基于最佳减震原则的新建隧道对既有隧道微差间隔研究

依托新建嘎拉山公路隧道钻爆法施工,利用有限元软件ANSYS/LS-DYNA建立新建隧道采用微差爆破的三维数值模型,模拟3段炸药不同间隔时间延时起爆引起既有隧道的动力响应,得到不同时间间隔微差爆破引起既有隧道二次衬砌质点最大振速点的振速时程曲线。计算结果表明:当新建隧道爆破的总药量分成等间隔时间的三段起爆,使不同段别炸药的作用在时间上和空间上错开,创造新的自由面,能够起到减震和良好的破岩效果。最大振速点发生在既有隧道迎爆侧拱墙上,随着微差间隔变大,既有隧道二次衬砌上振速峰值的发生时间延后。当总装药量相同时,微差爆破与瞬时起爆相比能够有效降低爆破振动对既有隧道的影响,且不同间隔时间下的减震效果有所差异。总药量分三段间隔起爆与瞬时起爆相比,振速峰值减小幅度达到63.1%。当起爆间隔大于20 ms后,每段炸药爆破对既有隧道的影响作用独立开来,振速峰值逐渐收敛于单个药包爆破引起的振速峰值。

Study on Difference Interval between New Tunnel and Existing Tunnel Based on Optimal Damping Principle

With reference to the new Gala mountain tunnel drilling and blasting construction,this paper establishes a three-dimensional numerical model of millisecond blasting with ANSYS/LS-DYNA for newly constructed tunnel. The dynamic responses of the existing tunnel caused by different time intervals of three-stage explosivesare simulated. The vibration velocity time-history curves of the maximum velocity points of the secondary lining particles of the existing tunnels are obtained by means of millisecond blasting in different time intervals. The results show that when the total explosives for the new tunnel blasting are divided into three sections of equal interval,the actions of the explosives in different sections are staggered in time and space to create new free surface so as to achieve with good results in damping and rock breaking. The maximum vibration velocity point appears on the sidewall of the existing tunnel,and with the increasing of the interval,the starting time of peak velocity on the secondary lining of the tunnel is delayed. When the total charges are the same,the millisecond blasting can effectively reduce the influence of blasting vibration on the existing tunnel compared with the instantaneous initiation,and the damping effects are different in different intervals. Compared with the instantaneous initiation,the peak amplitude of the three-stage interval is reduced by 63. 1%. When the initiation interval is more than 20 ms,the effect of each explosive blasting on the existing tunnel is independent,and the peak value of vibration velocity converges to the peak value of the vibration velocity caused by a single blasting.