The effect of increasing the reservoir capacity on the static stability of an earth dam (Case study: Kamal-Saleh earth dam)

Over time, as the population increases and the useful volume of the reservoir decreases as a result of sediment build-up, the need for more water storage increases. One option to obtain more water storage is to increase the reservoir capacity of the dam by increasing the level of the spillway. One of the necessary research to assess the feasibility of implementing this solution in earth dams is the analysis of the stability of dam slopes in the height-increasing state. In this study, the static stability analysis of the Kamal-Saleh dam was performed at current level of the spillway at end of construction, steady-state seepage, and rapid drawdown conditions using GeoStudio software and applying limit equilibrium methods of Bishop, Janbo, Morgenstern-Price, and ordinary. Also under steady-state seepage, the stability of the dam was analyzed during the steps to raise the level of the spillway (up to 4 meters of acceptable height based on seepage analysis). The results indicated the dam was stable for all three conditions in the current spillway level. Although in the case of rapid drawdown, the factor of safety (FOS) initially decreased to a minimum and then increased as the water level continued to decrease, however, acceptable stability was provided for the least amount of it. In the case of increasing the storage capacity of the dam up to 4 m, the FOS for downstream slope stability was reduced; however, in all methods, the magnitude of this reduction was not significant and the required FOS was still provided.