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Surface Fracture Development Over Longwall Panels in South-Central West Virginia.
MISSING :18 pages
The development of large open surface fractures over mined-out coal longwall panels is the focus of this U.S. Bureau of Mines report. The research concentrates on defining the fracture characteristics and their controlling variables. The investigation was conducted at two mines in south-central West Virginia. All but one of the fractures are subparallel to the trend of the underlying longwall panel. One fracture is perpendicular to the trend of a longwall panel. Overall length of the fractures ranges from 60 to 900 ft. In cross section they are v-shaped, ranging from a couple of inches to 25 ft in width at the surface, but narrowing as they increase in depth . Fracture depth varies from a few inches to over 50 ft into bedrock. A vertical fracture or joint plane was observed in the bedrock at several open zones along the fractures. All of the fractures vary in elevation and do not parallel surface contours. The fractures are aligned with local joint trends, they correlate with longwall development, and they are situated in an increased tensional area over the mined-out longwall panels. These observations indicate that the fractures are tensional openings along preexisting joint planes possibly triggered by longwall mining.
IH; Report of Investigations;
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division