FAILURE CRITERION FOR TRANSVERSELY ISOTROPIC ROCK MATERIALS

 For rock materials, a transversely isotropic failure criterion, established through the extended Lade-Duncan failure criterion incorporating an anisotropic state scalar parameter which is a joint invariant of deviatoric microstructure fabric tensor and a normalized deviatoric stress tensor, is verified by Tournemire shale triaxial compressive testing data. When the angle between the loading direction and principal direction of the transversely isotropic microstructure of rock material is changed from 30° to 60°, corresponding lower failure strengths are predicted, which is agreed with testing results. These predicting results show that the transversely isotropic failure criterion is reasonable.