A Study on optimum layout of drainage gallery for concrete dams


Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Turkey

Approval Date: 2018

Thesis Language: English

Student: Tameem Daghestani

Co-Supervisor: ALİ MELİH YANMAZ, Ali Yanmaz

Abstract:

Dams are generally massive structures retaining a large amount of water. Any failure could lead to a disaster. Therefore, keeping the dam within the required safety margins and maintaining those conditions is of the utmost importance. A gravity dam is held in place by its own weight. Uplift pressure reduces the effective weight of the dam, thus reducing its safety. Hence reducing the effect of uplift could have significant results in increasing the safety of the dam. In this study, the optimum location of the drainage gallery was studied by considering the impact of different locations of the gallery, the size and spacing of the drains for various loading conditions on multiple hypothetical cases and a case study. Results show that the presence of a drainage gallery can reduce uplift by over 60% compared to a non-drained case. As the drain diameter increases and/or the spacing between the drains decreases, the location of maximum uplift reduction shifts more towards the upstream face. The optimum horizontal position for the case study is at a distance of 10% of the base width away from the upstream face. The optimum vertical position for the gallery is below or at the level of the downstream water level. This location combined with the placement of post-tensioning cables on the downstream side, results in the lowest uplift pressure and small cracking on the downstream side.