Influence of Charge Hole Spacing on the Crack Propagation Behavior under the Effect of Empty‐Hole Directional Blasting

Abstract

In order to explore the reasonable spacing of charge holes in empty-hole directional blasting, based on the action mechanism of empty-hole directional blasting, the influence of charge hole spacing on crack propagation is studied, the calculation formula of charge hole spacing is deduced, and the blasting excavation process in Shijiazhuang South Ring Expressway Tunnel is simulated by finite element software. The results show that by setting empty holes on both sides of the charge holes in the peripheral blasting, the guiding cracks can be formed in the connecting direction between the empty hole and the charge hole, the propagation of cracks in other directions can be suppressed, and the spacing of charge holes can be enlarged. Reasonable charge hole spacing is very important to realize the effect of empty-hole directional blasting; the spacing is small, the rock will be overbroken, and the utilization ratio of explosives is reduced; large spacing, the guiding effect of empty holes is weak, and the effective directional cracks cannot be formed. The spacing between charge holes is closely related to the mechanical properties of rock, detonation parameters of explosive, and aperture of the charge hole and empty hole. According to the simulation results of crack propagation in different spacing, the blasting performance is the best when the charge hole spacing is 800–1000 mm, which is completely consistent with the theoretical calculation result of charge hole spacing 948 mm.

Study on blast‐induced cracks penetration characteristics of double water jet slotted boreholes

“…Based on explosion mechanics and the rock fracture mechanics theory, Zhang et al 13 discussed the main factors of directional fracture controlled crack penetration between blasted boreholes and analyzed and determined the corresponding parameters. Dai and Yang 14 and Tian et al 15 studied the reasonable hole spacing of smooth blasting according to the attenuation law of blasting load between two boreholes, the results show that improving the quality of hole plugging is more meaningful than improving the accuracy of the detonator initiation time to improve the spacing between boreholes under the same smooth blasting conditions. Based on the basic theory of manifold elements and the fracture mechanics theory, Huang et al 16 simulated the process of the generation and propagation of blast‐induced crack, the formation of blast‐induced block and blasting hopper for two initiation modes of double‐hole millisecond delay initiation and simultaneous initiation.…”

Research on the damage characteristics of rock masses based on double guide-hole blasting under high In-situ stress

“…Pu et al 22 explored the effects of hole spacing and delay time on the degree of crack extension in the case of double-hole blasting from a more systematic perspective. Li et al 23 found that the hollow hole between blasthole has a guiding Tian et al 24 derived the equation for the charge hole distance and found that the charge hole distance determines whether the directional crack effect along the guide hole can be achieved. Most of the above scholars in the direction of guide hole blasting are analyzed at the macroscopic perspective, practical application and other levels, and the local development of crack and fine contact of rock body are less analyzed, while the development state of crack and fine contact after explosive explosion are the key factors affecting the effect of rock breaking, so it is more valuable to study them.…”

Damage Analysis of Concrete Structure under Multidirectional Shaped Charge Blasting Using Model Experiment and Ultrasonic Testing

“…After the initiation, blasting-induced fractures mainly propagated in a shaped charge jet direction between the adjacent boreholes [6]. Tian et al used the action mechanism of empty-hole directional blasting to study the influence of charge hole spacing on crack propagation [7]. Song et al established five finite element models of cumulative blasting to study the effect of decoupling coefficient on cumulative blasting to improve coal seam permeability [8].…”