Abstract：
In the study on blasting excavation of the Donghuashan Tunnel in Bazhong, Sichuan, the velocity field and stress field distribution characteristics of lining structure of existing tunnel have been analyzed by using the dynamic finite element software LS-DYNA, the decoupled charging method and the fluid-structure interaction calculation method, and the correctness of the calculation result has been verified by using the monitoring data. On this basis and in view of how the angle of cut hole will affect the dynamic response in blasting excavation of tunnel, 6 sets of cases have been established in the range of 15°~75°, to investigate the law of dynamic response of existing tunnel lining. As the results suggest, the vertical vibration velocity of existing tunnel lining is the greatest of all vibration velocities, and the vertical peak vibration velocity is used to represent the maximum structural vibration characteristic; the maximum vertical vibration velocity of existing tunnel occurs behind the blasting face, and the maximum vertical vibration velocity of the least favorable cross-section appears at the arch bottom; the maximum principal stress peak is mainly present at the arch bottom and the left and right arch feet, and the maximum tensile stress appears at the left arch foot; greater included angle between cut hole and tunnel face means greater vibration velocity and greater maximum principal stress peak generated by the blasting, and there is a clear linear relation between the two parameters. The monitoring points should preferably be set at the arch bottom and foot of the lining behind the blasting face, and the vibration response can be abated by decreasing the angle of cut hole. Based on the stratum conditions and spatial characteristics of the tunnel of interest, the vibration velocity safety threshold of existing tunnel lining is 18.17 cm/s.
YUAN Ran1 LI Junhui1 CHU Zeyuan2 ZHANG Rui3 LUO Chunyu4
.Study on Dynamic Response in Cut Blasting in Closely-spaced Overlapping Tunnels[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(3): 146-155
2023, Vol. 60 