Abstract
In order to study the blasting effect and the damage to the rock mass when the cutting seam cartridge is eccentrically and uncoupled. The ANSYS/LS-DYNA® nonlinear dynamic platform was used to simulate the blasting effect of five eccentric uncoupled coefficients on the cutting seam cartridge, and the crack growth process under the condition of complete eccentricity was simulated. By comparing and analyzing the stress of measuring points in the direction of cutting seam, vertical cutting seam direction, and circumferential cutting seam pipe under different working conditions. It is concluded that the effect of detonation products is affected by the wrapping property of the cutting seam pipe and the eccentric uncoupled coefficient. With the increase of the eccentric uncoupled coefficient, the load distribution presents obvious non-uniformity. The pressure on the uncoupled side of the blasthole is smaller than that on the coupled side, and the peak time of the uncoupled side also lags behind that on the coupled side. When the eccentric uncoupled coefficient is 1, the peak pressure on the coupled side is 5.78 times that of the uncoupled side, and the explosive stress field is biased toward the coupled side. The existence of the cutting seam pipe causes stress concentration at the opening, which enhances the guiding effect of the initial crack, and the stress in the non-cutting seam direction is buffered. Therefore, the eccentric arrangement of the cutting seam pipe determines the formation of the initial crack and the subsequent blasting effect. When the cutting seam cartridge is arranged eccentrically and uncoupled, it will cause under-excavation at the connection direction of blasthole, which will cause less disturbance to the rock mass on the uncoupled side. If the retaining side rock mass is on the coupled side in actual blasting, the eccentric uncoupled arrangement will cause greater over-excavation and damage. Therefore, it is necessary to avoid this situation as far as possible and provide better guidance for the actual construction.
Highlights
In tunnel blasting and urban underground engineering, smooth blasting and pre-split blasting are usually used as control blasting techniques
Based on the LS-DYNA® explicit dynamic analysis platform, the dynamic information of the detonation product can be obtained by using the numerical simulation method, and the crack propagation process can be visually displayed [30]. Scholars such as Yang, R.S. et al [31] and Shen, T. et al [32] have used numerical simulation to study the cutting seam cartridge, and the results show that the numerical simulation results are consistent with the measured data
When t = 15.18 μs, the two circumfluence products converge at the vertical cutting seam direction, which strengthens the energy of the rock mass and forms the initial pressure peak to the vertical cutting seam direction
Summary
In tunnel blasting and urban underground engineering, smooth blasting and pre-split blasting are usually used as control blasting techniques. The essence of the cutting seam cartridge is to make use of the hard pipe with the axial slotted to make the detonation product act on the specific position of the blasthole wall first and precisely form the initial guiding crack, to meet the requirements of the flatness of blasting profile in directional blasting [5,6]. Since its proposal, it has been widely used in slope excavation, blasting around shafts, tunnel excavation, and other projects [7,8]. The cutting seam cartridge adopts an uncoupled charge structure, which can change the loading rate of the stress wave on the blasthole wall, prolong the action time of the stress wave and gas, increase the energy utilization rate of the explosive and improve the fragmentation distribution of blasting, which is more suitable for fracture forming controlled blasting technology such as directional fracture controlled blasting [10,11]
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