华北型石炭−二叠纪煤系基底普遍发育奥陶系灰岩含水层，煤炭开采受到底板承压含水层突水灾害和水资源流失的双重威胁，压剪耦合下岩石水力特性是大倾角承压水上开采底板岩层阻水性能评价的基础。综合采用理论分析及离散元数值计算等方法，建立了不同压剪比例下莫尔圆旋转的岩石失稳判据，揭示了压剪耦合作用下岩石强度衰减机制，提出了综合裂隙角度、裂隙扩展速度、改进体积应变等指标的应力阈值确定方法，明晰了不同加载角、渗透压差及围压条件下岩石微裂纹扩展及渗透性演化特征。主要结论如下：压剪耦合作用下岩石承载能力降低表现在强度降低与弹性模量增大2个方面；岩石弹性模量随加载角增大呈现先缓慢增大(0°～15°)后迅速增大(15°～30°)再减小(30°～45°)趋势，但仍大于初始值；岩石强度和加载角呈线性负相关关系，降低幅度和围压成正比，2 MPa围压下强度降低速度是无围压的1.9倍，由等效内摩擦角控制；随着加载角的增大岩石破坏程度降低、峰后应力由脆性跌落向塑性转变；压剪耦合作用下拉伸裂隙诱导起裂及拉剪复合裂隙主导非稳定扩展解释了不同压剪比例条件起裂应力、损伤应力阈值非线性演化的内在机制；渗透率回弹位置处于起裂与损伤应力阈值之间并接近后者，随着加载角的增大，拉剪复合裂隙(优势渗流路径)分布较为集中；岩石强度随渗透压差增大而降低，降低速率和加载角呈负相关关系；岩石峰值渗透率随着加载角的增大而减小，降低趋势随着渗透压差的增大由线性向非线性转变；加载角较大时，渗透压差与围压对岩石强度及渗透性控制作用减弱。

The Ordovician limestone aquifer is widely developed in the basement of the Carboniferous Permian coal bearing strata in North China. Coal mining is threatened by both water inrush disasters and water resource loss from the floor confined aquifer. The hydraulic characteristics of the rock under compression and shear coupling action are the basis for evaluating the water resistance performance of the mining floor strata on high inclined confined aquifer. Using theoretical analysis and discrete element numerical calculation methods, the rock instability criterion for the Mohr circle rotation under different compression and shear ratios was established, the mechanism of rock strength attenuation under compression and shear coupling action was revealed, the stress threshold determination method for comprehensive indicators such as crack angle, crack propagation speed, and improved volume strain was proposed, and the characteristics of rock microcrack propagation and permeability evolution under different loading angles, osmotic pressure differences, and confining pressure were clarified. The main conclusions are as follows. The reduction of rock bearing capacity under compression and shear coupling action is manifested in strength reduction and elastic modulus increase. The elastic modulus of rocks shows a trend of first slowly increasing (0°−15°), then rapidly increasing (15°−30°), and then decreasing (30°−45°) with the increase of loading angle, but is still greater than its initial value. There is a linear negative correlation between rock strength and loading angle, and the reduction amplitude is proportional to confining pressure. The rate of strength reduction under 2 MPa confining pressure is 1.9 times that without confining pressure, controlled by the equivalent internal friction angle. As the loading angle increases, the degree of rock failure decreases and the post peak stress drop transitions from brittle to plasticity. Under compression and shear coupling action, the induced initiation of tensile cracks and the dominant unstable propagation of tensile and shear composite cracks explain the inherent mechanism of nonlinear evolution of initiation stress and damage stress thresholds under different compression and shear ratios. The position of permeability rebound is between the threshold of initiation and damage stress, and as the loading angle increases, the distribution of tensile and shear composite cracks (dominant seepage paths) is more concentrated. The rock strength decreases with the increase of osmotic pressure difference, and the rate of decrease is negatively correlated with the loading angle. The peak permeability of rocks decreases with the increase of loading angle, and the decreasing trend changes from linear to nonlinear with the increase of osmotic pressure difference. When the loading angle is large, the control effect of osmotic pressure difference and confining pressure on rock strength and permeability weakens.