Tunnel millisecond-delay controlled blasting based on the delay time calculation method and digital electronic detonators to reduce structure vibration effects

Abstract

The reasonable delay time of millisecond-delay blasting using digital electronic detonators can significantly reduce the vibration effects induced by tunnel blasting. This study proposes a method for calculating the delay time for cut holes, easer holes and periphery holes, considering the rocks breaking effect as well as wave superposition theory. And then according to the actual layout diagram of the tunnel holes, the delay time calculation formulas of different holes are put forward. Then the delay times were calculated according to the formulas and applied in the field tests. The velocities, rocks breaking and wave superposition cancellation of the vibration using different delay times are analyzed with digital electronic detonators. Then the optimum delay times of different holes were obtained and applied to New Hongyan tunnel project. The velocity and frequency of the vibration with digital electronic detonators are analyzed, compared with non-electronic detonators. The effects of charge and delay time on the velocity and principal frequency of a blasting seismic wave are discussed. The results indicate that the delay time for the holes must be prioritized to achieve breaking effects in the rock with the simultaneous formation of a new free surface, next considering the wave superposition cancellation. When the delay time of cut holes was 5 ms, the rocks breaking effect and wave superposition cancellation effect both worked well. The velocity of the vibration induced by the cut holes blasting was about only 0.46–0.51 cm/s. When the delay time was 6 ms or much longer, the rocks breaking effect would fail. With regard to the easer holes and periphery holes, the optimum delay time of them were all 5ms. The vertical peak particle velocity was reduced from 2.974 cm/s to 0.901 cm/s with digital electronic detonators. Therefore, the velocity had decreased by 69.70% than non-electronic detonators, which was caused by reducing the single simultaneous explosive charge and setting optimum delay time. The proposed delay time calculation method is demonstrated to be sufficiently accurate and can thus be used as a guideline to reduce tunnel blasting vibrations.

Experimental Study on Frequency Modulation Damping Effect of Digital Detonator in Road Clearance Blasting

“…Because the actual and the nominal delay of detonator have large discreteness [37][38][39], there is normally a delay error. Terefore, in the actual initiation process, a hole-by-hole initiation with a small delay time was adopted [40][41][42][43]. Te time settings of hole initiation sequence are shown in Figure 4.…”

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

“…e particle vibration velocity can be effectively suppressed by controlling the explosive quantity for a single detonation. Moreover, the explosive consumption per cubic meter of rock in tunnel excavation is relatively fixed, and the quantity of a single stage is inversely proportional to the number of sections at a certain unit of explosive consumption [3,11,25]. erefore, the blasting technology using phase-difference vibration mitigation can be achieved via effectively controlling the time difference of single-stage detonation [23,25].…”

“…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.…”

Adjustment of the Yielding System of Mechanical Rock Bolts for Room and Pillar Mining Method in Stratified Rock Mass

“…Exploitation of the deposit by means of rock blasting technique has a positive importance in the aspect of ore extraction and in the fight against the threat of tremors arising in the upper floor layers, however, there is the possibility of harmful effects on the stability of the bolted roof in adjacent excavations. First of all, damages to the roof excavation may consist of an increasing number and extent of fractures [25][26][27]. In addition, loose irregular rock blocks may form in the roof space, which may move into the interior of the excavation.…”