| dc.description.abstract | The rock mass classification systems are commonly used to obtain data, parameters and inforamtion of greatest relevance in enginnering projects, overall in underground excavations. The Q and RMR (Rock Mass Rating) rock mass classification systems, developed by Barton et al. (1974) and Bieniawski (1992) respectively, were applied to hard itabirite and hematite rock masses at Córrego do Meio Mine, located in the Iron Quadrange Minas Gerais to potentially evaluate, the problems observed in the drilling operations. The low efficiency of mechanic and drilling equipment can be related to some properties such as: hardness, abrasiveness, compressive strength and rock mass structure that affectthe drillibity. These featurs are important in selecting the drilling equipment and acessories and bulldozers. Several procedures were undertaken in this study, for example: in situ slope observation and data gathering, accessing the hematite and hard itabirite abrasiveness through the Asmler Test, geomechanich compression and traction tests using a servo-controlled testing machine (MTS 815) and finally, mineralogical characterization (using a Eletronic Scanning Microscope).The obtained results showed that the main causes of low efficiecy of the equipments are associated with the high abrasiveness (0,2mm to hard itabirite and hematite) and the poor rock mass classification (RMR: regular rock class III for hard itabirite and fair rock class IV for hematite; Q: very poor for the hard itabirite and extremely poor for thehematite). | |
