Analysis Of Vibration Effect Of Drainage Tunnel Blasting On Adjacent Existing Tunnel Lining And Research On Controlled Blasting Technology

The construction of the drainage tunnel generally lags behind the tunnel,even when the tunnel has been operated,the drainage tunnel is still under construction.In engineering design,the distance between the drainage tunnel and the main tunnel is usually small,and the vibration which results from blasting excavation makes a threat to tunnel operation safety.In consequence,it makes huge difference to pore the effect of blasting vibration and control it to guarantee the safety of tunnel.This paper is based on the Beishan Ⅱ tunnel drainage project of Yueji section of Menghua Railway.When the Beishan Ⅱ tunnel drainage is constructed,the Beishan Ⅱtunnel has been put into operation.Under the original blasting scheme,the peak vibration velocity of the particle in the tunnel lining is larger,and after inspection,cracks are found on the surface of the lining of Beishan Ⅱ tunnel.The influence of blasting vibration of drainage tunnel and transverse channel on tunnel lining is analyzed by combining the method of field monitoring and numerical simulation,and the controlled blasting technology of drainage tunnel is studied.The following work is mainly done in this paper:(1)Under the original blasting scheme,the on-site monitoring data were analyzed and the vibration velocity change rule of the measuring point was summarized.The monitoring data show that most vibration velocities seriously exceed the limit.Taking Sadovsky’s empirical formula as the basic form,the blasting vibration attenuation formulas suitable for the drainage tunnel and the transverse channel are drawn up respectively.(2)Based on the original blasting scheme,by using ANSYS/LS-DYNA dynamic finite element software to simulate and analyze the dynamic response law of the tunnel when the drainage tunnel and the transverse channel are blasted,and the reasons for cracks were explored.(3)Simulate the dynamic response of tunnel lining with different net distances when the transverse passage approaches the tunnel lining gradually.And explore the dynamic response of tunnel lining under different grade of surrounding rock.The simulation results show that the impact of blasting vibration is highly sensitive to the net distance.With the increase of the net distance,the peak vibration velocity and stress of the measuring point decrease,and the attenuation range slows down.FromⅢ,IV to V grade surrounding rock,the peak vibration velocity and stress of each measuring point show a slight increase trend,indicating that the blasting vibration is less affected by the change of surrounding rock grade.(4)Optimize blasting parameters,blasting scheme optimization,simulation of drainage tunnel blasting and horizontal channel gradually close to the process of tunnel lining,in combination with the construction site monitoring and feedback,adjust the blasting parameters,ensure the blasting tunnel lining caused by particle vibration velocity is less than the safe speed limit,validate the rationality of the optimized blasting scheme,ensure the safety of the tunnel structure.