Abstract
In situ capture of crack network evolution is extremely difficult but necessary in fundamental research on mining mechanics and coalbed methane extraction. Systematic field monitoring of the mining-induced crack networks near three mining faces with vertical depths of 700 m, 850 m, and 1100 m in the **dingshan coal mine in China was conducted. By utilizing fractal geometry and an algorithm that predicts the connectivity rate, the changes in the fractal dimension and connectivity of the mining-induced crack network in these coal-rock masses with mining face advance were determined. The results indicate that the evolution of the crack network can be divided into three stages: a slow linear growth stage, an exponential growth stage, and a stable growth stage. As depth increases, the crack connectivity in a coal mass increases. The ranges of the mining influence zones at mining faces with vertical depths of 700 m, 850 m and 1100 m are approximately 50 m, 60 m and 75 m, respectively. The distances between the maximum mining pressures and the three corresponding coal mining faces are 15 m, 18 m and 25 m, respectively. At a depth of 1100 m, the crack connectivity of the coal-rock mass is 1.36 times that at a depth of 850 m and 1.58 times that at a depth of 700 m. A high crack connectivity can easily arise in thousand-meter-deep mines, which can lead to increased gas emissions and pose risks to production safety at the mining operation face.
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This work was financially supported by Sichuan International Technological innovation Cooperation Project (2018HH0159) and National Natural Science Foundation of China (U2013603; 52004167; 51827901; U1965203).
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Gao, M., **e, J., Guo, J. et al. Fractal evolution and connectivity characteristics of mining-induced crack networks in coal masses at different depths. Geomech. Geophys. Geo-energ. Geo-resour. 7, 9 (2021). https://doi.org/10.1007/s40948-020-00207-4
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DOI: https://doi.org/10.1007/s40948-020-00207-4