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Coal Mine Roof Rating (CMRR): A Practical Rock Mass Classification for Coal Mines.


PB94160041

Publication Date 1994
Personal Author Molinda, G. M.; Mark, C.
Page Count 90
Abstract The Coal Mine Roof Rating (CMRR) was developed by the U.S. Bureau of Mines as an engineering tool to quantify descriptive geologic information for use in coal mine design and roof support selection. The CMRR system combines the results of many years of geologic ground control research with worldwide experience with rock mass classification systems. Like other classification systems, the CMRR begins with the premise that the structural competence of mine roof rock is determined primarily by the discontinuities that weaken the rock fabric. The CMRR makes four unique contributions: (1) it is specifically designed for bedded coal measure rocks, (2) it concentrates on the bolted interval and its ability to form a stable mine structure, (3) it is applicable to all U.S. coal seams, and (4) it provides a methodology for data collection. Using only simple field tests and observations, the CMRR can be calculated from roof falls, overcasts, and highwall exposures.
Keywords
  • Coal mines
  • Roofs
  • Geological surveys
  • Hazards
  • Geological maps
  • Flow charts
  • Structural analysis
  • Lithology
  • Weight(Mass)
  • Ratings
  • Shear strength
  • Cohesion
  • Moisture
  • Sensitivity
  • Risk analysis
  • Spacing
  • Field tests
  • Unit discontinuities
Source Agency
  • Bureau of Mines
NTIS Subject Category
  • 48A - Mineral Industries
  • 48F - Geology & Geophysics
  • 89B - Architectural Design & Environmental Engineering
Corporate Authors Bureau of Mines, Pittsburgh, PA. Pittsburgh Research Center.
Supplemental Notes See also PB80-158983 and PB82-140344.
Document Type Technical Report
Title Note Information circular/1994.
NTIS Issue Number 199413
Coal Mine Roof Rating (CMRR): A Practical Rock Mass Classification for Coal Mines.
Coal Mine Roof Rating (CMRR): A Practical Rock Mass Classification for Coal Mines.
PB94160041

  • Coal mines
  • Roofs
  • Geological surveys
  • Hazards
  • Geological maps
  • Flow charts
  • Structural analysis
  • Lithology
  • Weight(Mass)
  • Ratings
  • Shear strength
  • Cohesion
  • Moisture
  • Sensitivity
  • Risk analysis
  • Spacing
  • Field tests
  • Unit discontinuities
  • Bureau of Mines
  • 48A - Mineral Industries
  • 48F - Geology & Geophysics
  • 89B - Architectural Design & Environmental Engineering
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