Ming Yang

Microscale characterization of spontaneous imbibition mechanisms is essential for improving the underground hydrogen storage efficiency and coal seam gas recovery. In this study, low-field nuclear magnetic resonance technology was employed to investigate dynamic water transport during coal imbibition through thermodynamic and temporal analyses of T2 spectra evolution. A coupled adsorption-kinetic and multistage seepage model was developed to describe the imbibition process. Anomalous imbibition coefficient behaviors were revealed, with pore structure impacts and engineering applications being systematically discussed. The results show that imbibition kinetics are governed by a dynamic capillary-viscous equilibrium, while water adsorption follows dual-process pseudo-first-order kinetics. The imbibition curves exhibit either two-stage (piston diffusion) or three-stage (single-tube piston diffusion) patterns, characterized by distinct temporal exponents (n). Specifically, the process involves preferential flow through dominant pathways (n = 1), pressure-driven piston-like even filling of accessible pores (n = 0.5), and diffusion-based saturation of micropores (n = 0.2). The capillary pressure can be derived from the intercept of the piston-like stage. Anomalous high imbibition coefficients (R > 1) are attributed to pore connectivity. From an engineering perspective, low-pressure injection at controlled critical rates is recommended for coals exhibiting three-stage imbibition to prevent water channeling, while preemptive modification of capillary properties is necessary for two-stage coals to mitigate water-blocking effects.

To reduce energy consumption in mine ventilation networks under dynamic air demand, this study proposes an Improved Cuckoo Search (ICS) algorithm for energy-efficient airflow regulation. A nonlinear optimization model is established incorporating airflow balance at nodes, air pressure balance in loops, and fan operating constraints; equality constraints are handled by an exterior penalty function and inequality constraints by an interior penalty function. To overcome standard Cuckoo Search’s insufficient convergence accuracy and premature convergence, adaptive step sizes, an adaptive discovery probability adjustment, and a hybrid update strategy with differential evolution are introduced to enhance global exploration and local exploitation, convergence speed, and stability. The method was validated on an intelligent ventilation platform using field data from the Second Panel of a coal mine in Shaanxi Province. Results show that ICS reduces total power consumption from 482.0 kW to 424.9 kW, achieving an energy-saving rate of 11.85%, and outperforms CS, PSO, and GWO in convergence efficiency, accuracy, and stability. Quantitatively, it converges in 130 iterations (190 for CS, 160 for GWO), with a 0.038 kW objective-function standard deviation (coefficient of variation 0.009%) over 30 runs and 0.22 s per run. The proposed method optimizes airflow distribution while satisfying air-demand constraints, offering a practical approach for energy-efficient mine ventilation.

Spontaneous imbibition in heterogeneous porous media is traditionally described using continuum-scale capillary theories. However, due to multiscale pore heterogeneity and strong interfacial confinement, imbibition kinetics deviate from single-mechanism descriptions and reflect the coupled evolution of distinct water states that cannot be captured by sequential adsorption models. A state-resolved, fractal-constrained kinetic framework is developed to characterize multi-rate imbibition and is validated by experimentally time-resolved low-field nuclear magnetic resonance spectroscopy combined with saturation-centrifugation fractal analysis. Four representative natural porous specimens provide experimental validation. Rigorous statistical model selection confirms the consistency of the dual-process formulation, and the kinetic parameters are correlated with structural and interfacial properties. A rapid increase in the short relaxation time signal accompanied by concurrent growth in longer relaxation times is observed, indicating coupled multistage imbibition rather than sequential layer-by-layer adsorption. The imbibition process is accurately described by a dual-process mechanism consisting of rapid surface-controlled adsorption and slower diffusion-dominated intra-matrix transport. The saturated fractal dimension constrains the effective sorption capacity, whereas the centrifuged fractal dimension governs the balance between the fast and slow processes. Cross-scale restrictions imposed by pore-throat bottlenecking are quantified using the disparity between the two fractal indicators. This framework establishes a link between multiscale pore structure and dynamic flow behavior in heterogeneous porous media.

Thermo-electromagnetic force plays a crucial role in tailoring the solidification microstructure by altering thermal-solutal buoyancy. However, while in situ synchrotron experiments offer some observations of microstructural evolution, their restricted spatial resolution and beam intensity prevent the full characterization of fluid flow and solute transport during solidification. To address this limitation, a calibrated model of a cellular automaton method coupled with a Eulerian multiphase approach is employed in this study to comprehensively investigate the impact of solute distribution on grain evolution during the directional solidification of an Al-2.5 wt.% Cu alloy under varying steady magnetic fields from 0.5 T to 4.0 T. The model incorporates heat and solute transport, nucleation, grain growth, and complex melt flows driven by thermal-solutal buoyancy, alongside thermo-electromagnetic effects and induced Lorentz forces. Simulations reveal that under a steady 0.5 T magnetic field, an elliptical copper-rich region forms near the solidification front. This solute redistribution significantly influences the development of a tilted solid–liquid interface, consistent with experimental observations. As the magnetic field strength increases, this copper-rich region transitions from an elliptical to a circular morphology. Notably, under a 4.0 T magnetic field, the tilted interface is effectively stabilized due to the suppression of grain growth. Furthermore, significant grain refinement is observed under a steady magnetic field, as the average grain size decreases from 209.3 μm without magnetic field to 122.5 μm of 0.5 T. This refinement is driven by redistribution of the copper concentration, which increases the undercooling from 1.4 K to 3.7 K and generates new nucleation zones. This solute-driven mechanism is identified as the primary cause of grain refinement under steady magnetic fields and is successfully validated by experimental results. These results shed new light on the mechanism of grain growth evolution under a steady magnetic field.

Gas adsorption-desorption hysteresis in coal affects gas storage, release, and extraction efficiency, particularly under in situ stress conditions. In this study, an adsorption-desorption (A-D) experimental system integrated with low-field nuclear magnetic resonance (NMR) was used to quantify gas occurrence in coal under three-dimensional stress. Mean effective stress (MES) was used to characterize the stress state and evaluate its influence on the hysteresis of adsorbed and free gas. The adsorbed gas content during adsorption was well fitted by the Langmuir-Freundlich model, whereas the desorption stage was better described by the Weibull model. Free gas content remained approximately linearly related to MES throughout the A-D process. As MES increased from 2.74 to 5.68 MPa, the hysteresis coefficient of adsorbed gas decreased from 21.17% to 19.91% and then increased to 27.67%, whereas that of free gas increased nearly linearly from 24.63% to 35.60%. This contrasting response was mainly controlled by reconstruction of the pore system. At relatively low MES levels, macropores were partly transformed into transitional pores and ink-bottle-shaped pore throats expanded, promoting gas desorption and diffusion. At higher MES levels, micropores became more dominant, pore throats contracted, and transitional pores and macropores were compacted or closed, thereby enhancing hysteresis. Multivariate regression indicated that pore pressure was the primary factor affecting adsorbed gas hysteresis, whereas free gas hysteresis was governed by the combined effect of MES. These results provide a basis for understanding stress-sensitive gas occurrence and optimizing coalbed gas extraction.

Noise pollution in fully mechanized mining workfaces threatens the occupational health and safety of miners. Obstacles such as mechanical equipment and pipelines in roadways can alter noise propagation patterns, and clarifying this influence is crucial for mine noise control and personal protection. This study established numerical simulation models for medium- and high-frequency noise propagation in fully mechanized mining workfaces using the finite element method and ray acoustics method within the acoustic module. The reliability of the models was validated by comparing the simulation results with field measurement data from test roadways. On this basis, the influence laws of key parameters such as obstacle obstruction rate, shape, number, and spacing on noise propagation were analyzed. The results show that the obstruction rate and shape of obstacles have a weak impact on the attenuation of mid-to-high-frequency noise, and the noise reduction effect is negligible. When the number of obstacles is fixed, a spacing of 1m achieves a significant noise reduction effect on high-frequency noise (sound pressure level change of approximately 20 dB) but has little impact on mid-frequency noise at 2000 Hz. The number of obstacles significantly affects high-frequency noise, and the optimal configuration is related to spacing—under a spacing of 1m, a single obstacle can achieve significant noise reduction (>10 dB); under a spacing of 3m, 1 or 4 obstacles yield the optimal effect (approximately 20 dB), while their impact on mid-frequency noise is negligible. The research results provide a key basis for mine noise control and obstacle configuration optimization, and have practical value for improving the occupational health protection of miners and ensuring the safe production of coal mines.

The instability and collapse of boreholes during coal seam gas extraction significantly affect the effectiveness of gas extraction. In response, this study selected human hair residue as the base material for composite protein foaming agents, leveraging the high protein content of animal hoof and hair materials to develop a high-strength, high-permeability, and environmentally friendly new type of foam concrete. This research found that the optimal ratio of foaming agent base solution to water is 1:4 when sodium hydroxide is used for protein hydrolysis. Comparing the foaming effects of sodium dodecyl sulfate (K12), α-sodium alpha-alkenyl sulfonate (AOS), sodium lauryl polyoxyethylene ether sulfate (SLS), and sodium dodecyl benzene sulfonate (LAS), sodium lauryl polyoxyethylene ether sulfate (SLS) exhibited the best foaming performance, while α-sodium alpha-alkenyl sulfonate (AOS) had the best foam stability. The optimal foam performance was achieved by mixing 2.0 g per liter of sodium lauryl polyoxyethylene ether sulfate and 0.3% calcium stearate. The experimental results showed that this foam concrete, with 25 mL of foaming agent, has a high strength exceeding 11 MPa and a high permeability with an average of 2.13 MD. This paper utilizes environmentally friendly materials and preparation processes. By using renewable resources such as human hair residue as raw materials, it helps reduce the dependence on natural resources and promotes sustainable development. This research demonstrates significant sustainability and provides the mining industry with an eco-friendly and efficient solution, with the potential to achieve positive economic and environmental benefits in practical applications.

The influence mechanism of different geological parameters on the activation of small faults under mining in the deep coal face was investigated by numerical simulation. The study shows that (1) the degree of influence of six parameters including the fault lateral pressure coefficient lambda, elastic modulus E, Poisson's ratio mu, cohesion c, internal friction angle phi, and fault inclination angle theta on the activation of small faults was ranked in order as theta > lambda > phi > mu > E > c. (2) The lateral pressure coefficient lambda of the fault zone rock mass, the internal friction angle phi, and the fault inclination angle theta had a great influence on the fault activation. The larger the lambda of the fault zone rock mass was, the smaller the phi was, the larger the subsidence amount drop of the rock layers on both sides of the fault was, and the greater the severity of the fault activation was. The fault activation degree decreased first, then increased, and then decreased with the increase of theta. When theta was 15 and 60 degrees, there was relatively severe fault activation. When theta was 75 degrees, the fault was not easy to activate. (3) Poisson's ratio mu, elastic-modulus E, and cohesion c of the fault zone rock mass had little effect on the fault activation. The larger the E of the fault zone rock mass was, the larger the mu was, the smaller the c was, and the possibility of fault activation increased slightly. The research results can provide important theoretical support for the theoretical research on fault activation, on-site roof management, and mining schedule arrangement in the mining process of deep coal face.