The bedding orientation influences the failure pattern and brittleness of shale. Clarifying the relation between acoustic emission and the effects of bedding orientation on the failure behaviors of shale is important to understand the mechanism of the formation of fracture networks. In this study, we analyzed the failure patterns and crack complexity of the shale specimens with various bedding orientations under uniaxial compression using X-ray computed tomography. We proposed an improved criterion based on the acoustic emission waveform parameters to identify the mechanism of the acoustic emission events and showed that the failure mechanism changed from tension to shear during the failure process of each specimen because the shear cracks link independent tensile cracks to form macrofractures in the later loading stage. The proportion of shear-mode events in the specimens declined when the bedding orientation angle increased from 0° to 90°, whereas that of the tensile-mode events exhibited an opposite trend; these changes were consistent with the observation results of X-ray images, indicating the transition of the dominant failure mechanisms with the bedding orientation. The large b value of the acoustic emission events corresponded to a complex crack distribution; thus, this b value may be useful to evaluate the brittleness of shale. These results denote the relation between the mechanisms of the failure patterns in shale and the acoustic emission activity and improve our recognition to the fracture network characteristics.

层理取向会影响页岩的破坏模式和脆性。弄清楚声发射与层理取向对页岩破坏行为的影响之间的关系对于理解裂缝网络的形成机理很重要。在这项研究中，我们使用X射线计算机断层摄影技术分析了在单轴压缩下具有不同层理取向的页岩标本的破坏模式和裂缝复杂性。我们提出了一种基于声发射波形参数的改进判据，以识别声发射事件的机理，并表明，在每个试样破坏过程中，破坏机制从拉伸改变为剪切，这是因为剪切裂纹将独立的拉伸裂纹连接起来形成了宏观断裂。在稍后的加载阶段。当层理取向角从0°增加到90°时，试样中的剪切模式事件所占比例下降，而拉伸模式事件中剪切模式事件所占比例却呈现相反的趋势。这些变化与X射线图像的观察结果一致，表明主要破坏机制随层理方向的转变。大b声发射事件的值对应于复杂的裂纹分布；因此，该b值可能有助于评估页岩的脆性。这些结果表明了页岩破坏模式的机理与声发射活动之间的关系，并提高了我们对裂缝网络特征的认识。