CO₂吸附会对煤体产生损伤劣化作用进而降低其稳定性，对CO₂封存的长期安全性提出挑战，明确CO₂劣化作用并建立本构模型至关重要。采用损伤力学理论和统计理论推导出能够综合反映CO₂吸附和荷载耦合作用下煤体总损伤变量的计算公式，并重点考虑了压密段的影响，分段建立了CO₂作用下煤体的细观统计损伤本构方程，明确了模型各参数的确定方法。最后通过CT扫描实验系统、MTS 816实验系统确定了本构模型参数，并采用自主研制的气−固耦合实验系统对不同CO₂压力下煤体进行了单轴压缩实验，验证了模型的合理性。研究结果表明：① 基于CT扫描获取的裂隙率和运用Weibull分布理论分别定义了吸附和受载作用下的损伤变量，结合损伤理论进一步得到二者耦合作用下的总损伤变量，并建立了细观统计损伤本构模型；② 基于CT扫描技术的裂隙三维重构真实反映了CO₂作用前后裂隙扩展特征，CO₂压力越高，裂隙扩展越充分，煤样三维裂隙参数和损伤变量越大，所形成的空间裂隙网络越复杂；③ CO₂对煤体力学性质劣化作用显著，煤体的抗压强度与弹性模量随CO₂压力增加分别降低了49.78%和22.63%，CO₂对煤体的溶胀效应、塑化效应和气楔效应的综合作用导致了力学参数的降低；④ 建立的CO₂作用下煤体细观统计损伤模型理论曲线与单轴实验曲线具有较高的吻合度，说明损伤本构模型能够较好地反映出CO₂对煤体力学特性的损伤劣化作用，体现了损伤本构模型及模型参数确定方法的合理性与适用性。

CO₂ adsorption causes damage degradation to the coal body and thus reduces its stability, challenging the long-term safety of CO₂ sequestration, and it is important to clarify the role of CO₂ degradation and establish an ontological model. The damage mechanics theory and statistical theory were used to derive the calculation formula that can comprehensively reflect the total damage variables of the coal body under CO₂ adsorption and load coupling, and focusing on the influence of the pressure-tight section, the fine statistical damage ontological equation of the coal body under the action of CO₂ was established by segmentation, and the method of determining each parameter of the model was clarified. Finally, the parameters of the constitutive model were determined by CT scanning experiment system and MTS 816 experiment system, and the uniaxial compression experiments of coal body under different CO₂ pressures were carried out by the self-developed gas-solid coupling experiment system to verify the rationality of the model. The results show that: ① The damage variables under adsorption and loading were defined based on the fracture rate obtained from CT scanning and by applying the Weibull distribution theory, respectively, and the total damage variable under the coupling of the two was further obtained by combining the damage theory, and a fine-scale statistical damage constitutive model was established; ② Three-dimensional reconstruction of the fracture based on CT scanning technology realistically reflects the fracture extension characteristics before and after CO₂ interaction, the higher the CO₂ pressure, the fuller the fracture expansion, the greater the three-dimensional fracture parameters and damage variables of the coal samples, and the more complex the spatial fracture network formed; ③ CO₂ had a significant deterioration effect on the physical properties of the coal body, and the compressive strength and modulus of elasticity of the coal body were both reduced by 49.78% and 22.63%, respectively, with the increase of CO₂ pressure, and the combined effect of dissolution, plasticization and air wedge effect of CO₂ on the coal body led to the reduction of the mechanical parameters; ④ The theoretical curves of the fine statistical damage model of the coal body under the action of CO₂ have a high degree of agreement with the uniaxial experimental curves, which indicates that the present structural model can better reflect the damage degradation effect of CO₂ on the physical properties of the coal body, and embodies the reasonableness and applicability of the constitutive model and the method for determining the model parameters.