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Gas-type-dependent impact-force response and fractal fragmentation of granular coal porous media under confined drop-hammer loading
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J
陈
H
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DOI：10.1016/j.colsurfa.2026.141499.png)
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Abstract
En 中文
Coal is a heterogeneous porous medium with abundant pore surfaces that provide adsorption sites and migration pathways for gas molecules. Gas-specific interactions at the coal pore surface, including adsorption, pore filling, adsorption-induced deformation and pore-pressure effects, may modify local particle-contact states and force-transmission pathways, thereby influencing impact-induced fragmentation. However, the relationship among gas adsorption affinity, gas-solid interfacial effects, impact-force response and post-impact fragmentation of granular coal remains insufficiently understood. In this study, confined drop-hammer impact tests were carried out on granular coal exposed to CO2, CH4, N2 and He under gas pressures ranging from 0.3 MPa to 1.2 MPa. The main pulse peak and main pulse duration were used to characterize the impact-force response, while the particle-size distribution and fractal dimension after hammering were used to describe the fragmentation characteristics. The results show that the main pulse peak generally decreases with increasing gas pressure, indicating that the concentrated force response of the coal-particle system is weakened under pressurized gas conditions. This effect is more evident for coal particles exposed to CO2 and CH4. The main pulse duration does not show a single monotonic trend, but varies with gas type, gas pressure and hammering sequence, reflecting the difference in stress adjustment during impact. For gases with stronger adsorption affinity, especially CO2 and CH4, adsorption-related deformation and pore-surface interaction tend to weaken the coal skeleton and enhance local structural adjustment, resulting in a higher retention of coarse particles after hammering. For N2 and He, the weaker adsorption affinity and stronger gas mobility are more favourable for stress dispersion and multi-point fracture propagation. At 0.6 MPa, the fractal dimension increased from 2.29616 for CO2-exposed coal particles to 2.40976 for He-exposed coal particles, indicating an increasing fragmentation degree with decreasing gas adsorption affinity under the investigated conditions. These results indicate that gas-specific pore-surface interactions may affect the dynamic response and fractal fragmentation of granular coal by modifying the gas occurrence state, local particle-contact configuration and force-transmission path. This study provides a macroscopic force-response perspective for understanding how gas adsorption affinity and gas-solid interfacial effects influence the fragmentation behaviour of confined granular coal porous media.
Keywords:
Granular coal porous media
Gas adsorption affinity
Impact force response
Force transmission
Fractal fragmentation
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