Application of multiple indicator Kriging for RMR value estimation in areas of new drift excavation during mine site redevelopment

Rock mass rating (RMR) values along additional drifts that are to be constructed during mine site redevelopment (Gagok mine, Korea) were estimated using multiple criteria indicator Kriging with borehole RMR and electrical resistivity tomography data. This study outlines two potential correction methods that supplement indicator Kriging and that can reduce error, allowing more accurate estimation of RMR values. The correction methods used a filtering of indirect data affected by drifts (FIED) method to reduce uncertainties and errors within electrical resistivity tomography data caused by changes in setup and the location of existing drifts. In addition, a correction indicating accurate representation of indirect data (CARI) method was used to resolve distortions in drilling log results. This meant that 73 % of the estimated RMR values were assigned to the correct RMR class, with only 1 % of these values being overestimated. The sensitivity of the FIED method was 4 %, with the linear CARI method having a sensitivity of 56–60 % and the logarithmic CARI method having a sensitivity of 61–65 %.