Evaluation of seepage and slope stability analysis of embankment dam: a case study of Shimburit micro earthen dam, Amhara region, Ethiopia

Nowadays, the primary and most significant reason for ensuring the overall safety of earthen dams is to monitor seepage and slope stability. This study was carried out to evaluate the static condition seepage and slope stability performances of the Shimburit earthen dam, which is located in the Amhara National Regional State, eastern zoning of Gojjam, D/Elias woreda, in particular kebele of Yegdad and Yekomit. PLAXIS 2D software was used to investigate the seepage and slope stability of the dam under various loading conditions in this study. The PLAXIS 2D program was used to simulate seepage analysis, which included determining the quantity of discharge per unit length, pore water distribution, and the location of the phreatic line. The maximum cross-section of the Shimburit main dam is expected to have a seepage flow rate of 10.31×10-6 m3/s/m through the dam body and 28.06×10-6 m3/s/m through the foundation at normal pool level without an upstream filter. Pore water pressure is zero at the normal pool level and 262.60 KN/m2 at the bottom of the boundary condition. The phreatic line emerged below the toe of the dam. This means that the dam is not at risk of sloughing. The most critical element affecting the stability of an earth dam is seepage. Three different loading conditions are studied for stability analysis: end-of-construction, steady-state seepage, and rapid drawdown. The FOS values obtained at the end of construction, steady-state, and rapid drawdown conditions were 1.5631, 1.4441, and 1.2338, respectively. As the loading situation increases, the factor of safety results drops, i.e. 1.5631 > 1.4441 > 1.2338. All the factor of safety is greater than one, therefore, the dam is safe at all critical conditions, or the probability of failures of the dam will not be likely to happen. Using recognized design standards such as the USACE, USBR, NRCS, and BDS, the dam is found to be stable under all critical loading conditions.