Influence of Rock Mass Properties and Discontinuity with Explosive Charge on Muck-Pile Size Distribution

The cost effective technique of generating heap of rock fragments is through blasting operation. The process of achieving optimum muck-pile fragment size distribution is complex and at same time the task of matching crusher’s gape to the appropriate mean fragment size for improved productivity of crusher had constituted a serious concern to mine managers and quarry operators. Therefore, this research is set to evaluate rock mass properties, map discontinuities, thereafter analyse the influence these properties with explosive usage on fragment size. In order to achieved the set of objectives two rock types coded STAK and FMIJ were selected from two operating quarries in Ondo State, Nigeria for this study. Forty (40) datasets were obtained for bulk density and rebound hardness values. Also, Rock Quality Designation (RQD) and Rock Mass Rating (RMR) were determined as part of the rock mass factors. Moreover, the discontinuities were mapped at the selected quarry faces, explosive data usage were obtained and digital image of the muck-piles were taken and analyzed. The results obtained revealed that bulk density and rebounds hardness varied from 2795.27-2902.25 kg/m3 and 2765.63 – 3193.80 kg/m3; 40 – 62 and 30 – 62 for STAK and FMIJ respectively. The RQD values of the rocks are 73% for STAK and 71% for FMIJ, hence, the two rocks are classified as good quality rocks. In addition, the RMR of the selected rocks varied from 52 – 80 and 58 – 92 for STAK and FMIJ respectively. The influence of the parameters will guide Mine Managers on explosive consumption and the various ranges of muck-pile sizes that will be generated after fragmentation. Keywords: Rock mass, explosive, charge, rock, quality, fragments, muck-pile