Creep Test of Hard Rock and Modified Generalized Kelvin Creep Model

Abstract

By a circular increment step load and unload method, a set of rheological experiments were performed to study the creep properties of amphibolite and the deformation data of instantaneous elasticity, instantaneous plasticity, viscoplasticity and viscoelasticity could be obtained. The results showed that: the creep threshold of amphibolite(σs1) was 25.46MPa; whenσs1s2, the proportion of plastic deformation in the total deformation was very small and the value of creep deformation always tended to a stable value; whenσ>σs2, the rock samples failed rapidly and had no obvious creep. According to the creep and failure properties of amphibolite, the generalized Kelvin creep model was acted in series with the Mohr-Coulomb criterion and a modified generalized Kelvin creep model was built and the corresponding visco-elasto-plastic constitutive relationships were deduced. The modified model could simulate visco-elasto-plastic deviatoric behavior and elasto-plastic volumetric behavior. The model parameters of amphibolite were fitted according to the data of rheological test. The testing curves were coincident well with the theoretic curves by comparison which showed the creep properties and the plastic flow of hard rock could be well simulated by the generalized Kelvin creep model.