Some Minor Dams
SOME MINOR DAMS

Some Minor Dams

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SOME MINOR DAMS

  • Arch dam, and buttress dams come under the category of medium dams, although their use is not very common.
  • They have been discussed quite in details.
  • Earth dams and gravity dams are the most commonly used dams.
  • They will be discussed in their full perspective in subsequent chapters separately.
  • Steel dams and timber dams are also sometimes adopted but only as a temporary measure of storing water.
  • A brief description of steel and timber dams which are considered as minor dams have been given here.

STEEL DAM

1. Steel dams.

  • These dams are not in common use.
  • No dam in Indian has yet been constructed of steel.
  • In USA some dams had been constructed in steel in early part of this century.
  • These dams consist of a deck slab made of steel plates.
  • These plates are supported by inclined struts.
  • These dams may also be of cantilever type.
  • In this, a frame work of steel sections is installed in the rigid foundation and deck plate is fixed on them.
  • In this case tensile forces one induced in deck plate and girders.

Advantages

  1. They are cheaper than other rigid dams.
  2. They can be built in very short time with modern methods of fabrication.
  3.  They are more adaptable in case of unequal settlement of foundation.
  4. They are more leak proof.
  5. Frost action does not have any adverse effect on steel.
  6. They can be repaired easily by welding.

Disadvantages

  1. Life is shorter than concrete or masonry dam.
  2. They require constant maintenance.
  3. They are not as adaptable to vibrations due to spilling water.
  4. This is because they are too light.
  5. They have to be anchored with foundation.
  6. Bearing stresses are excessive as bearing are in this case is very small.

(a) Framed timber dam (b) Beaver timber dam.

Timber Dams

  • They are also a sort of temporary dams.
  • They consist of a frame work of wooden bullies and planks.
  • Timber dams are usually of three types.

 

1. Rock Filled Crib Timber.

  • In such dams, crib piers of wooden members are erected at centre to centre distances of 2 to 2.5 m.
  • In order to impart stability to the piers, rock boulders are filled in the open spaces left in the wooden members.
  • After having erected all the crib piers, along the centre line of the dam, timber planks are fixed to prepare the face for retaining water.
  • If rock foundation is available at the site, the bottom of the cribs is anchored with the rock.
  • In case of earth foundation, sheet piles are driven both at the U/S as well as D/S side of the cribs.
  • System of sheet piles or that of anchoring with rock foundation is essential to maintain the cribs in position.

Rock Filled Crib Timber

2. Beaver Type Timber Dam.

  • This dam does not involve even driving of sheet piles or anchoring with foundation rocks.
  • This dam is suitable for small heights and also where plentry of timber is easily available.
  • The stock is finally covered on water face by wooden planks.
  • To avoid scouring and also to add to the stability of the dam, the lower U/S end should be covered with boulders and sand.

 

 

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