Mineralogical investigation of coal mine roof shales in part of the southern Appalachian coal field

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Virginia Polytechnic Institute

Many coal mines in southwestern Virginia and West Virginia are plagued with excessive deterioration of roof shales. Shale flakes and sheets spall off the roofs at unpredictable intervals and create hazards in many coal mines (P1.1). The failures are more frequent during the summer months when the incoming air is at a higher temperature than the roofs and walls of the mine. This differences in temperature causes the moisture of the air to condense on the cooler parts of the mine.

Prof. C.T. Holland, Department of Mining Engineering, Virginia Polytechnic Institute, has suggested that this type of roof failure may depend upon some mineralogical or chemical change caused by the increase in moisture on the rooms of the mine.

In addition to the weathering process, some roof shales are notoriously susceptible to failure in those places where ground-water seepage is prevalent. The failures caused by this type of situation at the entry of a mine are usually more predictable than those caused by weathering.

The purpose of this investigation was to determine if there were any significant differences in the mineral, chemical, or textural compositions of roof rocks which have failed and those which have not.