Q.98 Trapezoidal sections with rounded corners for large canals or triangular sections with circular bottoms for small canals are the most suitable sections for _______ canals.
- AlinedCorrect
- Bsemi-lined
- Cearthen
- DUnlined
Solution
Concept
Lined canals use trapezoidal sections with rounded corners (large canals) or triangular sections with a circular bottom (small canals).
Step-by-step solution
1. In lined canals, the lining (concrete, brick, etc.) is weak at sharp corners and cracks easily. 2. Rounded corners remove stress concentration and give better hydraulic efficiency. 3. For large discharge, a trapezoidal section with rounded corners is used. 4. For small discharge, a triangular section with a circular bottom is used. 5. So these sections suit lined canals. Answer is (A).
Explanation
Lined canals are designed for high velocity and less friction. Rounded corners make the lining strong and avoid cracks at corners. So trapezoidal sections with rounded corners and triangular sections with circular bottoms are used for lined canals.
Why the other options are wrong
(B) Semi-lined: this is not a standard section type for this shape. (C) Earthen: earthen canals use simple trapezoidal sections with side slopes and berms. (D) Unlined: this is the same as earthen; it does not need rounded corners.
Shortcut
Rounded corners or circular bottom means a lined canal.
Common mistake
Choosing earthen or unlined because those canals are also trapezoidal.
Correct answer: A) lined