MadSci Network: Earth Sciences

Re: Why doesn't air/oxygen travel more than 1500 ft below surface?

Date: Mon Oct 29 15:20:18 2001
Posted By: Leslie Allen, Staff, Laboratory Chemist, Valero Refining Company
Area of science: Earth Sciences
ID: 1003516679.Es

	In researching the air issue, I didn't find any reference to the 
depth at which air could or couldn't travel. Many references to "bad air" 
dealt with the accumulation of methane and carbon di/monoxide. The air 
quality issue also dealt with the accumulation of coal dust. Therefore, 
ventilation was used primarily for the removal of the bad air contributors.
	Ventilation was accomplished through drafting or through the use 
of ventilation shafts. Mechanical fans and cylinder air were mentioned 
when air flows couldn't be reached by the previous methods. However, these 
were costly when compared to gravity fed systems.
	At 5km the temperature of the rock can reach 700 degrees Celsius. 
The temperature of a certain depth is dependent on what type of rock your 
mining into. Another limit to how deep we can mine is the weight of rock. 
At 3.5km the pressure of rock laying above you is 9,500 tonnes per meter 
squared. When rock is removed through mining this pressure can rise 
threefold in the surrounding rock. This, and the cooling of the rock 
causes a phenomenon called rock bursts. 
Have a good day and stay away from any old mines!

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