Active thrust of sand with anisotropic seepage: a generalised limit equilibrium approach

Estimation of the magnitude and location of the lateral earth thrust on a retaining wall considering seepage flow effects within the backfill is necessary to examine the failures of such walls. In this work, the generalised limit equilibrium approach, based on the method of slices, was used to compute the magnitude and location of active earth thrust on the vertical face of a retaining wall taking into account steady seepage flow in the sand backfill. A drainage system along the backfill and wall interface and an anisotropic permeability characteristic of the backfill was considered for describing the pore pressure distribution within the backfill. Using force equilibrium conditions and an assumption regarding the direction of the interslice forces, the total normal stress distribution along the failure surface and the magnitude of total active earth thrust were determined. Subsequently, the location of the active earth thrust was determined to satisfy the moment equilibrium condition. Both planar and curvilinear failures surfaces were analysed to examine the impact on the solutions. It was confirmed that seepage flow within backfill substantially affects both the magnitude and location of active earth thrust, depending upon the degree of anisotropy.