Effect Of The Core On The Upstream Stability Of Dams Under Sudden Drawdown Conditions

Abstract

One of the major concerns in the behavior of a dam are the changes to exit gradient and the impact on the slope stability under sudden drawdown conditions. Drawdown increases the gradient difference between the internal areas (i.e., dam body) and the external areas (i.e., the reservoir). It can also cause increased seepage forces on the upstream slope and on the foundation surface which may result in movement of soil particles in the flow direction causing erosion problems. In this paper, a numerical approach, based on the finite element method (FEM) is used to analyze the seepage through the dam and its foundation to determine the upstream exit gradients and slope stability. GeoStudio programs using the FEM are used to conduct both steady-state and transient analyses. Three typical designs of earth dams, with and without the core, are used to study the seepage and the upstream slope stability before and after the upstream drawdown event. Water flux, flow direction, exit gradient, and the slope factor of safety are calculated in each case. The results show that the core is important in reducing the flux through the dam. Constructing a cutoff under the core increases the efficiency of the core and lowers the phreatic line. However, the results also showed that the submerged weight increases when the earth dam is constructed with a core or with a complete low permeability cutoff. Increasing the submerged weight, in turn, causes higher water flux to flow out of the dam under the drawdown condition increasing the exit gradient. The exit gradient at the upstream slope may reach critical levels and cause failure of the dam. The factor of safety of the slope is also reduced because of increasing the buoyancy of the soil at the upstream side of the dam. Some preliminary results are presented in this paper.

Publication Date

1-1-2018

Publication Title

Geotechnical Special Publication

Volume

2018-March

Issue

GSP 297

Number of Pages

324-332

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

DOI Link

https://doi.org/10.1061/9780784481608.031

Socpus ID

85048926589 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85048926589

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