Embankment dam

An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay, or rock. It has a semi-pervious waterproof natural covering for its surface and a dense, impervious core. This makes such a dam impervious to surface or seepage erosion.[1] Such a dam is composed of fragmented independent material particles. The friction and interaction of particles binds the particles together into a stable mass rather than by the use of a cementing substance.[2]

Tarbela
Tarbela Dam in Pakistan. It is the largest earth-filled dam in the world.

Types

Embankment dams come in two types: the earth-filled dam (also called an earthen dam or terrain dam) made of compacted earth, and the rock-filled dam. A cross-section of an embankment dam shows a shape like a bank, or hill. Most have a central section or core composed of an impermeable material to stop water from seeping through the dam. The core can be of clay, concrete, or asphalt concrete. This dam type is a good choice for sites with wide valleys. They can be built on hard rock or softer soils. For a rock-fill dam, rock-fill is blasted using explosives to break the rock. Additionally, the rock pieces may need to be crushed into smaller grades to get the right range of size for use in an embankment dam.[3]

Safety

The building of a dam and the filling of the reservoir behind it places a new weight on the floor and sides of a valley. The stress of the water increases linearly with its depth. Water also pushes against the upstream face of the dam, a nonrigid structure that under stress behaves semiplastically, and causes greater need for adjustment (flexibility) near the base of the dam than at shallower water levels. Thus the stress level of the dam must be calculated in advance of building to ensure that its break level threshold is not exceeded.[4]

Overtopping or overflow of an embankment dam beyond its spillway capacity will cause its eventual failure. The erosion of the dam's material by overtopping runoff will remove masses of material whose weight holds the dam in place and against the hydraulic forces acting to move the dam. Even a small sustained overtopping flow can remove thousands of tons of overburden soil from the mass of the dam within hours. The removal of this mass unbalances the forces that stabilize the dam against its reservoir as the mass of water still impounded behind the dam presses against the lightened mass of the embankment, made lighter by surface erosion. As the mass of the dam erodes, the force exerted by the reservoir begins to move the entire structure. The embankment, having almost no elastic strength, would begin to break into separate pieces, allowing the impounded reservoir water to flow between them, eroding and removing even more material as it passes through. In the final stages of failure the remaining pieces of the embankment would offer almost no resistance to the flow of the water and continue to fracture into smaller and smaller sections of earth or rock until these would disintegrate into a thick mud soup of earth, rocks and water.

Therefore, safety requirements for the spillway are high, and require it to be capable of containing a maximum flood stage. It is common for its specifications to be written such that it can contain a hundred year flood.[5] Recently a number of embankment dam overtopping protection systems have been developed.[6] These techniques include the concrete overtopping protection systems, timber cribs, sheet-piles, riprap and gabions, reinforced earth, minimum energy loss weirs, embankment overflow stepped spillways and the precast concrete block protection systems.

See also

Notes

  1. ^ "Dam Basics". PBS. Retrieved 2007-02-03.
  2. ^ "Introduction to rock filled dams". Retrieved 2007-02-05.
  3. ^ "About Dams". Retrieved 2007-02-03.
  4. ^ "Pressures Associated with Dams and Reservoirs". Retrieved 2007-02-05.
  5. ^ "Dams – Appurtenant Features". Retrieved 2007-02-05.
  6. ^ H. Chanson (2009). Embankment Overtopping Protections System and Earth Dam Spillways. in "Dams: Impact, Stability and Design", Nova Science Publishers, Hauppauge NY, USA, Ed. W.P. Hayes and M.C. Barnes, Chapter 4, pp. 101-132. ISBN 978-1-60692-618-5.

External links

Akköprü Dam

Akköprü Dam is an embankment dam on the Dalaman River in Muğla Province, Turkey, built between 1995 and 2009. It supports a 115 MW power station and provides water for the irrigation of 14,192 hectares (35,070 acres).

Bahçelik Dam

Bahçelik Dam is an embankment dam on the Zamanti River in Kayseri Province, Turkey, built between 1996 and 2002.

Berdan Dam

Berdan Dam is an embankment dam on the Berdan River in Mersin Province, Turkey. It was built between 1975 and 1984. It supports a 10 MW power station and provides water for the irrigation of 27,050 hectares (66,800 acres).

Derbent Dam

Derbent Dam is a gravity/embankment dam on the Kızılırmak River in Samsun Province, Turkey. The development was backed by the Turkish State Hydraulic Works.

Erzincan Dam

Erzincan Dam is an embankment dam on Cardakli Creek in Erzincan, Turkey. The development was backed by the Turkish State Hydraulic Works.

Glenbawn Dam

Glenbawn Dam is a major ungated earth and rock fill with clay core embankment dam with concrete chute spillway plus fuse plugs across the Hunter River upstream of Aberdeen in the Hunter region of New South Wales, Australia. The dam's purpose includes flood mitigation, hydro-electric power, irrigation, water supply and conservation. The impounded reservoir is called Lake Glenbawn.

Glenbawn Dam was created through enabling legislation enacted through the passage of the Glenbawn Dam Act, 1946 (NSW). The Act appropriated A£1,500,000 as the estimated cost of construction of the dam.

Kantale Dam

The Kantale Dam Tamil: கந்தளாய் அணை, translit. Kantaḷāy Aṇai) is a large embankment dam built in Kantale, Trincomalee District, Sri Lanka, used for irrigation. It is 14,000 ft (4,267 m) long, and over 50 ft (15 m) high. The dam breached on April 20, 1986 (1986-04-20), killing more than 120 people. It has since been reconstructed. The dam impounds the Per Aru, a small river discharging into the Koddiyar Bay, at Trincomalee Harbour.

Kapulukaya Dam

Kapulukaya Dam is an embankment dam on the Kızılırmak River in Kırıkkale Province, Turkey. The development was backed by the Turkish State Hydraulic Works.

Kozan Dam

The Kozan Dam is a dam is an embankment dam on the Kilgen River in Adana Province, Turkey. It is 8 km (5 mi) north of Kozan. Constructed between 1967 and 1972, the development was backed by the Turkish State Hydraulic Works. The purpose of the dam is flood control and irrigation. It helps irrigate 10,220 ha (25,254 acres) of land.

Köprübaşı Dam

Köprübaşı Dam is an embankment dam on the Bolu River Zonguldak Province, Turkey. The development was backed by the Turkish State Hydraulic Works.

Kızılcapınar Dam

Kızılcapınar Dam is an embankment dam on the Kızlar River Zonguldak Province, Turkey. The development was backed by the Turkish State Hydraulic Works.

Lostock Dam

Lostock Dam is a minor rockfill and clay core embankment dam with a concrete lined, flip bucket spillway across the Paterson River upstream of the village of East Gresford in the Hunter region of New South Wales, Australia. The dam's purpose includes flood mitigation, irrigation, water supply and conservation. Mini hydro-power facilities were retrofitted in 2010. The impounded reservoir is also called Lostock Dam.

Menzelet Dam

Menzelet Dam is an embankment dam on the Ceyhan River in Kahramanmaraş Province, Turkey. The development was backed by the Turkish State Hydraulic Works.

Obruk Dam

Obruk Dam is an embankment dam on the Kızılırmak River in Çorum Province, Turkey. Constructed between 1996 and 2007, the development was backed by the Turkish State Hydraulic Works. The dam supports a 203 MW power station.

Palandöken Dam

Palandöken Dam is a rock-fill embankment dam on the Lezgi River near Çat in Erzurum Province, Turkey. Constructed between 1985 and 1988, the development was backed by the Turkish State Hydraulic Works. The purpose of the dam is irrigation and it provides water for up to 11,678 ha (28,857 acres) of land.

Randenigala Dam

The Randenigala Dam is a large hydroelectric embankment dam at Rantembe, in the Central Province of Sri Lanka. Construction of the dam began in November 1982, and was completed in approximately 4 years. The dam and power station was ceremonially opened by then President J. R. Jayawardene in 1986.

Construction of the dam cost approximately Rs. 4.898 billion (1986), of which 24.6% (Rs. 1.207 billion) was funded by the local government, and the majority of the remainder by Germany.

Spring Creek Dam (New South Wales)

Spring Creek Dam is a minor embankment dam across the Spring Creek upstream of Orange in the central western region of New South Wales, Australia. The impounded reservoir is called the Spring Creek Reservoir.

Tercan Dam

Tercan Dam is an embankment dam on the Tuzla River in Erzincan Province, Turkey. Constructed between 1969 and 1988, the development was backed by the Turkish State Hydraulic Works. The dam has an installed capacity of 15 MW and provides water for the irrigation of 29,725 hectares (73,450 acres).

Çamlıgöze Dam

Çamlıgöze Dam is an embankment dam on the Kelkit River in Sivas Province, Turkey. The development was backed by the Turkish State Hydraulic Works.

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