Numerical Analysis About Blasting Effect of Digital Detonator and Millisecond Detonator in Upper and Lower Cross Tunnels

Abstract

In order to study on the vibration effect of the blasting in the upper and lower cross tunnels, depress the impact of blasting vibration on existing adjacent tunnel and acquire the sound way of tunnel blasting construction, the finite element software LS-DYNA was adopted to calculate what vibration effect of existing tunnel would be generated by the different detonation modes (simultaneous initiation and hole-by-hole initiation) and the different cut modes (parallel cut and oblique cut). In general, the results of numerical simulation compared with the results measured in real, they are generally consistent. Results show that the vibration velocity of hole-by-hole initiation of digital electronic detonator is 40% lower than ordinary simultaneous initiation of millisecond detonator, and the vibration acceleration is reduced by 24%. As regards vibration displacement, the distinction between the two detonation modes is small. The rule of velocity decay with increasing distance from the initiating position is similar in this two cases. Meanwhile, the vibration velocity of oblique cut is lower than parallel cut. But, for the vibration acceleration, the oblique cut is 15% higher than parallel cut. For oblique cut, the seismic waves show a pronounced periodicity and the energy is relatively concentrated. The fact is quite opposite when the parallel cut applied. In the case of explosion of hard rock strata, the effect of oblique cut is better than parallel cut. KEY WORDSTunnel engineering, Explosion vibration, Numerical simulation, LS-DYNA In recent years, with the rapid economic growth in China and the booming development of the national transport industry, the subway construction has become an essential development project in large and medium-sized cities. In that cities, such as Chongqing, Xiamen and Qingdao, the drilling and blasting method usually used to subway construction in hard rock strata. In addition, Article no. 16 THE CIVIL ENGINEERING JOURNAL 2-2019-` due to the outward expansion of the city and the characteristics of the original terrain, a lot of "mountain city" appeared. As a result, many mountain hard rock tunnels have emerged in the construction of municipal roads and subway traffic. So, the surrounding buildings, especially cultural building relics, will be impacted by blasting construction in central urban area. How to choose a reasonable tunnel blasting method to reduce the impact of blasting vibration on the surrounding buildings is a considerable issue.As the science and computer technology progressed, the method of numerical simulation of blasting vibration effect and evaluating structural safety is widely used. Singh P K (2002) delved into the destruction problems of underground tunnels in the effect of adjacent tunnel blasting [1] . There are research results indicate that blasting vibrations induced by a new tunnel excavation might cause spalling, fissures, or even collapse of existing tunnel linings [2] . Yao et al. (2004) conducted numerical simulations on the blasting construction process ...

Mechanism and Application of Blasting Technology Using Phase-Difference Vibration Mitigation on Adjacent Railway Tunnel

“…Previous studies have shown that the superposition and attenuation of stress waves for porous blasting are related to both the time difference of detonation and the physical property of the surrounding rock [12]. With the development and application of digital electronic detonator technology [24,25], it is possible to reduce the blasting vibration velocity by the time difference of detonation on the basis of the superposition principle of blasting stress waves. Subject to the complexity of the actual working conditions, the amount of experimental and theoretical research conducted in this area is very limited; especially in a new tunnel excavation adjacent railway tunnel, the construction standard is extremely strict and the specification cannot be unified.…”