Journal of Hydraulics

Journal of Hydraulics

The influence of the position of the clay core in the earth dam on the probabilistic stability analysis in the rapid drawdown condition

Document Type : Research Article

Authors
Seyed ali asghari pari 1
Seyed Amin Asghari Pari 2
1 Assistant Professor, Department of Civil Engineering, Faculty of Engineering, Khatam Al Anbia Behbahan University of Technology
2 Associate Professor, Department of Civil Engineering, Behbahan Khatam Alanbia University of Technology, Behbahan, Iran
10.30482/jhyd.2025.469729.1711
Abstract
In applied civil engineering, slope stability analysis and seepage analysis are often performed using a deterministic approach, where soil properties are assumed constant. However, this simplistic assumption cannot explain the inherent uncertainties associated with the materials and models used to analyze them. Incorporating the stochastic nature of soil properties, rather than relying solely on deterministic values, can provide a more accurate representation of system behavior and lead to more informed decision making. Also, the stability of earthen dams is a critical concern, as the failure of such structures can have catastrophic consequences. The aim of this study is to provide a comprehensive understanding of the factors that affect the stability and overall performance of earthen dams, focusing on the role of clay core location. For this research, the Sidon dam in Iran has been analyzed by Slide2 software in the conditions of rapid reservoir discharge. The results show that moving the clay core from the upstream side to the downstream side of the dam increases the safety factor and reliability of the upstream side. Also, the sensitivity analysis shows that the friction angle of the dam shell has the highest linear correlation with the slope safety factor.
The research results are as follows.
1- Moving the clay core from the upstream side to the downstream side of the dam increases the safety factor and reliability of the upstream side.
2- The results of the analysis of global probabilities show that in cases 1 and 2 of placing the clay core (on the upstream side of the dam), the reliability index of the slope is lower than the value of 2. While in other situations, this index is always more than 3.
3- The results of the analysis of global probabilities show that, contrary to the idea, in some cases of core placement (cases 4 and 5), the lowest safety factor occurs in a time less than the time of drawdown.
4- The results of the minimum Reliability slope analysis show that the critical slope in this case is not the same as the global probabilistic analysis. On the other hand, the safety factor value is higher and the RI value is lower. Only in the case of core number 3 and 4, the reliability index was greater than 2.5 at all times.
5- The results of the sensitivity analysis show that the friction angle of the shell material will have the greatest effect on the safety factor of the dam slope in all situations of transient analysis times.
6- The results show that in cases 1 and 2 of core placement, the unit weight of the shell material has the highest linear correlation with the upstream safety factor. Meanwhile, for the rest of the core location, the most linear correlation is between the shell friction angle and the upstream safety factor.
Keywords
Probabilistic analysis
rapid drawdown
sensitivity analysis
clay core

Subjects

Ahadiyan, J., Bahmanpouri, F., Adeli, A., Gualtieri, C. & Khoshkonesh, A. (2022). Riprap Effect on Hydraulic Fracturing Process of Cohesive and Noncohesive Protective Levees. Water Resources Management, 36(2), 625-639. https://doi.org/10. 1007/s11269-021-03044-6.
Ahmed, A.T. & Elsanabary, M.H. (2015). Hydrological and environmental impacts of Grand Ethiopian Renaissance Dam on the Nile River. In Proceedings of the Eighteenth International Water Technology Conference, IWTC18, Sharm El Sheikh, Egypt, 12-14.
Akbas, S.O. & Kulhawy, F.H. (2010). Characterization and estimation of geotechnical variability in Ankara clay: a case history. Geotechnical and Geological Engineering, 28, 619-631.
Alonso, E. & Pinyol N. (2009). Slope stability under rapid drawdown conditions. First Italian Workshop on Landslides, Napols, 11–27.
Asadi, M. & Khazaei, J. (2014). Seepage analysis in body and foundation of Dam using the Seep/3D and Seep/W. Journal home page: http://www. journalsci. com ISSN, 2322, 326X.
Berilgen, M.M. (2007). Investigation of stability of slopes under drawdown conditions. Comput Geotech, 34, 81–91.
Calamak, M., Yilmaz, A.N. & Yanmaz, A.M. (2018). Performance evaluation of internal drains of earthen dams. Journal of Performance of Constructed Facilities, 32(6), 04018085, https:// doi.org/10.1061/(ASCE)CF.1943-5509.0001232.
Combelles, J., Goube, A., Llopis, N. & Paccard, M. (1985). Measures to improve the safety of hydraulic structures in dams (in French). Trans 15th Int Congr Large Dams, Lausanne, Q59 R46.
Cornell, C.A. & Vanmarcke, E.H. (1969). The major influences on seismic risk. In: Proceedings of the Fourth World Conference on earthquake engineering, Santiago, Chile.
Einstein, H.H. & Baecher, G.B. (1983). Probabilistic and statistical methods in engineering geology: Specific methods and examples part I: Exploration. Rock mechanics and rock engineering, 16, 39-72.
Environment Agency (2017a). Guide to drawdown capacity for reservoir safety and emergency planning. Vol. 1, Environment Agency, Horizon House, Deanery Road, Bristol, BS1 9AH.
Environment Agency (2017b). Guide to drawdown capacity for reservoir safety and emergency planning. Vol. 2, Environment Agency, Horizon House, Deanery Road, Bristol, BS1 9AH.
Eslamian, M.B.S. & Hajiannia, G.S.A. (2021). 2D and 3D Modeling of Transient Seepage from Earth Dams Thorough Finite Element Model (Case Study: Kordaliya Dam). Water Resources, 14(48), 86-97.
Faridmehr, I., YazdaniPour, M.R., Jokar, M.J. & Ozbakkaloglu, T. (2019). Construction and monitoring of cement/bentonite cutoff walls: case study of Karkheh Dam, Iran. Studia Geotechnica et Mechanica, 41(4), 184-199.
Fredlund, D.G. & Rahardjo, H. (1993). An overview of unsaturated soil behavior. Reprinted from UNSATURATED SOILS, Sponsored by the Geotechnical Engineering Division/ASCE, Held October 24-28, 1993, Dallas, Texas.
Fredlund, M.D. (2000). The role of unsaturated soil property functions in the practice of unsaturated soil mechanics, Doctoral dissertation, University of Saskatchewan.
Gao, X., Liu, H., Zhang, W., Wang, W. & Wang, Z. (2019). Influences of reservoir water level drawdown on slope stability and reliability analysis. Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 13(2), 145-153.
Gosden, J., Hart, D. & Dutton, T. (2014). Guide to drawdown capacity for reservoir safety and emergency planning. Dams Reserv, 24, 134–135.
Haghdoost, M., Sajjadi, S.M., Ahadiyan, J., Norouzi, R. & Abraham, J. (2024). The effect of sheet piles’ inclination angle, number, and distance on seepage through an earthfill dam. Ain Shams Engineering Journal, 15(12), 103056, https://doi.org/10.1016/ j.asej.2024.103056.
Haghdoost, M., Lakzian, E., Norouzi, R. Abraham, J., Sajjadi, S.M. & Ahadiyan. J. (2023). Numerical simulation using the finite element method to investigate the effect of internal cutoff walls on seepage and hydraulic gradients in homogeneous earth dams, Model Earth System Environment, 9, 3851–3864.
Khanna, R., Datta, M. & Ramana, G.V. (2014a). Influence of thickness of a vertical core on the slope stability of earth and rockfill dams. Dams and Reservoirs, 24(4), 152-167.
Khanna, R., Datta, M. & Ramana, G.V. (2014b). Influence of inclination of thin core on the stability of upstream slope of earth and rockfill dams. Electronic J Geotech Eng, Boundle (U), 6293-6306.
Khanna, R., Datta, M. & Ramana, G.V. (2019). Influence of core thickness on stability of downstream slope of earth and rockfill dams under end-of-construction and steady-state-seepage: a comparison. International Journal of Geotechnical Engineering, 13(1), 25-31.
Kiyani, A.M., Zeinivand, M., Ahadiyan, J. & Falorca, I. (2024). Experimental Investigation of Embankment Wedge Failure’s Stability under the Effect of the Number and Spacing of Geotextile Layers in the Reinforced Retaining Wall. JWSS, 28(2), 177-194.
Kulhawy, F.H. & Phoon, K.K. (2006). Some critical issues in Geo-RBD calibrations for foundations. In: GeoCongress 2006: Geotechnical engineering in the information technology age, 1-6, https://doi.org/ 10.1061/40803(187)197.
Lane, P.A. & Griffiths, D.V. (2000). Assessment of stability of slopes under drawdown conditions. J Geotech Geoenviron Eng, 126(5), 443, https:// doi.org/10.1061/(ASCE)1090-0241(2000)126:5 (443).
Ma, H. & Chi, F. (2016). Major technologies for safe construction of high earth-rockfill dams. Engineering, 2(4), 498-509.
Mansuri, B., Salmasi, F. & Oghati, B. (2014). Effect of location and angle of cutoff wall on uplift pressure in diversion dam. Geotechnical and Geological Engineering, 32, 1165-1173.
Memarian, S., Ahadiyan, J. & Karimi, H.R. (2023). Assessment of vertical pile reinforcement effect on behavior of foundations placed on Slopes: An experimental and numerical study, Ain Shams Engineering Journal, 14(12), 102233, https://doi.org/10.1016/j.asej.2023.102233.
Nayebzadeh, R. & Mohammadi, M. (2011). The effect of impervious clay core shape on the stability of embankment dams. Geotechnical and Geological Engineering, 29, 627-635.
Nouri, S. & Nohani, E. (2014). Numerical study of flow patterns in lateral intakes upstream and downstream (case study: Gotvand diversion Dam). Advances in Environmental Biology, 8(21), 1202-1208.
Pham, H.Q. (2001). An engineering model of hysteresis for soil-water characteristic curves, Doctoral dissertation, University of Saskatchewan.
Phoon, K.K. & Kulhawy, F.H. (2008). Serviceability limits state reliability-based design. In: Reliability-based Design in Geotechnical Engineering, 356-396, CRC Press.
Pinyol, N.M., Alonso, E.E. & Olivella, S. (2008). Rapid drawdown in slopes and embankments. Water Resour Res, 44(5), https://doi.org/10.1029/ 2007WR006525.
Prentice, J. (2005). Minimum discharge capacity of impounding reservoirs – Northumbria Water’s experience and results capital spend. Dams Reserv, 15(1), 17–8.
Salmasi, F. & Mansuri, B. (2014). Effect of homogeneous earth dam hydraulic conductivity ratio (Kx/Ky) with horizontal drain on seepage. Indian Geotechnical Journal, 44, 322-328.
Shole, D.G. & Belayneh, M.Z. (2019). The effect of side slope and clay core shape on the stability of embankment dam: Southern Ethiopia. International Journal of Environmental Science and Technology, 16, 5871-5880.
Sica, S., Pagano, L. & Rotili, F. (2019). Rapid drawdown on earth dam stability after a strong earthquake. Comput Geotech, 116, 103187, https://doi.org/10.1016/j.compgeo.2019.103187.
Song, K., Yan, E., Zhang, G., Lu, S. & Yi, Q. (2015). Effect of hydraulic properties of soil and fluctuation velocity of reservoir water on landslide stability. Environ Earth Sci, 74, 5319–5329.
Teimouri, A.B.B. & Khalkhali, A.B. (2018). Stability control of Narmab Dam and sensitivity analysis of reliability coefficients. Civil Engineering Journal, 4(9), 2197-2209.
USACE. (2016). Design criteria for dam and lake projects, Part 220. In: U.S. Corps of Engineers – Department of the Army, editor. Title 33 - Navig. Navig. waters. 33 CFR 220, Washington, DC: United States Corps of Engineers.
USBR (1990). Criteria and guidelines for evacuating storage reservoirs and sizing of low-level outlet works. ACER TECHN MEMORANDUM No. 3, Denver, Colorado.
Varde, P.V. & Pecht, M.G. (2018). Risk-Based Engineering: An Integrated Approach to Complex Systems--Special Reference to Nuclear Plants. Springer Singapore.
Water and Electricity Organization of Khuzestan Province. (2010). Water resource planning studies (Final Report), The first stage of the Seydon Reservoir Dam project.

  • Receive Date 25 July 2024
  • Revise Date 09 November 2024
  • Accept Date 22 January 2025