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Limestone was used to resist erosion and wave action.Was constructed to prevent erosion and reduce treat of flooding.Large slabs were used as core and external were made with masonry.
design of gravity dam
Analysis and design of gravity dam in seismic zone V Project by: • Mr. Risso Johnny • Mr. Kapu Takar • Mr. Atan Ketan • Mr. Manoj Thorat • Mr. Shaikh Arshanaj.
Dam• Dam is a solid barrier constructed at a suitable location across a river valley to store flowing water. Need and Necessity:• Irrigation• Water for domestic consumption• Drought and flood control• For navigational facilities• Hydroelectric power generation• Recreation• Development of fish & wild life• Soil conservation 2
History of Dams• First dam was constructed by the Egyptians in 2950-2750 B.C, using stone/ brick masonry.• Earth dam was built first in Mesopotamia around 2000 B.C.• Romans used concrete and mortars around 100 AD.• Due to large size and amount of building material need to construct earth and gravity dams 3
Grand Anicut (Kallanai)The oldest dam in the worldBuilt by Chola king Karikalan around the 2nd Century AD to divert the waters of the Kaveri across the fertile delta region for irrigation via canals. It is constructed from unhewn stone spanning the Kaveri and is 329 m (1,079 ft.) long, 20 m (66 ft.) wide and 5.4 m (18 ft.) high 4
Structure of Dam Crest Spillway (inside dam)MWLMax. level NWL Normal water level Upstream Down streamFree board Sluice way Gallery Heel Toe
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: small rooms like structure left within the dam for checking operations. Diversion tunnel: Tunnels are constructed for diverting water before the construction of dam. This helps in keeping the river bed dry. 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. 6
TYPES OF DAMS: Gravity Dams:Reservoir • These dams are heavyForce and massive wall-like structures of concrete in which the whole weight acts vertically downwardsAs the entire load is transmitted on the small area of foundation,such dams are constructed where rocks are competent and stable 7
ButtressDam: • 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 structureThis type of structure can be considered even if the foundation rocks are littleweaker 8
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. 9
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. • Earthen dams are relatively smaller in height and broad at the base • They are mainly built with clay, sand and gravel, hence they are also known as Earth fill dam or Rock fill dam 11
Dam Building Project• Planning - Reconnaissance Study - Feasibility Study - Environmental Document• Design - Preliminary (Conceptual) Design - Detailed Design - Construction Documents (plans & specifications)• Construction• Startup and testing• Operation 12
Necessary Data• Location and site map• Hydrologic data• Climatic data• Geological data• Water demand data• Dam site data (foundation,material, tailwater) 13
SELECTION OF SITESPLACE MUST BE SUITABLENARROW GORGE OR SMALL VALLEY WITH ENOUGH CATCHMENT AREA WHY DO WE TO STORE A NEED A CALCULATED LARGE VOLUME OF CATCHMENT WATER AREA? 14
Large storage capacityLength of dam to constructed is less.Water-tightness of reservoir.Good hydrological conditionsDeep reservoirSmall submerged areaLow silt inflowNo objectionable mineralsLow cost of real estateSite easily accessible 15
Engineering surveys Conducted for dam, reservoir and other associated work. Topographic survey of the area is carried out and the contour plan is prepared The horizontal control is usually provided by triangulation survey, and the vertical control by precise levelling 17
Geological investigation Geological investigations of the dam and reservoir site are done for the following purposes. (i) Suitability of foundation for the dam. (ii) Water-tightness of the reservoir basin (iii) Location of the quarry sites for the construction materials. 18
Hydrological investigations The hydrological investigations are conducted for the following purposes : (i) To study the runoff pattern and storage capacity. (ii) To determine the maximum discharge at the site. 19
Requirements for Stability• Modes of failure of a gravity dam: Overturning Sliding Compression or Crushing Tension.The design shall satisfy the following requirements ofstability: The dam shall be safe against sliding on any plane or combination of planes within the dam, at the foundation orwithin the foundation; The dam shall be safe against overturning at any plane within the dam, at the base, or at any plane below the base; and 20 The safe unit stresses in the concrete or masonry of the
Reservoir Sedimentation It is a difficult problem for which an economical solution has not yet been discovered, except by providing a “dead storage” to accommodate the deposits during the life of the dam. Disintegration, erosion, transportation, and sedimentation, are the different stages leading to silting of reservoir. 21
Causes of sedimentation Nature of soil in catchment area Topography of the catchment area Cultivation in catchment area Vegetation cover in catchment area Intensity of rainfall in catchment area 22
Sediment Management• water with Maximum efforts should be released so that less Wooden barriers sediments should retain in reservoir.Following options are: – Catchment Vegetation – Construction of coffer dams/low height Sediment sluicing barriers – Flushing and desilting of sediments – Low level outlets / sediment sluicing 23
SpillwaysUsed to pass excess flow in a controlled fashion• Two main types: Control section – Unregulated – Regulated Terminal structure Discharge channel 24
SPILLWAYSTypes of Spillways a. Overflow spillways b. Chute spillways c. Side-channel spillways d. Shaft spillways e. Siphon spillways f. Service & Emergency spillways 25
Energy Dissipiators• Hydraulic Jump type – induce a hydraulic jump at the end of spillway to dissipate energy• Bureau of Reclamation did extensive experimental studies to determine structure size and arrangements – empirical charts and data as design basis 27