4. INTRODUCTION
Dam
A dam is a hydraulic structure of fairly impervious material built
across a river to create a reservoir on its upstream side for
impounding water for various purposes.
Reservoir
A reservoir is a man-made lake that is primarily used for storing
water which is located at the back side of Dam.
๏ถ A dam and a reservoir are complements of each other.
6. Purpose of Dams
๏ด Generation of hydropower electricity
๏ด For agricultural & irrigation purposes
๏ด For fishery
๏ด To prevent the flooding
๏ด To diverse the water
13. Components of Dam
Abutment
The part of a valley side (wall) against which a dam is
constructed. An artificial abutment is sometimes constructed as
a concrete gravity section, to take the thrust of an arch dam
where there is no suitable natural abutment. Right and left
abutments are those on respective sides of an observer looking
downstream.
15. Components of Dam
Gallery
๏ง A passageway within the body of a dam or
abutment; hence the terms "grouting gallery",
"inspection gallery", and "drainage gallery".
๏ง A long and rather narrow hall; hence the
following terms for a power plant: "valve
gallery", "transformer gallery", and "busbar
galleryโ
16. Spillway
A structure over or through which flood flows are
discharged.
โข Controlled Spillway
If the flow is controlled by gates, it is called a
controlled spillway
โข Uncontrolled Spillway
If the elevation of the spillway crest is the only
control, it is called an uncontrolled spillway
Fig - 1
Fig - 2
Components of Dam
17. Types of Spillway
๏ Auxiliary Spillway
๏ Bell mouth spillway
๏ Fuse Plug Spillway
๏ Siphon Spillway
Components of Dam
18. Auxiliary Spillway
A dam spillway built to carry runoff in excess of that carried by the principal
spillway; a secondary spillway designed to operate only during exceptionally
large floods. Also referred to as Emergency Spillway
Components of Dam
19. Bell mouth spillway
Some spillways are designed like an inverted bell so that water can
enter all around the perimeter.
Components of Dam
20. Fuse Plug Spillway
A fuse plug is a collapsible dam installed on spillways in dams to increase the
dam's capacity.
Components of Dam
21. A siphon makes use of the difference in the height between the
intake and the outlet to create a pressure difference needed to
remove excess water.
Siphon Spillway
Components of Dam
22. Crest: The top of the Dam. These may
in some cases be used for providing a
roadway or walkway over the dam.
Parapet walls: Low Protective walls on
either side of the roadway or walkway
on the crest.
Heel: Portion of Dam in contact with
ground or river-bed at upstream side.
Toe: Portion of dam in contact with
ground or river-bed at downstream side.
Components of Dam
23. Sluice way: Opening in the dam near the base,
provided to clear the silt accumulation in the
reservoir.
Free board: The space between the highest level of
water in the reservoir and the top of the dam.
Dead Storage level: Level of permanent storage
below which the water will not be withdrawn.
Components of Dam
26. Components of Dam
Energy Dissipation
Stilling Basin
A basin constructed to dissipate the energy of fast-flowing water,
e.g., from a spillway or outlet, to prevent undercutting of the dam
and to protect the streambed from erosion.
๏ถ In latest techniques some spillways are design in such a
manner that do not required stilling basin.
Example: Ohio Dam USA
29. Components of Dam
Energy Dissipation
Stilling Basin Continueโฆ
Certain auxiliary devices are usually provided in stilling basins to
reduce the length of the jump.
(1) Chute Blocks
(2) Baffle walls
(3) Sills
๏ถ These devices also improve the dissipation action of the basin
& stabilize the jump.
30. Components of Dam
Energy Dissipation
Chute Block
๏ด Installed at the toe of spillway
๏ด Furrow the incoming jet
Baffle Block
๏ด Installed at the mid of stilling basin
๏ด Increase the turbulence
Dentated Sills
๏ด Installed at the end of stilling basin
๏ด Decrease the velocity of jet
34. Foundation Treatment Techniques for
Dams
Various techniques are used for foundation treatment of dams,
The most common techniques are as follows:
Grouting
Holes are drilled at shallow as well as deep and cement grouting
is filled to establish an effective barrier to seepage under the
dam and to consolidate the foundation.
(A) Consolidation Grouting
(B) Curtain Grouting
35. Grouting
Consolidation Grouting
Low-pressure grouting to fill voids, fracture zones, and
cracks at and below the surface of the excavated
foundation is accomplished by drilling and grouting
relatively shallow holes.
37. Grouting
Curtain Grouting
Construction of a deep grout curtain near the heel of the
dam to control seepage is accomplished by drilling deep
holes and grouting them using higher pressure.
