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Seepage and Slope Stability Analysis of Earthen Dam: A Case Study of Koga Dam, Ethiopia

100%

Zewdu A.

vol. 26

191-217

Evaluations of an earth-fill dam throughout its service life must ensure the stability of it against seepage and slope failure. This study presents the seepage and slope stability of the Koga earth-fill dam. The analyses were carried out using a finite element based PLAXIS 2D software, and covers the whole dam body; including 20 m of foundation depth. The behavior of both the body and the foundation of the dam were described using the Mohr-Coulomb criterion. Assessments of safety factor and quantity of seepage through the main body of the dam and foundation were carried out at different critical loading conditions. In this study, seepage analysis was undertaken of flow rate, pore water distribution and location of phreatic line. Additional actual field data measurements and observatory investigation were also carried out. From the simulated results, the average flow rate of seepage for the entire length of the body of the dam at normal pool level was equal to 0.06085 m3/s, whereas the figure for that through the foundation of the dam was 0.01937 m3/s. Moreover, total seepage through the main body of the dam at the current reservoir level was 0.04982 m3/s, while the actually measured quantity of seepage accumulated at the downstream toe of the dam was 0.04644 m3/s. The simulated and measured seepage discharges are 93.2 % similar. Based on the result of this study, the resulting factor of safety values during end of construction, steady state condition and rapid drawdown condition were 1.6221, 1.6136 and 1.2199, respectively. Using recommended design standards: United States army corps of engineers (USACE), British dam society (BDS) and Canadian dam association (CDA), the slope stability analysis of the Koga earth dam at all critical loading conditions are safe.

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

88%

Belew A. Z., Jegnie T., Mulat A., Getacher H., Abebaw D., Desie T.

World News of Natural Sciences

2022

vol. 40

26-48

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.

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2 World News of Natural Sciences

1 2022

1 2019

1 Abebaw D.

1 Belew A. Z.

1 Desie T.

1 Getacher H.

1 Jegnie T.

1 Mulat A.

1 Zewdu A.

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Seepage and Slope Stability Analysis of Earthen Dam: A Case Study of Koga Dam, Ethiopia

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