Mechanical Behavior and Permeability Evolution of Coal under Different Mining-Induced Stress Conditions and Gas Pressures

Zetian Zhang, Ru Zhang, Zhiguo Cao, Mingzhong Gao, Yong Zhang and Jing Xie
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Zetian Zhang: State Key Laboratory of Water Resource Protection and Utilization in Coal Mining, China Energy Investment Co. LTD, Beijing 100011, China
Ru Zhang: MOE Key Laboratory of Deep Earth Science and Engineering, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China
Zhiguo Cao: State Key Laboratory of Water Resource Protection and Utilization in Coal Mining, China Energy Investment Co. LTD, Beijing 100011, China
Mingzhong Gao: MOE Key Laboratory of Deep Earth Science and Engineering, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China
Yong Zhang: State Key Laboratory of Water Resource Protection and Utilization in Coal Mining, China Energy Investment Co. LTD, Beijing 100011, China
Jing Xie: MOE Key Laboratory of Deep Earth Science and Engineering, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China

Energies, 2020, vol. 13, issue 11, 1-26

Abstract: The gas permeability and mechanical properties of coal, which are seriously influenced by mining-induced stress evolution and gas pressure conditions, are key issues in coal mining and enhanced coalbed methane recovery. To obtain a comprehensive understanding of the effects of mining-induced stress conditions and gas pressures on the mechanical behavior and permeability evolution of coal, a series of mining-induced stress unloading experiments at different gas pressures were conducted. The test results are compared with the results of conventional triaxial compression tests also conducted at different gas pressures, and the different mechanisms between these two methods were theoretically analyzed. The test results show that under the same mining-induced stress conditions, the strength of the coal mass decreases with increasing gas pressure, while the absolute deformation of the coal mass increases. Under real mining-induced stress conditions, the volumetric strain of the coal mass remains negative, which means that the volume of the coal mass continues to increase. The volumetric strain corresponding to the peak stress of the coal mass increases with gas pressure in the same mining layout simulation. However, in conventional triaxial compression tests, the coal mass volume continues to decrease and in a compressional state, and there is no obvious deformation stage that occurs during the mining-induced stress unloading tests. The theoretical and experimental analyses show that mining-induced stress unloading and gas pressure changes greatly impact the deformation, failure mechanism and permeability enhancement of coal.

Keywords: coalbed methane; mining-induced stress unloading; gas pressure; mechanical behavior; permeability evolution (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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