Tunnel Construction MCQ with answer and solution

Concept

Different tunnel shapes serve different structural and functional purposes. Circular sections are best for uniform pressure, while horse-shoe sections are ideal for soft rocks and traffic clearance.

Step-by-step solution

1. Understand the structural properties of different tunnel shapes (Circular, Horse-shoe, Elliptical, Segmental, etc.). 2. Recognize that circular sections provide the most uniform resistance against external/internal hydrostatic pressures. 3. Identify that the horse-shoe section is most suitable for soft rocks and provides adequate space for traffic (highway/railway), making options A, B, and C correct statements. 4. Conclude that option D is incorrect because circular, not horse-shoe, is the best theoretical section for resisting uniform pressures.

Explanation

The circular section is the best theoretical section for resisting internal or external fluid or hydrostatic pressures uniformly. The horse-shoe section is generally used for carrying sewage or water under pressure or for soft rocks, but it is not the best theoretical section for hydrostatic pressure resistance compared to a circle.

Why the other options are wrong

A: Horse-shoe section is indeed widely used and suitable for soft rocks. B: It provides a wide base and sufficient headroom, making it common for highways and railways. C: The flat bottom and arched top make it well-suited for traffic purposes.

Shortcut

Remember: Circular = Best for pressure; Horse-shoe = Best for soft rock and traffic.

Common mistake

Confusing the best shape for traffic/soft rocks (horse-shoe) with the best theoretical shape for uniform pressure resistance (circular).