types of dam

 INTRODUCTION
 TYPES OF DAMS
 STRUCTURE OF DAM
 PRELIMINARY INVESTIGATION
 SITE SELECTION F0R DAM
 FACTORS AFFECTING ON DAM
 PURPOSES OF DAM
 FAILURE OF DAM
 CONCLUSION
 REFERENCES

WHAT IS DAM ?
 A dam is a barrier constructed across a river or a natural stream to
create a reservoir for impounding water or to facilitate diversion of
water from the river.
 At back side of this barrier water gets collected, forming a pool of water,
the side on which water gets collected is called as upstream side and the
other side of barrier is called as downstream side. The lake of water
which is collected on upstream side of dam is called as a reservoir.
 Dam is a very large structure, generally length is about half kilometer
constructed across the river to storage a water for many purposes like,
irrigation, industrial supply, hydropower, recreation etc.

 Generally, the dam should be constructed of ‘V’ shape thus to achieve
economy in it’s construction.
 The tallest dam in the world is ‘NUREK DAM’ in Tajikistan has 300m high
and the ‘BHAKRA DAM’ is the highest in Asia and second highest in the
world. The BHAKRA dam is constructed across river SULTEJ in Himachal
Pradesh and has 246m high, the construction of this dam was started in
the year 1948 and was completed in 1963.
 RAW MATERIALS :
Dams may be constructed of raw materials like, masonry, timber, steel,
gravel, clay, sand and silt etc.

The type of dam depends upon the condition of dam site, the main
Type of dam are as follows :-
 Earthen dam
 Gravity dam
 Arch dam
 Buttress dam

 The dams which are constructed of
earthen materials such as gravel sand,
silt and clay are called as ‘ Earthen Dam’.
 They are ‘trapezoidal’ in shape. Earthen dams are relatively smaller in
height and broad at the base.
 Earthen dams are constructed where the foundation or the underlaying
materials or rocks are weak to support the masonry dam or where the
suitable competent rock are at greater depth.

 Gravity dam is a solid structure made up
of masonry or concrete and are
constructed across the river to resist the
forces exerted upon it by it’s own weight.
 These dams are heavy and massive wall like structures of concrete in
which the whole weight act vertically downwards.
 As the entire load is transmitted on the small area of foundation, such
dams are constructed where rocks are competent and stable.
 Example :- ‘BHAKRA DAM’ is the highest concrete gravity dam.

 These types of dams are constructed
of concrete or masonry dams which
are curved or convex upstream in
plan.
 This shape helps to transmit the major part of the water load to the
abutment.
 Arch dams are built across narrow, deep river gorges, but now in recent
years they have been considered even for little wider valleys.

 ‘Buttress’ means a support that
transmits a force from a roof or
wall to another supporting
structure.
 Buttress dam is a gravity dam
reinforced by structural supports.
 This type of structure can be considered even if the foundation rocks are
little weaker.

 HEEL :- Contact with the ground on the upstream side.
 TOE :- Contact on the downstream side.
 ABUTMENT :- Sides of the valley on which the structure of the dam rest.
 GALLERIES :- A gallery is an opening provided in a dam for obtaining
access to the interior of dam.
 SPILLWAY :- It is the arrangement near the top to release the excess
water of the reservoir to downstream side.
 SLUICE WAY:- It is an opening in the dam near the ground level, which is
used to clear the silt accumulation in the reservoir side.
 FREE BOARD :- It is the vertical distance between top bund level and high
flood level.

 To do all preliminary survey like engineering, hydrological, geological
and detailed survey etc.
 To collect the report about maximum height of flood level by past 35
years at dam site.
 To know the soil condition and bearing capacity, to decide the type of
dam to be constructed at dam site.
 To collect the information about people getting benefit from the dam and
maximum area is to be irrigated by the dam.
 To know the maximum annual rainfall at the dam site.

 Good foundation should be available.
 It should be located in a narrow valley.
 It should have sufficient space for spillway.
 It should fulfill the purpose i.e. irrigation, drinking etc.
 Material should be easily available near by site.
 It should be easily accessible throughout the year.

 Funds available
 Topography
 Availability of materials
 Nature of foundation
 Spillway position
 Height of dam
 Earthquakes

Dams are constructed for following purposes :-
 Irrigation
 Hydropower generation
 Water supply
 Flood control
 Recreation
 Industrial water supply

The cause may be occur due to the following reasons :-
 Poor surveying
 Spillway design error
 Extreme rainfall
 Due to earthquakes
 Human, computer or design error
 Poor maintenance

 From above this it is clear that , before constructing dam the site
selection and preliminary investigation is very important factor
while designing the dam and the selection of type of dam are also
depending on the soil condition at dam site.

types of dam

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types of dam