Analysis on mechanism and influencing factors of drilling pressure relief to prevent rock burst

In order to prevent rock burst of the coal body, based on the theory of rockburst stress control, the pressure relief mechanism of the boreholes was studied, the boundary equation of the borehole pressure relief area was derived, and the influence of coal properties, the diameter of borehole and stress environment on the distribution of borehole pressure relief zone was analyzed. The research results show that the weakened zone formed by drilling damages the bearing structure of the coal body, resulting in a significant decrease in the internal friction angle and cohesion at the interface between the roof rock and the coal body, greatly reduces the stress of the shallow coal mass in the roadway and destroys the stress conditions of rock burst. With the decrease of coal cohesion and internal friction angle and the decrease of the distance between drilling and working face, the pressure relief zone of the borehole increases and the boundary shape changes from an "oval" to an "X" shape. As the borehole diameter increases, the pressure relief zone increases but its boundary shape does not change. With this method, the design of drilling arrangement parameters for the prevention of coal rock burst is adopted. The pressure relief during drilling reduces the coal rock stress in the shallow part of the coal pillar, and the stress peak area is shifted to the deep part of the coal pillar, which destroyed the coal rock's rock burst conditions and prevented the occurrence of coal rock pressure, and a good pressure relief effect was achieved.