterial prepared from sand (S), bottom ash (10-50% by dry weight), and plastic strips (0.5-1.25% by dry weight) together as backfill, behind the wall to improve the deformation characteristics of the wall and reduce lateral soil pressure. At the interface between the wall and the backfill, geofoam with densities 11D, 16D, and 34D, where D is measured in kg/m3 was used as an absorber to reduce wall lateral movement, settlement, and lateral push acting on the wall. To determine the efficacy of geofoam inclusion, parametric studies were carried out with a range of factors, including geofoam density, backfill characteristics, and surcharge load on the backfill. The model retaining wall was backfilled with either sand or geomaterial under simple strain circumstances. Plaxis 2D numerical modeling was performed for similar conditions and backfill types showed test results from both approaches exhibit excellent agreement. Results from numerical analysis and experimental method gave an optimal mix of the geomaterial (Sand + 50% BA + 1% PS) and geofoam density (34D in case of settlement reduction and 11D in case of lateral movement reduction and earth pressure reduction) that can yield maximum reduction of earth pressure with minimal deformation characteristics was suggested. When 34D geofoam was laid behind the wall backfilled with S, 50% BA, and 1% PS resulted in 172% and 178% improvement in bearing capacities for tests conducted experimentally and numerically. The corresponding settlement reduction values were 73% and 75%. The wall deflection reduction at locations 300 mm (H1) and 500 mm (H2) from the base of wall and earth pressure reduction for 11 D as CI and same backfill were about 82%, 82%, and 43% respectively for both analyses. Conclusively, the provision of geofoam as CI at the interface of the wall and backfill manifests to be a feast alternative for improving the performance of the retaining wall in terms of increasing bearing capacity, reducing settlement, lateral deformation, and earth pressure.