Inflatable Dams
The principle was invented in 1947 by M. Mesnager, Professor of Engineering. The first inflatable dam was produced in the USA in 1959 to supply water to Los Angeles. EdF (French national electric utility) built its first inflatable dam at Aubas, on the Vezere, in 1960. The 60s and 70s saw ten inflatable dams being built in France, including four for EdF, Around half these structures are still giving satisfactory service.
Satujo built a new, experimental structure on the Meuse in 1985 at the behest of the Maritime Ports and Navigable Waterways Centralised Technical Department.
Initiated by CNEPE, EdF`s specialist nuclear design office, a new structure was built for EdF for the Civaux nuclear power plant on the Vienne. During this time, a hundred or so structures were produced in the USA plus over 2,000 throughout the world in under twenty years!
Design:
The most common design is a rectangular membrane the length of the horizontal raft, ending in two triangles on the sloping dock walls.
The membrane is anchored over its entire area along an upstream and a downstream line, which meet at the extreme tips of the triangles.
Dimensions:
The rated height (H) to date is 6m. There is no limit as to width (W) as several bays can be placed side-by-side. In practical terms, the vast majority of current structures are formed of 2- to 4-metre high bays, between 20 and 50 m wide. The practical maximum is between H2m x WlOOm and H6m x W20m for each bay.
Inflation
The structure is usually inflated with air or occasionally water.
Air is normally chosen because there is no risk of freezing and it is more rapidly manoeuvrable. Conversely, the transverse dimensions are lower (-30on the effective length of the membrane, reducing the raft dimension by the same amount). Nevertheless, in a traditional section, there is more limitation in the maximum height of the spilling water:
- usually 0.20 x H for air inflation.
- against 0.50 x H for water inflation.
- for dynamic reasons. However, overflow requirements of more than 20can be met by modifying the section when inflating with air.
Deflation (draining) is automatic, triggered by overshooting a setting on the upstream water level. All possibilities exist in this field.