Question

Match the shaft sinking method with its applicability.

Shaft sinking method	Applicability
(P) Piling system	(1) Strata consisting of alternate strong and loose soil, and drum sinks down by its own weight
(Q) Caisson method	(2) Sinking through the loose ground near the surface
(R) Cementation	(3) Heavily watery strata, including quick sand
(S) Freezing	(4) Fissured water bearing strata without running sand

• A. \( P \rightarrow 2,\ Q \rightarrow 3,\ R \rightarrow 4,\ S \rightarrow 1 \)
• B. \( P \rightarrow 4,\ Q \rightarrow 1,\ R \rightarrow 2,\ S \rightarrow 3 \)
• C. \( P \rightarrow 2,\ Q \rightarrow 1,\ R \rightarrow 4,\ S \rightarrow 3 \)
• D. \( P \rightarrow 4,\ Q \rightarrow 3,\ R \rightarrow 2,\ S \rightarrow 1 \)

Hint:

Think about which method can handle running or quick sand, and which one only works in shallow, loose ground near the surface.

Answer 1

The Correct Option is C

This question checks if you know why each shaft sinking method is chosen for a particular ground condition. Instead of matching P, Q, R, S one at a time, it helps to test each of the four given options against what you know about piling, caisson, cementation and freezing.

1. Option (A): P to 2, Q to 3, R to 4, S to 1: P to 2 (piling for loose ground near the surface) is fine. But Q to 3 is wrong, a caisson does not handle heavily watery ground with quick sand, that is freezing's job. This option fails.
2. Option (B): P to 4, Q to 1, R to 2, S to 3: P to 4 is wrong. Piling only works in shallow loose ground, it cannot hold back fissured water bearing rock. This option fails at the very first pair.
3. Option (C): P to 2, Q to 1, R to 4, S to 3: P to 2 fits, piling suits loose ground near the surface. Q to 1 fits, a caisson (drum) sinks under its own weight through strata that alternate between strong and loose bands. R to 4 fits, cementation grouts fissures shut, but only where there is no running sand. S to 3 fits, freezing is kept for the worst case, heavily watery ground with quick sand. Every pair checks out.
4. Option (D): P to 4, Q to 3, R to 2, S to 1: P to 4 repeats the same mistake as option (B), piling cannot cope with fissured water bearing strata. This option fails.

Only option (C) survives the check on all four pairs, so P to 2, Q to 1, R to 4, S to 3 is correct.

Let's summarize:

• Piling: shallow, loose ground near the surface.
• Caisson (drum): alternating strong and loose strata, sinks under its own weight.
• Cementation: fissured, water bearing strata, but no running sand.
• Freezing: the toughest ground, heavily watery strata with quick sand.

So the answer is option (C), P to 2, Q to 1, R to 4, S to 3.