SHPB冲击作用下层状千枚岩多尺度破坏机理研究

通过分离式霍普金森杆对层状千枚岩施加动态载荷,得到不同层理倾角下层状千枚岩的动态抗压强度与宏观破坏模式。采用三维激光仪获得断裂面细观形貌,引入分形几何定量计算断口面粗糙度;结合SEM观察到的微观尺度下不同层理倾角断口破坏机理,分析了不同层理倾角下层状岩石的动态破坏机制。研究结果表明:动态压缩下层理弱面对岩石的抗压强度影响较大;不同层理倾角千枚岩的断口形貌分形维数随层理倾角增大呈U型变化;从强度与裂纹扩展两方面考虑层理弱面对层状岩石破坏特征的影响,对于层理倾角为0°的试样,强度由岩石基质控制,但层理弱面仍对岩石破坏的裂纹分布与走向产生较大影响;对于层理倾角为22.5°的试样,强度与裂纹走向受岩石基质与层理弱面共同控制;对于层理倾角为45°~67.5°的试样,强度与裂纹走向受层理弱面控制;而对于层理倾角为90°的试样,动态抗压强度受岩石基质的影响较大,在层理弱面较早形成纵向宏观裂纹,导致该层理弱面角度下裂纹受层理弱面的影响较大。

Multi-scale failure mechanism analysis of layered phyllite subject to impact loading

The dynamic compressive strength characteristics and macroscopic failure modes of layered phyllite are carried out by the Split Hopkinson Pressure Bar. The micromorphology of fracture surface was obtained by 3D laser instrument, and the fractal geometry was introduced to quantitatively describe the roughness of fracture surface. Based on the fracture mechanism observed by SEM, the dynamic failure mechanism of layered rock with different bedding angles is analyzed. The results indicate that the weak bedding plane has a great influence on the dynamic compressive strength of layered rock. The fractal dimension of layered phyllite changes in U-shape with the increase of bedding angle. The influence of bedding plane on the failure characteristics of layered rocks is examined according to strength and crack propagation. For specimens with bedding angle of 0°, the failure strength is controlled by rock matrix, but the weak bedding plane still has a large impact on the distribution and trend of cracks in rock failure. For specimens with bedding angle of 22.5°, strength and direction of cracks are controlled by both the rock matrix and weak bedding plane. For specimens with bedding dip angle ranging from 45° to 67.5°, strength and direction of cracks are controlled by weak bedding plane. For the bedding angle of 90°, the dynamic compressive strength of the specimen is affected by the rock matrix, and longitudinal macro-cracks are formed early on the weak plane of the bedding, which results in that the cracks are greatly affected by the bedding plane.