Hydraulic Model Studies of Upper Stillwater Dam Stepped Spillway and Outlet Works

摘要

Hydraulic model studies were made to aid in the design of a stepped spillway. Stepped spillways, economically constructed of slip-formed conventional concrete, may be used where the unit discharge is low and the stilling basin size must be limited. An outlet works stilling basin, designed for submerged operation of a 14-inch jet-flow gate, was also studied. The results of the stepped spillway model study indicated that the crest shape is vital to efficient hydraulic operation and that the energy contained in the jet is minimal because of the tumbling action induced by the steps. Impact and subatmospheric pressures on the steps of the spillway face were also investigated. The outlet works stilling basin design was based on operation of the submerged 14-inch jet-flow gate under a maximum head of 207.5 feet and a discharge of 29 cu ft/s. Impact pressures, wave heights, and debris handling were investigated with the model.