Elastoplastic Model for Transversely Isotropic Rocks

Abstract

The structure of the layered rocks is characterized by oriented bedding planes, resulting in transverse isotropy in deformation and strength. An elastoplastic constitutive model was proposed for transversely isotropic (TI) rock in this study. In the model, the generalized Hooke’s law was adopted for the elastic behavior. For the plastic behavior, the yield criterion and plastic potential are formulated as functions of the generalized octahedral shear stress and the first invariant of stress tensor. A nonassociated flow rule and a stress-dependent hardening rule were adopted in the model. The plastic model can be simplified to the Drucker-Prager model for isotropic rocks. A methodology for the determination of model parameters was developed. The parameters can be determined by combining triaxial compression tests with torsion tests on specimens with different bedding directions. The constraint on plastic parameters was theoretically identified. The proposed model and the parameter determination methodology were applied to modeling the TI elastoplastic property of carbonaceous slate in triaxial compression. The results show that the model proposed in this study can well describe the transverse isotropic elastoplastic property of the rock, and the parameter determination methodology is simple and effective.