Abstract
In order to optimize the arrangement of cutting holes in tunnel blast in Dahongshan Copper Mine, theoretical analysis and numerical simulation were combined to preliminarily determine the diameter of the hollow hole and the distance between the charge hole and the hollow hole during cut blast, which was verified through the field blast test. The research results show that with the increase of the hole diameter, the peak compressive stress of rock surrounding the empty hole gradually decreases, and the peak tensile stress gradually increases, which is consistent with the calculation results; when the hole diameter is 10 cm, the two first blast holes are arranged horizontally and 30 cm from the empty hole, two second blast holes are arranged vertically and 40 cm away from the empty hole, and the four third blast holes are arranged at a horizontal distance of 45 cm and a vertical distance of 45 cm from the empty hole; the contour area in numerical simulation is the maximum. The difference in contour area, contour width, and contour and contour height between the measured value and the simulation result is 5.3%, 3.3%, and 3.4%, respectively, indicating that the combination of theoretical calculation and numerical simulation is suitable for prediction of cavity section after blast in tunnel excavation.
Highlights
Cutting blast is a widely used technology for tunnel excavation, which creates a new free surface and more favorable blast conditions for other blast holes
Tian et al [9] based on the action mechanism of empty hole directional blasting, the influence of charge hole spacing on crack propagation is studied, deduced the calculation formula of charge hole spacing, and carried out numerical simulate of tunnel blasting excavation process
When the spacing increases from 35 cm to 40 cm, the peak stress of the wall of the second blast hole is reduced by 36.6%, but when the spacing increases from 40 cm to 45 cm, the peak pressure is only reduced by 2.8%, indicating when the spacing is increased to a certain extent, the decreased amplitude of the pressure of the hole wall will be reduced
Summary
Cutting blast is a widely used technology for tunnel excavation, which creates a new free surface and more favorable blast conditions for other blast holes. Tian et al [9] based on the action mechanism of empty hole directional blasting, the influence of charge hole spacing on crack propagation is studied, deduced the calculation formula of charge hole spacing, and carried out numerical simulate of tunnel blasting excavation process. Zheng [11] used ANSYS simulation software to realize the visualization of the cavity formation and pressure propagation of cut blast and concluded that the blast effect is related to the distance between the charging hole to the empty hole. By establishing the basic mechanical model of the straight hole cutting, Zhang Qi [15] quantitatively analyzed the influence of hole diameter on cutting effect of straight hole by numerical calculation; Li et al [16] used explicit dynamic analysis software to simulate the crack penetration between the cut hole and empty holes with different diameters. The test results show that the combination of theoretical calculations and numerical simulations can be used to predict the contour section after the blast of the cutting hole in tunnel excavation
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