Experimental Investigation on the Deformation Characteristics and Mechanical Behaviors of Tectonic Coal under Complex Unloading Confining Pressure

Deyi Gao, Shuxun Sang (), Shiqi Liu (), Wenkai Wang and Hang Mo
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Deyi Gao: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, China University of Mining and Technology, Xuzhou 221008, China
Shuxun Sang: School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221008, China
Shiqi Liu: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, China University of Mining and Technology, Xuzhou 221008, China
Wenkai Wang: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, China University of Mining and Technology, Xuzhou 221008, China
Hang Mo: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, China University of Mining and Technology, Xuzhou 221008, China

Energies, 2023, vol. 16, issue 4, 1-18

Abstract: Conventional and cyclic unloading tests with different unloading rates were conducted to study the influences of unloading patterns and rates on the deformation characteristics and mechanical properties of tectonic coal. The results demonstrate that, under continuous unloading, a lower unloading rate promotes an increase in the circumferential strain but inhibits increases in axial strain. A lower unloading rate was found to be able to promote volume expansion under the cyclic unloading path, and the axial, circumferential, and volume strains increased stepwise with the unloading levels, but the increment of the strains decreased with the number of cycles in the same unloading level. It was easier for tectonic coal to reach the elastic limit by a low speed unloading rate when the unloading level was small, and volume dilatation was promoted when the unloading level was large. In both unloading patterns, the tangential modulus and the Poisson ratio were proportional to the unloading rate. Compared with continuous unloading, the cyclic unloading pattern was found to have a significant delaying and inhibiting effect on damage expansion, and thus higher mechanical strength and more structurally stable tectonic coal responses were observed.

Keywords: tectonic coal; unloading confining pressure; mechanical behavior; deformation characteristic (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: 2023
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