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Longwall mine design for control of horizontal stress.

Mark-C; Mucho-TP
New Technology for Longwall Ground Control. Proceedings: U.S. Bureau of Mines Technology Transfer Seminar. Pittsburgh, PA: U.S. Bureau of Mines, 1994 Aug; :53-76
Horizontal stress is a significant, although often overlooked, factor in ground control in longwall mines. It can be particularly destructive in development and headgate entries, where it can cause persistent compressive-type roof failure called cutter roof, roof guttering, or kink roof. This paper presents the current state of the art in detecting and controlling horizontal stress. The information was collected through detailed site investigations at several eastern U.S. longwall mines, a survey of ground conditions at 50 U.S. longwalls, and an international literature review. This paper begins with a discussion of the present knowledge of regional in situ stress fields in the United States. A compilation of underground stress measurements from 47 U.S. coal mines is presented. The measurements indicate a persistent trend of high horizontal stresses trending east-northeast to east-west in the Eastern United States. The direction and magnitude of horizontal stress does not appear to be significantly affected by ancient geologic structures in the East, but surface topography may have an important effect. Horizontal stresses in the Western United States are less consistent in direction and are generally lower relative to the vertical stress. These observations are consistent with the regional stress fields identified by the geophysicists of the World Stress Map Project, who have lately presented convincing evidence that the horizontal stresses observed underground are linked to plate-tectonic processes. Next, experience with horizontal stress in longwall mines is addressed. The paper focuses on the northern Appalachian region, where the effects of horizontal stress have been most evident. Three case histories are de- scribed in detail, and the solutions developed are highlight- ed. Evidence of horizontal stress observed underground in Illinois, Alabama, and the Western United States is also discussed. The degree of horizontal stress damage to longwall gate entries appears to vary by region and by roof geology. Laminated shale roofs, particularly in the northern Appalachian Mountains and in Illinois, appear to be at the greatest risk. Some simple, in-mine, stress mapping techniques are described. Control techniques discussed include panel orientation, cut sequencing, softened entries, and roof support. ,
Longwall-mining; Mining-industry; Ground-control; Ground-stability; Geology; Computer-software; Computer-models
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Document Type
Book or book chapter
Mark-C; Tuchman-RJ; Repsher-RC; Simon-CL
Fiscal Year
NTIS Accession No.
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NIOSH Division
Source Name
New Technology for Longwall Ground Control. Proceedings: U.S. Bureau of Mines Technology Transfer Seminar. Pittsburgh, PA: U.S. Bureau of Mines