Abstract
Coal pillar bursts continue to be a severe dynamic hazard. Understanding its mechanism is of paramount importance and crucial in preventing and controlling its occurrence. The extreme roadway deformations from the asymmetric isolated coal pillars in the central mining district of YaoQiao Coal Mine have responded with frequent intense tremors, with risky isolated coal pillar bursts. The theoretical analysis, numerical simulation, and field measurements were done to research the impact of spatial overburden structure and stress distribution characteristics on the isolated coal pillar area, aiming to reveal the mechanism of coal pillar burst leading to the practice of prevention and control in the asymmetric isolated coal pillar area. The study shows that the overburden structure of the asymmetric is an asymmetric “T” structure in the strike-profile, and the stress in the coal pillar is mostly asymmetric “saddle-shaped” distribution, with the peak stress in the east side of the coal pillar, and the coal pillar is a “high stress serrated isolated coal pillar.” Numerical simulation results showed that the support pressure in the isolated coal pillar area on the strike profile was asymmetrically “saddle-shaped” distribution. The peak vertical stress in the coal pillar area continued to rise and gradually shifted to the mining district's deep part. As a result, the response of the roadway sides to the dynamic load disturbance was more pronounced. They developed a coal burst prevention and control program of deep-hole blasting in the roof of asymmetrical isolated coal pillar roof and unloading pressure from coal seam borehole. Monitored data confirmed that the stress concentration was influential in the roadway’s surrounding rock in the asymmetric isolated coal pillar area, circumventing coal pillar burst accidents. The research outcomes reference the prevention and control of coal bursts at isolated working faces of coal pillars under similar conditions.
Highlights
IntroductionA dynamic geological hazard in underground coal mining, are characterized by coal and rock masses’ sudden and violent failure with a significant energy release
Coal bursts, a dynamic geological hazard in underground coal mining, are characterized by coal and rock masses’ sudden and violent failure with a significant energy release.ey posed a severe threat to the production and safety of underground coal mining or surface buildings and, in some cases, resulted in injury and loss of life [1, 2]
It was common in mine production to form isolated protection coal pillars after extensive hollowing on both sides of the mining district. erefore, it was essential to study the mechanism of coal bursts in isolated protection coal pillar areas to protect the pedestrian and ventilation and transportation tasks in the mining district roadway
Summary
A dynamic geological hazard in underground coal mining, are characterized by coal and rock masses’ sudden and violent failure with a significant energy release. With the gradual hollowing out of the working face on both sides of the mining district roadway, the protection coal pillar area gradually formed an isolated structure. With hollowing on both sides, the static stress load concentration of the roadway surrounding the rock system in the isolated coal pillar area is high. When it was affected by thick and hard rock layer breaking and working face mining disturbance, the isolated coal pillar area was affected by the superposition. On August 25, 2016, a coal burst event (Figure 1, red star area), magnitude up to 1.9 on the Richter scale, resulting in the return roadway over a 60 m range, of the return roadway, track roadway nearly 70 m range of the bottom of the drum, flake gang, roof cracking, the roadway damage as severe. erefore, the paper analyzed the spatial overburden structure and stress distribution characteristics of the asymmetric coal pillar area in the mining district, explored the mechanism of coal burst occurrence in the asymmetric isolated coal pillar area, and formulated a coal burst prevention plan for the coal pillar area, aiming to provide a valuable reference for coal burst prevention in the isolated protected coal pillar area under similar conditions
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