Study on evolution laws of permeability and mechanical properties of anthracite under supercritical CO₂ action

To investigate the evolution of the physical and mechanical properties of anthracite under the action of supercritical CO₂, permeability tests and uniaxial compression experiments were conducted on dry and water-saturated anthracite specimens immersed in supercritical CO₂ for different durations. The results show that supercritical CO₂ significantly affects the physical and mechanical properties of anthracite. With increasing immersion time, the permeability of anthracite gradually increases, while its compressive strength and elastic modulus gradually decrease. The degradation degree of coal specimens approximately follows a logarithmic function with immersion time and a linear relationship with permeability. Water content is an important factor influencing the physical and mechanical properties of anthracite. Compared with dry specimens, water-saturated specimens exhibit lower compressive strength and elastic modulus but higher permeability under the same immersion time. The difference in physical and mechanical parameters caused by water content reaches its maximum at an immersion time of 5 days. With a further increase in immersion time, the overall difference in physical and mechanical parameters induced by water content shows a decreasing trend.