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Case history of the response of a longwall entry subjected to concentrated horizontal stress.

Authors
Mark-C; Gale-W; Oyler-D; Chen-J
Source
Int J Rock Mech Min Sci 2007 Feb; 44(2):210-221
NIOSHTIC No.
20031461
Abstract
The National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Research Laboratory (PRL), RAG Pennsylvania and Strata Control Technologies of Australia collaborated in an intensive study of ground behavior, reinforcement performance, and stress redistribution at the Emerald Mine in Southwestern Pennsylvania. The study site was a longwall tailgate subjected to a severe horizontal stress concentration. Field measurements indicated that the stresses applied to the study site nearly doubled during longwall mining, resulting in roof deformations extending to a height of 4.8 m (16 ft) above the entry. A computer simulation of the field site was conducted using FLAC-2D, incorporating a broad range of rock behaviors and failure mechanisms. Comparison between the measurements and the simulation showed that the model was able to capture the most significant aspects of the roof and support system behavior, particularly, the extensive slip along bedding that created a partially destressed "softened" zone in the immediate roof. The model also showed that supplementing the normal roof bolt support pattern with cable bolts would allow the entry to survive a further 20-25% increase in the applied horizontal stress. Such information could have very practical application to the design of roof support systems for coal mines.
Keywords
Mining-industry; Geology; Rock-mechanics; Underground-mining; Coal-mining; Longwall-mining; Models; Computer-models; Computer-software; Simulation-methods
Contact
NIOSH, Rock Safety Engineering Branch, Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236, USA
Publication Date
20070201
Document Type
Journal Article
Email Address
cmark@cdc.gov
Fiscal Year
2007
NTIS Accession No.
NTIS Price
Issue of Publication
2
ISSN
1365-1609
NIOSH Division
PRL
Source Name
International Journal of Rock Mechanics and Mining Sciences
State
PA
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