Upstream Cutoff and Downstream Filters to Control of Seepage in Dams
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Upstream Cutoff and Downstream Filters to Control of Seepage in Dams Farzin Salmasi 1
2
& Meysam Nouri & John Abraham
3
Received: 11 February 2019 / Accepted: 16 September 2020/ # Springer Nature B.V. 2020
Abstract
The finite element method was used in this study to investigate cutoff walls and downstream filters to control seepage, the exit hydraulic gradient, and uplift forces for dams. Experimental data was used for validating the numerical modelling. The effective parameters are the length of filter and its distance downstream from the dam, the depth of the cutoff walls, the upstream dam head, and the thickness of alluvial foundation. The results show that by increasing filter length, the exit hydraulic gradient, uplift force, and seepage are reduced. The optimum relative length of the filter is L/H = 0.028 which results in a decrease of about 65% in the exit hydraulic gradient, a 35% decrease in seepage and 10% reduction in the uplift force at the upstream foundation and a 60% decrease in the uplift force at the downstream foundation. Increase of cutoff wall depth reduces the exit hydraulic gradient, uplift force, and seepage. Using two cutoff walls both upstream and downstream of the dam decreases seepage, hydraulic gradient, and uplift force 132%, 450% and 11% respectively. However, using an upstream cutoff and downstream filter decreases seepage, hydraulic gradient, and uplift force by 180%, 490%, and 119% respectively. Thus, based on this study, recommendations for suitable combinations of upstream cutoff and downstream filter are provided. Keywords Cutoff wall . Filter . Hydraulic . Seepage . Gradient, uplift
* Farzin Salmasi [email protected] Meysam Nouri [email protected] John Abraham [email protected]
1
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
2
Department of water engineering, Faculty of Agriculture, University of Urmia, Urmia, Iran
3
University of St. Thomas, Minnesota, School of Engineering, 2115 Summit Avenue, St. Paul, MN 55105, USA
Salmasi F. et al.
1 Introduction Hydraulic structures are used for flow control in rivers and distribution of water in farms for irrigation. Most of these structures are built on alluvial foundations and depend on the permeability of foundation materials; seepage occurs from the foundation of these structures. Seepage under structures will cause an uplift force, a high exit hydraulic gradient, and piping under the structures. These dangerous phenomena are reasons for failure of structures and reduce their stability. For this purpose, several studies are carried out dealing with the stability of structures resting on permeable foundations and finding methods to control seepage and structural stability. One of the methods to control seepage and prevent piping is by appropriate downstream filters. Filters with high permeability (16–25 times greater than the protected soil materials) facilitate output flow, prevent soil migration and can increase structure stability (Salmasi et al. 2020). E
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