Abstract: The large blocks left in the roadway of Beiminghe underground iron mine are difficult to efficiently handle. The surface symmetrical metal energy-concentrating cover is used to realize the rapid splitting of the large blocks. Six sets of blasting tests are performed on the large blocks in the iron mine roadway. Compare the fragmentation distribution， average fragmentation and blasting morphology when the explosion height is 0， 1 explosion height and 2 explosion height， to study the influence of the explosion height and the unit consumption of the explosive on the crushing effect of large block in the parameters of the shaped charge. The results show that when there is no height， the fragments are mainly distributed in the interval of large size 60~80 cm； with the increase of the height of explosion， the fragments are mainly distributed in the interval of medium size 20~60 cm； the favorable height of the explosion makes the large size The average block size in the interval is reduced by about 10%， and the average block size increase in the medium-sized interval is about 30%~45%； under the same explosive height condition， the slight change of explosive unit consumption has little effect on the average value in the interval； the blasting shape is influenced by metal jet morphology， with the increase of the blast height， the degree of secondary crushing of large pieces increases， and the fragments change from axial symmetry to cross-symmetrical. The application of energy-accumulating blasting can effectively realize the controlled splitting of large pieces.

Key words: underground mining, cumulative blasting, secondary breakup, blasting fragmentation, control cleavage