Abstract：Triaxial rheological tests are carried out on marble samples from Jinping Hydropower Station on TLW–2000 creep testing machine. The stress-strain-time curves of the marble samples are obtained under the condition of step unloading confining pressure and constant axial pressure. According to the rheological deformation properties of marble samples under unloading condition，a 3D elasto-viscoplastic constitutive model based on Cristescu consititutive model is developed considering the effect of lateral unloading；and the parameters of the model are obtained. The model overcomes the defects of 3D component models which can not consider the effect of stress path and hardly show the lateral rheological deformation law. Comparison between the results obtained from the improved model and tests shows that the proposed rheological model can describe the overall rheological deformation law of rock with time under unloading stress path.
