A correlation of four rock mass classification systems through their fabric indices

Four classification systems are investigated in this work, RMR, Q, GSI and RMi. The common parameters of these systems, which concern and characterize solely the rock mass, are those used for rating the rock structure and the joint surface conditions. Rock structure is quantified by the block size or the discontinuity spacing ratings (BS) and the joint surface conditions are quantified by the joint conditions ratings (JC). A Rock Mass Fabric Index, denoted as F  , may thus be defined as a scalar function of the components rock structure and joint conditions i.e., F=F(BS,JC)F=F(BS,JC). All rock mass classification systems’ ratings are grouped together in a common Fabric Index chart. The validity of the chart is tested using data extracted from various projects. The use of the chart simplifies input, correlates rock mass classification systems and improves their utility.