Abstract
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.
Highlights
With the rapid development of China’s traffic construction, the construction problems of tunnels passing through the existing buildings at close range will appear in large numbers [1,2,3,4]
Wang et al [14] used the LS-DYNA program to study the propagation characteristics represented by the timespace change of surface acceleration. e results show that the maximum main stress decreases with the increase in the distance from the source
It can be seen that the maximum vibration velocity of blasting occurs in the two-stage cut blasting. e maximum vibration velocity generated is greatly reduced before the optimization of the cut blasting, and the vibration velocity generated by each blasting is significantly reduced, indicating that the damping hole technology reduces the blasting vibration during the blasting vibration propagation process
Summary
With the rapid development of China’s traffic construction, the construction problems of tunnels passing through the existing buildings (structures) at close range will appear in large numbers [1,2,3,4]. Erefore, studying the propagation law of tunnel blasting vibration in the formation, and optimizing the blasting scheme based on this, has important practical significance for controlling the blasting vibration effect and ensuring the safety of adjacent buildings (structures) [9,10,11]. Ere are few studies on controlled blasting technology of super-large section mountain tunnel excavated by the two-step method under close-distance crossing dense buildings. Erefore, based on the propagation law of the tunnel blasting vibration in the stratum, it is very necessary to study the blasting vibration reduction technology of super-large section tunnel excavated by the two-step method under existing buildings for the realization of efficient, rapid, and safe construction of tunnels. Once the vibration speed is too high or the main frequency of blasting vibration is close to the natural frequency of the building, it may lead to the destruction of the building and cause accidents [26,27,28]
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