An arch-gravity dam or arched dam is a dam with the characteristics of both an

arch dam An arch dam is a concrete dam that is curved upstream in plan. The arch dam is designed so that the force of the water against it, known as hydrostatic pressure, presses against the arch, causing the arch to straighten slightly and strength ...

and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the water pressure against the

canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to cut ...

rock walls, providing the force to compress the dam. It combines the strengths of two common dam forms and is considered a compromise between the two. They are made of conventional

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most ...

, roller-compacted concrete (RCC), or

masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar; the term ''masonry'' can also refer to the units themselves. The common materials of masonry construction are bricks, building ...

. Arch-gravity dams are not reinforced except at the

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure t ...

. A typical example of the conventional

dam is the Hoover Dam. Changuinola Dam is an example of the RCC arch-gravity dam. A gravity dam requires a large volume of internal fill. An arch-gravity dam can be thinner than the pure gravity dam and requires less internal fill.

Overview

Arch-gravity dams are dams that resist the thrust of water by their weight using the force of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the str ...

and the arch action. An arch-gravity dam incorporates the

arch An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it. Arches may be synonymous with vau ...

's curved design which is effective in supporting the water in narrow, rocky locations where the

gorge A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to c ...

's sides are of hard rock and the water is forced into a narrow channel. Therefore, the span needed for the dam is also relatively narrow, and the dam's curved design effectively holds the water back while using less construction material compared to a pure arch dam or gravity dam. These dams are more reliable than arch dams. Typically, arch-gravity dams are built in canyon-like terrain, with the surrounding cliffs serving as supporting walls. Such dams are usually up to hundreds of metres thick at the base, gradually decreasing to 10-30 metres towards the crest. The use of an arch-shaped bank-fill dam reduces the overall mass of the structure and the cost of construction compared to purely gravity dams. For this reason, along with arch dams, arch-gravity dams are most commonly used in hydraulic structures of more than 100 m in height.

Footnotes

{{reflist, 25em 01 Dams by type Arches and vaults Concrete buildings and structures Masonry dams

Overview

See also

Footnotes