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Smith Mountain Dam, Virginia

 

Smith Mountain Dam is a double-curvature arch structure rising 235 feet above the bedrock foundation, with a crest elevation of 812 feet and a crest length of 816 feet. The dam varies in thickness from 9.5 feet at the crest to 32 feet at the base. Constructed in the period of 1960 to 1966, the thin arch structure is the principal element of the Smith Mountain Pumped Storage and Hydroelectric Project. Five steel penstocks, two of 20 ft and three of 26 ft in diameter, penetrate the arch dam and convey stored water to the five turbines that collectively can generate 565 MW of power. The three larger penstocks penetrate the dam at elevation 750 ft, while the other two penetrate the dam at elevations 665 ft and 605 ft.

Three-dimensional finite-element stress analyses, abutment wedge stability analyses, and overtopping scour assessment were conducted to evaluate static stability conditions of Smith Mountain Dam. Two finite-element models with and without the penstock openings were developed and analyzed for separate and combined action of gravity, hydrostatic, and temperature loads to investigate the effects of penstock openings on dam stresses.

The sliding stability of right abutment was evaluated for four potential sliding modes and the most critical mode was analyzed to compute factor of safety. The loading from the arch dam and thrust blocks, hydrostatic forces, and the rock loading were applied in the stability analysis.

The potential for abutment scour due to overtopping flow under probable maximum flood conditions was investigated making use of Annandale's Erodibility Index Method. The method relates the relative ability of rock to resist scour to the erosive power of water by means of an empirical erosion threshold line.



 

 

 

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