Effects of late Paleozoic foreland deformation on underground coal mine ground instability, Illinois and Appalachian Basins

Slickensides are commonly associated with potentially hazardous ground conditions in underground coal mines. Investigations by the Mine Safety and Health Administration's Roof Control Division indicate that slickensided drag folds in the immediate roof of Pennsylvanian-age coal seams represent instances of ground instability of various scales, from skin control hazards to roof falls that block travelways and belt entries. The occurrence of features in the roof of the Illinois Basin's Springfield coal seam that are identical to structures interpreted as drag folds in Pennsylvanian-age coal measure rocks of the Appalachian Basin suggests that tectonic stress associated with the late Pennsylvanian-Permian Alleghanian orogeny was transmitted into the mid-continent. This paper relates slickenside occurrences in the Pennsylvanian-age Springfield coal seam to local structural geologic features that are associated with the late Pennsylvanian-Permian Alleghanian orogeny. Because the slickensides discussed are interpreted to have formed in response to regional tectonic stress, small-scale controls on coal mine ground instability can be related to large-scale, regional tectonic processes. Field investigations indicate that mine-wide geologic mapping of structural geologic features can be used to project zones of subtle, yet problematic, structural weakness in advance of face positions. By incorporating this style of structural geologic hazard mapping in mine planning and operation, miners can be prepared to install appropriate supplemental support, or reduce the effects of structural weaknesses with local modifications to mine design. Published by Elsevier B.V.