Title: Deformation characteristics and structural evolution mechanism of bituminous coal under thermo-hydro-mechanical-chemical coupling

Authors: Jianhang Shi; Zengchao Feng; Zhenhua Li; Guoying Wang; Dong Zhou

Addresses: School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, 454002, China; Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Jiaozuo, 454002, Henan, China ' Key-Laboratory of In-situ Property-improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China ' School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, 454002, China; Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Jiaozuo, 454002, Henan, China ' School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, 454002, China; Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Jiaozuo, 454002, Henan, China ' Key-Laboratory of In-situ Property-improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China; College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan, 030024, China

Abstract: Studying the thermal deformation characteristics of coal under thermo-hydro-mechanical-chemical coupling is crucial for analysing roof stability, surface subsidence, and heat injection channel formation during the in situ pyrolysis mining of coal. Therefore, in this study, the deformation characteristics, gas production characteristics, and pore structure evolution as well as strength of bituminous coal during carbonisation and steam pyrolysis were explored. The results show that: 1) coal sample deformation can be divided into two stages: softening and pyrolysis deformation. Softening deformation depends solely on temperature, and pyrolysis deformation is affected by the severity of coal pyrolysis; 2) the deformation of bituminous coal and the evolution of pore and crack structures influence each other. Deformation promotes changes in pore and crack structures, and these structural changes serve as the internal drivers of deformation; 3) below 400°C, steam injection accelerates the softening deformation of bituminous coal. Meanwhile, above 400°C, deformation intensifies considerably under steam pyrolysis conditions owing to increased gas production of the coal sample compared to that during carbonisation. [Received: August 12, 2024; Accepted: April 9, 2025]

Keywords: bituminous coal; carbonisation; steam pyrolysis; deformation; high temperature and high pressure.

DOI: 10.1504/IJOGCT.2026.153020

International Journal of Oil, Gas and Coal Technology, 2026 Vol.39 No.3, pp.344 - 367

Received: 31 Jul 2024
Accepted: 09 Apr 2025
Published online: 20 Apr 2026 *

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