Stress evolution law of single and double roadway roof blasting in working face
Hard roof is an important factor affecting the burst risk of the working face,and blasting technology is often used in practice to pre-split and relieve pressure on the working face roof.We took the 7202 working face with a hard roof above the No.3 coal seam of Tianchen Coal Mine as the object,applied methods such as theoretical analysis,numerical simulation,and industrial tests to study the stress evolution of surrounding rock and the law of micro-seismic events under different blasting heights,single and double roadway roof blasting in the working face.The results show that when using single or double roadway blasting for low level sub-key stratum,the higher the blasting height,the lower the peak stress of the surrounding rock in the roadway,and the pressure relief effect is positively correlated to the blasting height.However,when using double roadway blasting and increasing the blasting height to more than 6 times the mining height(at the mid-section of the sub-key strata),the stress increases in the central area of the working face,and the shorter the working face,the more obvious the stress increase.During the initial mining stage of the 7202 working face,when single roadway roof blasting with a height of 3 times the mining height was carried out,the microseisms were mostly concentrated in the roadway area,and the pressure relief effect was moderate.After changing to double roadway roof blasting and increasing the blasting height to 6 times the mining height,the microseisms were mostly concentrated in the central area of the working face,without the occurrence of high-energy micro-seismic events.The number of stress monitoring warnings was also significantly reduced,and the pressure relief effect in the roadway area was favorable.
rock bursthard roofsingle and double roadway roof blastingblasting heightstress evolution
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