Coal pillar burst mechanism and prevention based on local mine stiffness (LMS) criterion

The frequent occurrence of coal burst seriously threatens the safe and efficient recovery of coal resources. The research on the mechanism of coal burst is the basis of prediction and disaster prevention. Aiming at the coal burst event under the condition that the stress environment is stable and not affected by dynamic load, the concept of local mine stiffness (LMS) is introduced. Taking the mining area with complex mining layout of the mine as the engineering background, the mechanical response of coal pillar in the process of large-scale mining is analyzed by comprehensively using numerical analysis and field measurement, The evolution of LMS in this process is investigated. It is pointed out that the mining leads to the reduction of LMS, the rapid accumulation of energy in the coal seam and its roof and floor system, and the rapid release of energy when the coal pillar is unstable, resulting in impact damage. The engineering verification is carried out by comparing the evolution of LMS with the mining and the field measured ground sound and microseismic data. The research shows that:①the deformation, load and elastic energy accumulation of coal pillar increase with the overall mining operation, but the LMS decreases. The mining space size and the distance between the mining space and the research area are the main influencing factors. The response degree of the two to the mining of the working face is significantly greater than that of the roadway excavation. The significant influence range of the mining of the working face on the LMS reduction is 3.67 times that of the roadway excavation, and the LMS reduction under the unit advancing distance is 6.41 times that of the roadway excavation.②The good correspondence between the evolution of local mine stiffness with the advancement of the working face and the on-site ground sound and microseismic data indicates that the reduction of local mine stiffness caused by coal mining directly affects the failure mode of coal pillars. The energy in the coal seams and their roof and floor systems accumulates rapidly with the reduction of local mine stiffness and is released rapidly when the bearing capacity of coal pillars decreases, resulting in impact damage. ③After using large-diameter drilling to weaken the coal body, the microseismic energy and frequency are significantly reduced, indicating that large-diameter drilling destroys the coal body in this area, reduces its post peak stiffness, and effectively realizes the impact prevention effect.