Injecting carbon dioxide CO₂ into a coal seam is an important way to improve coalbed methane recovery and to store geological carbon. The fracture mechanical characteristics of bituminous coal determine the propagation and evolution of cracks, which directly affect CO₂ storage in coal seams and the efficiency of resource recovery. This study applied CO₂ adsorption and three-point bending fracture experiments using bituminous coal samples in a gaseous state (4 MPa), subcritical state (6 MPa), and supercritical state (8 and 12 MPa) to investigate the influence of CO₂ state and anisotropy on the fracture-related mechanical response of bituminous coal. The results show that the change in mechanical properties caused by CO₂ adsorption is CO₂ state-dependent. The supercritical CO₂ adsorption at 8 MPa causes the largest decrease in the mode-I fracture toughness (K_IC), which is 63.6% lower than the toughness before CO₂ adsorption. The instability characteristics of bituminous coal show the transformation trend of “sudden-gradual-sudden fracture”. With or without CO₂ adsorption, the order of the K_IC associated with three types of bituminous coal specimens is crack-divider type > crack-arrester type > crack-short transverse type. Phenomenologically, the fracture toughness of bituminous coal is positively correlated with its specific surface area and total pore volume; the toughness is negatively correlated with its average pore size.

将二氧化碳CO ₂注入煤层是提高煤层气采收率和封存地质碳的重要途径。烟煤的断裂力学特性决定了裂隙的扩展和演化，直接影响煤层CO _{2封存和资源回收效率。}本研究采用气态 (4 MPa)、亚临界状态 (6 MPa) 和超临界状态 (8 MPa 和 12 MPa) 烟煤样品进行 CO 2 吸附和三点弯曲断裂实验，以研究 CO 2_状态的影响和各向异性对烟煤断裂相关力学响应的影响。_{结果表明，CO 2}引起的力学性能变化吸附是CO ₂状态依赖性的。8 MPa 下的超临界CO ₂吸附导致模式-I断裂韧性（K _IC ）的最大降低，比吸附CO ₂之前的韧性低63.6％ 。烟煤的失稳特征呈现出“突然-逐渐-突然破裂”的转变趋势。有无CO _2吸附， K _IC的顺序与三种类型的烟煤试样相关联的是裂纹分隔型>裂纹抑制器型>裂纹短横向型。现象学上，烟煤的断裂韧性与其比表面积和总孔容呈正相关；韧性与其平均孔径呈负相关。