Abstract
Coal mine pillar burst frequently occurs in Western China, which seriously restricts safe production. This paper takes the 35 m coal pillar of the 3102 working face of MKQ coal mine as the engineering background. The mechanism and evolution control of pillar bursts in multithick key strata are studied using field investigation, theoretical analysis, and numerical simulation. The mechanism of dynamic and static stress‐induced pillar bursts was revealed combining the “O‐X” broken features for key strata and numerical simulation of pillar stress evolution. A prevention scheme is put forward for strata presplit blasting and adjusting coal pillar width to minimize the dynamic and static stresses. The results demonstrate the following. (1) In the multithick strata, the first and second near‐field subkey strata have perpendicular “O‐X” broken features, whereas the third far‐field subkey has parallel “O‐X” broken features. The working face has three kinds of periodic weighting phenomena: long, medium, and short. (2) The simulated vertical stress curve of 35 m coal pillar goes through three states: two‐peak, asymmetric trapezoidal and symmetrical trapezoidal shape with the different advancing position of working face. The stress concentration is extensively promoting a high‐risk area for rock burst. (3) The coal pillar burst was induced by the superposition of energy released by the key strata breaking and the elastic energy accumulated in the wide coal pillar. (4) The monitoring data showed that the long, medium, and short periodic weighting steps of multithick key strata are 141.6 m, 43.2–49.6 m, and 17.6–27.2 m, respectively. The microseismic events energy, frequency, and stress of hydraulic support increment are the highest during the long periodic weighting, and the spatial distribution of microseismic events coincides with the stress concentration area. The theoretical analysis is confirmed with the field practice.
Highlights
Introduction e mining depth ofChina’s coal mines often exceeds 600–800 m, so rock burst has become one of the major disasters restricting coal mines’ safe and efficient production under high in situ stress and complex geological conditions [1]
On November 11, 2017, when the 702 working face of Hongyangsan Coal Mine advanced to 1740 m, a rock burst occurred in the air-return roadway, and the 32 m coal pillar slid into the middle of the working face by 1–3 m, resulting in 10 deaths and one injury [5]
According to the width mechanism of coal pillar burst induced by multithick key strata, coal pillar burst is related to stope stress evolution and key strata activity. is section analyzes the appearance law of rock burst in LW3102 based on the time-series development of MS energy, frequency, and hydraulic support resistance that reflected the direction of key strata activity and the MS events spatial development that demonstrated the stope stress [31]
Summary
E rock burst of these three mines is located in the gob-side roadway, and the distribution range is about 0–300 m ahead of the working face. In “4.8” rock burst, at 12 : 59 : 51 on April 8, 2018, a rock burst occurred in LW3102 with source energy of 3.0 × 107 J, and the source location of MS was 150 m ahead of the working face. E six rock burst space locations were in 35 m coal pillars near goaves, and all occurred during periodic weighting of LW3102. Erefore, according to rock burst’s occurrence space and time and the strata distribution above 3–1 coal seam, 35 m coal pillar burst was closely related to multithick key strata E six rock burst space locations were in 35 m coal pillars near goaves, and all occurred during periodic weighting of LW3102. erefore, according to rock burst’s occurrence space and time and the strata distribution above 3–1 coal seam, 35 m coal pillar burst was closely related to multithick key strata
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