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CHAPTER1:INTRODUCTION TO DAMS

Dams
It is an obstruction or barrier constructed across a stream
or a river
...

Storage of water is utilized for following objectives:
 Hydropower
 Irrigation
 Water for domestic consumption
 Drought and flood control
 For navigational facilities
 Other additional utilization is to develop fisheries

Structure of Dam
Upstream

Crest

Down stream
Spillway
(inside dam)

MWL
Max
...


 Diversion tunnel: Tunnels are constructed for diverting water before

the construction of dam
...


 Spillways: It is the arrangement near the top to release the excess

water of the reservoir to downstream side

 Sluice way: An opening in the dam near the ground level, which is

used to clear the silt accumulation in the reservoir side
...

2
...

4
...

6
...

8
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Good foundation should be available
It should be located in a narrow valley
It should have sufficient space for spillway
It should have impervious bed and sides so as to reduce errosion
It should fullfil the purpose like irrigation,drinking etc
Materials should be easily available near by site
It should have less submergence area i
...


Classification of Dams
Basis of
classification
• According to
use

Types
• Storage dam
• Detention
dam
• Diversion
Dam
• Coffer Dam

Examples
• Gravity dam
• Earth dam
• Arch dam ,etc
• Dike ,Debris dam

Classification of Dams
Basis of
classification
• According to
Hydraulic
Design

Types

Examples

• Over flow
dam

• Spill way dams

• Non over
flow dam

• Gravity dam
• Earthen dam
• Rock Fill dam

Classification of Dams
Basis of
classification
• According to
Material

Types
• Rigid dam

• Non-Rigid
dam

Examples
•
•
•
•

Gravity dams
Arch dams
Steel dams
Timber dams

• Earth dam
• Rock Fill dam

Classification of Dams

Basis of
classification
• According to
Structural
Behavior

Types

•
•
•
•

gravity dam
Arch dam
Buttress dam
Earth dam

Classification based on function or use
 Storage Dam

It is constructed to store water when excess supply is
available and to provide it later during the periods of deficiency
...
Sometimes no openings are provided and
water is allowed to percolate through banks and foundations to
add in the water of adjoining areas which may reduce necessity of
surface watering
...

Sometimes they are constructed to arrest and trap the
sediments flowing from the tributaries and keep the main
reservoir on main river free from sedimentation
...


Classification based on function or use
 Diversion Dam

They are used to raise the water level slightly to divert the
water in canals or ditches or conveyance systems
...
Generally it is in the form of weir or barrage
...


Classification based on function or use
 Coffer Dam

Temporary dam constructed to exclude water from a
specific area
...


Classification according to Hydraulic Design
 Non-Overflow Dam

Water is not allowed to flow over the crest
...

Non-overflow dams are constructed using wide variety of
materials such as earth, rock fill, masonry, concrete, etc
...

Some length of dam is kept at lower height than the remaining
one
...
They are made up of materials
which will not be eroded by discharge
...


Classification according to Material
 Rigid Dams

Constructed with rigid materials like masonry, concrete
steel or timber
...
Masonry is almost replaced
by concrete
...

Earth
:gravel, sand silt , clay
...

Rock fill
:Fragmental rock materials supporting
water tight membrane on U/S
...

84% dams are of embankment type
10% gravity, 45% arch, 1% buttress &
0
...
They may be straight or
curve in plan
...
Well adapted
for use as an spillway, can be constructed of any height, requires
least maintenance
...
g
...


TYPES OF DAMS
 Gravity Dams:
Reservoir
Force

 These dams are heavy and

massive
wall-like
structures of concrete in
which the whole weight
acts vertically downwards

As the entire load is transmitted on the small area of foundation, such dams are constructed where rocks
are competent and stable
...


 Bhakra Dam is across river

Sutlej in Himachal Pradesh

 The

construction of this
project was started in the year
1948 and was completed in
1963
...
high above the deepest foundation as straight concrete dam being more than three times the height
of Qutab Minar
...
16 m (1700 feet); Width at base 190
...
14 m (30 feet)
Bhakra Dam is the highest Concrete Gravity dam in Asia and Second Highest in the world
...
Resists the external
force by strong constructed in the region where foundation is not
strong enough
...


Earth Dams:
 They are trapezoidal in shape
 Earth dams are constructed

where the foundation or the
underlying material or rocks
are weak to support the
masonry dam or where the
suitable competent rocks are
at greater depth
...
Best suited when
the dam must be extremely high and narrow
...
g
...


Arch Dams:
 These type of dams are 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
abutments
 Arch dams are built across narrow,

deep river gorges, but now in
recent years they have been
considered even for little wider
valleys
...
C
...
or masonry wall type buttresses
...


Buttress Dam:
 Buttress Dam – Is a gravity

dam reinforced by structural
supports
 Buttress - a support that
transmits a force from a roof
or wall to another supporting
structure

This type of structure can be considered even if the foundation rocks are little weaker

•

Prepare a note on advantages & disadvantages
1
...

3
...


Gravity dam
Earthen dam
Arch dam
Buttress dam

Dams and earthquakes

Dams and climate change

Economic height of dam
 The height for which the cost of dam per unit storage is

minimum, then such height is called as economic height of a
dam
 So as to obtain the economic height, the various estimates are
prepared for construction costs by considering serial heights
of the dam

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