Geology Reference
In-Depth Information
A
Borehole
Burning
coal
Mine void
Injected
grout
B
Hot
coal
Solidified
grout
Figure 1.2.7. Sketch of the use of grout with concrete to encapsulate burning coal. A: Injection to encapsulate
burning coal; B: Solidified grout for O
2
exclusion while hot material cools to below the reignition point. From Kim
and Chaiken 1993, p. 36.
Surface sealing is a relatively inexpensive method of controlling abandoned mine fires. It is intended to inhibit
ventilation of the fire zone. The exclusion of air and the accumulation of combustion products suppress the rate of
fire propagation. If the seal can be maintained while all the stored heat dissipates, the fire may eventually be
extinguished. During this period, the seal must be maintained. In general, most surface seals can be expected to fail
between 1 and 3 years after construction. Failure may be related to settling, shrinkage, drying, or increased fire
activity.
In the Western United States, 85% of fire abatement projects were surface seals. This is due to the relatively low
cost, the topography of the area, and the lack of H
2
O needed to implement other methods (Shellenberger and
Donner, 1979).
-
Surface sealing suppresses surface evidence of a fire. If the seal is maintained for a sufficient length of time (10
20
years), the fire may be extinguished. Surface seals adequately control subsidence, inhibit unsightly venting and
limit the emission of noxious fumes. In these circumstances, surface seals with regular and periodic maintenance
provide an adequate control mechanism (Kim and Chaiken, 1993).
Conventional methods of controlling and/or extinguishing AML fires comprise a limited arsenal of dealing with the
problem. None of the methods are routinely successful. Most of the methods involve some degree of hazard, have
varying costs and may disrupt more surface area than the fire threatens.
Conclusions
T
he problem of coal fires is a serious one. Such fires can involve a high degree of hazard and can be less amenable
to solution. Given the nature of these fires, it is unlikely that the extent of the problem or the cost of solutions will
decrease in the near future. Although new techniques for locating fires and for controlling and extinguishing fires
may be developed, the majority of current fire control projects utilize conventional methods and techniques.
Coal fires have occurred in the United States for over 200 years and, they may continue to occur. Experience has
shown that they are difficult and expensive to control. Currently available technology used to control them is less
than 70% effective. Research in new technology and in the adaptation of technology available in other fields may
significantly improve the effectiveness of fire-control methods.
