Dynamic response of coal under impact load after supercritical CO2 -water-coal interaction

In order to study the mechanical behavior of coal after CO2 injection in closed / abandoned mines,the ϕ50 mm split Hopkinson pressure bar (SHPB) test system was used. This dynamic compression tests were carried out on the natural state coal, saturated state and supercritical CO2 -water-coal interacted coal samples. Thus, the failure modes,energy characteristics and dynamic mechanical parameters of three state coal samples under impact load were analyzed. The test results show that ① with the increase of strain rate,compared with the natural and saturated state coal samples,the coal samples treated by supercritical CO2 -water-coal interaction have more fragments and smaller particles. ② With the increase of incident energy,the linear trend of energy reflectance,transmittance and dissipation rate of three state coal samples are different. Coals after supercritical CO2 -water-coal interaction show that if energy reflectivity significantly increase,the energy dissipation rate will significantly decrease. ③ Compared with the natural and saturated state coal samples,the properties of coal are weakened after supercritical CO2 -water-coal interaction,and the dissipated energy density is increased by the micro-crack germination expansion under impact load. Besides,the curves of dynamic compressive strength-dissipated energy and dynamic elastic modulus-dissipated energy density vibrate be-tween natural state and saturated state. The experimental results show that the factors such as mineral chemical reac-tion,microstructure change induced by adsorption expansion,and surface energy reduction of cracks can significantly affect the dynamic response characteristics of coal samples. Although the experimental methods in this paper cannot fully reflect the real situation of CO2 storage in closed / abandoned,this study provides a relevant reference information for the further research of the dynamic response characteristics of coal samples under the CO2 -water-coal interaction.