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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

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