Analysis of Stress Removal Effect of Borehole Depth and Position on Coal-Rock with Shock Tendency

With the increase of mining depth and scale, mine dynamic disasters related to coal-rock instability, such as rock burst, are becoming more and more serious, so it is very urgent to predict them accurately. At present, the method of borehole pressure relief is relatively effective for the prediction and control of rock burst. In this paper, the numerical simulation software PFC was used to study the influence of different drilling depth and location on mechanical properties, acoustic emission characteristics and damage evolution characteristics of coal-rock mass. The results show that the greater the drilling depth and the closer the drilling location is to the upper coal seam, the better the effect of destabilizing the impact-prone coal seam is. With the increase of drilling depth, the maximum value of acoustic emission events in coal-rock mass decreases first, and then stabilizes; with the increase of drilling location (height), the maximum value of acoustic emission events in coal-rock mass increases first, and then decreases; the stability of coal-rock can be monitored by the evolution law of acoustic emission. The failure modes of coal-rock samples with different drilling depths and locations are different, and large cracks mostly exist in the local part of coal-rock samples. The damage evolution of coal-rock mass can be divided into three stages: initial non-damage stage, slow increase stage and rapid increase stage. Different drilling depth and location have different effects on rock damage evolution characteristics.