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Types of
DAMSArvind Gupta
M. Tech.-AHES(1st Yr.)
12512006
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Contents:
Definitions
Purposes
Classifications On the basis of size
On the basis of structure and material used
Environmental issues References
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Definitions:
A dam is a structure which prevents the flow of
water and accumulates it in a reservoir
Dam is a solid barrier constructed at a suitablelocation across a river valley to store flowing water.
A barrier constructed across a waterway to controlthe flow or raise the level of water.
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Purpose:
1. Drinking and domestic water supply2. Flood control3. Irrigation
4. Industrial water supply5. Hydroelectric energy production6. Retention and control of sediments7. Inland navigation
8. Improvement of water quality9. Fish Farming10. Recreation facilities
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Classification of Dams
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According to size of a Dam
Large dams
Small dams
According to International commission on Large
Dams, a dam is big if height is more than 15m.
According to ICOLD, if the height is between 10m-
15m the dams is big:
If the crest length is bigger than 500m
If the reservoir capacity is larger than 1 million m3
If the flood discharge is more than 2000 m3/s
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According to Height of dam
High Dam
If the height is more than 100m.
Medium Dam
If the height is between 50-100m
Low Dam
If the height is below 50
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According to structure and materials
used
Gravity dams
Arch dams
Arch-gravity dams
Buttress dams
Barrages
Embankment dams Homogeneous earth dams
Non-Homogeneous (zoned) earth dams Rolled fill earth dams
Hydraulic fill dam
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Gravity Dams
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Gravity dams are dams which resist the horizontal thrust of
the water entirely by their own weight. They use their weight
to hold back the water in the reservoir.
The section of the gravity dam is approximately triangular in
shape, with its apex at its top and maximum width at bottom.
A gravity dam is generally straight in plan and, therefore, it is
also called straight gravity dam.
A gravity dam is made of concrete or masonry.
It requires great quantities of material to construct.
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Section of a Gravity Dam
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The non-overflow section and
The over flow section or spillway section.
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Bhakra Dam, Himachal Pradesh - India's second tallest at 225.55 m
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Arch Dam
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An arch dam is curved in plan, with its convexity towards the
upstream side. They transfers the water pressure and other forces
mainly to the abutments by arch action.
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An arch dam is quite suitable for narrow canyons withstrong flanks.
The section of an arch dam is approximately triangularlike a gravity dam but the section is comparativelythinner.
An arch dam is most suitable for narrow gorges.
Since they are thinner than any other dam type, theyrequire much less construction material, making them
economical and practical in remote areas.
The foundation or abutments for an arch dam must bevery stable and proportionate to the concrete.
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There are two basic designs for an arch dam:
constant-radius dams, which have constant radiusof curvature, and
variable-radius dams, which have both upstream
and downstream curves that systematically
decrease in radius below the crest
A dam that is double-curvedin both its
horizontal and vertical planes may be calleda dome dam.
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Idukki Dam, Kerala- First Arch dam in India
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Arch-Gravity Dam
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An arch-gravity dam, curved-gravitydam or arched dam is a dam with the
characteristics of both an arch dam and a gravitydam.
It combines the strengths of two common dam
forms and is considered a compromise betweenthe two.
A gravity dam can be combined with an arch dam
into an arch-gravity dam for areas with massiveamounts of water flow but less material availablefor a purely gravity dam.
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Hoover dam, Arizona, US
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Buttress dams
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A buttress dam or hollow dam is a dam with asolid, water-tight upstream side that is supportedat intervals on the downstream side by a seriesof buttresses or supports.
The dam wall may be flat or curved.
In comparison with massive gravity dams,buttress dams save 40 percent and more inconcrete and costs.
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Buttress Dam
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Buttress Dam
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Barrages
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A barrage dam is a special kind of dam whichconsists of a line of large gates that can be
opened or closed to control the amount ofwater passing the dam.
The gates are set between flanking pierswhich are responsible for supporting thewater load.
They are often used to control and stabilizewater flow of rivers for irrigation systems.
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Farakka barrage, WB
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Embankment Dams
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A dam composed of any type of soil including rock isknown as embankment dams. These are classified into
two main categories :
Earth-fill dams
An earthfill dam is an embankment dam, constructed
primarily of compacted earth, either homogeneous or
zoned, and containing more than 50% of earth.
Rock-fill dams
An embankment type of dam, dependent for its stabilityprimarily on rock.
The earth utilized often contains a large percentage of
large particles hence the term rock-fill.
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Rock-fill Dam:
An embankment consisting of various sizes of rock to
provide stability and an impervious core of membrane to
provide water-tightness.
The impervious zone may be on the upstream face and
made of masonry, concrete, plastic membrane, steel
sheet piles, timber or other material.
The impervious zone may also be within the
embankment in which case it is referred to as a core.
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Central core
Sloping core
Upstream core
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New Melones Dam, California, US
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Earthfill dams:
. Local available soil is the main construction material
It must be sufficiently impervious to prevent excessive
loss of water through the dam.
The soil should develop a maximum practical shear
strength under compaction and maintain most of it after
the filling of the reservoir;
It must not consolidate, soften or liquify upon saturation.
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Ranjit Sagar Dam, Punjab
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Types of Earthfill dams:
Homogeneous earth dams
Non-Homogeneous (zoned) earth dams
Rolled fill earth dams
Hydraulic fill dam
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Homogeneous earth dams
These dams are constructed with uniform andhomogeneous materials. It is suitable for low height
dams (up to 10m).
The seepage action of such dams are not favourable,
therefore, for safety in case of rapid drawdown, the
upstream slope is kept relatively flat (3:1)
Homogeneous section is modified by constructing rock
toe at the downstream lower end and providing
horizontal filter drain.
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Homogeneous earth dams
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Non-Homogeneous (zoned) earth
dams
These are dams with the central portions called core
or hearting made from materials which are relatively
impervious.
The thickness of the core wall is made sufficiently
thick to prevent leakage of water through the bodyof the dam.
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Rolled fill earth dams
An embankment dam of earth or rock in which the
material is placed in layers and compacted by the use of
rollers or rolling equipment.
In this type of dams, successive layers of moistened or
damp soils are laid one over the other. Each layer not
exceeding 20 cm in thickness is properly consolidated at
optimum moisture content, only then is the next layer
laid.
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Hydraulic Fill dams
During construction, a mixture of excavated materials in slurry
condition is pumped and discharged at the edges.
When it is discharged near the outer edges, the coarser
materials settle first at the edges, while the finer materials
move to the middle and settle there.
Fine particles are deposited in the central portion to form a
water tight central core. In this method, compaction is not
required.
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Rubber Dam
Inflatable rubber dams are cylindrical rubber fabrics
placed across channels, streams and weir or dam
crests to raise the upstream water level when inflated.
The membrane is a multi-layer fabric made of synthetic
fibre (usually nylon)and rubberised on one or both
sides.
The fabric is quite flexible and yet exhibits good wear-
resistance characteristics
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Jhanjavathi Rubber Dam, Andhra Pradesh- Indias 1st Rubber dam
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Environmental Issues:
Dams disturb natural fluctuations in water flow
Dams block migratory fish species from their spawning
and feeding sites
Water quality can be degraded The transport of sediment along the river is disrupted
Reservoirs can emit climate-changing greenhouse gases
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References
Varshney, R. S., Hydro Power Structures
Wikipedia http://en.wikipedia.org/wiki/Dam
http://www.idk.kerala.gov.in/index.php?option=com_content&view=article&id=85
&Itemid=58\
http://nptel.iitm.ac.in/courses/Webcourse-
contents/IIT%20Kharagpur/Water%20Resource%20Engg/
pdf/m4l06.pdf
http://beengineeringinfo.blogspot.in/2012/04/types-of-dams-introduction-
and.html
http://www.dur.ac.uk/~des0www4/cal/dams/emba/emba.htm
http://theconstructor.org/water-resources/earthfill-dams-its-classification/2273/
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Thank You!
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Questions..??