Study On Dynamic Influence Of Existing Highway Tunnel Caused By Blasting Construction Of Diversion Tunnel Passing Under It

The paper is based on the diversion tunnel of Ma'anshan tunnel underpass the existing Ma'anshan tunnel.The angle between the two tunnels is 45 degrees and minimum proximity distance is 9.0 meters,The explosion wave generated by the blasting construction of the new diversion tunnel will have a vibration effect on the surrounding rock and the existing tunnel lining.In this paper,GTS NX finite element software is used to analyze dynamic influence on existing tunnel caused by blasting construction of diversion tunnel and got the propagation rule of the shock wave in the surrounding rock and the existing tunnel,which would provides some reference for the construction of the similar engineering.The main contents and results of the study are as follows:(1)According to blasting monitoring data of existing Ma'anshan tunnel,The formula for the vibration attenuation of the existing tunnel lining particles was obtained by linear regression analysis which could predict the maximum allowable single-segment dose for the blasting construction of the new diversion tunnel.(2)Starting from the actual engineering and vibration control standards,the impact of blasting excavation on the lining of the existing tunnel is analyzed.The analysis is mainly done from the variation law of the typical node vibration velocity and the distribution pattern and time history of the principal stress of the existing tunnel lining structure,and the area with high sensitivity to blasting impact is obtained.(3)Based on different proximity distance,analyze the dynamic impact of the existing tunnel lining under the blasting of cross section,and obtain the law of the variation of the vibration velocity and stress of the existing tunnel lining with the proximity distance,but also got to the critical proximity which is 2.0 D when blasting full face method of construction.(4)Change the surrounding rock conditions and analyze the variation law of vibration velocity and stress of the existing tunnel lining.It is concluded that with the increase of the surrounding rock grade,the peak value of the vibration velocity and stress of the same position is higher,the longer it reaches peak value.In addition,under the five grade surrounding rock,the maximum vibration velocity of the existing tunnel lining exceeds the control standard of vibration velocity and under other grades of surrounding rock,the existing tunnels are all in a safe state.