Match the following lists :
| List-I | List-II |
|---|---|
| P.Cut and Cover | 1.Circular Tunnel |
| Q.Shield Driven | 2.Horseshoe Tunnel |
| R.Sequential Excavation | 3.Rectangular Tunnel |
Select the correct answer using the code given below :
- A1 2 3
- B3 1 2Correct
- C1 3 2
- D3 2 1
Solution
Concept
Tunnelling method and typical shape
Step-by-step solution
1. Cut and cover: trench excavated from the top, so a box (rectangular) section → 3. 2. Shield driven: circular shield with circular lining → 1. 3. Sequential excavation (NATM): arch (horseshoe) profile → 2.
Explanation
The tunnelling method decides the cross-section. The cut-and-cover method uses rectangular boxes, shields are circular and sequential excavation uses a horseshoe-shaped opening that is supported progressively.
Why the other options are wrong
The other codes associate shield tunnelling with rectangular or horseshoe shapes, which is not their normal form.
Shortcut
Cut & cover = box; shield = circle; sequential = horseshoe.
Common mistake
Linking the shield with a horseshoe shape.
Correct answer: B) 3 1 2