Understanding the creep deformation behavior and the evolution of pore-fracture structures(FPSs)in coal under cyclic loading-unloading is crucial for safe extraction and efficient methane utilization.Coal samples were...Understanding the creep deformation behavior and the evolution of pore-fracture structures(FPSs)in coal under cyclic loading-unloading is crucial for safe extraction and efficient methane utilization.Coal samples were subjected to cyclic loading-unloading creep experiments using online Nuclear Magnetic Resonance(NMR)and Nuclear Magnetic Resonance Imaging(NMRI)techniques.The results revealed the significance of instantaneous plastic and viscoplastic strains during creep,with creep failure modes analyzed using NMRI data and macroscopic fracture distribution.Viscoplastic strain was identified as a key indicator of accelerated failure,and NMRI revealed a transition from splitting-shear to V-shaped shear failure under increasing confining pressure.From a microscopic perspective,real-time T2 spectra monitoring tracked the evolution of FPS at different loading levels,and the geometric mean of the pore structure(T2g)quantitatively described the co-evolution of various pore types.A generalized model was developed to describe coal creep under cyclic loading-unloading,integrating microscopic and macroscopic deformation features and refined using fractal theory.These findings provide theoretical insights and practical guidance for coal extraction and methane management under cyclic loading-unloading creep.展开更多
基金supported by Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(No.2024ZD1003902)S&T Innovation and Development Project of Information Institution of Ministry of Emergency Management(No.2025506)+2 种基金Special Project for Intergovernmental Cooperation in Scientific and Technological Innovation of National Key Research and Development Program(No.2025YFE0109800)National Natural Science Foundation of China(Nos.52121003 and 51827901)European Commission Horizon Europe Marie Skłodowska-Curie Actions Staff Exchanges Project-LOC3G(No.101129729)。
摘要Understanding the creep deformation behavior and the evolution of pore-fracture structures(FPSs)in coal under cyclic loading-unloading is crucial for safe extraction and efficient methane utilization.Coal samples were subjected to cyclic loading-unloading creep experiments using online Nuclear Magnetic Resonance(NMR)and Nuclear Magnetic Resonance Imaging(NMRI)techniques.The results revealed the significance of instantaneous plastic and viscoplastic strains during creep,with creep failure modes analyzed using NMRI data and macroscopic fracture distribution.Viscoplastic strain was identified as a key indicator of accelerated failure,and NMRI revealed a transition from splitting-shear to V-shaped shear failure under increasing confining pressure.From a microscopic perspective,real-time T2 spectra monitoring tracked the evolution of FPS at different loading levels,and the geometric mean of the pore structure(T2g)quantitatively described the co-evolution of various pore types.A generalized model was developed to describe coal creep under cyclic loading-unloading,integrating microscopic and macroscopic deformation features and refined using fractal theory.These findings provide theoretical insights and practical guidance for coal extraction and methane management under cyclic loading-unloading creep.