Abstract：Regarding single rock fracture as a non-associated elastic-perfectly plastic medium，an analytical model of the mechanical aperture and the hydraulic conductivity is developed for the fracture subjected to normal and shear loadings，and the model is validated by an existing shear-flow coupling test under wide range of constant normal stress and increasing shear displacement. On this basis，by regarding rock mass as an anisotropic continuum with one or multiple sets of critically oriented fractures，a methodology is developed to address the change in hydraulic conductivity resulted from engineering disturbance under the framework of material nonlinearity. An equivalent non-associated elastic-perfectly plastic constitutive model with mobilized dilatancy is presented to describe the global nonlinear response of the rock system under complex loading conditions. By resolving the deformation of fractures from the equivalent medium，a strain-dependent hydraulic conductivity tensor suitable for numerical analysis is formulated，where the normal compressive deformations of the fractures are considered；and more importantly， the effects of material nonlinearity and post-peak shear dilatancy are integrated. The proposed model is capable of describing the reality of the post-peak dilatancy behavior，deformation characteristic and changes in hydraulic conductivity of a real fracture and fractured rock mass by using non-associated flow rule with a mobilized dilatancy angle. Numerical simulations are performed to investigate the changes in hydraulic conductivities of rock masses under mechanical loading or excavation.
