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Reinforcing coal mine roof with polyurethane injection: 4 case studies.

Authors
Molinda-G
Source
Geotech Geol Eng 2008 Oct; 26(5):553-566
NIOSHTIC No.
20034612
Abstract
NIOSH has recently completed a study of the interaction between polyurethane (PUR) and coal mine roof in order to determine the mechanism of reinforcement, in both highly fractured rock and unfractured rock. Four case studies of PUR reinforcement are presented. At a West Virginia site, a borehole camera revealed the location of roof voids and guided the PUR injection. By injecting polyurethane into a zone from 0.6 to 1.8 m (2-6 ft.) high in the roof, a roof beam was created and ongoing intersection falls were halted. In another highly fractured roof in a western Pennsylvania mine, a total of 5.8 cm (2.3 in.) of rubbleized rock was found in a zone up to 3 m (10 ft.) into the roof. Untargeted PUR injection filled approximately 1/2 of the fractures. These two case studies showed that it is not necessary to fill up 100% of the void space to create stability. In the other two field sites, polyurethane was injected into weak, but unfractured roof. Post-injection video monitoring showed that weak bedding planes were hydraulically wedged open and polyurethane injected along bedding. The reinforcement value of this injection method is limited because of the wafer-thin layer of PUR introduced along bedding, and the lack of a PUR "webbing" which would serve as a structural framework to provide strength. It was determined that video inspection prior to PUR injection can aid in identifying the fracture zones to target, and minimize "blind" pumping and loss of PUR.
Keywords
Mining-industry; Underground-mining; Ground-control; Ground-stability; Coal-mining; Control-technology; Engineering-controls; Accident-prevention
Contact
G. Molinda, Pittsburgh Research Laboratory, National Institute for Occupational Safety and Health (NIOSH), Cochrans Mill Road, P. O. Box 18070, Pittsburgh, PA, USA
CODEN
GGENE3
Publication Date
20081001
Document Type
Journal Article
Email Address
Gdm4@cdc.gov
Fiscal Year
2009
NTIS Accession No.
NTIS Price
Issue of Publication
5
ISSN
0960-3182
NIOSH Division
PRL
Source Name
Geotechnical and Geological Engineering
State
PA; WV
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