Comments on the mode II fracture from disk-type specimens for rock-type materials

Laboratory determination of the mode II fracture toughness KIIC for rocks and rock-type materials remains a challenge task. One of the testing approaches is the compression of disk-type specimens, which is simple and convenient. However, although the notch in disk-type specimen is under mode II loading, the detailed studies reveal the drawbacks about interpretations of the disk-type specimens: (i) mode II fracture is only assumed without careful...