中国矿山工程

Mining with block caving is extremely severity for rockmass occurrence characteristics, and rockmass caveability directly affects caving rate and secondary fragmentation of block caving mines. It is a vital technology to realize ore and rock pre-conditioning by increasing internal fractures with artificial auxiliary fracturing, which is currently a routine production process of block caving mines abroad. Based on Tongkuangyu mining project of the first block caving mine in China transferring to the deep, a detailed investigation of rockmass occurrence characteristics and a field test on rockmass pre-conditioning by hydraulic fracturing were carried out. The results show that rockmass at the start caving area of No. 5 orebody in Level 410m of Tongkuangyu mine is hard rock with medium to less integrity, rockmass quality classification is II to III and rockmass caveability is moderately to hard, which would result in caving mining with medium broken and more bulk. Detailed investigation of rockmass occurrence characteristics is the basis for in-depth understanding of rockmass caveability. Borehole wall images before and after preconditioning tests by hydraulic fracturing were obtained and newly generated hydraulic fractures were observed, which could effectively improve the degree of rockmass structure development. Based on analysis of caving front monitoring and drawpoint fragmentation distribution, a more than 3 times increase in caving rate and a 58.3% reduction in secondary fragmentation were achieved in production period of the start caving area, which provide a solid support for steady convergence of production capacity in transition period of mine to the deep. The technology of rockmass pre-conditioning by hydraulic fracturing and related equipment system were initially formed which could support a further development of modern block caving mining in China.