An Embankment dam is a massive semi-plastic mound of earth and/or rock with a dense, waterproof core.[1] The force of the dammed water pushes the heavy weight of the dam down into the ground, strengthening the dam and preventing it from falling over.[2] 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 the use of a cementing substance.[3]
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Types
Embankment dams come in two types: the earth filled dam (or earthen 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. Since they exert little pressure on their foundations, they can be built on hard rock or softer soils. For a rockfill dam, rockfill is blasted using explosives to break the rock. Additionally. the rock pieces may need to be crushed into smaller chunks to get the right range of size for use in an embankment dam.[4]
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.[5] Overflow of an embankment dam outside of its spillways can cause disastrous flooding. Therefore safety requirements for the spillway are high, requiring the spillway to be capable of containing a maximum flood stage. Specifying a spillway able to contain a hundred year flood is common.[6]
See also
Notes
- ^ Dam Basics. PBS. Retrieved on 2007-02-03.
- ^ Embankment dam: forces. PBS. Retrieved on 2007-02-03.
- ^ Introduction to rock filled dams. Retrieved on 2007-02-05.
- ^ About Dams. Retrieved on 2007-02-03.
- ^ Pressures Associated with Dams and Reservoirs. Retrieved on 2007-02-05.
- ^ Dams - Appurtenant Features. Retrieved on 2007-02-05.
