Instability mechanism and prevention of wide coal pillar with three strong stress disturbances under hard roof

In the Inner Mongolia and Shaanxi mining area，many mines adopt the double roadway driving technol⁃ ogy. The width between the two roadways is wide，which will cause the roadways along the goaf to be disturbed for many times. Under the influence of goaf roof and coal pillar size，the surrounding rock of roadway shows the phenomenon of stress concentration，even rock burst. Taking the 21103 working face of Hulusu coal mine as an engineering case，the three disturbances of roadway were analyzed by numerical simulation. The three stages include the stage when the upper working face is mined，the stage after the upper working face is mined and the stage when the working face is mined. The microseismic monitoring and stress monitoring were carried out on site to analyze the variation of stress in the coal pillars and the characteristics of surrounding rock activity. On the basis of the above research，the technical scheme of rock burst prevention and control for thick hard roof and wide coal pillar was put forward. The results show that 1 under mining disturbance， the internal stress of wide coal pillar increases gradually，forming a stress concentration. 2 The bending，sinking and lagging collapse of goaf roof bring a strong disturbance. 3 The contact roadway increases the stress concentration，which is easy to reach the critical condition and induce impact. 4 The “drilling⁃cutting⁃pressuring” roof pressure relief meas⁃ ures can reduce the concentrated static load and dynamic load，and the implement of large diameter drilling can reduce the stress concentration. Through the implementation of the anti⁃scour scheme，the stress growth of sur⁃ rounding rock of gob side entry is controlled， and the large energy events are greatly reduced， which pro⁃ vides guidance for the prevention and control of rock burst.