Classification Dams According the Material used:
Most engineers
recognize seven general types of dams. Three of them are ancient in origin, and
four have come into general use only in the last about 100 years or so.
The three older types
of dams are :
1) Earth Dams
2) Rock-fill dams
3)
Solid masonry
gravity dams.
4)
Hollow masonary
gravity dams,
5)
Timber dams,
6)
Steel dams and
7)
Arch dams
These types are discussed below:
1. Earth Dams. Earth dams are made of soil that is pounded down
solidly. They are built in areas where the foundation is not strong enough to
bear the weight of a concrete dam, and where earth is more easily available as
a building material compared to concrete or stone or rock.
2. Rockfill Dams. Rockfill Dams are formed of loose
rocks and boulders piled in the river bed. A slab of reinforced concrete is
often laid across the upstream face of a rockfill dams to make it water tight.
3.
Solid-masonry Gravity dams. These are familiar to us by now, after we have talked about
Aswan, Roosevelt, Hoover, and above all Bhakra dam.
These big dams are expensive to be built but are more durable
and solid than earth and rock dams. They can be constructed on any dam site,
where there is a natural foundation strong enough to bear the great weight of
the dam.
4. Hollow masonry gravity dams. These are essentially designed on the
same lines on which the solid masonry gravity dams are designed. But they
contain less concrete or masonry; about 35 to 40% or so. Generally, the weight
of water is carried by a deck of R.C.C. or by arches that share the weight
burden. They are difficult to build and are adopted only if very skilled
labours are easily available.
5. Steel Dams. These are
not used for major works. Today, steel dams are used as temporary coffer dams
needed for the construction of permanent dams. Steel coffer dams are usually
reinforced with timber or earthfill.
6. Timber Dams. These are short lived, since in a few
years time, rotting sets in. Their life is not more than 30 to 40 years and
must have regular maintenance during that time. However they are valuable in
agricultural areas, where a cattle raiser may need a pool for his live stock to
drink from, and for meeting other such low level needs.
7. Arch Dams. Arch dams are very complex and complicated.
They make use if the horizontal arch action in place of weight to hold back the
water. They are best suited at sites where the dam must be extremely high and
narrow. Example, Idduki dam in Kerala State across the Periyar river, which is
only arch dam in India. It is 366 m long double curvature arch dam, made in
concrete, and has a height of about 170 m.
