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Modern underground coal mines commonly employ retreating longwall mining techniques to increase productivity and resource recovery and decrease mining cost. Although longwall mining is generally the most efficient method used today, its effectiveness can be impaired by intersecting localized areas of coal thinner than the minimum mining height of the equipment.
Coal seams within western coalfields are generally lenticular. Localized areas of thin coal overlain by fluvial sandstone deposits that are scoured into the coal are common on many properties and may be encountered by retreating longwalls. This can severely impact productivity and degrade the run of mine coal quality.
The use of Radio Imaging Method (RIM) is being tested to map coal seam thickness within a developed longwall panel. Although coal seams are poor electrical conductors, electromagnetic signals can be transmitted through the coal within a longwall panel. These signals are attenuated as they pass through the longwall panel. The degree of attenuation for a given distance of signal travel is largely a function of the coal seam height. This relationship enables RIM to detect changes in coal seam height within a longwall panel that may or may not be evident from the development entries.
Initial testing of RIM in a few developed longwall panels has proved successful in identifying at least three areas of thin coal that were later confirmed by drilling and mining.
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