The practice on decreasing the rate of big block in the surface mining of Yichun Tantalum and Niobium Mine

Focus on the characteristics of rock's “block state” in Yichun Tantalum and Niobium Mine, the paper analyses the reasons of high big_block's rate produced in deep-hole explosion.The differential explosion technology of wide_hole distance and big row span are applied in the explosion, the productive rae of big block is controlled below 5 percent.Some problems of restricting big_block rate's decreasing are proposed.