Faults and Their Effect on Coal Mining in Illinois

摘要

Faults are one of many types of geologic disturbances that affect coal seams. They are common in coal seams of Illinois and have considerable effects on coal mining, such as: offsetting of the coal seams, creation of grades too steep for mining equipment to follow, weakening of roof and ribs, admission of water and gas into workings, and introduction of clay and other impurities into the coal. Faults can be grouped into tectonic faults and nontectonic faults. The presence of most tectonic faults can be predicted before mining begins and their location determined by drilling, seismic exploration, and other means. The major systems of tectonic faults in Illinois that influence coal mining are located in the southern part of the state. They include the Cottage Grove, Wabash Valley, and Rend Lake Fault Systems, the Dowell Fault Zone and Centralia Fault, the Shawneetown Fault Zone, and faults in the Eagle Valley Syncline. Nontectonic faults are found in every mine in the state, although they are more troublesome in some areas than in others. Many nontectonic faults are strongly controlled by lithologic patterns in the rocks above a coal seam. The relationship of nontectonic faults to lithology often can be mapped so that the presence of the faults can be predicted a short distance ahead of the face. Mining plans should be as flexible as possible to allow adaptation to local conditions in faulted areas.