Numerical investigation of relief well performance for decreasing uplift pressure under embankment dams
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ORIGINAL PAPER
Numerical investigation of relief well performance for decreasing uplift pressure under embankment dams F. Salmasi1 · B. Nourani1 · J. Abraham2 · R. Norouzi1 Received: 25 July 2020 / Revised: 6 November 2020 / Accepted: 9 November 2020 © Islamic Azad University (IAU) 2020
Abstract Drainage systems for embankment dams are arrangements that collect seepage water in downstream areas. A relief well downstream of a hydraulic structures is one way to reduce the water pressure underneath the structure and thereby improve stability. The design of relief wells includes the determination of the distance of the relief wells from each other, their location, and the well diameters. This study investigates the effects of relief wells on uplift pressure in earthen dams. Solutions were obtained by the finite element method which was used to assess different configurations of the relief wells. For validation, a comparison between analytical solutions and numerical calculations shows good agreement for uplift pressure prediction. Reducing the distance between relief wells or increasing the well diameters results in a reduction of uplift pressure. A two-row arrangement of relief wells showed that a zigzag deployment is superior to a non-zigzag deployment. Linear and nonlinear regression relations are presented for uplift pressure prediction. Keywords Embankment · Relief wells · Seepage · Uplift pressure · Finite element method Abbreviations Ud Uplift pressure with relief well (kpa) Uo Uplift pressure without relief well (kpa) H Total height water reservoir relative to wells output elevation (m) Hm Piezometric head between wells (m) n Relief well distance (m) d Diameter of the relief wells (m) s Distance from upstream of the dam (m) z Two-row wells spacing (m) k Hydraulic conductivity coefficient (m/s) kx Hydraulic conduction in direction x (m/s) ky Hydraulic conduction in direction y (m/s) A Cross section of flow (m2) Q Flow discharge (m3/s) q Flow discharge in unit width of the dam (m2/s) and ∂h/∂s Hydraulic gradient (dimensionless) Editorial responsibility: Samareh Mirkia. * F. Salmasi [email protected] 1
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
University of St. Thomas, Minnesota, School of Engineering, 2115 Summit Avenue, Saint Paul, MN 55105, USA
2
Introduction Seepage near embankment dams is a vital aspect that helps determine dam stability, particularly with respect to the piping phenomenon and soil movement (Farzampour et al. 2014). Failure in embankment dams may occur by piping (undermining) in the foundation; piping is caused by high pressure under the foundation of the dam that causes movement of the soil particles. Creation of water pressure under the foundation of a dam is referred to as uplift pressure. In the design of irrigation canals, seepage under the canal lining can result in the creation of cracks in the lining and this can lead to excessive water loss (Salmasi and Abraham 2020). Some methods are recommended to
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