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| Study on permeability law of intact and fractured coals under cyclic loading and unloading |
| ZHANG Lei1，KAN Zihao1，XUE Junhua2，LI Mingxue3，ZHANG Cun4 |
(1. School of Mines，China University of Mining and Technology，Xuzhou，Jiangsu 221116，China；2. School of Safety Science and Engineering，Xi'an University of Science and Technology，Xi'an，Shaanxi 710054，China；3. School of Materials Science and Physics，China University of Mining and Technology，Xuzhou，Jiangsu 221116，China；4. School of Resource and Safety Engineering，China University of Mining and Technology(Beijing)，Beijing 100083，China) |
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Abstract In order to obtain the seepage characteristics of the protected layers under repeated mining，this paper summarizes the stress path of the protected layers as three stages of loading，unloading and recovery，and carries out simulating repeated mining seepage tests by a self-made gas injection and displacement gas tester to analyze the seepage law of two types of intact and fractured coal samples. The results show that the more the mining times，the more obvious the permeability changes，and the unloading stage is the main stage of permeability change. The stress sensitivity of two kinds of coal samples decreases along with increasing the mining times in the loading stage，while increases with increasing the mining times in unloading and recovery stages. The stress sensitivity of the intact coal samples under the first and second mining is greater than that of the fractured coal samples，while the stress sensitivity of the fractured coal samples under the third mining is greater than that of the intact coal samples. The first and second mining is the compaction stage of two types of coal samples，and the third mining is the permeability increasing stage. The permeability increasing effect of the third mining is greater than that of the first and second mining，and the permeability increasing effect of repeated mining on the fractured coal samples is greater than that of the intact coal samples.
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2021, Vol. 40 
