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.
