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Mining Publication: Application of the Coal Mine Roof Rating (CMRR) to Extended Cuts
Keywords: CMRR Extended cut mining Mining, tunneling, and excavating machinery Roof falls Span design
Original creation date: April 1999
Authors: C Mark
Peer Reviewed Journal Article - April 1999
Download PDF Document (0.31 MB)
NIOSHTIC2 Number: 20025245
Min Eng 1999 51(4):52-56
Since it was 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 (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 fall accidents. When extended cuts are attempted in weak roof, the roof may collapse before it can be bolted, causing hazardous conditions. 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 7 states. It was found that when the CMRR was greater than 55, deep cuts were routine in nearly every case. When the CMRR was less than 37, extended cuts were almost never taken. Between 38 and 55, extended cuts were feasible sometimes but not others. The data also shows that extended cuts are less likely to be stable if either the entry span or the depth of cover increases.
Image of publication Application of the Coal Mine Roof Rating (CMRR) to Extended CutsPeer Reviewed Journal Article - April 1999
Download PDF Document (0.31 MB)
NIOSHTIC2 Number: 20025245
Min Eng 1999 51(4):52-56
See Also
Development and Application of the Coal Mine Roof Rating (CMRR)
Dynamic Failure in Deep Coal: Recent Trends and a Path Forward
Engineering Considerations and Selection Criteria for Proximity Warning Systems for Mining Operations
Factors Influencing Intersection Stability in U.S. Coal Mines
Geologic Characterization
Make it Safer with Roof Screen
New Developments with the Coal Mine Roof Rating
Optimizing Secondary Roof Support with the NIOSH Support Technology Optimization Program (STOP)
Overview of Coal Mine Ground Control Issues in the Illinois Basin
Roof Screening: Best Practices and Roof Bolting Machines
Technology News 483 - Safety Training Tools for Rock Scaling Personnel
Page last reviewed: September 21, 2012
Page last updated: September 21, 2012
Content source: National Institute for Occupational Safety and Health, Mining Program
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