How many meters into the tunnel will mechanical ventilation begin?
The installation of ventilation pipes should meet the following requirements:
1. The inlet pipe mouth of the separate pressing type or the outlet pipe mouth of the suction type should be located outside the hole. The former should be more than 20m away from the hole, and the latter should be made into a chimney.
2. The distance between the ventilation pipe and the excavation working face should be determined according to the specific situation. The distance between the outlet of the thrust ventilation pipe and the excavation face should be determined by calculation.
3. When mixed ventilation is used, when one group of fans moves forward, the pipes of the other group of fans should be lengthled accordingly. The staggered distance between two groups of ventilation pipes shall not be less than 20 ~ 30m.
4. The installation of the ventilation pipe should be smooth, the joint should be tight, and the average air leakage rate per 100m should not be greater than 2%. The radius of the elbow shall not be less than 3 times the diameter of the ventilation pipe.
5. When the ventilation pipe uses a hose, the strengthened air pipe should be used near the fan.