Active Earth Pressures for Unsaturated Retaining Structures

Abstract

Although commonly ignored in classical earth pressure methods, precipitation-induced failures in retaining structures highlight a need for explicit consideration of negative pore pressures or matric suction. Changes in the degree of saturation in the backfill can significantly affect active earth pressures. This paper presents an analytical framework for calculating the thrust of active earth pressures under unsaturated steady flow conditions. The proposed method addresses limitations associated with the collapse mechanism and effective stress representation in alternative analytical methods. The formulation was derived by implementing an analytical solution for one-dimensional (1D) steady flow into a limit equilibrium–based effective stress analysis. A closed-form solution for the thrust was obtained by employing a log spiral surface, considering the effect of tension cracks, backslope inclination, and batter for