Roof layer presplitting blasting is widely employed in underground coal mines to prevent rockbursts and strong seismic events caused by roof fracturing.The critical factor in the process is forming a penetrating presp...Roof layer presplitting blasting is widely employed in underground coal mines to prevent rockbursts and strong seismic events caused by roof fracturing.The critical factor in the process is forming a penetrating presplitting surface between blastholes.Conventional blasting(CB)faces the challenge of disordered crack propagation,which does not guarantee the formation of penetrating cracks.This study proposes an innovative satellite empty-hole controlled blasting(SECB)technique,which involves placing empty-holes symmetrically above and below the blasthole in a direction perpendicular to the line connecting the blastholes.Emptyholes are used to reflectblast waves to promote longer cracks in the controlled direction.Numerical models of SECB and CB were developed using LS-DYNA software to validate the feasibility of the SECB technique.Results show that SECB achieves better blasting performance compared to CB,with a 27.61%increase in maximum crack length in the controlled direction.SECB generates higher and more slowly decaying tensile stress beyond the blasting crushed zone,contributing to longer directional cracks and fewer remaining cracks.Analysis of blasting parameters reveals that 1.25-1.75 is the optimal decoupled coefficientinterval,and SECB has the best blasting performance.Optimal crack propagation occurs when the satellite's empty-hole radius is approximately half the blasthole radius,with less inter-hole rock fragmentation.Effective crack control is achieved with a spacing between the satellite empty-hole and blasthole of 4-8 times the blasthole radius.These findingsshow that the SECB technique offers new insights for enhancing roof layer presplitting blasting effectiveness.展开更多
基金funded by the projects:National Natural Science Foundation of China(Grant No.52274098)National Key Research and Development Program of China(Grant No.2022YFC3004603)Jiangsu Province International Collaboration Program-Key National Industrial Technology Research And Development Cooperation projects(Grant No.BZ2023050).
文摘Roof layer presplitting blasting is widely employed in underground coal mines to prevent rockbursts and strong seismic events caused by roof fracturing.The critical factor in the process is forming a penetrating presplitting surface between blastholes.Conventional blasting(CB)faces the challenge of disordered crack propagation,which does not guarantee the formation of penetrating cracks.This study proposes an innovative satellite empty-hole controlled blasting(SECB)technique,which involves placing empty-holes symmetrically above and below the blasthole in a direction perpendicular to the line connecting the blastholes.Emptyholes are used to reflectblast waves to promote longer cracks in the controlled direction.Numerical models of SECB and CB were developed using LS-DYNA software to validate the feasibility of the SECB technique.Results show that SECB achieves better blasting performance compared to CB,with a 27.61%increase in maximum crack length in the controlled direction.SECB generates higher and more slowly decaying tensile stress beyond the blasting crushed zone,contributing to longer directional cracks and fewer remaining cracks.Analysis of blasting parameters reveals that 1.25-1.75 is the optimal decoupled coefficientinterval,and SECB has the best blasting performance.Optimal crack propagation occurs when the satellite's empty-hole radius is approximately half the blasthole radius,with less inter-hole rock fragmentation.Effective crack control is achieved with a spacing between the satellite empty-hole and blasthole of 4-8 times the blasthole radius.These findingsshow that the SECB technique offers new insights for enhancing roof layer presplitting blasting effectiveness.
