2039 Table 5 – Blasting tests and blast design results for 9” hole diameter Blasting Data 2025 Lithology Mesh (m²) H (m) Holes Q(Kg) FC(g/t) P80(mm) 1 16/sep F, SC, C 32 9,8 154 42.921 322 71 2 30/sep F 37 9,8 116 22.369 190 39 3 01/oct F, SC, C 29 9,8 316 62.900 252 51 4 03/oct F, SC, C 27 10,4 162 33.571 250 141 5 10/oct F, SC, C 27 10,3 117 31.944 331 133 6 13/oct F 39 9,8 153 33.394 216 7 7 03/nov F 34 8,2 202 42.682 261,2 Fine 8 03/nov F 32 9,1 124 24.144 232 Fine 9 05/nov F 32 9,6 240 51.783 244 5 10 06/nov F, SC 29 9,9 185 49.218 347 51 11 07/nov F, C 27 9 185 46.250 327 272 12 11/nov F, SC, C 30 9,1 222 52.191 306 55 13 14/nov F, SC, C 25 9,7 93 24.553 337 124 14 14/nov F, SC, C 25 7,4 149 29.453 372 125 15 01/dec F 40 9,4 187 44.780 246 30 In the 15 tests carried out, the result was mostly fine fragmentation, meaning that for the lithology detonated in utmost cases it was high, and the blasting plan that achieved the optimum of 28 to 32 cm was test 11 in friable and compact rock, with a fragmentation next to 28 cm, with a mesh (burden x spacing) of 27 m2, explosive of 250 kg/hole and powder factor of 327 g/t. 5. CONCLUSIONS The quantitative models developed to minimize the cost of the drilling–blasting–loading– hauling and primary crushing operation chain as a function of fragmentation, as well as those for the fragmentation of banded iron formation (BIF) rocks, are innovative and applicable at an industrial scale. Application to the Brucutu mine showed that fragmentations smaller than 28 cm and greater than 32 cm minimize costs, with drilling–blasting–loading–hauling costs of US$ 4.6/t in friable lithologies, US$ 5.0/t in semi-compact lithologies, and US$ 5.7/t in compact lithologies. The optimal blast patterns that allow these results to be achieved use a 21 m² pattern for 7 7/8” holes and a 32 m² pattern for 9” holes. ACKNOWLEDGEMENTS The authors would like to thank Vale Institute of Technology of Vale S.A. for the resources used to prepare this study. REFERENCES Adel, G.; kojovic, T.; Thornton, D. Mine-to-mill optimization of aggregate production. 168 p., 2006. Cameron, P.; Drinkwater, D.; Pease, J. (2017). The ABC of mine to mill and metal price cycles. AusIMM Bulletin, 9 p. Campos Gonçalves, G. M. (2020). Technological characterization of the itabirite ... Brucutu-MG. Master’s thesis. Federal University of Ouro Preto.
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