Shale formations suffer dynamic loading and unloading stresses during hydraulic fracturing processes that cause cracks to open and shear-slip to develop, while simultaneously producing microseismicity. Incremental cyclic loading tests were conducted on shale specimens using various stress levels and measured via real-time acoustic emission (AE) monitoring at the laboratory scale because AE parameters are useful in understanding heterogeneous material damage behaviour. Parallel (θ = 0°) and vertically (θ = 90°) cored shale specimens were cyclically loaded from lower stress levels of 0.3 and 0.47 and higher stress levels of 0.8 and 0.84, respectively, to analyze the effects of the bedding plane and loading level on the fracture process. Based on temporal variation of the AE amplitude in response to the stress paths, the longer AE activity quiet period noted during the loading stage in each cycle for 90° shale specimens shows that the Kaiser effect is more pronounced for vertically cored specimens than for parallel cored specimens. This phenomenon is also evidenced by the smaller load ratios observed with θ = 0° (as compared to θ = 90°) specimens. This indicates easier crack generation at lower stresses and is independent of the loading path. Meanwhile, high calm ratios indicate the initiation of numerous cracks during the unloading stage. Therefore, the load ratio can be combined with the calm ratio to evaluate the difficulty of crack generation in shale. In addition, the AE amplitude distribution shows that the proportion of large cracks increases when shale specimens are loaded from higher stress levels. Moreover, the average frequency and RA value (obtained from the rise time and amplitude) were used to characterize damage mechanisms. A decreasing average frequency and increasing RA value for parallel cored specimens from lower stress levels or small average frequency and large RA value from higher stress levels both indicate the dominant shear type that contributes to the failure process and causes splitting along the bedding plane. The higher average frequency and lower RA values noted for vertically cored specimens imply that tensile modes control the failure process and cause finally side-step main fracture plane across the bedding plane.

页岩地层在水力压裂过程中承受动态加载和卸载应力，导致裂缝张开和剪切滑移，同时产生微地震。使用各种应力水平对页岩样本进行了增量循环载荷测试，并通过实验室规模的实时声发射 (AE) 监测进行测量，因为 AE 参数有助于理解异质材料损伤行为。平行 ( θ  = 0°) 和垂直 ( θ = 90°) 取芯页岩标本分别从 0.3 和 0.47 的较低应力水平和 0.8 和 0.84 的较高应力水平循环加载，以分析层理平面和加载水平对断裂过程的影响。基于 AE 振幅响应应力路径的时间变化，90°页岩样本在每个循环加载阶段注意到的更长的 AE 活动安静期表明，垂直取芯试样的 Kaiser 效应比平行取芯试样的更显着。标本。在θ  = 0° 时观察到的较小负载比也证明了这种现象（与θ = 90°) 样品。这表明在较低应力下更容易产生裂纹，并且与加载路径无关。同时，高平静比表明在卸载阶段产生了大量裂纹。因此，载荷比可以结合静力比来评价页岩裂缝产生的难易程度。此外，声发射振幅分布表明，当页岩试样从较高应力水平加载时，大裂缝的比例增加。此外，平均频率和 RA 值（从上升时间和幅度获得）用于表征损伤机制。来自较低应力水平的平行岩心试样的平均频率降低和 RA 值增加，或来自较高应力水平的小平均频率和大 RA 值都表明主要剪切类型有助于破坏过程并导致沿层理平面分裂。垂直取芯试样的较高平均频率和较低的 RA 值意味着拉伸模式控制着破坏过程，并最终导致跨层理平面的侧台阶主断裂面。