Understanding the variations in microscopic pore-fracture structures (MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxial creep test on deep coal at various pore pressures using a test system that combines in-situ mechanical loading with real-time nuclear magnetic resonance (NMR) detection was conducted. Full-scale quantitative characterization, online real-time detection, and visualization of MPFS during coal creep influenced by pore pressure and stress coupling were performed using NMR and NMR imaging (NMRI) techniques. The results revealed that seepage pores and microfractures (SPM) undergo the most significant changes during coal creep, with creep failure gradually expanding from dense primary pore fractures. Pore pressure presence promotes MPFS development primarily by inhibiting SPM compression and encouraging adsorption pores (AP) to evolve into SPM. Coal enters the accelerated creep stage earlier at lower stress levels, resulting in more pronounced creep deformation. The connection between the micro and macro values was established, demonstrating that increased porosity at different pore pressures leads to a negative exponential decay of the viscosity coefficient. The Newton dashpot in the ideal viscoplastic body and the Burgers model was improved using NMR experimental results, and a creep model that considers pore pressure and stress coupling using variable-order fractional operators was developed. The model’s reasonableness was confirmed using creep experimental data. The damage-state adjustment factors ω and β were identified through a parameter sensitivity analysis to characterize the effect of pore pressure and stress coupling on the creep damage characteristics (size and degree of difficulty) of coal.

了解孔隙压力和应力耦合下煤炭蠕变过程中微观孔隙-裂缝结构（MPFS）的变化对于煤炭开采和有效瓦斯处理至关重要。在这份手稿中，使用将原位机械加载与实时核磁共振（NMR）检测相结合的测试系统，对深部煤在不同孔隙压力下进行了三轴蠕变测试。利用核磁共振和核磁共振成像（NMRI）技术对受孔隙压力和应力耦合影响的煤蠕变过程中MPFS进行全尺寸定量表征、在线实时检测和可视化。结果表明，煤蠕变过程中渗流孔隙和微裂缝（SPM）变化最为显着，蠕变破坏从致密的原生孔隙裂缝逐渐扩展。孔隙压力的存在主要通过抑制 SPM 压缩并鼓励吸附孔 (AP) 演变成 SPM 来促进 MPFS 的发展。煤在较低的应力水平下较早进入加速蠕变阶段，从而导致更明显的蠕变变形。微观值和宏观值之间建立了联系，表明不同孔隙压力下孔隙率的增加会导致粘度系数呈负指数衰减。利用核磁共振实验结果对理想粘塑性体中的牛顿阻尼器和Burgers模型进行了改进，并开发了使用变阶分数算子考虑孔隙压力和应力耦合的蠕变模型。利用蠕变实验数据验证了模型的合理性。通过参数敏感性分析确定损伤状态调整因子ω和β，表征孔隙压力和应力耦合对煤蠕变损伤特征（大小和难度）的影响。