The dam which can be seen curved in plan with its convexity to the upstream side is called Arch dam.
It transfers the water pressure and other forces towards the abutments by arch action.
Classification:
Arch dams can be classified mainly into three types which are as follows:
- Single Curvature arch dam
- Double Curvature arch dam
- Arch-Gravity dam
1.Single curvature arch dam:
There are three types of single curvature arch dams as follows:
- Constant Radius
- Variable Radius
- Constant angle
A.Constant Radius:
- In such dams,radius of extrados(i.e outside curved surface of arch) is kept constant at all elevations from top of dam to the base.
- Centres of extrados,intrados and middle line of horizontal arch rings all lie at one common point.
- In this, the U/s face is vertical and the thickness of the arch is kept proportional to the height.
- For construction of such dam,U-shaped valley is more suitable.
B.Variable Radius:
- These are the dams in which the radii of the extrados and intrados curves becomes vary at different elevations.
- In this, radii at the top oddam is maximum whereas they are minimum at the base.
- Such dam is more economical than constant radius dam.
C.Constant angle:
- In these dams,the central angle of arch rings at various elevation is constant and radii are variable.
- It is a special type of variable radius arch dam.
- It is quite suitable for a narrow V-shaped valley.
2.Double Curvature arch dam:
- It is also termed as “shell dam” because its seems to be like shell structure.
- Comparatively such dams has smaller thickness than that of single curvature one.
- Due to small thickness, it is more economical in India.
- Idduki dam in Kerala is the type of double curvature.
3.Arch-Gravity dam:
- In this, the thickness of the arch is more.
- There are extrados of the arch rings with gradually increasing radii in lower portion of valley.
- In U.S.A, the famous floorer dam is its type.
Advantages:
Advantages are as follows:
- Firstly, Problems of uplift pressure are minor due to much less width.
- Secondly, When the length is small in comparison with height, the arch dams are more suitable.
- Arch dams require less material, hence economical.
- Lastly, One can construct it in moderate foundation.
Disadvantages:
Disadvantages are as follows:
- Firstly, The speed of construction is generally low.
- It requires skilled labour.
- Needs sophisticated formwork.
- Lastly, it requires special design.
Interested in learning about similar topics? Here are a few hand-picked blogs for you!