Geomechanics classification of jointed rock masses: mining applications

The classification procedure for calculation of the in-situ rating of a jointed rock mass is described. A rating range, from 0 (very poor) to 100 (very good) is used to give the relative strengths. The need to ensure a good sampling of the area is stressed. The classification rating may be adjusted according to weathering, field and induced stresses, change in stress due to mining, the orientation and type of excavation with respect to geological structures and blasting effects. The in-situ and adjusted ratings are used for selection of the mining method for siting development and major excavations, for assessment of the support requirements and for the definition of cave angles and the extent of failure zones. Practical benefits based on case histories are discussed.