Model and Prototype Tests of Buoyant Spillway Gates

Design of a radial gate, modified to obtain an opening torque, and with an additional upstream projection to obtain buoyancy for fail-safe operation is presented. Operating requirements for a full reservoir during the winter storm period precluded an uncontrolled spillway or holding gates open. An earth and rock fill dam, on the contrary, required fail-safe spillway control. A difficult site added to the design and cost problems. The gate, which evolved, can open to pass in excess of the flood of record without an external power source or without float wells, tripping devices, counterweights, or other accessories. Model tests were conducted to determine downpull effects of flow under the gate and through adjacent gates. Prototype tests under actual operating conditions were also conducted. Prototype and model test results are compared. Adjustable side plates replace conventional seals to eliminate seal friction but keep leakage to a tolerable limit. Operating experiences are also considered.