Earth pressure profiles in unsaturated soils under transient flow

Abstract

Assessing the effect of heavy precipitations on earthen structures warrants studying earth pressure profiles in unsaturated soils under transient flow. This paper presents an analytical framework to determine the changes in at-rest, active, and passive earth pressures of unsaturated soils due to transient infiltration. A closed-from solution for one-dimensional transient unsaturated flow is incorporated into a suction stress-based representation of effective stress to obtain the tempo-spatial changes in matric suction, suction stress, and effective stress. The profiles are used to extend Hooke's law and Rankine's earth pressure theory, leading to the determination of unsaturated at-rest, active, and passive earth pressures at different depths and times. The analytical framework is used in a set of parametric study for three hypothetical soils of clay, silt, and fine sand. The results reveal the nonlinear characteristics of earth pressure profiles during transient infiltration for all three soils, whereas a linear trend is generally seen under steady-state flow conditions. Further, the depth of tension crack under transient flow is different than the one resulted from steady-state analysis. A transition from tension to compression stress is seen near the soil surface. This observation can be particularly important for fine-grained soils, implying that the depth of tension zone is affected by suction stress changes. Findings of this study can contribute toward a better understanding of service state behavior and forensic studies of earthen structures under heavy precipitations.