Wednesday, 6 July 2011

Gravity dam

Gravity dam

Gravity dam - Dworshak Dam
The gravity dam is a massive structure made of masonry or concrete with earth and rock fill. Gravity dams use their own weight to resist opposing forces and as such require a hard bedrock foundation.[4] They rely on their great weight and size for stability.[7] The gravity dam is the most commonly built dam in the world. One of the reasons for this is the simplicity of design. Unfortunately it requires great quantities of material to construct.[8]

Arch dam

Glen Canyon Dam
Mratinje Dam in Montenegro
An arch dam is a thin, curved concrete or masonry dam structure, with the concave side of the curve downstream. Therefore, the force of the water against the canyon wall squeezes the arch, compressing and strengthening its structure and pushing it into the ground.[9] An arch dam is a good dam type for a narrow gorge in a mountainous area with steep walls of rock.[10] It generally has steel rods or prestressed steel cable reinforcements and therefore requires less concrete than a gravity or arch-gravity dam. However, the bedrock in the foundation and abutments must be sound to withstand the pressure of the water.[11]
Arch dams with more than one contiguous arch or plane are described as multiple arch dams. A double arch dam has two contiguous arches. A dam that is curved in both its horizontal and vertical planes may be called a dome dam.[11]

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