Fracture structure and dynamic characteristics of coal after various soaking times with supercritical CO2.

Current research on the mechanical properties and damage of coal after supercritical CO2 (sCO2) soaking has focused on static investigations. To understand the dynamic characteristics, researchers often analyze the parameters characterizing the fracture and three-dimensional strain fields of coal before and after sCO2 soaking. We explored the relationship between the time-dependent damage to coal and the deterioration of dynamic parameters. The damage variable was defined by the increase in fracture volume, while a dynamic damage constitutive model of coal was established for various sCO2 soaking durations. Soaking initiated and expanded coal pore fractures and altered strain variables in the coal matrix. The fracture volume and fractal dimension of the coal increased with soaking time, whereas the strain area expanded. After sCO2 soaking, the dynamic peak strength and elastic modulus of coal displayed time-dependent decreases. The damage variable was positively correlated with soaking time.