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Diagnosing and controlling moisture-sensitive roof in coal mines.

Authors
Molinda-G; Klemetti-T
Source
Electron J Geotech Eng 2008 Jan; 13(A):1-20
NIOSHTIC No.
20034613
Abstract
Historically, coal miners have known that roof shales can deteriorate in contact with humid mine air, causing massive roof falls and injuries from falling rock. It is critical to recognize rocks prone to weathering and to adequately support these rocks in order to ensure the long-term stability of the openings. In a recent study, NIOSH has used a wet/dry cycling test to determine the moisture sensitivity of over 800 specimens of roof rock from 25 U.S. coal mines. Fireclays and some gray shales are the most moisture-sensitive. Rocks with disturbed bedding, in contrast to flat-bedded rocks, are also more sensitive to water. Black shales are relatively un-reactive to moisture and serve to protect more reactive gray shales above. Mines that have roof rocks with moisture-sensitivity indexes above 40% can experience slaking roof conditions, and many require high coverage surface controls. Three case studies are presented in which the moisture-sensitivity index is correlated to roof conditions underground, and can be used to indicate long term deterioration. Engineering measures are described to control moisture-sensitive roof. In one case, roof screen not only reduces injuries from rock fall but also is shown to reduce roof falls.
Keywords
Mining-industry; Underground-mining; Ground-control; Ground-stability; Rock-falls; Rock-mechanics; Rock-bursts; Engineering-controls; Control-technology
CODEN
EJGEFK
Publication Date
20080101
Document Type
Journal Article
Email Address
GMolinda@cdc.gov
Fiscal Year
2008
NTIS Accession No.
NTIS Price
Issue of Publication
A
ISSN
1089-3032
NIOSH Division
PRL
Priority Area
Mining
Source Name
The Electronic Journal of Geotechnical Engineering
State
PA
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