Research and application of influencing factors of key parameters of roof cutting and pressure relief by dense drilling

The technology of roof cutting by dense drilling is mainly through the transformation of the surrounding rock structure of the lateral roof of the stope, and the use of overburden load and roof weight to cut off the basic roof can effectively reduce the roof pressure of the roadway. This paper analyzes the key parameters of drilling and the effect of retaining roadway by analyzing the roof cutting and pressure relief by dense drilling technology along the empty roadway in some mines in China, and studies the main influencing factors of the key parameters of roof cutting by dense drilling. The results show that the technology of roof cutting by dense drilling is suitable for coal seams with different thicknesses, and the effect of roof cutting depends on whether the cutting height, cutting angle, drilling diameter and spacing are reasonable. Because the roof is not completely broken before recovery when the roof is cut by dense drilling, after recovery, the greater the thickness of the coal seam, the greater the tensile stress generated by the roof subsidence and rotation around the drilling, the more easily the roof with the dense drilling is to break, and the increase of coal thickness is conducive to the independent breaking of the roof. The roof cutting height of dense drilling increases with the increase of coal thickness and main roof thickness. With the increase of coal thickness, the influence of drilling angle on roof cutting gradually decreases, and the drilling angle shows a decreasing trend. The combined effect of dense drilling aperture and spacing affects the fracture effect of roof with dense drilling. The D / B value (the ratio of drilling spacing to drilling diameter) increases with the increase of coal thickness within a certain range, and decreases with the increase of main roof strength. According to the statistical results, the engineering analogy method is adopted, and combined with the research results of the main influencing factors of roof cutting by dense drilling, the method for determining the key parameters of roof cutting by dense drilling is put forward. The test of roof cutting by dense drilling and retaining roadway is carried out in the return laneway of 11210 working face in Zhaojiazhai Mine. The effect of roadway retaining is good, which proves that the method is practical and effective, and has certain engineering reference value.