SOCIETY FOR MINING, METALLURGY, AND EXPLORATION Vol. 320 • 2006 TRANSACTIONS 133 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 PROOF COPY Impact of burden and spacing on fragment size distribution and total cost in quarry mining V. Kecojevic Assistant professor of mining engineering, The Pennsylvania State University, University Park, Pennsylvania D. Komljenovic —TITLE—, Department of Industrial Engineering, University of Quebec, Trois-Rivières, Canada Abstract Quarry mining operations consist of a chain of processes, including drilling, blasting, loading, haul- ing and crushing. Drilling and blasting result in fragmentation that can affect downstream processes. The resulting oversized and/or undersized fragmentation can determine the value of the final product, the production cost and the energy consumption. Though most previously completed research studies pointed out the benefits of taking a holistic approach to the entire mining process, this study undertakes a novel approach in determining the impact of drilling and blasting geometry (burden and spacing) on fragment size distribution and the total cost of a quarry operation. Mathematical modeling is used and the process is coded within the MS Excel environment. A study on fragment size distribution and mining cost was performed on an operating quarry in eastern Pennsylvania. The obtained results show that a new drilling/blasting geometry may reduce the total mining cost by 8.6%. The research presented contributes to the domain of surface mining engineering and can be used by quarry professionals to evaluate different drilling and blasting scenarios. Introduction Most mining operations consist of a chain of several processes, including drilling, blasting, loading, hauling and crushing. The main objective of drilling and blasting, the first elements of the ore extraction process, is to fracture the in situ rock mass while maintaining safety and environmental standards. This subprocess needs to produce fragment size distribu- tions tailored to minimize the production costs and energy consumption in downstream processes, including loading, hauling and crushing. P&H Mining Pro data indicate that drilling and blasting typically account for 15%, loading and hauling account for 75% and ancillary operations account for 10% of the total cost of primary mining process (Harnischfeger Corp., 2003). When the cost of mining and processing operations are considered together, drilling and blasting account for 6%, loading and hauling account for 30%, ancillary operations account for 4% and processing accounts for 60%. The latter shows the need to reduce costs at the processing step, where the consumption of energy and cost is the highest. A study performed by Fernberg (2005) shows that a typical cost distribution in quarry mining is as follows: drilling and blasting account for 25%; loading and transport account for 25 %; and crushing, screening and storage account for 50%. Crushing, screening and storage represent about half of the cost, whereas drilling represents less than 10% of the total cost. Hagan (1983) states that of the three most important prop- erties of muck piles, i.e., fragmentation, looseness and shape, fragmentation has the greatest affect on mining costs. Studies by Persson et al. (1994) and Scott and McKee (1994) yielded results showing that the degree of fragmentation influences the economy of the excavation. Moody et al. (1996) found that power consumption at the crusher is more sensitive to rock dimensions than to tonnage. A study by McKee et al. (1995) showed that the benefits of good fragmentation can extend fur- ther to the grinding circuits because most of the power/energy used at a mine is consumed by crushing and grinding. In most cases, the drilling and blasting regime depends on the requirements for the final product size of the ore being mined. Copper ore, for instance, may end up in a powder form Paper number TP-06-009. Original manuscript submitted online March 2006. Revised manuscript accepted for publication June 2006. Discussion of this peer-reviewed and approved paper is invited and must be submitted to SME Publications Dept. prior to Sept 30, 2007. Copyright 2006, Society for Mining, Metallurgy, and Exploration, Inc.