Print this pageRegional analysis of mined coal beds, mine visits, and discussions with mine inspectors and engineers are used to summarize critical mining geology factors in western Kentucky underground coal mines. Although mines are susceptible to roof falls caused by facies changes in mine roofs, the lateral continuity of coal seams and surrounding strata in western Kentucky causes most of these facies-change obstacles to be very localized, especially when compared to those in the Eastern Kentucky Coal Field. The widespread continuity leads to specific geologic conditions for each seam, rather than similar conditions for all seams, a factor that should be recognized in geologic modeling.
The most common roof problems in Springfield (W. Ky. No. 9) coal mines are "slips" or slickensided fractures, which appear to be more developed in the hard, black shale above this coal than in shales above other coals. Locally, Springfield coal mines also encounter floor heaving related to thick, relatively moist underclays. Similar heaving is noted in the Herrin coal, but Herrin mine roofs have problems related to a weak, calcareous claystone, which degrades rapidly on exposure, rather than roof slips. The Baker coal (W. Ky. No. 13) also has a claystone roof, but it is a seat earth, and roof problems in it are related to the height of rider coals, which are not common above other mined coals. In contrast to these three coals, mines in the W. Ky. No. 4 coal more commonly encounter geologic obstacles related to narrow paleochannels, stackrock, and undulating floor elevations associated with syndepositional faulting, not commonly observed in the other coals. Superimposed on all of these features, in each of the coals, are regional faulting, north-south oriented regional stress fractures, and fractures below areas of low cover. Fractures and faulting may also act as conduits for water and sulfate-bearing fluids, both locally affect the mining geology of western Kentucky coals.
AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana