The concept of fusegate spillways was developed by Hydroplus Inc. (France). These spillways operate as labyrinth weirs divided into segments or individual fusegates. Each fusegate sits on a concrete base and remains in place by gravity and two concrete abutment blocks that prevent sliding. The individual fusegates are designed to tip backwards and tumble downstream when a certain pool elevation is reached in the reservoir.
Tipping of a fusegate is initiated by water entering the base chamber of the fusegate through an intake well set to the design water elevation. The model study was unique in that the model fusegates were completely functional and operated in the same manner as the prototype. In typical fusegate applications, fusegates have been designed with individual wells on each fusegate, the fusegates are normally located directly at the reservoir outlet, and the fusegates operate in an un-submerged downstream flow condition.
Both the Terminus model and spillway designs were unique in the positioning of the fusegates in an inlet channel with high approach velocities, the location of the fusegate wells combined into an intake tower adjacent to the spillway sill, and the operation of the fusegates in a submerged condition with high tailwater.
Construction of Fusegates and Spillway (model on the left) at Terminus Dam, Lake Kaweah, California.
Fusegates and Spillway Model. Terminus Dam, Lake Kaweah, California.