Laboratory results and field studies support the effectiveness and applicability of the U.S. Bureau of Mines mine fire diagnostic technique to the problems of locating and monitoring abandoned mine fires. For the bituminous samples studied, values of the concentration ratio, r1, increased with increasing temperature and decreased during cooling. Although values of r1 do not correspond to a particular temperature, elevated values of r1 are due only to the presence of heated coal. Time-dependent monitoring of changes in r1 reflect changes in the average temperature of the coal. The ratio, r1, was not applicable to anthracite samples because of the lower rate of hydrocarbon emission and the very low concentration of higher hydrocarbons. However, variations in the absolute concentration of methane seemed to be indicative of changes in temperature. The mine fire diagnostic method incorporates a sampling method that increases the detection zone of normal point source measurements through a gas movement scheme. Measuring one of the characteristics of this moving gas, in this case changes in hydrocarbon concentration, and plotting the results as vectors (magnitude and direction) rather than point source (magnitude) measurements, expands and bounds the area(s) affected by combustion, as well as the areas(s) not affected by combustion. These factors make the Bureau's methodology a significant improvement in locating and monitoring abandoned mine fires.
Proc. Symp. Evolution of Abandoned Mine Land Tech., Wyoming Dept. Environ. Qual., 1989, 20 PP.