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The coal mine roof rating in mining engineering practice.
Fourth Underground Coal Operators' Conference. Carlton, Victoria, Australia: Australasian Institute of Mining and Metallurgy (AusIMM), 2003 Feb; :50-62
The Coal Mine Roof Rating (CMRR) system was developed 10 years ago to fill the gap between geologic characterization and engineering design. It combines many years of geologic studies in underground coal mines and 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 mainly by the discontinuities that weaken the rock fabric. Since its introduction, the CMRR has been incorporated into many aspects of mine planning, including longwall pillar design, roof support selection, feasibility studies, and extended-cut evaluation. It has also become truly international; it is involved in mine designs and funded research projects in the Republic of South Africa, Canada, and Australia. Most recently, a new streamlined process to determine the CMRR from exploratory drill cores has been developed. Only three types of information are now required: (1) fracture spacing Rock Quality Designation (RQD) from a standard geotechnical drill log, (2) uniaxial compressive strength from standard lab tests, geophysical downhole logging, or axial-point load tests, and (3) diametral point-load testing. The CMRR has been implemented in a computer program, which can be obtained from NIOSH free of charge. The program facilitates calculation of the CMRR from either underground or drillcore data. Values from many locations can be saved in a single file, and an interface with AutoCAD allows CMRR contour plots to be integrated into mine planning.
Ground-control; Geology; Underground-mining; Coal-mining; Hazards; Computer-software; Longwall-mining; Mine-design
NIOSH Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236
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Fourth Underground Coal Operators' Conference
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division