Seepage and Stability Analysis of the Eyvashan Earth Dam under Drawdown Conditions

Komasi, Mehdi; Beiranvand, Behrang

doi:10.22059/ceij.2020.293429.1634

Seepage and Stability Analysis of the Eyvashan Earth Dam under Drawdown Conditions

Document Type : Research Papers

Authors

Mehdi komasi ¹
Behrang Beiranvand ²

¹ Assistant Professor, Department of Civil Engineering, University of Ayatollah Ozma Borujerdi, Borujerd, Iran. komasi@abru.ac.ir

² Ms. Graduated, Water Engineering, and Hydraulic Structures, University of Ayatollah Ozma Borujerdi, Borujerd, Iran.

10.22059/ceij.2020.293429.1634

Abstract

The rapid drawdown condition to control floods and irrigation is one of the things that may occur over the lifetime of the dam. Also, the stability of the dam at the rapid drawdown will be more important due to the faster reduction of the water level of the dam reservoir than the pore water pressure. In this study, the finite element method and GeoStudio software used to study the seepage from the body earth dam. Also, the complete elastic-plastic model of Mohr-Coulomb is considered in the analysis. In this study, the stability analysis of the Eyvshvan earth dam after rapid drawdown due water to release of the dam reservoir to downstream agricultural lands during drought crisis, is investigated. For the validation, first, the results of the pore water pressure instrument were compared with the results of numerical analysis. The results of multivariate regression analysis (coefficient of determination) showed very good agreement (R²=0.98). The results showed that the phreatic line remains after 29 days from the start of the rapid drawdown of the reservoir, while half of the volume of the drained reservoir remains at 1842 masl (1/3 of the crest). The analysis of dam stability during rapid drawdown using both Morgenstern-Price and Bishop Methods showed that the most critical situation would occur after 42 days of discharge with a factor of safety (FoS) of 1.71, with no stability hazard and the upstream slope would be safe.

Keywords

Abadjiev, C.B. (1994). "Safety assessment and stability improvement of the upstream slope of earth dams", Proceedings of the 18th ICOLD Congress, Durban, South Africa, 1, 261-273.

Alonso, E.E., and Pinyol, N.M. (2016). “Numerical analysis of rapid drawdown: Applications in real cases”, Water Science and Engineering, 9(3), 175-182.

Bahrami, A., Teimouri, B. and Khalkhali, A.B. (2018). "Stability control of Narmab Dam and sensitivity analysis of reliability coefficients", Civil Engineering Journal, 4(9), 2197-2209.

Berilgen, M.M. (2007). "Investigation of stability of slope under drawdown condition", Computers and Geotechnics, 34, 81-91.

Boroomand, M.R. and Mohammadi, A. (2019). "Evaluation of earth dam leakage considering the uncertainty in soil hydraulic parameters ", Civil Engineering Journal, 5(7), 1543-1556

Fattah, M.Y. Omran, H.A. and Hassan, M.A. (2017). "Flow and stability of Al-Wand earth dam during the rapid drawdown of water in the reservoir", Acta Montanistica Slovaca, 1(22), 43-57

Lane, P.A. and Griffiths, D.V. (2000). "Assessment of stability of slopes under drawdown conditions", Journal of Geotechnical and Geoenvironmental Engineering, (ASCE), 126(5), 443-450.

López-Acosta, N., Sánchez, M., Auvinet, G. and Pereira, J. (2014). "Assessment of exit hydraulic gradients at the toe of levees in water drawdown conditions", In: Scour and Erosion, 171-181.

Nian, T., Jiang, J., Wan, Sh. and Luan, M. (2011). "Strength reduction FE analysis of the stability of bank slopes subjected to transient unsaturated seepage", Electronic Journal of Geotechnical Engineering, 16, 165-177.

Salmasi, F., Mansuri, B. and Raoufi, A. (2015). "Use of numerical simulation to measure the effect of relief wells for decreasing uplift in a homogeneous earth dam", Civil Engineering Infrastructures Journal, 48(1), 35-45.

SEEP/W. (2016). "Seepage modeling with SEEP/W: An engineering methodology, GEO-SLOPE International Ltd.

Siacara, A.T. Beck, A.T. and Futai, M.M. (2020). "Reliability analysis of rapid drawdown of an earth dam using direct coupling", Computers and Geotechnics, 118, 1-16

Sica, S., Pagano, L. and Rotili, F. (2019). "Rapid drawdown on earth dam stability after a strong earthquake", Computers and Geotechnics, 116, 1-15

Stark, T.D., and Jafari, N.H. (2018). "San Luis dam case history: Seepage and slope stability analyses and lessons learned", In: IFCEE 2018, pp. 317-329.

United States Bureau of Reclamation (USBR), (1987). Design of small dams, Department of Interior, Col., USA.

Vanapalli, S.K. Fredlund, D.G., Pufahl, D.E. and Clifton, A.W. (1996). "Model for the prediction of shear strength with respect to soil suction", Canadian Geotechnical Journal, 3, 379-392.

Viratjandr, C. and Michalowski, R.L. (2006). "Limit analysis of submerged slopes subjected to water drawdown", Canadian Geotechnical Journal, 43(8), 802-814.

Wang, J.J. Zhang, H.P. Zhang, L. and Liang, Y. (2012). "Experimental study of heterogeneous slope responses to drawdown", Engineering Geology, 147, 52-56.

Yan, Z.L., Wang, J.J. and Chai, H.J. (2010). "Influence of water level fluctuation on phreatic line in silty soil model slope", Engineering Geology, 113(1-4), 90-98.

Zedan, A.J., Faris, M.R. and Abdulsattar, A.A. (2018). "Slope stability of an earth dam during drawdown conditions (Khasa Chai Dam) as a case study", International Journal of Engineering and Technology, 7(37), 17-21.

Zhang, G. and Luo, F. (2017). "Simplified stability analysis of strain-softening slopes under drawdown conditions", Environmental Earth Sciences, 76(4), 151.

Zomorodian, S.M.A. and Abodollahzadeh, S.M. (2010). "Effect of horizontal drains on upstream slope stability during rapid drawdown condition", International Journal of Geology, 4(4), 85-90.

References