Consider the following statements regarding full face method for tunneling in hard rocks : 1. An entire section of the tunnel is tackled at one time. 2. Mucking tracks can be laid on the tunnel floor and extended as the work progresses. 3. It is suitable for unstable rocks. Which of the above statements are correct ?
- A1 and 2 onlyCorrect
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3
Solution
Concept
Full-face method of tunnelling
Step-by-step solution
1. The whole section is excavated at once (true). 2. Mucking tracks are laid along the floor and extended as work proceeds (true). 3. It needs strong rock; unstable ground requires heading-and-bench or other staged methods (false).
Explanation
The full-face method suits hard, stable rock, where a large opening can stand unsupported.
Why the other options are wrong
Statement 3 contradicts the requirement of stable rock.
Shortcut
Full face = hard, stable rock.
Common mistake
Accepting statement 3.
Correct answer: A) 1 and 2 only