Case Studies in Thermal Engineering (Dec 2021)
Study on vibration effect of pre-splitting crack in tunnel excavation under thermal explosion loading
Abstract
The rapid development of the city has brought the traffic serious problems, the subway construction greatly alleviates the heavy traffic. Due to the limitation of geology and mechanical equipment, mining method is often used in subway construction. However, the vibration caused by blasting rock is the most obvious disaster of this method. For solving this problem, this paper, taking a metro station as a case, verified the effectiveness of the pre-splitting crack on the damping above the tunnel face by simulation. Furthermore, the article examines the effect of material of the medium, pre-splitting crack width and the number of blasting holes on the damping vibration. The results show that the increase in diameter improves the energy and vibration absorption performances of damping hole better than the decrease in the distance. In addition, damping performance in gas and liquid medium is better than that in solid medium. The results show that the particle vibration velocity in Z direction increased near the tunnel vault (within 5 m), which does not conform to the vibration attenuation law of Sadovsky's formula. This suggests that the vibration velocity at the ground measuring point is not the maximum. The pre-splitting crack interfered with the propagation of seismic wave, and its barrier greatly weakened the vibration velocity of ground measuring points. Compared with the ground of the tunnel without pre-splitting crack, the vibration velocity is reduced by about 40%. In addition, damping performance in gas and liquid medium is better than that in solid medium. Increasing the width of pre-splitting crack would not enhance the damping performance. What's more, the number of blasting holes does not affect the damping performance of the pre-splitting crack.
