Dear Sir
I feel compelled to respond to the article “Clearing the air on long tunnel drives” in the March 2005 edition of T&T International.
The dismissing of exhaust ventilation as a standard method of underground environment cleansing is a massive mistake that costs lives, year after year.
The basic principle of underground ventilation is to collect the contaminants in the vent line as soon as possible and evacuate them out of the tunnel atmosphere.
Use of soft vent line is a cost cutting method that works against the safety of underground workers in every installation and costs lives of workers and escalates injury rates. This folly must come to an end before another major accident occurs.
Rigid vent line that can stand reversibility is the only logical method that should be used in tunnelling.
Fragility of soft vent line, no matter the high-quality, is the Achilles Heal of that method of ventilation. Moisture collection within the line, tearing of the line by equipment, patching and pinched sections radically reduce air flow and raise the coefficient of friction. The author admits that “Suction-evacuation of used air from the face by suction from outside through stiff ducts. This allows rapid evacuation of the blasting fumes from the face; fresh air is sucked along in the tunnel. It appears this method is popular in more permanent situations, like mining, and is not common in tunnelling.”
In California, we have learned a hard, deadly lesson from this kind of non-historical, backward thinking and will not succumb again. All tunnels are excavated on the exhaust system with hard vent line that will withstand reversibility, unless permission is granted by the State in writing to reverse the air flow.
I await reasoned response to these comments.
Byron M Ishkanian PE
Mine and Tunnel Safety Engineer
California
