Abstract: To obtain three-dimensional anisotropic deformation field characteristics of bedded shale, uniaxial compression experiments were carried out on laminated shale of Longmaxi Formation in Sichuan Basin. The digital images obtained by in-situ scanning through Micro-CT were used as the deformation information carrier. The deformation field of bedding shale under uniaxial compression conditions was calculated based on local DVC and global DVC. The bedding effect of shale deformation evolution was explored. The following results indicate that: with the increase of load, the gradient of the overall displacement field of shale specimens gradually evolved towards the bedding direction. The high-strain concentration zones of shale specimens with different bedding exhibit different patterns. As for the 0° specimen, there is obvious strain concentration in the middle zone and the fracture is concentrated in the middle zone under the joint influence of tensile and shear action. As for the 45°specimen, the concentration zones of tensile strain and shear strain appear at the same time during the late loading period; there is an obvious bending at the bedding plane for fracture development and the fracture evolution is jointly controlled by tensile and shear action. For the 90° specimen, there is obvious tensile strain concentration during the whole loading process; the cracks developed parallel to the vertical bedding plane, and the failure of the specimen is controlled by the tensile action. The deformation field and strain field obtained by Micro-CT high-resolution in-situ scanning images combined with local and global DVC can reflect the deformation and failure law of anisotropic shale, which provide a method for studying the bedding effect of shale deformation evolution.

Key words: shale bedding plane, digital volume correlation (DVC), CT in-situ scanning, deformation field