composite thick and hard roof, high and low level enhanced blasting, mechanized charging, micro-seismic activity, end resistance of bracket, suspended roof, Mining engineering. Metallurgy, TN1-997

In order to control the dynamic pressure behavior of the working face under the condition of composite thick and hard roof, taking a mine in Ordos as an example, through theoretical analysis, it is clarified that the instability of small coal pillar roadway with thick and hard roof is mainly divided into deformation instability and impact instability. Combined with micro-seismic monitoring and surface rock movement observation, the potential impact of overlying rock movement on dynamic pressure manifestation is analyzed, and the necessity of pre-pressure relief of high roof is clarified. On this basis, a high-low reinforcement blasting scheme for the roof was designed, and mechanized charging equipment was put into practice. The results showed that after using mechanized charging, the number of people in a single group was reduced from 6 to 3, and the duration of single hole charging for ultra-deep holes was controlled within 50 minutes. The micro-seismic activity in the secondary “square” area of the 33109 working face showed a trend of low frequency and low energy. The distribution range of micro-seismic events in advance had decreased from 238 m to 168 m, and the affected area had decreased by 29.4%. The overall resistance at the end of the support showed a decreasing trend, especially within the range from the middle of the working face to the side of the return air channel, where the decrease was more significant. The collapse of the roof on one side of the return airway could closely follow the end support, and the length of the suspended roof on the transport roadway side was generally not more than 5 m.