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.

Seminar by: Mr.Risso Johnny

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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

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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

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Grand Anicut (Kallanai)

The oldest dam in the world

Built 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

Structure of DamCrest

Gallery

Spillway(inside dam)

NWLNormalwater level

MWLMax. level

Free boardSluice way

Upstream Down stream

Heel Toe

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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.

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TYPES OF DAMS:

Gravity Dams:• 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

ReservoirForce

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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

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• 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.

Arch Dams:

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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

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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

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Necessary Data

• Location and site map• Hydrologic data• Climatic data• Geological data• Water demand data• Dam site data (foundation, material, tailwater)

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SELECTION OF SITES

PLACE MUST BE SUITABLE NARROW GORGE OR SMALL VALLEY WITH ENOUGH CATCHMENT AREA

WHY DO WE NEED A LARGE CATCHMENT AREA?

TO STORE A CALCULATED VOLUME OF WATER

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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

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INVESTTIGATIONS

Engineering surveys

Geological investigations

Hydrological investigations

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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

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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.

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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.

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Requirements for Stability

• Modes of failure of a gravity dam:OverturningSlidingCompression or CrushingTension.

The design shall satisfy the following requirements of stability: The dam shall be safe against sliding

on any plane or combination of planes within the dam, at the foundation or

within 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

The safe unit stresses in the concrete or masonry of the dam or in the foundation material shall not be exceeded

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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.

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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

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Sediment Management• water with Maximum

efforts should be released so that less sediments should retain in reservoir.

Following options are:

– Catchment Vegetation– Construction of coffer

dams/low height barriers

– Flushing and desilting of sediments

– Low level outlets / sediment sluicing

Wooden barriers

Sediment sluicing

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SpillwaysUsed to pass excess flow in a controlled fashion

• Two main types:– Unregulated– Regulated

Control section

Terminal structure Discharge channel

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SPILLWAYS

Types of Spillwaysa. Overflow spillways

b. Chute spillways

c. Side-channel spillways

d. Shaft spillways

e. Siphon spillways

f. Service & Emergency spillways

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side-channel spillwayOverflow spillway

Chute spillway Morning glory spillway

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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

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Stilling basin Hydraulic jump

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THANK YOU!!!