Lateral earth pressures on flexible cantilever retaining walls with deformable geofoam inclusions

• Physical and numerical modeling studies are performed on flexible retaining walls.
• Geofoam inclusions provide reduction in lateral earth pressures.
• Contribution of the compressible buffer decreases as wall flexibility increases.
• Formation of a wider failure zone reduces lateral earth pressures.
• Design charts were proposed to predict active lateral pressure coefficients.

The present study explores the potential application of geofoam in reducing the lateral earth pressures on flexible cantilever walls retaining cohesionless and dry backfills. Results of 1-g physical model tests addressing the behavior of yielding cantilever retaining walls with expanded polystyrene (EPS) and extruded polystyrene (XPS) geofoam compressible inclusions are discussed. The effect of relative flexibility of the wall as well as the characteristics of the cohesionless backfill and geofoam on the active earth pressures were investigated in this context. A finite difference code was validated against the lateral earth pressures and backfill strains observed in the tests. Experimental results indicate that the shape of active pressure distribution diagram behind a cantilever retaining wall is non-linear and varies depending on the wall flexibility and characteristics of deformable layer. Geofoam inclusions provide reduction in lateral earth pressures, however the positive contribution of the compressible buffer decreases as wall relative flexibility increases. Reduction of the lateral earth loads is associated with the formation of a wider, non-linear and more stable failure zone induced from the combined influence of the flexural deformations of the cantilever wall and the arching effect induced at the lower half portion of the cohesionless backfill retained by the flexible wall-deformable panel system. Parametric numerical analyses were performed to extend the predictions of the lateral earth pressure coefficients for various combinations of backfill, deformable inclusion and structural attributes by validated numerical model. Based on the results of the parametric analyses, design charts and regression models were proposed to predict active lateral earth pressure coefficients and point of application of the lateral load on the flexible cantilever earth retaining walls with and without deformable geofoam layers.