Damage Evolution of Onnagawa Shale by Postmortem Thresholding of X‐Ray Computed Tomography

Onnagawa shale samples are deformed through the brittle‐ductile transition by increasing the confining pressure. Brittle deformation is characterized by longitudinal splitting of the sample at 3% axial strain. A distributed conjugate fracture network characterizes the macroscopic deformation in the ductile field with strain hardening. The onset of transition from brittle to ductile deformation is between 4% and 5% axial strain with a single...