Due to the complexity of the internal structure of natural coal and its characteristic of multicomponent, the depth of its methane adsorption potential well is nonuniform, which makes it difficult to accurately evaluate the adsorption capacity of coal. Besides, in order to find out the factors affecting the depth distribution of potential wells in natural coal, this paper calculated the depth and number of potential wells during methane adsorption in coal according to the Langmuir adsorption kinetics process. Coal samples with different metamorphic degrees were tested and analyzed by infrared spectroscopy diffraction technology. The relationship between the structural parameters of functional groups in coal samples with different metamorphic degrees and the distribution of different depths of adsorption potential wells in coal samples was studied. Some main conclusions are as follows: The number of adsorption potential wells at different depths in natural coal with different metamorphic degrees has multipeak distribution characteristics. With the increase of the metamorphic degree of coal sample, the structures such as aliphatic branched chain structure and oxygen-containing functional groups in coal structure break, fall off, and deoxygenate. The relative content of aliphatic hydrocarbons is significantly reduced and condensed into aromatic hydrocarbons and aromatic ring structures. The different types and quantities of functional groups on the surface of coal samples lead to different forces between coal molecules and methane gas molecules, thus affecting the distribution of different depths of adsorption potential wells in coal samples.

To study the influence of gas adsorption‐desorption on the resistivity of coal, the resistivity changes in conditions of continuous adsorption/desorption and isovolumetric adsorption/desorption were tested by high‐precision resistance measurement, and the relationship between coal resistivity and gas content was investigated. The results show that gas adsorption/desorption has obvious effects on the resistivity of coal. Similar behavior was observed both in continuous adsorption/desorption and in isovolumetric adsorption/desorption experiments. The coal resistivity decreased gradually at the very beginning and then tended to stabilize as the gas adsorption capacity increased; in the process of gas desorption, the resistivity demonstrated a linear relationship with gas content. When comparing resistivities for the different adsorption modes, it was found that, for the same gas content in each mode, the resistivity change in the isovolumetric adsorption experiment was more obvious than in the continuous adsorption experiment. Also, the coal resistivity in the isovolumetric experiment differed further from the original figure when the desorption ended. The results are significant for predicting gas content in the coal mining process.

Cyclic high-pressure gas impact is a promising waterless stimulation method for enhancing permeability in deep low-permeability coal seams. However, the nonlinear fracture evolution, cumulative fatigue damage, and coupled fracturing mechanisms during repeated gas impacts remain insufficiently understood. In this study, cyclic high-pressure gas impact tests were conducted on unconfined synthetic rock-like specimens under gas pressures of 5 MPa and 7.5 MPa. The macroscopic crack networks induced by repeated impacts were quantitatively characterized using digital image processing and box-counting fractal analysis. Ultrasonic P-wave velocity measurements were used to reconstruct the spatial evolution of internal damage after each impact, and an empirical Weibull statistical damage model was established to describe the nonlinear fatigue degradation process. In addition, two-dimensional LS-DYNA numerical simulations were performed to reveal the transient stress wave propagation and stress-field evolution during cyclic impacts. The results show that fracture propagation under cyclic gas impacts exhibits a distinct nonlinear pattern, characterized by slow early-stage damage incubation followed by rapid late-stage crack coalescence. The fractal dimension of the surface crack network increased markedly after repeated impacts, reaching a maximum of 1.51 under the 7.5 MPa condition. Ultrasonic damage analysis further indicates that, based on path-averaged evaluations, apparent damage is more pronounced near boundaries at the lower pressure, whereas higher pressure induces severe structural degradation along the central measurement paths, with a maximum damage value of 0.47. The combined experimental and numerical results suggest that the initial impacts generate transient stress waves and cumulative microcracking, thereby progressively weakening the rock matrix. This progressive degradation subsequently enables quasi-static gas wedging to drive macroscopic crack propagation and coalescence. These findings provide a preliminary phenomenological baseline for understanding cyclic gas-induced cracking, providing a preliminary basis for understanding waterless reservoir stimulation by cyclic gas impacts.