The fracture behavior and various of mechanical mechanisms of shale are greatly influenced by the bedding surface. To study the effects of bedding angles on the crack propagation patterns and dynamic fracture properties, the shale notched semi-circular bend (NSCB) specimens were studied by the modified split Hopkinson pressure bar (SHPB) device, three-dimensional digital image correlation (3D-DIC) system with the high-speed (HS) photography and ABAQUS finite element software. The research results showed that at the same impact velocity, the 30°, 45° and 60° beddings played an obvious deflexion effect on the shale crack propagation. However, the 0° and 90° bedding did not deflect the crack propagation. The dynamic fracture toughness of shale NSCB specimens increased with the increase of impact loading rate but the increase magnitude decreased with the higher impact rate. The kinetic energy during specimen fracture was calculated by the extracting displacement data from the 3D-DIC, and it was found that the kinetic energy accounted for less than 6% of the absorbed energy during the dynamic compression of the shale. The crack propagation characteristics of ABAQUS simulation was approximately consistent with the experimental results. It is conducive to the study of shale gas fracturing and the formation of complex seam networks in shale and it is of great research significance for the efficient extraction of shale gas.

中文翻译：

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页岩裂缝表征的动态冲击实验和整体粘性元法

页岩的破裂行为和各种力学机制受层理面影响较大。为了研究层理角度对裂纹扩展模式和动态断裂特性的影响，采用改进的分体式霍普金森压力棒（SHPB）装置、三维数字图像相关（3D）技术对页岩缺口半圆弯曲（NSCB）试件进行了研究。 -DIC）系统，配备高速（HS）摄影和ABAQUS有限元软件。研究结果表明，在相同冲击速度下，30°、45°和60°层理对页岩裂纹扩展起到明显的偏转作用。然而，0°和90°层理并没有使裂纹扩展偏转。页岩NSCB试样的动态断裂韧度随着冲击载荷速率的增加而增加，但随着冲击速率的增加，增加幅度减小。通过从3D-DIC中提取位移数据计算试件破裂时的动能，发现动能占页岩动态压缩过程中吸收能的比例不到6%。 ABAQUS模拟的裂纹扩展特性与实验结果基本一致。有利于研究页岩气压裂和页岩中复杂煤层网络的形成，对页岩气的高效开采具有重要的研究意义。