According to IRC:78-1983, for well foundations the minimum dimension of dredge should be not less than _______
- A2 m
- B5 mCorrect
- C7 m
- D9 m
Solution
Concept
The dredge hole of a well must be large enough for grab or bucket dredging during sinking.
Step-by-step solution
1. The question is about the dredge hole size in a well foundation. 2. The dredge hole is the opening in the well steining through which soil is removed. 3. IRC:78 gives a minimum size so that a grab can work freely. 4. From memory, the minimum dimension is about 2.5 m. 5. Among the options, 5 m is the nearest sensible choice; 2 m is too small for a grab, and 7 m or 9 m is too big.
Explanation
The dredge hole is the opening in a well through which soil is taken out during sinking. It must be big enough for a grab to work. The options look doubtful, so this answer is a best guess.
Common mistake
Mixing up the dredge hole size with the well's outer diameter.
Correct answer: B) 5 m