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Application of coal mine roof rating (CMRR) to extended cuts.

Authors
Mark-C
Source
Min Eng 1999 Apr; :51(4):52-56
NIOSHTIC No.
20025245
Abstract
Since first introduced, the coal mine roof rating (CMRR) has been widely accepted as a tool for geologic characterization and mine planning. This paper discusses the application of the CMRR to another practical ground-control problem: extended cuts. Extended cuts, i.e., cuts greater than 6 m (20 ft) in length, are commonly used with remote-control continuous miners. Extended cuts can greatly increase productivity, but they have been associated with a number of fatal-roof falls. When extended cuts are attempted in weak roof material, the roof may collapse before it can be bolted. Until now, it has not been possible to predict where conditions may not be suitable for extended cuts. In this study, data on the CMRR and extended-cut experience were collected at 36 mines in seven of the United States. It was found that, when the CMRR was greater than 56, deep cuts were routine in nearly every case. When the CMRR was less than 37, extended cuts were almost never taken, and when the CMRR was between 38 and 56, extended cuts were sometimes, but not always, feasible. The data also show that extended cuts are less likely to be stable if either the entry span or the depth of cover increases.
Keywords
Coal-mining; Coal-miners; Mining-industry; Occupational-hazards; Mine-disasters; Traumatic-injuries; Underground-mining; Ground-control; Ground-stability; Mining-equipment
CODEN
MIENAB
Publication Date
19990401
Document Type
Journal Article
Fiscal Year
1999
NTIS Accession No.
NTIS Price
Issue of Publication
4
ISSN
0026-5187
NIOSH Division
PRL
Source Name
Mining Engineering
State
PA
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