According to the on-site vibration velocity monitoring and peak vibration velocity prediction, it is found that the maximum vibration velocity generated by the existing Dizong blasting scheme does not meet the requirements of the maximum allowable vibration velocity of houses. Therefore, the existing blasting scheme is optimized by reducing the maximum single-segment charge and a variety of damping measures such as multistage duplex wedge groove, adding damping hole, and millisecond blasting. In addition, the blasting data before and after optimization are analyzed and compared by wavelet (packet) technology. The results show that the optimized blasting main frequency domain is increased to 50∼150 Hz and the maximum vibration intensity value is reduced by 79.8%. Based on the time-energy analysis, the maximum energy value is reduced by 67.75% compared with the original scheme, and the dominant energy of the original scheme is reduced by 97.81%, 71.49%, 82.44%, 95.93%, and 93.03%, respectively, after optimization. The maximum vibration velocity generated by the optimized blasting scheme construction is 1.12 cm/s, which is less than the maximum allowable vibration velocity of the building of 1.2 cm/s, which meets the maximum allowable vibration velocity requirements of the building. The optimized blasting scheme realizes the safe and rapid construction of the two steps of the Dizong tunnel, which can provide a reference for similar engineering construction in the future.
The surrounding rock may become unstable or even fall down and the initial support may crack and be destroyed when the construction method of the underground excavation tunnel is not properly selected in the turn line of metro. . A section of the Santunbei turn line of Urumqi Metro Line 1# was taken as the engineering background. The proposed construction method was analyzed by numerical simulation. Numerical analysis shows that the final surface settlement caused by the proposed construction method is 3.0 mm and the horizontal convergence is 3.2 mm. It also turns out that the proposed construction method causes less deformation, and the method can be applied to the construction of the small interval tunnel in the Santunbei turn line of metro. The rationality of the method and numerical model was further verified by comparison between the monitored data of surface settlement, horizontal convergence and vault sinking, and numerical simulation results. Finally, the deformation and stress of the six construction methods were compared. The deformation and stress caused by the six construction methods are almost the same. It indicates that the construction spacing between the left and right tunnels does not affect the safety of tunnel construction. Therefore, the appropriate construction spacing could be selected according to the resource configuration, instead of deformation and stress.
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