预裂爆破成缝宽度与线装药密度关系试验研究

随着我国露天矿山高台阶陡帮开采工艺的应用，预裂爆破控制技术成为保护边坡、控制爆破振动次生灾害的重要手段。为了对矿山临帮区域的预裂爆破关键工艺参数（线装药密度）及不同线装药密度下的 预裂成缝宽度进行精确计算，以乌山铜钼矿为例，结合岩体破坏判据及炸药爆炸压力作用规律，对预裂爆破线装药密度计算公式进行了理论推导，得出预裂孔开裂及预裂缝贯通时的线装药密度理论公式。结合矿山典 型岩性——黑云母花岗岩物理力学测试参数，计算得出矿山典型岩石开裂及预裂缝贯通时的线装药密度分别为0.196 kg/m、0.528 kg/m。通过数值模拟及回归分析，讨论了线装药密度与预裂爆破成缝宽度之间的关系 ，选取线装药密度0.50、0.54、0.57、0.60 kg/m 4种方案，对预裂孔自起爆至形成贯通裂缝全过程的网格单元失效情况进行了统计，结果表明：线装药密度为0.5~0.6 kg/m时，预裂缝宽度与线装药密度可用如下函数 关系描述：y=-172x2+213x-60 （R2=0.98），且预裂缝宽度随着线装药密度增加而增大。在试验矿山开展了现场预裂爆破试验，并对预裂缝后方30 m处的爆破振动情况进行了监测。结果表明：贯通的预裂缝后方30 m 处综合减振率达31.3%以上；未贯通的预裂缝存在沾帮联结现象，且减振效果明显降低，相对于预裂缝贯通时，减振率降低了4.3%~5.6%；当预裂缝贯通后，线装药密度进一步增加0.06 kg/m，降振率仅提高了1.3%，进 一步分析认为：当预裂缝完全贯通后，继续增大线装药密度对降振效果的提升意义不明显。

Experimental Study on the Relationship Between the Width of Pre-split Blasting Joints and the Density of Line Charges

With the application of high-step steep slope mining technology in open-pit mines in China，pre-splitting blasting control technology has become an important means to protect slopes and control secondary disasters caused by blasting vibration. In order to accurately calculate the key process parameters of pre-splitting blasting (line charge density) and the width of pre-splitting joints under different line charge densities in the mine's adjacent area， the Wushan Copper-molybdenum Mine was taken as an example， combined with rock mass failure judgment and the explosive pressure law of explosives， the formula for calculating the charge density of the pre-split blasting line was theoretically deduced，and the theoretical formula for the charge density of the pre-split blasting line when the pre-split hole was cracked and the pre-crack penetrates was obtained， combined with the typical mine lithology-biotite granite，the physical and mechanical test parameters were calculated.It is showed that the linear charge density of typical rock cracking and pre-fracture penetration in the mine were 0.196 kg/m and 0.528 kg/m， respectively.Through numerical simulation and regression analysis， the relationship between the line charge density and the width of the pre-splitting blasting seam was analyzed， and four schemes of line charge density 0.50， 0.54， 0.57， and 0.6 kg/m were selected. Statistics on the failure of grid elements in the whole process of forming through cracks showed that when the linear charge density was 0.5~0.6 kg/m， the pre-fracture width and the linear charge density could be described by the following functional relationship: y=- 172x2+213x-60 （R2=0.98）， and the width of the pre-crack increased with the increase of the line charge density. An on-site pre-splitting blasting test was carried out in the test mine， and the blasting vibration at 30 m behind the pre-crack was monitored. The results showed that the comprehensive vibration reduction rate at 30 m behind the penetrating pre-crack reached more than 31.3%； The pre-crack has the phenomenon of bonding and bonding， and the damping effect was significantly reduced. Compared with the pre-crack penetration， the vibration damping rate wasreduced by 4.3% to 5.6%； When the pre-crack is penetrated， the line charge density further increased to 0.06 kg/m，the vibration reduction rate was only increased by 1.3%.The further analysis showed that after the pre-crack was completely penetrated， continuing to increase the line charge density has no obvious significance for the improvement of the vibration reduction effect.