Seminar On Dams
Dams
Definition:-
Dam is a solid barrier constructed at a suitable location across a river valley to store flowing water.
Storage of water is utilized for following objectives:
• Hydropower
• Irrigation
• Water for domestic consumption
• Drought and flood control
• For navigational facilities
• Other additional utilization is to develop fisheries
TYPES OF DAMS
GRAVITY DAMS:
These dams are heavy and massive wall-like structures of concrete in which the whole weight acts vertically downwards
Bhakra Dam is the highest Concrete Gravity dam in Asia and Second Highest in the world.
Bhakra Dam is across river Sutlej in Himachal Pradesh
The construction of this project was started in the year 1948 and was completed in 1963 .
In a gravity dam, the force that holds the dam in place against the push from the water is Earth’s gravity pulling down on the weight of the dam itself. In a gravity dam, stability is secured by making it of such a size and shape that it will resist overturning, sliding and crushing at the toe. The dam will not overturn provided that the moment around the turning point, caused by the water pressure, is smaller than the moment caused by the weight of the dam
ARCH DAM
Arch dams are built across narrow, deep river gorges, but now in recent years they have beenconsidered even for little wider valleys.
An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes into its foundation or abutments. An arch dam is most suitable for narrow gorges or canyons with steep walls of stable rock to support the structure and stresses.
EARTH DAMS:
An embankment dam is a massive artificial water barrier. It is typically created by the emplacement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and a dense, waterproof core. This makes such a dam impervious to surface or seepageerosion.
They are mainly built with clay, sand and gravel, hence they are also known as Earth fill dam or Rock fill dam
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
Embankment dams are made from compacted earth, and have two main types, rock-fill and earth-fill dams. Embankment dams rely on their weight to hold back the force of water, like the gravity dams made from concrete.
TYPES OF EMBANKMENT DAMS
• Simple Embankment (homogeneous throughout)
• Impervious Foundation
• Impervious Core (Zoned embankments)
DISADVANTAGE:
Water can easily pass through it and less durable than other type dams.
The height of this dam is less
SELECTION OF SITES
1. Topographically:-
• Place must be suitable.
• Narrow gorge or small valley with enough catchment areas.
2. Technically:-
• Should be strong, impermeable, and stable.
• Strong rocks leads to better designs.
• impermeable sites ensures better storage
• Stability with reference seismic shocks and slope failures around the dam are a great relief to the public as well as the engineering.
3. Constructionally: -
• Should be not far off from deposits of materials which would be useful for construction
• Natural materials of cons. Like earth, sand, gravel,
and rock should be easily feasible or the cost will increase.
4. Economically: -
• Benefits arising should be realistic and justified in terms
of land irrigated or power generated or floods averted or water stored.
5. Environmentally: –
• The site of the dam should not involve ecological disorder (in the life of plants, animals and man).
• The fishes in the streams are also affected, so things should also be considered.
• The dam and the associated reservoir should become an acceptable element of the ecological set up of the area.