Deep Hole Pre-grouting Technology in Abnormal Area of Large Mining Height Working Face

In order to reduce the impact of abnormal area on high mining height working face, the site observation was applied to analyze the fracture development laws of coal seam in abnormal area, and grouting reinforcement scheme is proposed. The results show that the abnormal area of coal fracture shows the development law of the first opening and then closing; the fracture begins to open at advanced working face of 40 m and develops to the maximum value at 30 m; the best grouting area is the 40 m to 30 m range of advanced working face; through the abnormal area grouting reinforcement, the frequency and depth of rib spalling at working face is reduced, which provides the conditions for the working face passing through abnormal area safely and effectively.