A constitutive model for rock materials subjected to triaxial cyclic compression

Abstract

Underground rock engineering projects are often subjected to cyclic loading such as earthquake, rock blasting. A suitable constitutive model for rock materials modeling the deformation failure characteristics of rock materials subjected to triaxial cyclic loading is significant when evaluating the long-term stability of the engineering. To date, however, there have been notably few studies on proposing constitutive models for rock materials under triaxial cyclic loading. The paper presents and validates the formulation of a new constitutive model able to reproduce the cyclic behavior of rock materials under triaxial cyclic loading. The constitutive model is based on the subloading surface theory and the modified cohesion weakening and frictional strengthening (CWFS) model. It contains kinematic hardening of the subloading surface, isotropic softening on the cohesion and isotropic hardening on the friction angle, and the effect of confining stress. Further, the model is numerically implemented in a self-developed finite element program using elastic prediction-plasticity correction method. In addition, the model is validated against two different rock materials (T2b marble and crystalline marble) under triaxial damage-controlled and constant amplitude cyclic compression loading. A reasonable consistency is observed between the numerical and experimental results for the stress-strain curves, the evolution of residual strain with number of cycles, degradation of strength and the effect of confining stress. It shows that the model can effectively reproduce the cumulative plastic deformation, hysteretic loop, damage and the effect of confining stress of rock materials under triaxial cyclic loading. Therefore, the proposed model can provide a helpful method to describe the main deformation and strength properties of rock materials under triaxial cyclic loading, and lays a foundation for the accurate analysis of the response of underground rock engineering under cyclic loading.