Abstract:
The service life of underground engineering is so long that the creep deformation of the surrounding rock can be intensified in the water environment. The permeability shows an anisotropic trend under the three-dimension stresses. The rock is simplified as a cube model, and a rock creep permeability model is established in stages based on the creep characteristics. At the viscoelastic stage, the ratio of viscosity coefficients between cracks and rocks is defined, and a lateral influence coefficient is introduced to represent the influence of lateral stress on crack opening. In the viscoplastic stage, a correction coefficient is defined to represent the influences of cracks on seepage channels. An anisotropic creep-permeability model is established combined with the anisotropic creep damage model for rock, cubic law, and the permeability model for fractured rock. The creep-seepage tests under true triaxial conditions are performed, and the anisotropic creep-permeability model is validated. The parameters can be determined and the permeability evolution under different conditions is analyzed. The proposed model shows the higher accuracy by comparing with the traditional K-C model and the previously anisotropic creep-permeability model. It can be used to describe the trend that the permeability decreases due to the gradual compaction of pores and cracks at the viscoelastic stage, and it increases suddenly caused by the gradual convergence of cracks at the accelerated creep stage. The sensitivity analysis is conducted on the parameters in the anisotropic creep-permeability model. As the viscosity coefficient ratio increases, the permeability decays fast and the stable permeability decreases. As the viscosity coefficient increases, the initial decay rate of permeability increases, and the stable permeability decreases. At the accelerated creep stage, as the correction coefficient increases, the permeability increases significantly.