Gravity Dam is defined as the type of dam that is primarily constructed using concrete or stone masonry and hold backwater with the aid of the used materials itself. It essentially utilizes its self-weight to resist the horizontal pressure of water pushing against it. The design of this dam is done in such a way that each part of the section of the dam is stable and is independent of any other section. These are massive engineering structures used extensively throughout the world. Since these dams are hold down on the ground by the force of gravity; they are given the name gravity dam.
Gravity dam can be used to hold or store a large amount of water. The concept of this dam began as early as 400 B.C. The most ancient gravity dam was built in Egypt and consisted of uncemented masonry. These dams are very desirable in areas with gorges with steep slopes. These types of dams can be constructed up to any height. The highest gravity dam in the world is the Grande Dixence Dam in Switzerland.
Uses of Gravity Dam
Gravity dams are multifunctional and serve a variety of purpose. They help to control the flow of melting snow in a river during winter and spring and store water in the dry season. These dams can store a large amount of water which can be used for drinking water supply, electricity generation, irrigation etc. They are also used as flood and erosion control structures.
Types of Gravity Dam
I. Based on the construction material used
1. Concrete Dam:
As the name itself implies, concrete dams are essentially made up of concrete. The concrete used for the construction may be conventional concrete or roller- compacted concrete.
2. Composite Dam:
Composite dams are the type of dams that are intermediate between the concrete and embankment dam. They consist of filler materials and concrete as the material of construction.
II. Based on the shape or plan
a. Straight Dam
b. Curved Dam
III. Based on the structural height
1. Low Dam ( up to 100 feet)
2. Medium Dam ( between 100 feet to 300 feet)
3. High Dam ( over 300 feet)
Advantages of Gravity Dam
1. It is highly suitable in narrow valleys.
2. The maintenance cost is relatively lower.
3. Such dams offer great flexibility in height.
4. Sudden failure of the dam does not occur.
5. The problem of seepage is lower.
Disadvantages of Gravity Dam
1. The investment cost of such dam is quite high.
2. Needs skilled labour for construction.
3. The design of this dam is complex.
4. The foundation must be strong for the construction of the dam.
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