Key Takeaways & Executive Findings
- •• The energy-focusing blast achieves directional fracturing through a two-stage mechanism: suppression of explosion energy in non-focusing directions and redirection of energy to produce tensile stress in the focusing direction. • The filling medium critically influences energy regulation; water, with higher wave impedance and lower compressibility, yields the highest shaped-energy coefficient (6.12) and most uniform stress distribution, enhancing directional crack growth. • Sand as a filling medium increases crack irregularity (fractal dimension 1.112) due to its granularity and heterogeneity, while air and water produce more uniform stress fields and smoother cracks. • Water strikes an optimal balance between energy transition and distribution, maintaining the least flatness of directional cracks, making it the most effective filling medium for energy-focusing blasts.
Abstract
The energy-focusing blast is an innovative and ingenious method to achieve directional fracturing. Understanding its energy regulation mechanism is critical to enhancing its practical effectiveness. This study investigates the energy regulation mechanism and explores the medium-filling effects within the energy-focusing blast by employing theoretical analysis, numerical simulations, and model tests. The findings by theoretical and numerical analysis first reveal that two stages of the fracturing and tensile stage govern the directionally crack propagation, in which the explosion energy in the non-energy-focusing direction is suppressed, compressing the borehole wall, while redirected energy produces tensile stress in the energy-focusing direction, driving the formation of directional cracks. The choice of filling medium significantly affects directional cracking due to its impact on energy distribution and regulation, and key properties such as wave impedance and compressibility of the filling medium are critical. Experimental comparisons using air, sand, and water as filling media further disclose the distinct effects of the medium on energy regulation and directional crack growth of the energy-focusing blast. The maximum shaped-energy coefficients for air, sand, and water are 1.30, 4.41, and 6.12 in the energy-focusing direction, respectively. Meanwhile, the stress attenuation rate of air, sand, and water increases in that order. The higher wave impedance and lower compressibility of water support efficient and uniform energy propagation, which subtly enhances the tensile actions in the focusing direction and intensifies the overall stress impact of the energy-focusing blast. In addition, the stresses in the non-energy-focusing directions decrease as the angle from the energy-focusing direction increases, while the stresses are relatively uniform for both air and water but noticeably uneven for sand; meanwhile, the fractal dimensions of blasting cracks in the case of air, water, and sand are 1.076, 1.068, and 1.112, respectively. Sand as a filling medium leads to increased crack irregularities due to its granularity and heterogeneity. The water medium strikes an optimal balance by promoting the blasting energy transition and optimizing the energy distribution, maintaining the least flatness of the directional crack during energy-focusing blasts.
1. Introduction
Directional blasting serves as a versatile technique with many applications in various engineering domains, including roadway excavation in underground mining, controlled demolition of concrete structures, tunnel excavation, and landslide impact mitigation [1–3]. Researchers and engineers have developed and advanced the directional blast through various approaches, such as the use of blasthole slotting techniques [4,5], shaped charge cartridges [6,7], the implementation of slitting charges [8,9], and the application of energy-focusing tubes [10,11].
Meanwhile, comprehensive investigations have been conducted into the propagation behavior of directional cracks and the dynamics of stress waves, which reveal significant influences of stress distribution, wave interactions, and material heterogeneity on crack initiation, trajectory, and velocity. For instance, Li et al. [12] investigated ...
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GUO Pengfei, ZHANG Xingyu, YE Kengkeng, WANG Xu, HUANG Man, HU Jinzhu, HE Manchao (2025). Energy regulation mechanism and medium-filling effect of energy-focusing blast. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.03.010
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Frequently Asked Questions
What is the energy regulation mechanism in energy-focusing blasts?
The energy-focusing blast suppresses explosion energy in non-focusing directions, compressing the borehole wall, while redirecting energy to produce tensile stress in the focusing direction, driving directional crack formation.
How does the filling medium affect energy-focusing blasts?
The filling medium significantly influences energy distribution and regulation. Key properties like wave impedance and compressibility determine the efficiency of energy transfer. Water, with high wave impedance and low compressibility, yields the highest shaped-energy coefficient and most uniform stress distribution.
Which filling medium is most effective for energy-focusing blasts?
Water is the most effective, as it promotes efficient energy transition, optimizes energy distribution, and maintains the least flatness of directional cracks, achieving the highest shaped-energy coefficient of 6.12.
What are the shaped-energy coefficients for air, sand, and water?
The maximum shaped-energy coefficients are 1.30 for air, 4.41 for sand, and 6.12 for water in the energy-focusing direction.
How does sand affect crack irregularity in energy-focusing blasts?
Sand leads to increased crack irregularities due to its granularity and heterogeneity, resulting in a higher fractal dimension of 1.112 compared to air (1.076) and water (1.068).
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