Selection of Blast Design for Kofi C Pit of Endeavour Mining Corporation, Mali
The Kofi Gold Mine (KGM) of Endeavour Mining Corporation in Mali needed to select one of two alternative blast designs, Blast Design 1 (BD1) and Blast Design 2 (BD2), for the fresh rocks of the deposit, both ore and waste, in their Kofi C Pit. BD1 has a burden of 3.2 m, a spacing of 3.5 m, a bench height of 5.0 m and a sub drill of 0.5 m. BD2 has a burden of 3.5 m, a spacing of 4.0 m, a bench height of 10.0 m and a sub drill of 0.8 m. Both designs have the same hole diameter of 115 mm and powder factor of 0.68 kg/m3. The Modified Kuz-Ram Fragmentation Model was used to estimate and compare the fragmentation of the two designs. The modelling results showed that the fragmentation of BD1 would be better than that of BD2 but cost analysis revealed that the drilling and blasting cost of BD2 would be lower than that of BD1. Consequently, BD2 was modified into Blast Design 3 (BD3) to improve the fragmentation without exceeding the drilling and blasting cost of BD1. The modification was done by increasing the powder factor of BD2 by 16.18 %. Subsequent fragmentation modelling and cost analysis revealed that BD3 and BD1 would now have the same fragmentation and the same drilling and blasting cost but BD3 would give a higher productivity. It was therefore recommended that KGM selects BD3 over BD1 and BD2 for ore drilling and blasting. BD2 could be considered for waste drilling and blasting because its lower fragmentation, which is not good enough when the rock is ore, is acceptable when the rock is waste.
Keywords: Blast Design, Cost Analysis, Drilling and Blasting Productivity, Kuz-Ram Fragmentation Model