Moisture in coal seams significantly impacts methane adsorption/desorption, yet its microscopic mechanism in intact coal remains poorly characterized due to methodological limitations. This study introduces a novel approach that integrates low-field nuclear magnetic resonance (LF-NMR) with volumetric analysis to quantify, in real-time, the effect of moisture on methane dynamics in intact coal samples. The results quantitatively demonstrate that micropores (relative specific surface area > 700 m²/cm³) are the primary adsorption sites, accounting for over 95% of the stored gas. Moisture drastically reduces the adsorption capacity (by ~72% at 0.29 MPa and ~57% at 1.83 MPa) and inhibits the desorption process, evidenced by a strong linear decrease in desorption ratio (DR) (R² = 0.906) and a sharp exponential drop in the initial desorption rate (R² = 0.999) with increasing moisture content. The findings provide a mechanistic understanding that is crucial for optimizing coalbed methane (CBM) recovery and enhancing strategies for outburst prevention and methane emission mitigation. The results reveal distinct adsorption and desorption features of intact coal compared with coal powder, which can be useful in total methane utilization and mining safety enhancement.

Computed tomography (CT) scans were performed on samples of an outburst-prone coal seam at different loading stages. The area and roundness of the CT images were used to quantify the degree of the coal macroscopic deformation under different loads. A spatial matching algorithm was used to calculate the three-dimensional (3D) displacement fields of different regions of interest (ROIs, containing primary fractures, minerals, and only coal) under different loads. The presence of fractures and minerals were found to promote and inhibit displacement, respectively, and the 3D displacement field data followed a normal distribution. A meshfree numerical simulation was used to determine the 3D maximum principal stress, shear stress and displacement fields under different loads. The following results were obtained: fractures and minerals significantly affect the stress state and displacement field distribution features, the maximum principal stresses and shear stresses in different matrices differ significantly, and the presence of minerals and fractures induce a prevalent shear stress in coal and make coal prone to stress concentration.