Practice of "high +low" roof breaking blasting for large mining height withdrawal channel
The risk of rock burst during the final mining period of the high mining height rock burst working face is extreme-ly high.In order to solve the problem of rock burst prevention and control in this type of working face,the design,compari-son,and optimization of blasting schemes are carried out from the perspective of stress blocking in the overlying rock burst layer and positive protection of the retreat channel,in response to the disposal of the roof during the final mining stage of the high mining height working face in Nalinhe No.2 Mine,It has been preliminarily confirmed that"high +low"has two obvi-ous technical advantages.Firstly,in terms of the fracturing and fragmentation of the overlying rock caused by blasting,the series initiation enhances the effect of blasting fracturing and the fragmentation of blocks in the blasting area.At the same time,the stress gradient in the area is significantly reduced,which better blocks the transmission of high stress;The second aspect is the scale of blasting coverage,which achieves stress blocking throughout the entire layer and avoids blind spots in pressure relief.On this basis,the distribution range and concentration degree of the peak pressure of the working face in the final mining stage are significantly reduced.At the same time,the mean value and standard deviation in the normal distribu-tion of the resistance of the hydraulic support in the final mining stage are reduced,and 10%～37%of the stress gauges ap-pear unloading states with varying degrees,which confirms that the"high +low"blasting has a positive protective effect on the final mining stage,the withdrawal channel and the isolated coal body.
rock burstfinal mining and anti-impactbroken roof blastingstress changemicro-seismic monitoring
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