邻空巷坚硬顶板预裂爆破防冲机理及效果检验

Rockburst prevention mechanism and effect test of blast presplitting of hard roof in gob-side roadway

顶板预裂爆破技术是防治冲击矿压的重要手段。以鄂尔多斯地区坚硬顶板邻空侧巷道频繁发生冲击矿压为背景,建立了邻空巷侧向覆岩结构的力学模型及UDEC数值模型,对比了顶板预裂爆破前后邻空侧向覆岩结构及应力演化特征,揭示了顶板预裂爆破防冲机理,开展了预裂爆破防冲实践,并通过现场钻孔探查、窥视、应力监测、微震等多种手段对爆破前后邻空侧向覆岩结构、煤体应力进行了实测,得出:①顶板预裂爆破能促使邻空侧向覆岩发生长臂“F”型→长臂“L”型→短臂“L”型结构转换,缩短了关键层悬臂长度,降低了邻空侧煤体的静载应力,促使煤体应力峰值向深部转移,同时削弱了侧向覆岩破断动载,降低冲击危险;②爆破前后实测低位岩层破断角由57°增大到72°,悬臂长度降低了8.7 m,中高位关键层悬臂长度至少降低了6.8 m,低位岩层预裂爆破诱发中高位关键层破断,证实了邻空侧向覆岩结构发生转换;③爆破前后模拟计算邻空侧煤体应力峰值降幅为5.36 MPa,实测煤体应力最大降幅为5.4 MPa,微震事件能量、频次均明显降低,实测与理论数值结果相一致;④形成了钻孔探查、窥视、应力与微震监测等多手段结合的爆破防冲效果检验方法。

Roof blast presplitting technology is an important means to preventing rockburst.Taking the frequent occurrence of rockburst in the gob-side roadway with hard roof in Ordos as background,the mechanical and UDEC numerical models of gob-side roadway overburden structure are established.The characteristics of overlying rock structure and stress evolution before and after roof presplitting blasting are compared.The rockburst prevention mechanism of blast presplitting in gob-side roadway is revealed.The practice of preventing rockburst with blasting is carried out.The lateral overburden structure and coal stress in gob-side roadway before and after blasting are measured by means of drilling exploration,peeping,stress monitoring,and microseismic.The following conclusions are drawn:①roof presplitting blasting can promote the structural transformation of long-arm“F”→long-arm“L”→short-arm“L”type of the lateral overburden,shorten the cantilever length of key layer,reduce the static load stress of coal seam,promote the peak stress of coal seam to transfer to the deep,and weaken the dynamic load of lateral overburden,reduce the risk of rockburst.②Before and after blasting,the measured fracture angle of lower rock stratum increases from 57°to 72°,and the cantilever length de-creases by 8.7 m,while the cantilever length of the middle-high level key layer decreases by at least 6.8 m.The pre-split-ting blasting of lower rock stratum induces the fracture of middle-high level key stratum,confirming the transformation of overlying rock structure in gob-side.③Before and after blasting,the numerical calculation shows that the peak stress re-duction of the coal in gob-side is 5.36 MPa,and the measured maximum stress reduction of coal seam is 5.4 MPa,the en-ergy and frequency of microseismic events are significantly reduced,the measured and theoretical results are consistent.④A method for testing the rockburst prevention effect of blasting by combining multiple means such as borehole explora-tion,peeping,stress and microseismic monitoring has been formed.