为从细观层面揭示不同围压作用下套筒压裂岩石破坏机理及能量运移规律，基于套筒压裂试验以及膨胀力测定试验构建了PFC^3D数值模型，采用离散元法对套筒压裂过程开展数值模拟，结合声发射信息探究了套筒压裂过程中不同围压对岩石细观裂隙及能量变化的影响规律，并依据弹性力学揭示了套筒压裂力学机制，研究结果表明：①套筒注液过程存在压力损失，依据注液压力损失率可将注液过程大致划分为充填阶段、增压阶段、快速增压阶段。注液压力与套筒膨胀力呈线性关系，其修正系数为0.678。②基于PFC^3D所构建的数值模型能够较好的反映套筒压裂过程中岩石力学性质与变形破坏特征，岩石压裂过程以张拉破坏为主。围压决定着裂缝的扩展路径，并对岩石内部微裂纹的生成起抑制作用。随着应力差的逐渐增大，岩石内部剪切裂纹数量及占比均逐渐增大。③声发射信号可分为平静期与活跃期，累计裂缝数目曲线呈现阶梯状上升。无围压条件下，声发射特征呈现单峰值分布；有围压条件下，声发射特征呈现多峰值分布，压裂过程存在多个破坏阶段。④套筒膨胀力作用范围有限，环向拉应力作用范围与套筒膨胀力呈现对数关系。切向应力随应力差的增大而增大，当夹角φ取值为45°或135°时，岩石内部剪切破坏最明显。⑤同一膨胀力作用下，围压越大岩石内部输入能越小。不同围压条件下岩石的输入能、弹性能、耗散能均出现不同程度的激增，这主要是由于宏观裂缝的形成引发了钻孔扩容；耗散能平均增长速率更快，为弹性能的1.27～1.55倍。

In order to reveal the micromechanics of rock failure mechanisms and energy transfer patterns under different confining pressures during sleeve fracturing, a PFC^3D numerical model was established based on sleeve fracturing tests and expansive force measurement experiments. The discrete element method was employed for the numerical simulation of the sleeve fracturing process. In addition, by integrating acoustic emission data, the influence of varying confining pressures on the development of microcracks in rocks and the corresponding energy variations were explored. Furthermore, the mechanical mechanism for sleeve fracturing was revealed based on the principles of elasticity. The results show that : ① There is a pressure loss in the process of sleeve liquid injection. According to the pressure loss rate, the liquid injection process can be divided into three stages: filling, pressurization, and rapid pressurization. The expansion force of the sleeve exhibits a linear relationship with the injection pressure, with a correction coefficient of 0.678. ② The PFC^3D numerical model effectively represents the mechanical properties and deformation failure characteristics of rocks during sleeve fracturing, where tensile failure is the predominant mode of rock fracturing. The propagation path of cracks is determined by the confining pressure, which also suppresses the generation of microcracks within the rock. As the differential stress increases, both the number and proportion of shear cracks inside the rock gradually increase. ③ Acoustic emission signals can be divided into quiescent and active periods, with the cumulative number of cracks showing a stepwise increase. The characteristics of acoustic emission exhibit a single-peak distribution under unconfined conditions and a multi-peak distribution under confined conditions, indicating the presence of multiple fracture stages. ④ The influence scope of the sleeve expansion force is limited, and the sleeve expansion force exhibits a logarithmic correlation with the circumferential tensile stress. The tangential stress increases with the increase of stress difference. When the angle φ is 45° or 135°, the shear damage inside the rock is most obvious. ⑤ The energy input into the rock decreases as the confining pressure increases under the same expansive force. Under different confining pressures, the input energy, elastic energy, and dissipation energy of rock increase sharply in different degrees, which is mainly due to the expansion of the borehole caused by the formation of macro cracks. The growth rate of dissipative energy is faster than the elastic energy, approximately 1.27 to 1.55 times that of the elastic energy.