Match the following lists :
| List-I (Type of soil) | List-II (Method of tunneling) |
|---|---|
| P.Silt | 1.One or two ports are opened and the material flows continuously into the tunnel. |
| Q.Clay | 2.One or two port doors are opened. The material is excavated and deposited at the bottom of the tunnel. |
| R.Sand | 3.Tunneling is of the open type. The material settles on the floor of the shield and it should be continuously removed. |
Select the correct answer using the code given below :
- A2 1 3Correct
- B3 1 2
- C3 2 1
- D2 3 1
Solution
Concept
Shield tunnelling procedure for different soils
Step-by-step solution
1. Soft clay squeezes in through the ports and flows continuously → 1. 2. Silt is excavated through the port doors and deposited at the bottom → 2. 3. Sand is loose and is handled in an open shield; the material settles on the floor of the shield and is removed continuously → 3.
Explanation
The shield method is adapted to the soil: closed-port methods for soft cohesive soil and an open shield for granular soil.
Why the other options are wrong
The other codes interchange the behaviour of clay and sand.
Shortcut
Clay flows in; sand settles on the floor.
Correct answer: A) 2 1 3