Analysis on weakening hard rock used by long-hole presplitting blast in fully mechanized coal face with water-gel explosive grain

Aimed to the hard rock fault in rock path of the coal working faces and the low efficiency of rock breaking directly by coal cutter,the long-hole presplitting blast is done by self-made water-gel explosive grain of long-range booster, numerical simulation and design of reasonable blasting parameters. The results show that the long-range booster water-gel explosive has high reliability and when the blasting hole diameter is 75 mm, the diameter of charge is 63 mm, the radius of crushing zone is 0.4-0.5m and the radius of cracks is 0.5-1.0 m. When the distance between neighboring blasting hole is about 1.6-2.2 m, the damage cracks are future extended after long-hole blasting, it satisfies the requirement of rock breaking used by coal cutter, which ensures that the fully mechanized coal face passes through the hard fault of rock successfully.