Numerical Investigation of Granular Cushion Inclusions in Reinforced Walls with Geosynthetics Using Cohesive–Frictional Soils

Abstract

The stability of geosynthetic-reinforced soil (GRS) relies on the frictional interaction and load transfer between the reinforcement and the compacted backfill. In general, non-cohesive granular soils are utilised as backfill due to their high frictional interaction with geosynthetics, which optimises reinforcement mobilisation and overall structural stability. However, sourcing high-quality granular fill can be challenging and costly. To improve economic and environmental sustainability, residual soils are increasingly employed as backfill. Although these soils, especially tropical residual soils, may perform adequately when properly compacted, concerns persist regarding soil–geosynthetic interaction and overall wall serviceability. As an alternative to mitigate these issues, sand cushions may be implemented as thin, localized layers of granular material around the reinforcement. This paper presents a numerical parametric study, using the Finite Element Method (FEM), to investigate the combined effects of reinforcement distribution and sand cushion thickness on GRS wall performance. The study evaluates facing displacements, reinforcement tensile loads, and global stability, providing insights about the use of a sand transition zone with tropical soil in GRS applications.