Numerical Analysis for Dynamic Response of In Situ Blasting Expansion of Large Cross-Section Tunnel with Small Net Distance

Based on the Damaoshan Highway Tunnel Reconstruction and Expansion Project, the dynamic response of adjacent tunnels during the blasting excavation of existing tunnels is analyzed by using the LS_DYNA finite element software, and the blasting vibration response and lining stress change in the blasting process are studied. Taking the particle peak vibration speed as the criterion, the traffic safety of the adjacent operating tunnels is determined. Moreover, the stress changes of the adjacent tunnel lining caused by blasting excavation are studied through the maximum principal stress. The results show that the particle peak vibration speed on the front explosion side is significantly greater than that on the back explosion side, and the maximum particle peak vibration speed on the road surface is 13 cm/s, which is greater than the allowable safety standard. Besides, the maximum principal stress on the front explosion side is about 1.5 times of that on the back explosion side, showing a “quasi-bias” phenomenon. Therefore, it is recommended to control the operation of the tunnel during the blasting process and especially focus on monitoring the vibration responses and stress changes of the lining of the operating tunnel during the construction period.