Which of the following is a main reason ventilation is provided during tunnel construction?

To dilute or exhaust blasting fumes, CO, NOx and natural gases such as methane

To increase the strength of the lining concrete

To lower the water table around the tunnel

To reduce the weight of the rock above the tunnel

Why is continuous ventilation needed where methane may seep into a tunnel?

It stops gas accumulating to explosive concentration

Methane makes the air too humid

It makes methane heavier so it settles on the floor

It cools the rock so methane cannot form

In an operating road tunnel, ventilation is mainly used to:

Dilute vehicle emissions to permissible limits, keep visibility and control smoke in fire

Supply compressed air to drilling machines

Cool the tunnel lining after concreting

Remove blasting fumes after every round of drilling

2070 Chaitra (old course) · 4 marks

Short note: importance of ventilation in tunnelling

Short answer

Ventilation removes harmful gases (CO, NOx, methane), supplies oxygen, clears dust and smoke, controls temperature and humidity, prevents explosive gas build-up, and aids firefighting. In operating road tunnels it dilutes vehicle emissions to permissible limits and maintains visibility.

Write a short note on importance of ventilation in tunnelling.

Ventilation is essential in tunnelling because the air in a tunnel quickly becomes unsafe.

Removes harmful gases: blasting fumes, CO, NOx, diesel exhaust and natural gases (methane, H2S, CO2) are diluted or exhausted.
Supplies oxygen for workers and combustion engines, protecting health and life.
Clears dust and smoke after blasting and drilling, improving visibility and the speed of work.
Controls temperature and humidity, which rise at depth, and reduces worker fatigue.
Prevents the build-up of explosive gas and helps in firefighting and rescue.
In an operating road tunnel, it dilutes vehicle emissions to permissible limits (IRC:SP:91, PIARC), maintains visibility and controls smoke during a fire.

Methods include natural ventilation, longitudinal (jet fan), semi-transverse and transverse systems, and ducted forced or exhaust ventilation during construction.

✓ Answer checked by Claude Opus 5.5 (high effort)

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