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Rating Coal Mine Roof Strength From Exploratory Drill Core
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Citation (Style = APA)
Mark, C. (1996). Rating Coal Mine Roof Strength From Exploratory Drill Core. Proceedings 15th International Conference On Ground Control In Mining
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Reference Manager (RIS)
SpreadSheed (CSV)
Mark, C. (1996). Rating Coal Mine Roof Strength From Exploratory Drill Core. Proceedings 15th International Conference On Ground Control In Mining
Citation Downloads
Reference Manager (RIS)
SpreadSheed (CSV)
Organization: International Conference on Ground Control in Mining
Pages: 14
Publication Date:
Jan 1, 1996
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Abstract
Abstract
| Characterizing coal mine roof rock is extremely important for hazard assessment, reinforcement, and entry design. The Coal Mine Roof Rating (CMRR) is an innovative rock mass classification that has found acceptance in the coal mining industry. A disadvantage of the original CMRR is that it cannot be determined in advance of mining, because it requires underground observations. An entirely new set of procedures have now been developed to determine the CMRR from exploratory drill core, as described in this paper. The new procedures employ Point Load Tests (PLT) to determine strength parameters that account for approximately 60% of the rating. Both diametral (parallel to bedding) and axial (perpendicular to bedding) PLT are conducted. The diametral tests allow estimates of bedding plane cohesion and rock anisotropy, both of which are critical to estimating susceptibility to horizontal stress. Traditional core logging procedures are used to determine discontinuity spacing and roughness. To ensure compatibility with the original CMRR, the new rating scales were verified by comparing drill core results with nearby underground exposures. To assist mine planners in using the new CMRR procedures, a large database of strength ratings of roof rocks was assembled through extensive point load testing and logging. Over 2000 point load tests (both axial and diametral) have been made on 30 common coal measure rock types from mines representing most U.S. coalfields. This database has been merged with the popular core rating system of J.C. Ferm into a field guide for geologists and engineers. By using the pictorial classification system of Ferm to identify the rock, typical CMRR can be compared with values calculated using the new CMRR procedures. |
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