To investigate the mechanical damage characteristics and energy evolution laws of primary coal–rock combinations with different coal–rock ratios, uniaxial compression tests were conducted. Combined with acoustic emission monitoring results, a comparative analysis was performed on the yield strength, elastic modulus, acoustic emission signal characteristics, failure characteristics, and energy accumulation–dissipation characteristics of five different coal–rock ratio specimens. The study reveals the following: (1) Defect structures and dimensions of coal bodies influence the strength of specimens, with the peak stress and elastic modulus of specimens showing a decreasing trend with an increasing coal–rock ratio. (2) The transitional zone of primary coal–rock composite exhibits distinct interface effects on coal and rock components. Coal-derived stresses manifest as horizontal tensile stresses, promoting deformation at the interface between coal and rock, whereas rock-derived stresses at the interface manifest as horizontal compressive stresses, restricting deformation at the coal–rock interface. Moreover, positions closer to the interface experience stronger limitations due to the interface effects. (3) Coal–rock interface cracks are more developed in the primary coal–rock composite, with multipoint cracking occurring at the interface during failure, and a feedback mechanism between coal and rock failure exacerbates the damage and dynamic manifestation intensity of coal bodies. (4) The acoustic emission signals from single-rock samples indicate shear failure of the specimens. Conversely, the acoustic emission signals from single-coal samples and combinations suggest that tensile failure is the primary destabilizing factor. Moreover, with an increase in the proportion of coal, specimens transition from tensile failure to tensile–shear composite failure.

The process of rock damage and failure is accompanied by the dissipation of energy and an increase in plastic strain. This study attempts to determine the relationship between dissipated energy and plastic strain in sandstone during the damage and failure process. A conventional triaxial cyclic loading and unloading test was conducted on sandstone samples to analyze the energy evolution and plastic strain characteristics of rock during the mechanical performance degradation and deformation failure process. The analysis results indicate that the evolution law of rock energy dissipation and plastic growth during the whole stress–strain process is highly consistent. Before the peak stress, dissipated energy and plastic strain increased linearly with input energy and axial strain, respectively. In the residual stress stage, there is an approximate linear evolution relationship between dissipated energy and plastic strain. Based on the correlation characteristics of energy dissipation and plastic growth, a modified damage model was established by characterizing plastic deformation by damage. In addition, a numerical program was developed using the Finite Volume Method (FVM) based on the damage model. The rock damage model has been validated by experimental results and numerical test. The research findings may provide valuable insights into the correlation mechanism between energy dissipation and plastic growth.

A quantitative characterization of the change in coal molecular structures with different cyclical microwave modification parameters and a better understanding of the reaction mechanism of the modification are of great significance for the commercial extraction of coal bed methane (CBM). Therefore, long-flame coal samples obtained from the Ordos Basin, China, were modified by microwave radiation with different times, and the long-flame coal molecular structure parameters were determined by solid-state ¹³C nuclear magnetic resonance (ss¹³C NMR), Fourier transform infrared (FTIR) spectrometry, and X-ray photoelectron spectrometry (XPS). Atomistic representations of the raw long-flame coal molecular model and modified long-flame coal molecular models were established. The temperature rise, pore volume increase, mineral removal, and functional group changes after the modification have a negative effect on methane adsorption. After the modification, the decrease in surface area of the micropores reduced the adsorption site of methane in coal. As a result, the methane adsorption amount decreased linearly with the decreasing surface area. The CH₄ adsorption isotherms of the long-flame models were dynamically simulated and analyzed. The results of this study can prove that after multiple cycles of microwave modifications, the functional groups in long-flame coal were fractured, and the number of micropores was reduced, which effectively decreased the methane adsorption performance in long-flame coal seams, thereby promoting methane extraction. Microwave modification is a promising method for enhancing CBM recovery.

Coal mine dust is a critical hazard that can trigger explosions and cause pneumoconiosis, thereby severely threatening mine safety and occupational health. Although long-forcing and short-exhausting ventilation are commonly adopted in long-distance heading faces, their parameters are often determined empirically, leading to suboptimal dust control efficiency. This study utilizes numerical simulations via FLUENT to investigate dust migration patterns under five key ventilation parameters in the 2-2 Upper Coal Working Face of the Xintai Taigemiao Mining Area. The results reveal a zonal distribution of dust: a high-concentration accumulation zone within 0–15 m, a medium-concentration transition zone between 15 and 35 m, and a low-concentration settling zone beyond 35 m. Diffusion rates vary significantly across zones under different ventilation settings. The optimized parameters for the 20 m² cross-section roadway in this study include: exhausting duct set 0.3 m from the return-side wall, exhausting inlet at a distance of 4 m (0.9√A, A is the roadway cross-sectional area) from the face, forcing inlet at 20 m (4.5√A) from the face, duct installation height of 0.75 times the roadway height, and a forcing-to-exhausting air volume ratio between 1.2 and 1.6. Compared with the non-optimized scheme, this configuration reduces the average dust concentration in the breathing zone (1.2 m height) by up to 62.3%, and restricts 85% of the high-concentration dust within 0–15 m from the heading face, effectively suppressing dust dispersion to the rear roadway. This study provides a quantitative reference and theoretical strategy for engineering applications of dust prevention in similar large-section long-distance heading faces within the scope of numerical simulation.

Fully mechanized coal mining is a key method of coal extraction. As mining intensity increases, dust pollution in fully mechanized mining faces has become increasingly severe, significantly hindering the coal industry‘s alignment with the “Healthy China” strategy. To address the prominent dust pollution and the inefficiency of current spray dust suppression methods, this study proposes a combined spray dust suppression system. Using the Taigemiao mining area—where the coal dust exhibits hydrophilic characteristics—as a case study, we investigate the system’s spray flow field characteristics via numerical simulation. The results indicate that activating the shearer‘s external nozzles increases the airflow velocity near the shearer to 4 m/s, with the droplet concentration at the breathing zone height peaking at 28,786 mg/m³. Furthermore, activating the inter-support spray-induced dust removal device boosts the airflow velocity to 15.8 m/s, generating negative pressure at the dust suction inlet and forming a high-concentration droplet zone near the coal wall. During the operation of the combined system, the droplet distribution is characterized by “three high-concentration areas” and “post-nozzle attenuation.” The optimal droplet proportion reaches 93.81%, maintaining an appropriate velocity within the efficient dust capture range. Overall, the dust capture efficiency of the combined system is significantly superior to that of a single spray system.

The essence of coal-rock dynamic disasters is the instantaneous instability that occurs when the coal-rock combination system reaches its strength limit. The differing mechanical properties of coal and rock lead to mismatching deformation within the combination, thereby altering the mechanical characteristics of the coal-rock body under combination structures. Consequently, studying the mismatching horizontal deformation of coal-rock combinations is significant for the prevention and control of coal-rock dynamic disasters. To investigate the mismatching horizontal deformation characteristics of primary coal-rock combinations, this study conducted uniaxial and conventional triaxial loading experiments on primary coal-rock combinations to obtain their strength and horizontal deformation characteristics. Subsequently, numerical simulations were performed to analyze the factors influencing the horizontal deformation of primary coal-rock combinations, ultimately leading to the construction of a horizontal deformation distribution model for primary coal-rock combinations. The research results indicate that due to the influence of the coal-rock interface, the primary coal-rock combinations exhibit continuous and smooth mismatching horizontal deformation under loading conditions, with the magnitude of deformation ordered as coal > interface > rock. The influence of the interface on the horizontal deformation of the coal-rock body does not suddenly vanish; rather, it gradually diminishes with increasing distance from the interface, becoming negligible at approximately 48% of the model’s lateral dimensions. A horizontal deformation mismatch distribution model for primary coal-rock combinations was established based on the Sigmoid function, and the key parameter b in the model was obtained through fitting with numerical simulation results. The reliability of the model was subsequently validated through experimental results. The findings of this study provide a basis for further research on the mechanical properties and deformation characteristics of coal-rock combinations.