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Dams are specific to mountainous regions because electricity production depends on the head height and the water flow rate. Four types of dam are used, depending on geographic, geological and volumetric criteria:
Gravity dam (example in the Valais: Grande Dixence)
This type has, in principle, a triangular cross-section which is very wide at its base and narrows towards its peak. It is the weight of the concrete wall which resists the thrust of the water.
The arch-gravity dam is an intermediate solution. Its stability depends as much on its own weight as on the transfer of the thrust of the water to the valley walls.
Arch dam (example in the Valais: Mauvoisin)
This type combines spare lines and an impression of lightness. Rather than resisting the weight of the water directly, an arch dam deflects the thrust of the water back onto the valley walls by means of a concrete wall which curves both horizontally and vertically. The construction of a dam of this type is dependent on the shape of the valley and the topography of the land.
Buttress dam (example in the Valais: Cleuson)
The concrete wall of this type of dam is supported by reinforced concrete buttresses set into its foundation. These deflect the thrust of the water onto the lower foundations and onto the side walls. Buttress dams are generally built in valleys which are too wide for an arch dam, where the construction of a gravity dam, which requires a large quantity of material, would be too costly.
Embankment dam (example in the Valais: Mattmark)
An embankment dam is made of a quantity of materials built up to retain the water. Its centre consists of a completely waterproof core, reinforced upstream and downstream by backfill and layers of rock. The cross section of an embankment dam, unlike that of a concrete dam, is much wider than it is high. |
