8/7/2019 STRUCTURES SEMINAR DAM

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A concrete gravity dam has a cross section such that with a flat bottom, the da mis free standing. That is, the dam has a center of gravity low enough that thedam will not topple if unsupported at the abutments. Gravity dams requiremaximum amounts of concrete for their construction as compared with otherkinds of concrete dams, and resist dislocation by the hydrostatic pressure ofreservoir water by sheer weight. A favourable site usually is one in a constrictionin a valley where the sound bedrock is reasonably close to the surface both inthe floor and abutments of the d am. The availability of suitable aggregate formanufacture of concrete is also an important consideration. Masonry dams thatrelied upon their weight for stability against sliding and overturning date back3000 to 4000 years, both upstream and downstream faces were sloped and thebase thickness was many times the height. In 1872 Rankine proposed that thereshould be no tensile stress in a gravity dam. In 1895 Levy proposed that thecompressive stress in the material of the dam at the upstream face should begreater than the water pressure at the corresponding depth in the reservoir.The danger from uplift had been recognised in 1882, and the danger of slidingwas highlighted by the failure of the Austin Dam, USA. The most recent advanc ehas been in the ap plication of the finite element method of analysis.

Bhakra Nangal Dam is a concrete gravity dam across the Sutlej River, near the border

between Punjab and Himachal Pradesh. The dam, located in the village of Bhakra in the

Bilaspur region of Himachal Pradesh. It is the highest gravity dam in the world. The length of

the dam (measured from the road above it) is 518.25 m; it is 304.84 m broad. Its reservoir,

known as the "Gobind Sagar", stores up to 9340 million cu m of water, enough to drain the

whole of Chandigarh, parts of Haryana, Punjab and Delhi. The 90 km long reservoir created

by the Bhakra Nangal Dam is spread over an area of 168.35 km2. In terms of storage of

water, it is the second largest dam in India, the first being Indira Sagar dam in Madhya

Pradesh with capacity of 12.22 billion cu m.

Bhakra Nangaldam houses hydroelectric power generators, which are situated on both the

sides of the dam. It has 4 flood gates & has 2 power- stations situated on the either side of

the dam. Each of the power p lants comprise of 5 generators, and a power station.

Two power houses with a total capacity of 1000 MW flank the dam. The Bhakra Dam is

situated in the Indian state of Himachal Pradesh (India), 80/90% of the electricity produced is

given to Delhi leaving only 10/20% to Punjab which faces a lack of electricity itself.

Total power produces by the Bhakra dam is 1209 MW.

STATISTICS :Project took 15 years to construct and employ3000 workmen and 300 engineers.

Over 52 lakh cubic metres of concrete , 1.02lakh metric tonnes steel and 8.13 lakh tonnesof cement used.

Total investment amonted to 235 crore.

Useful life of dam estimated at over 400 yrs.

Type of Dam: Concrete Straight Gravity

Height: 740 ft (225.55 m)Height (above river bed): 550 ft (170 m)Length at top: 1,700 ft (520 m)Width at top: 30 ft (9.1 m)Length at bottom: 325 ft (99 m)Width at base: 625 ft (191 m)Elevation at top of dam: 1700 ft (above sealevel)Steel used: 100000 tons

Dams are structural barriers built to obstruct or control the flow of water in rivers and streams.They are designed to serve two broad functions. The first is the storage of water to compensatefor fluctuations in river discharge (flow) or in demand for water and energy. The second is theincrease ofhydraulic head , or the difference in height between water levels in the lake createdupstream of the dam and the downstream river.By creating additional storage and head, dams can serve one or more purposes:Generating electricity;Supplying water for agricultural, industrial, and household needs;Controlling the impact of floodwaters; andEnhancing river navigation.They can be op erated in a manner that simultaneously augments downstream water quality,

enhances fish and wildlife habitat, and provides for a variety of recreational activities, such asfishing, boating, and swimming.

Dams can be classified as per their sizes and construction method.

International standards define large dams as higher than 15-20 meters and major dams as over150-250 meters in height.

A saddle dam is an auxiliary dam c onstructed to confine the reservoir created by a primary dameither to permit a higher water elevation and storage or to limit the extent of a reservoir forincreased efficiency. An auxiliary dam is constructed in a low spot or saddle through which thereservoir would otherwise escape.

An overflow dam is designed to be over topped.

A check dam is a small dam designed to reduce flow velocity and control soil erosion.Conversely, a wing dam is a structure that only partly restricts a waterway, creating a fasterchannel that resists the accumulation of sediment.

A dry dam is a dam d esigned to control flooding. It normally holds back no water and allows thechannel to flow freely, except during periods of intense flow that would otherwise cause floodingdownstream.

A diversionary dam is a structure designed to divert all or a portion of the flow of a river from itsnatural course.

By structure or construction methods dams can be classified asMasonry damTimber damEmbankment damSteel dam

Masonry dams are further classified asArch damGravity dam

Embankment dams have the following classifications:Rock-fill damEarth-fill damAsphalt-concrete dam.

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