管棚超前支护隧道掘进周边控制爆破方法

Controlled perimeter blasting method for tunnel driving with advance canopy support

为了改善松软岩隧道,采用管棚超前支护条件下的周边爆破效果,分析了隧道开挖周边爆破效果差的原因,以及改善周边控制爆破效果的方法。研究表明:周边眼及二圈眼应以较大角度向外倾斜钻进,通过按光面爆破要求进行二圈眼爆破参数设计,实行间隔炮眼不等装药,间隔分段起爆等,可为周边眼爆破创造良好条件;进一步得到了相应的二圈眼和周边眼爆破参数确定方法,有助于达到充分利用炸药能量,降低周边控制爆破对隧道围岩的损伤,实现良好的周边控制爆破效果;算例表明:二圈眼间距和最小抵抗线均小于周边眼的相应值,计算结果与工程实践相符。对提高松软岩石的爆破施工效率有参考价值。

In order to produce the better result of contour blasting for driving tunnel through soft rocks with advance canopy support,this paper investigates the reasons causing bad result on contour blasting and the method for a better contour blasting.The analysis shows that the blast holes on and next to the perimeter should be drilled outwards with a larger angle,and the blasting parameters for the perimeter holes and the holes next to the perimeter should be designed according to the requirements for smooth blasting.Furthermore,the formulae for calculating the controlled perimeter blasting are presented so that the full utilization of explosive energy can be achieved and the blasting damage in remaining rock of tunnel can be minimized.A case study demonstrates that the parameters for blast holes next to the perimeter are smaller than those for perimeter blast holes.Such results are consistent with engineering practice.It is of significance for obtaining a better result in tunnel-driving through soft rock.