Which type of dam is constructed as a concrete or masonry wall across a valley?
- A) Arch Dam
- B) Gravity Dam
- C) Embankment Dam
- D) Buttress Dam
The correct answer and explanation is:
Correct Answer:
B) Gravity Dam
Explanation:
A gravity dam is a type of dam constructed as a massive concrete or masonry wall across a valley. It relies on its own weight to resist the force of water pushing against it. The design of a gravity dam ensures stability by utilizing the force of gravity to hold it in place, preventing overturning or sliding.
Key Features of a Gravity Dam:
- Massive Structure: Gravity dams are typically made of concrete or masonry, with a thick base that gradually narrows towards the top.
- Resists Water Pressure: The weight of the dam counteracts the horizontal thrust of water.
- Durability: These dams are highly durable and can last for centuries with proper maintenance.
- Suitable Locations: Gravity dams are best suited for narrow valleys with strong bedrock foundations that can support their weight.
Advantages:
- Long Lifespan: Since they are made of concrete or masonry, they are resistant to erosion and degradation over time.
- Minimal Maintenance: Unlike embankment dams, gravity dams require less frequent repairs.
- High Structural Strength: Can withstand large water pressures and external forces like earthquakes.
Disadvantages:
- High Construction Cost: Requires a significant amount of materials and labor.
- Longer Construction Time: Due to their size and structural complexity, gravity dams take more time to build.
- Foundation Requirements: They need a solid rock foundation to ensure stability.
Examples of Gravity Dams:
- Hoover Dam (USA)
- Bhakra Dam (India)
- Grand Coulee Dam (USA)