Application of Deep Borehole Pre-cracking Blasting Technology to Floor of High Gassy Fully Mechanized Top Coal Caving Face

The main roof above No. S2206 high gassy fully mechanized top coal caving mining face in Yuwu Mining was high in thickness,compact and hard. During the initial mining period,a large area suspended roof could be easily formed. When the large area suspended roof suddenly collapsed,serious mine strata pressure behaviors and gas content suddenly increased problems would be caused in the coal mining face. Based on the circumstances,a roof weakening conducted before the initial mining of No. S2206 coal mining face was proposed. With the deep borehole pre-cracking blasting in the open-off cut of the coal mining face,the integrality of the roof above the open-off cut could broke in advance,a cycle distance of the roof initial falling was reduced and a danger of large roof pressure could eliminated. Thus the top coal could be recovered in advance and a safety and high efficient production of No. S2206 coal mining face was realized.