Experimental study on damage characteristics of coal body in concentrated shaped charge blasting under in⁃situ stress

This study is aimed at revealing the damage characteristics and crack propagation law of coal during concentrated shaped charge blasting under the influence of in⁃situ stress. First, based on the mechanism of concentrated shaped charge blasting and the circumferential stress distribution law of blast hole under in⁃situ stress, the crack propagation law of coal during concentrated shaped charge blasting under in⁃situ stress was investigated by combining similar simulation experiments and numerical simula⁃ tions with the fractal dimension method. According to the experimental results, compared to the case without in⁃situ stress, the stress magnitude and dynamic loading time at the 1# monitoring point decrease in all the three groups of control experiments, indicating that in⁃situ stress has an inhibitory effect on concentrated shaped charge blasting. The influence of in⁃situ stress on concentrated shaped charge blasting reduces the length of generated cracks, but concentrated shaped charge blasting still manages to ensure the oriented crack growth. When the direction of concentrated shaped charge is parallel to that of the maximum principal stress, cracks in the direction of concentrated shaped charge will be extended; otherwise, the crack length will be shortened. The concentrated shaped charge blasting simulation on coal under different lateral pressure coefficients (k) using ANSYS/ LS⁃DYNA reveals that a larger k value leads to a more significant inhibitory effect on crack propagation in the direction of concentrated shaped charge, while a smaller k value promotes such crack propagation in turn. In addition, a function relationship between the damage amount w and the fractal dimension D was obtained through linear fit⁃ ting, and a prediction model for coal damage was established. © 2024 China University of Mining and Technology. All rights reserved.