Application of Deep-hole Pre-cracking Blasting in the Preserved Roadway beside the Gob for Working Gaolin in Coal Seams

In working Gaolin in the Suoli Mine of Huaibei Area, the roof strata of the gob approaches the working face to a great extent, offering difficulties for ventilation and pedestrian. To solve the problem, experiments are carried out by the haulage way of the working face by drilling upward a series of holes in the roof of the wall to be worked for deephole pre-cracking blasting so that a cracked surface is formed between the roof of the haulage way and the roof of the working area. In this way, the problem is solved which is attributable to the great approaching movement of the rock strata in the roof and the floor of the gob. Careful observation shows that with the blasting carried out, the presupporting resistance and the approaching movement of the rock strata of the roof and floor of the haulage way are not significantly varied. And in the area behind the working face, the rock strata approaching movement is apparently reduced.