The correlation between dynamic phenomena of boreholes for outburst prediction and outburst risks during coal roadways driving

Coal and gas outburst accidents occurring in underground coal mines generally cause great casualties and economic losses, especially in construction areas of coal seams where the outburst risks are not accurately evaluated. Therefore, accurately identifying the outburst risks of coal seams is necessary and critical to prevent and control outbursts. In order to improve the prediction accuracy for outbursts in working faces of coal roadways, a self-designed drilling device that can simulate the in-situ outburst prediction of coal roadways was used in this study. We used the coal samples with different coal ranks to adsorb CO2 and N-2 with different pressures in the laboratory, so as to simulate the coal seams with different outburst risks. Finally, boreholes for predicting the outburst risk were drilled in the simulated coal seams to study the correlation between common dynamic phenomena (e.g. gas and coal being ejected from the borehole (GCEB) and drill pipe being stuck by coal mass in the borehole (DPSC)) and outburst risks. The results show that the greater the outburst risks of coal seams, the more frequent the occurrence of GCEB and DPSC is. The GCEB phenomenon for outburst prediction is attributed to small-sized coal and gas outbursts in boreholes, while the occurrence of DPSC phenomenon does not affirm that there definitely are outburst risks on working faces. The DPSC phenomenon indicating outburst risks is generally accompanied with GCEB, which form a linkage system and are triggered successively.