Assessment on anisotropy degree and fracture modes for weakly anisotropic sandstone using the acoustic emission technique

Abstract

AbstractComprehensive understanding of anisotropy characteristics and fracture modes for weakly anisotropic rocks is required for engineering safety and energy exploitation. To investigate the fracture mechanisms, the uniaxial compression testing with AE (acoustic emission) technique is implemented on the weakly anisotropic sandstone because of its capability to provide the essential and frequently‐used mechanical parameters. This research first adopts the longitudinal wave velocity and T2 spectrum to validate the weak anisotropy of the bedded sandstone. The results experimentally indicate that both uniaxial compressive strength and Young's modulus have a negligible dependence on different bedding orientation angles, but both permeability and macroscopic failure patterns are considerably controlled by the bedding direction. The conventional AE index analysis indicates that the tension‐dependent failure occurs in the bedded sandstone under the uniaxial compression. Interestingly, the developed k‐means clustering method is consistent with both the latest crack classification concept and macroscopic failure patterns.