Hydraulic Model Investigation. Spillway Pier Shape at Stoplog Slot for Chief Joseph Dam , Columbia River, Washington.
ARMY ENGINEER DIV NORTH PACIFIC BONNEVILLE OR DIV HYDRAULIC LAB
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The Chief Joseph Dam project was modified in the late 1970s to accommodate a 10-foot pool raise. Modification included raising and widening of the spillway piers. Inspection of the piers reconstructed early in the modification contact revealed that the as-built pier shape in the vicinity of the stoplog slots was considerably out of tolerance from the design shape. The as-built shape raised concern over potential for cavitation resulting from localized areas of low pressure near the stoplog slots. A 130 scale model was used to study the pressure regime in the area of the stoplog slot for design shape, three as-built shapes, and three alternative shapes to evaluate limiting criteria for correction of the misalignment if required. Study results indicate that during spillway design flood conditions pressures on the as-built piers tested could result in cavitational damage. During the later stages of construction, the piers conformed closely to the design shape, and the Seattle District decided that modification of the earlier reconstructed piers was not warranted. Author
- Civil Engineering