dams - arvindgupta-12march13

7/28/2019 Dams - ArvindGupta-12March13

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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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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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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..??

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