隧道周边孔毫秒延时爆破围岩损伤数值分析研究

Numerical analysis of surrounding rock damage caused by millisecond delay blasting of tunnel peripheral holes

隧道爆破开挖引起的围岩损伤对隧道的安全施工和支护成本有重要影响,为研究隧道周边孔毫秒延时爆破对围岩损伤的影响,以重庆北大道隧道为研究背景,通过Hypermesh软件建立隧道34个周边孔三维数值计算模型,利用LS-DYNA软件计算得到不同爆破参数的围岩损伤,分析研究爆破损伤与孔间延时、药量和围岩岩性的关系规律。结果表明:孔间延时的取值对损伤范围有较大影响,孔间延时在一定范围内,损伤范围随着延时的增大而减小,当孔间延时继续增大时损伤范围趋于稳定值;损伤范围随着药量的增大而增大,当孔间延时增大时,不同药量的损伤范围差值逐渐减小。花岗岩的周边孔爆破损伤范围小于砂岩,不同延时下花岗岩周边孔爆破损伤范围变化较小,而砂岩的损伤范围变化较大。根据数值计算结果确定了现场周边孔爆破参数,隧道轮廓成型平整,较好地控制了爆破围岩损伤。

The surrounding rock damage caused by tunnel blasting excavation has an important impact on the safe construction and support cost of the tunnel.In order to study the effect of millisecond delay blasting on the surrounding rock damage of the tunnel,taking Chongqing North Avenue Tunnel as the research background,a three-dimensional numerical calculation model of 34 surrounding holes of the tunnel was established through Hypermesh,the surrounding rock damage of different blasting parameters was calculated by LS-DYNA,and the relationship between blasting damage and inter-hole delay time,charge and surrounding rock lithology was analyzed and studied.Results show that the value of inter-hole delay time has great influence on the damage range.Within a certain range,the damage range decreases with the delay time.When the inter-hole delay time continues to increase,the damage range tends to a stable value.The damage range increases with the charge.When the delay time between holes increases,the difference of the damage range of different charges gradually decreases.The damage range of the peripheral hole blasting of granite is smaller than that of sandstone.Under different delay time initiation of peripheral holes,the difference of damage range of granite peripheral holes is small,while that of sandstone is large.According to the numerical calculation results,the blasting parameters of the peripheral holes on the site were determined.The tunnel contour was formed smoothly,and the damage of the surrounding rock was controlled well.