Discussion on the necessity of ventilation of tunnel construction(1)
During the construction of a highway tunnel, due to factors such as drilling eye, explosive blasting, residue, jet concrete, internal combustion machinery and transportation vehicles, harmful gases in the strata during the excavation, which greatly reduces the oxygen in the cave. The harmful gases and rock dust are dirty in the cave. As the tunnel continues to excavate and continuously extends to the depths of the mountains, the temperature and humidity in the cave will be improved accordingly, which will have a serious impact on the health of the workers in the cave. Due to the difficulty of construction ventilation. In order to replace and purify the air in the tunnel, sufficient fresh air in the cave, dilute, dilute, eliminate harmful gases, and reduce the concentration of dust, to improve labor conditions, ensure the health of construction operators, ensure normal safety production, and improve labor labor Productivity, etc., must conduct technical research on construction ventilation system.
2. Construction ventilation control standards
2.1 oxygen content
The oxygen content in the tunnel is not less than 20%at a volume ratio.
2.2 Dust concentration
The dust per cubic meter of air contains less than 2mg from the silicon dioxide; the cement dust dust containing less than 10%less than 10%is not greater than 6mg: the silicon dioxide content is below 10%, and the mineral nature does not contain toxic substances The dust of the animal and plant is not greater than 10mg.
2.3 harmful gas
2.3.1 Carbon monoxide: No greater than 30 mg/m3: When the construction personnel enters the excavation working surface inspection, the concentration can be 100mg/m3. However, it must be reduced to 30 mg/m3 within 30 minutes ~ 35 minutes;
2.3.2 Carbon dioxide: no more than 0.5%by volume;
2.3.3 Nitrogen oxides converted into nitric oxide and controlled below 5mg/m3.
The temperature in the tunnel must not exceed 28 ° C.
2.5 air volume
During the construction of the tunnel, the fresh air volume of each person is not less than 3m3/min. When using internal combustion mechanical operations, the supply air supply of .1KW is not less than 3m3/min.
2.6 wind speed
When the tunnel is excavated, the full section wind speed is not less than 0.15m/s, and the tunnel is not less than 0.25m/s.