在深部煤层( > 800 m) CO₂地质封存过程中，受高温高压作用影响，CO₂常以超临界态存在。受非均匀地应力及注入流体压力作用下，煤层中发育的大量节理、裂隙等结构面会发生剪切滑移，进而影响煤体力学性能并增加CO₂泄露风险。因此，揭示超临界CO₂长期作用下煤体结构面剪切力学特性，是保证封存安全性的关键。通过开展超临界CO₂不同浸泡时间后的煤体结构面直剪力学试验，结果表明：① 随着超临界CO₂作用时间增加，煤体结构面剪切强度和剪切刚度均逐渐减小；超临界CO₂浸泡14 d后，煤体结构面剪切强度和剪切刚度分别降低40%和28%。② 超临界CO₂作用时间增加会导致煤体结构面剪胀变形减小，剪缩效应明显，同时造成结构面微凸体破碎体积增加；超临界CO₂浸泡14 d后，煤体结构面破碎体积量增加至未浸泡的1.5倍。③ 煤体结构面剪切过程中剪应力与声发射参数之间存在着很强的相关性，振铃计数在峰值应力处增至最大；随着超临界CO₂作用时间增加，声发射累计振铃计数、累计撞击数与累计能量等参数均逐渐减小，煤体结构面脆性破裂特征减弱，塑性增强。④ 未浸泡煤体结构面呈现出明显剪切软化特征，而超临界CO₂作用后煤体结构面剪切向硬化特征转变，通过建立一种新的结构面剪切本构模型，能够很好表征上述转变特征，且模型理论值与试验值有较高拟合程度。

In the process of CO₂ geological storage in deep coal seam (> 800 m), CO₂ often exists in supercritical state under the influence of high temperature and pressure. Due to the non-uniform in-situ stress and the injected fluid pressure, a large number of joints, cracks and other fractures developed in coal seam will cause shear slip, which will further affect the mechanical properties of coal and increase the risk of CO₂ leakage. Therefore, revealing the shear mechanical properties of coal structural plane under the long-term effect of supercritical CO₂ is the key to ensure the safety of CO₂ storage. Through the direct shear mechanical tests of coal structural plane after soaking in supercritical CO₂ for different times, the results show that: ① With the increase of soaking time in supercritical CO₂, the shear strength and shear stiffness of coal structural plane decrease gradually. After soaking for 14 days, the shear strength and shear stiffness decreased by 40% and 28%, respectively. ② The increase of supercritical CO₂ soaking time will reduce the dilatancy deformation of coal structural plane, causing obvious shear contraction, at the same time, increasing the crushing volume of fracture asperity. After soaking for 14 days, the crushing volume of fracture asperity increased 1.5 times. ③ There is a strong correlation between shear stress and acoustic emission parameters during the shearing process of coal structural plane. The ringing down count increases to the maximum at the peak stress. With the increase of supercritical CO₂ soaking time, the cumulative ringing down count, hit number and energy of acoustic emission gradually decrease, and the brittle fracture characteristics of coal structural plane are weakened while the plasticity is enhanced. ④ The untreated coal structural plane samples show some obvious shear softening characteristics, but the shear characteristics change to hardening after soaking in supercritical CO₂. By establishing a new shear constitutive model of structural plane, the above transformation characteristics can be well characterized, and the theoretical value of the model has a high degree of fitting with the experimental value.