Gravity Dam – Hydraulic Structure15th July 2019
It is constructed with masonry or concrete it resists the force acting on it by its own weight.
Where Gravity Dam Are Constructed?
- Good soil area
- For large spillway
- In granite basalt area
- For large height and small length dam
- For long time
Forces Acting On Gravity Dam
Following are the 6 major forces which acting on the dam
1. Weight of Dam
The total weight of the dam acts at the C.G of its section.
2. Water Pressure
The horizontal water pressure P = wh²/2, this acts at height h/3 from the base of the dam.
3. Pressure Due to Earth Quak
In this case two types of pressure acts
- Horizontal acceleration force FH = W.α
- Vertical acceleration force Fv = W(1- α)
(Where W = weight of dam and α = acceleration)
4. Uplift Pressure
The uplift pressure is an upward pressure of water as it flows through the body of the dam or its foundation.
- Uplift pressure at the heel, A = wh
- Uplift pressure at the toe, F = wh՛
- Uplift pressure at gallery = w[h + 1/3(h-h՛)]
Mode of Failure of Gravity Dam
- By overturning
- By rupture from tension
- By sliding
- For crushing by compressing
- By uplift of floatation
The Force That Gives Stability To The Dam
- Self-weight of the dam
- Trust of the tail water