Abstract
The factors affecting permeability change under repeated mining of coal seams are important study aspects that need to be explored. This study combined various stress variation characteristics of protective seam mining and simplified the stress path of repeated mining in protective seam mines. Based on the results from the bespoke gas flow and displacement testing apparatus, seepage tests for simulated repetitive mining were carried out. The results simulated the actual behavior very well. With any drastic increase in the mining influence, the axial deviation stress in the stress path increased, and the greater the difference in coal permeability during the unloading and stress recovery stage, the more substantial the increase in permeability. The change in coal permeability was significantly influenced by the severity of simulated repeated mining cycles. When the mining stress exceeded a critical value, the permeability of the coal sample increased with the increase in the number of loading and unloading cycles, but the reverse was true when the mining stress was lower than the critical value. The effective sensitivity of seepage to the applied stress decreased with an increase in the number of stress cycles. With a decrease in the deviation stress, that is, with lower severity of mining influence, the effective sensitivity of coal seepage to stress gradually decreased.
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The data used to support the findings of this study are available from the corresponding author upon request.
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Acknowledgments
This research is supported by the National Natural Science Foundation of China (51704274), the Young Elite Scientists Sponsorship Program by CAST (2017QNRC001), the Beijing Natural Science Foundation (8184082), the State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan Polytechnic University) (WS2017B02), and the Priority Academic Programme Development of Higher Education Institutions in Jiangsu Province.
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Huang, M., Zhang, L., Zhang, C. et al. Characteristics of Permeability Changes in Bituminous Coal Under Conditions of Stress Variation Due to Repeated Mining Activities. Nat Resour Res 29, 1687–1704 (2020). https://doi.org/10.1007/s11053-019-09542-0
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DOI: https://doi.org/10.1007/s11053-019-09542-0