Safety Distance of Shotcrete Subjected to Blasting Vibration in Large‐Span High‐Speed Railway Tunnels

Abstract

e drill and blast method is widely used in constructing tunnels in rock. Unfortunately, blasting vibration can damage newly performed shotcrete layers which are major support structures to stabilize surrounding structures. erefore, investigation of the influence of blasting on shotcrete and determining reasonable distance between blasting work face and shotcrete position is of great importance. In this paper, a large-span tunnel excavated by drill and blast method acting as a high-speed railway station has been investigated. Blast vibration in the tunnel was recorded using microseismic monitoring technique. Empirical prediction equations for peak particle velocity (PPV) were obtained through regression analysis based on the obtained monitoring data. e attenuation law of tensile stress imposed on shotcrete layer due to blasting and bond strength of shotcrete-rock interface was also investigated. Minimum safety distance between shotcrete and blasting positions was calculated based on bond failure criterion. Evolution law considering different factors including blasting charge, rock mass class, and setting time of shotcrete was also obtained, which could be applied to determine blast charge shotcrete arrangements for tunnel constructions in future. e obtained results showed that the safety of shotcrete could be ensured and shotcrete falling off the rock could be prevented under current blast constructions.

Experimental Investigation on Time-Frequency Characteristics of Microseismic Signals in the Damage Evolution Process of Coal and Rock

“…In order to illustrate the shape of the signal after denoising, 1 s signal with obvious change in 89. 5 Through the above analysis, there was an obvious cutoff point of the noise-dominant mode and signal-dominant mode in the fracture process under uniaxial compression, and the order of the cutoff point was 3. Namely, IMF1 and IMF2 were the noise-dominant mode, which contained more noise composition.…”

“…As a form of energy dissipation in the process of coal and rock damage, MS accompany the whole process of deformation and fracture of coal and rock and can reflect the internal damage evolution process of coal and rock in real time. MS monitoring technology has been widely applied to source location [3,4], safety design [5], prediction and early warning of disasters [6,7], etc. in mine, tunnel cavern, diversion tunnel of hydropower station, underground storage cavern, slope excavation, etc.…”

Effect of Blasting During Tunnel Excavation on an Existing Adjacent Tunnel

“…In addition, some authors also studied the impact of blasting on existing tunnel structure such as following cases: The effect of an internal explosion in a tunnel on a neighboring buried tunnel and free surface [1]; the impact of the explosion which is placed on the ground to the tunnels; the impact of a bomb explosion at the surface on fortifications [7], [11]. The paper was used the measuring results at Croix-Rousse tunnel project, Lyon, France to study to establish empirical (regression function) between PPV and parameters according to many criteria simultaneous influences (multiple variables).…”

Combined Application of Pipe Roof Pre-SUPPORT and Curtain Grouting Pre-Reinforcement in Closely Spaced Large Span Triple Tunnels

“…This station will serve for the 2022 Beijing Winter Olympics. More information associated with the excavation design and the structural response of this station could be found in the studies by Zhang's research group [19][20][21][22]. This station consists of the concourse and the platform, and the platform was constructed earlier than the concourse.…”