Performance of the horizontal drains in upstream shell of earth dams on the upstream slope stability during rapid drawdo
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ORIGINAL PAPER
Performance of the horizontal drains in upstream shell of earth dams on the upstream slope stability during rapid drawdown conditions Abdolreza Moharrami & Yousef Hassanzadeh & Farzin Salmasi & Gholam Moradi & Gholamreza Moharrami
Received: 25 August 2012 / Accepted: 25 January 2013 # Saudi Society for Geosciences 2013
Abstract Slope stability analysis during rapid drawdown is an important consideration in the design of embankment dams. During rapid drawdown, the stabilizing effect of the water on the upstream face is lost, but the pore water pressures within the embankment may remain high. As a result, the stability of the upstream face of the dam can be much reduced. Installing horizontal drains is a very efficient and cost-effective method for reducing the pore water pressure and increasing the stability of the upstream slope. The theory of horizontal drains in the upstream shell of earth dams is well established, but there seems to be limited resources available for the design of this type of horizontal drains. Hence, this study is focused on the performance of horizontal drains in the upstream shell of the slope of earth dams on the upstream slope stability during rapid drawdown
Electronic supplementary material The online version of this article (doi:10.1007/s12517-013-0872-y) contains supplementary material, which is available to authorized users. A. Moharrami (*) : Y. Hassanzadeh : G. Moradi Civil Engineering Department, Tabriz University, Tabriz, Iran e-mail: [email protected] Y. Hassanzadeh e-mail: [email protected] G. Moradi e-mail: [email protected] F. Salmasi Water Engineering Department, Faculty of Agriculture, Tabriz University, Tabriz, Iran e-mail: [email protected] G. Moharrami Civil Engineering Department, Urmia University, Urmia, Iran e-mail: [email protected]
conditions. The parametric study has been conducted on the variation of horizontal drain parameters such as the number of drains, their length, and their location. In this study, ten scenarios were analyzed based on different drainage configurations and the performance of each scenario is investigated on the seepage and the upstream slope stability during rapid drawdown conditions using finite element and limit equilibrium methods. The results demonstrated that the stability of the upstream slope during rapid drawdown conditions increases by increasing the number of drains. The length of drains extending further from its intersection with the critical failure surface does not provide any significant change in the factor of safety. Finally, the study also found that installing drains in the lower region of the upstream shell of earth dams gives more stability than those installed in higher elevations. Keywords Slope stability . Rapid drawdown . Pore water pressure . Horizontal drains
Introduction When the water level at a dam drops, the stabilizing force due to the weight of the water becomes absent. If the dam material has a low permeability and the water level drops quickly, then excess pore p
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