State Key Lab for Geomechanics and Deep Underground Engineering, China University of Mining and Technology(Beijing) School of Mechanics and Civil Engineering, China University of Mining and Technology(Beijing)

为在坚硬软弱复合顶板切顶卸压沿空留巷时取得较好预裂爆破效果,通过现场试验和分析,采用合理的双向聚能张拉爆破技术,对巷道顶煤强度较小、直接顶较软弱、基本顶坚硬的复合顶板进行了有效的预裂爆破。结果表明:对于软弱岩层,爆破能量易沿孔壁原生裂隙发生冲楔作用,聚能效果较差,深12 m的炮孔内裂缝长度只有1.2 m,并且孔口易出现爆破漏斗,对巷道原有支护造成破坏;对于坚硬岩层,随着装药线密度增大,聚能方向裂缝率逐渐增大,当单个炮孔装药量为7卷、药卷长度和空气柱长度的比值为3.348、填塞位置位于坚硬岩层时,普氏系数为12的中砂岩段炮孔内沿预裂方向全部产生张拉裂缝,裂缝长度达5 m,裂缝率达100%。因此,对于坚硬软弱复合复合顶板,使坚硬岩层沿预裂方向产生有效的裂缝,软弱岩层自行垮落,能够取得满意的预裂效果。

In order to have a good pre-fracturing effect of the bilateral accumulative tensile blasting in the hard and weak complex roof obtained in the gateway reta ined along the goaf with the roof cutting and pressure released, with the site test and analysis, the rational bilateral accumulative tensile blasting technology was applied to the effective pre-fracturing blasting under the conditions of the complex roof with the low top coal strength above the gateway, soft and weak immediate roof and hard basic roof. The results showed that in the sot and weak rock stratum, the blasting energy would cause a wedging role along the in-situ cracks of the borehole wall and the energy accumulation effect was poor. In the blasting borehole with a depth of 12 m, the cracking length was 1.2 m only,a blasting funnel would be easily occurred att he orifice of the borehole and would cause a failure to the previous support. As for the hard rock, with the charge line density increased, the cracking rate along the accu mulative direction would be steadily increased. When an explosive charge of a single borehole was even cartridges, the ratio of the cartridge length and the air columnl ength was 3.348. When the filling location was at the hard rock, in medium sandstone section with a Protodyakonov coefficient of 12, all tensile cracking would be occured along the pre-fracturing direction within the borehole, the cracking length would be 5 m and cracking rate would be 100%. Therefore, as the complex roof, the hard roc k would cause effective cracks along the pre-cracking direction and the soft and weak rock would automatically collapse and would have the satisfactory pre-cracking ef fect.

教育部高校博士点基金资助项目(20130023120011)；中央高校基本科研业务资金资助项目(2012800015DQ)；