Air interval charge blasting is widely used in tunnelling,with the non-coupling coefficient as the key factor to ensure smooth blasting effect.Given that the QBT project site utilizes merely a 32 mm diameter cartridge,we conducted numerical investigation by using LS-DYNA program to enhance the blasting effect.The study focused on the axial uncoupling coefficient Kl and analyzed the stress field,velocity field and damage characteristics of the blast hole wall with Kl values of 2.41,3.22 and 4.83.We further compared the findings with those obtained from continuous charge structure with a small diameter cartridge (25 mm) in smooth blasting.This comparison revealed the influence of Kl on blasting effect and suggested the optimal value of Kl.The results show that peak effective stress is inversely proportional to Kl,while the degree of stress attenuation is directly proportional to Kl.Particle peak velocity decreased by a rate of 64%-82%,effectively reducing blasting vibration.Larger Kl enhances the ability to control the vibration.However,insufficient distribution of rock damage may result in "curtain-like rock residues" at the borehole entrance due to incomplete fragmentation.
维普
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