Application of CMRR classification system to determine rock mass design parameters in underground coal mines

Abstract

The Coal Mine Roof Rating (CMRR) classification system has been applied in a number of coal mines worldwide including Australia. This system is very useful for mine planners as it provides reliable and repeatable information about the roof properties, however, CMRR is limited in its application as it cannot provide rock mass design data required to simulate underground coal mines using computation methods. In this study, eight case studies; Riccall, Daw Mill and Rossington mines from United Kingdom, Eliza and Ashton mines from Australia, Colowyo mine from USA, Waterberg mine from South Africa and Tabas mine from Iran were analyzed to stablish correlations between Geological Strength Index (GSI), Rock Mass Rating (RMR) and CMRR classification system. A methodology is developed to derive the in situ stratified rock mass input parameters for numerical computational analysis using CMRR system. For the case of Ricall mine, following the developed methodology, rock mass parameters were defined and implemented as input parameters for numerical models of the roadways using FLAC and FLAC3D software. The new application of CMRR to define rock mass properties was validated by making comparison between results of numerical modeling and actual in situ monitoring data.