Ultrasonic wave propagation characteristics for typical anisotropic failure modes of shale under uniaxial compression and real-time ultrasonic experiments

Abstract

Uniaxial loading and real-time ultrasonic experiments on shales were conducted to study the progressive failure of shale and the ultrasonic propagation characteristics during loading. The results show that the variations in P-wave and S-wave velocities with stress correspond to the crack damage process for the typical anisotropic failure of shale, and that the S-wave amplitude is sensitive to the damage that arises in shale during loading. If the bedding participates relatively simply in the failure (0° and 60° inclinations), the spectrum and the main frequency shape are simple and remain basically unchanged during loading. In the cases where the failure mode is complicated by the participation of the bedding and the matrix (30° and 90° inclinations), the spectrum and the main frequency shape are complex and change dynamically with loading. These results indicate that ultrasonic dynamic parameters reflect the differences in the failure of shale.