Study on the Decoupled Charge Effect in Deep‐Hole Cumulative Blasting of Coal Seam

Abstract

Five models of cumulative blasting are established by using ANSYS/LS-DYNA to study the effect of decoupling coefficient on cumulative blasting to improve coal seam permeability. The formation and migration process of the shaped energy jets with two kinds of decoupling coefficient are compared and analyzed; also, the propagation of explosive stress waves is represented. The result showed that the air in the blast hole is the key to the formation and migration of the condensing jet. The air in the hole also could reduce the attenuation of stress wave in a certain range. However, if the decoupling coefficient is too large, the air in the hole will consume excessive explosive energy, which is also not conducive to energy transfer. Therefore, there is an optimum decoupling coefficient which can minimize the coal crushing area, increase the coal fissure area, and improve the gas extraction rate. Besides, the cumulative blasting tests were carried out in a coal seam. The test results show that decoupling charge could effectively improve coal seam permeability, and the blasting effect was better when the decoupling coefficient is between 1.67 and 2.

Study on parameter optimization of deep hole cumulative blasting in low permeability coal seams

“…The material model of the explosive employed is MAT_HIGH_EXPLOSIVE_BURN, which corresponds to the JWL equation of state. The relationship between the pressure and the specific volume in the detonation process is given as 24 : where P is the detonation pressure (MPa), A, B , , R 1, and R 2 are explosive property constants, V is the mass volume of the gas products(m 3 ), and E 0 is the energy of the gas product when it explodes (MJ). The three-stage emulsion explosive is used in cumulative blasting in coal mines.…”

“…Guo et al 22 , 23 studied the influence of blasting hole spacing, the distance between blasting hole and extraction hole, and the distance from blasting hole to roof and floor of the coal seam on blasting effect by cumulative blasting experiment in the Jiulishan coal mine. Song et al 24 proposed that when the decoupling coefficient of cumulative blasting radial charge is from 1.67 to 2, the permeability of coal seam is significantly improved.…”

Research progress on permeability improvement mechanisms and technologies of coalbed deep-hole cumulative blasting

“…This brings about damage to the roof/floor stability and places the coal surface support in danger. Therefore, the spacing between the blasthole and the roof/ floor should be more than 1.5 m. To avoid energy waste due to insufficient spacing between blasting holes and poor extraction due to excess blasting hole spacing, the rational blasting hole spacing should be set to 15-20 m. Moreover, a comparative study on the influence of the decoupling coefficient of radial charge on the permeability effect of cumulative blasting was carried out by setting the decoupling coefficients to 1, 1.33, 1.67, 2, and 2.5 (Song et al 2019). According to the results, coalbed permeability can be effectively enhanced by cumulative blasting when the decoupling coefficient is from 1.67-2.…”

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

“…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]. In the abovementioned studies, a good application effect was achieved by the bidirectional linear-shaped charge blasting on smooth blasting.…”