Embankment Dams -1-

http://www.britishdams.org/about_dams/embankment.htm

Embankment dams are made mainly from natural materials. The two main types are earthfill dams and rockfill dams. Earthfill dams are made up mostly from compacted earth, while rockfill dams are made up mainly from dumped and compacted rockfill. The materials are usually excavated or quarried from nearby sites, preferably within the reservoir basin. A cross-section (or slice) through an embankment dam shows that it is shaped like a bank, or hill. Most embankment dams have a central section, called the core, made from an impermeable material to stop water passing through the dam. Clayey soils, concrete or asphaltic concrete can be used for the core. Rockfill dams are permeable. They can have a core or an impermeable cover on the upstream face. Materials used for the cover include reinforced concrete and asphaltic concrete. Embankment dams are usually chosen for sites with wide valleys. They can be built on hard rock or softer soils, as they do not exert too much pressure on their foundations. The main type of dam in Britain is the embankment dam, and there are over 3000 of them. Some of them date back to the 9th Century, including Fishers Pond Dam, near Winchester, which was built by monks to provide fish. The average age of our embankment dams is over 100 years old.