a mobile structure for completely or partially closing a water-release aperture in a hydroengineering installation (such as an overflow dam, lock, pipeline, fish ladder, or hydraulic tunnel). A hydraulic floodgate serves to control the level and consumption of water or the passage of floating bodies (such as ships, timber, ice, or silt) under the various operating conditions of a hydro-engineering installation.
The main elements of a hydraulic floodgate are the movable structure, support members (stationary components set into the body of the structure), and seals to prevent water from coming between the moving parts and the mounting. The floodgates are opened and closed by stationary or mobile machinery (including winches, cranes, and hydraulic hoists), by water pressure (water-powered hydraulic floodgates), or, for small water-release openings, by hand. Remote and automatic controls are often used to operate hydraulic floodgates.
Hydraulic floodgates are classified according to their location in a hydroengineering installation: they may be surface gates (on the crest of a spillway) or submerged gates (below the surface of the headrace). They are also classified by purpose as main (working), repair, damage, construction, and spare floodgates; and by materials used as metal (steel), wooden, reinforced-concrete, plastic, or combined floodgates.
Mechanically operated surface floodgates are the most widespread, in view of their simplicity, dependability, and good operational and technical-economic indexes. They span openings up to 45 m wide and up to 20 m high. Sectional and bear-trap gates span bays up to 50 m in size. Turning girders or frames and valve-type gates are among the types used to block the navigation passages in dams with spans up to 200 m and more.
Submerged floodgates, sometimes several hundred meters deep, work under high pressures. They are opened where the water flows at considerable speeds, a circumstance that involves the possibility of a vacuum and the development of cavitation and also vibration of the gate. In order to avoid this, the gate and water conduits are designed with flow characteristics to make sure that air is delivered to the region where a vacuum might form. At heads of up to 100 m and where the opening to be blocked is large, sectional and flat floodgates are used. In order to control expenditures of water at heads up to 800 m, needle-shaped gates with high performance characteristics are used.
REFERENCEBerezinskii, A. R. Verkhnee stroenie plotiny. Moscow, 1949.
Grishin, M. M. Gidrotekhnicheskie sooruzheniia. Moscow, 1968.
A. R. BEREZINSKII