Abstract
Various factors influence seepage and stability in earth dams. One of the important factors in the analysis of earthen dams is the unsaturated condition of the soil. Accurately understanding soil behavior in earth dams necessitates the application of unsaturated soil mechanics principles. Typically, unsaturated soil mechanics is plagued by many unknowns because of the complexity of soil behavior in unsaturated conditions. In this study, the effect of unsaturated soils on seepage discharge and the safety factor of the downstream slope are numerically investigated. For this study, the Doiraj Dam, which is located in the southwest of Ilam province, Iran, is studied. The results show that use of a constant hydraulic conductivity causes the capillary fringe flow above the phreatic line in the saturated model to be greater than in the unsaturated-saturated model. The seepage rate in the saturated model is 3.60% higher than that in the unsaturated-saturated model. The results also revealed that an accurate representation of the hydraulic conductivity function for the soil materials of the dam body brings the phreatic line into closer agreement with the actual value, and the amount of seepage flow can be accurately estimated. In addition, the slope stability analysis shows that the safety factor of the slope increases about 3.50% with respect to the saturated model.