Abstract
Based on LS-DYNA numerical simulation analysis and comparison with laboratory tests, the blasting crack development dynamic evolution mechanism of elliptical bipolar linear shaped charge is analyzed. The development law of rock crack and optimal radial decoupling coefficient under different blast hole diameters were studied. The results revealed that the blasting with elliptical bipolar linear shaped charge had a remarkable effect on the directional crack formation, and the maximum effective stress of rock close to the position of shaped charge in the direction of concentrating energy is about 2.3 times of that in the direction of nonconcentrated energy. Moreover, the directional crack could be formed by blasting with elliptical bipolar linear shaped charge with different hole diameters, whilst the length of the main crack was related to the radial decoupling coefficient. Particularly, the main crack reached the longest when the radial decoupling coefficient was 3.36.
Highlights
China has become the country with the largest scale, the largest number, and the highest difficulty of tunnel construction in the world [1]
Li et al [17, 18] further conducted theoretical analysis, numerical simulation, and experimental research on the blasting of elliptical bipolar linear shaped charge (EBLSC), and the research showed that this charge structure has a good application effect and prospect in presplit blasting
Wu et al [19,20,21] carried out a preliminary study on the blasting mechanism, influencing factors, and crack development of elliptical bipolar linear shaped charge blasting
Summary
China has become the country with the largest scale, the largest number, and the highest difficulty of tunnel construction in the world [1]. Yang et al [5,6,7,8] adopted a testing system of digital laser dynamic caustics to study the influence of different cutting angle, depth, initial stress field, and other factors on the crack propagation of slotted cartridge blasting and analyzed the mechanism of crack extension and penetration. The rock failure mechanism, the temporal and spatial law of crack development, and decoupling coefficient of elliptical bipolar linear shaped charge blasting were studied. E shaped charge jet penetrates the rock and produces the initial guide crack, which provides a directional effect for the subsequent explosion stress wave and blasting gas to further expand the crack. Erefore, while the structure of the shaped charge leads to an increase in the evolution ability of cracks in the direction of concentrating energy, it reduces the ability of evolution of cracks in the direction of nonconcentrated energy
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