Coupled Effect of Suction Stress and Unit Weight on the Active Earth Pressure of Unsaturated Backfills

Abstract

In this study, limit equilibrium-based semianalytical solution has been developed to compute the distribution of active pressure and the magnitude and point of application of the total active thrust resulting from unsaturated backfills against inclined walls. Unlike earlier studies, the coupled effects of saturation-dependent suction stress and unit weight of the unsaturated soil mass above the water table has been considered to provide a realistic solution. Two separate analyses have been carried out to examine the potential impact of steady infiltration flow rates for the no-seismic case and for pseudostatic horizontal seismic forces for the no-flow case on the active pressure of unsaturated backfills. The results of the present analyses clearly reveal the potential effects of different parameters and tensile stress on the wall resulting from cohesion and suction stress components of unsaturated soil mass. It was noted that the nature of the variation of the active soil pressure distribution is highly dependent upon the hydraulic and mechanical properties of the unsaturated soils. This paper presents a simple, yet valuable, method for assessing the service state stability and performing forensic analyses of earth retention structures with unsaturated soil backfills.