Test study on crack propagation laws of directional gathered energy blasting in deep high-gas and low-permeability coal seams

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Journal of Vibration and Shock ›› 2024, Vol. 43 ›› Issue (13) : 217-226.

ZHANG Xin1, LIU Zegong1,2, GAO Kui1,2, ZHANG Jianyu1, FU Shigui1, QIAO Guodong1, YANG Shuai1

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Abstract

For the deep high gas low permeability coal seam blasting penetration of blasting effective fracturing range is small, low utilization rate of blasting energy problems, in the analysis of in-situ stress on the blasting in the remote area of the impact of explosive stress waves and directional aggregation of energy blasting mechanism of rock breakage on the theoretical basis, carried out with or without the in-situ stress ordinary blasting and in-situ stress blasting penetration of different aggregation of different directions of the blasting experimental research. According to the propagation law of the explosive stress wave, establish the mechanical model of the propagation of the explosive stress wave around the drill hole under the ground stress field, and then compare and analyze the crack extension and stress development law of the four groups of test blocks after blasting, so as to obtain the extension law of the explosive cracks and the relationship between the increase of the peak stress. Firstly, according to the propagation and superposition of the blasting stress wave, the stress distribution law around the hole is theoretically analyzed under the coupling effect of the ground stress and the blasting load; then the blasting test platform built independently is used to carry out the research of ordinary blasting with or without the ground stress and the blasting test under the ground stress with different energy gathering direction; finally, the crack extension and stress development law of the four groups of test blocks after blasting are respectively analyzed in a comparative manner, and the relationship between the extension law of the blast crack and the peak stress value is obtained. Finally, four groups of test blocks were compared and analyzed for crack expansion and stress development after blasting, and the relationship between the expansion pattern of the blasted cracks and the increase of the stress peak was obtained. The results show that in terms of crack propagation, the presence of in-situ stress inhibits the propagation of ordinary burst rupture in coal rock mass, and the crack propagation range is small and oval distribution. When the direction of energy concentration is consistent with the direction of the principal stress with a large horizontal level, it is conducive to the propagation of directional cracks, and the overall crack propagation range is large. When the direction of energy concentration is consistent with the direction of vertical small principal stress, the crack propagation in the direction of energy concentration due to the concentration effect in the early stage of blasting is large, and in the later stage of crack propagation, the tangential compressive stress of the coal rock mass in the vertical direction affected by the in-situ stress is large, which restricts the propagation of directional cracks, and the overall crack propagation range is small. In terms of stress propagation, when loading ground stress and ordinary blasting without ground stress, the stress around the blasting hole showed a downward trend, with the highest reduction rate reaching 39.1%. Compared with ordinary blasting, the peak stress in the concentrated energy direction is increased by 72.2% under in-situ stress. The research results are applied to the concentrated energy blasting of deep high gas low permeability coal seam, which can effectively improve the blasting energy utilization rate and crack propagation range, which has positive significance for gas desorption.

Key words

in-situ stress / cumulative blasting / blasting stress wave / crack propagation scope / damage characteristics

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ZHANG Xin1, LIU Zegong1,2, GAO Kui1,2, ZHANG Jianyu1, FU Shigui1, QIAO Guodong1, YANG Shuai1. Test study on crack propagation laws of directional gathered energy blasting in deep high-gas and low-permeability coal seams[J]. Journal of Vibration and Shock, 2024, 43(13): 217-226

References

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