Abstract: The coupled thermo-hydro-mechanical (T-H-M) model for dual- pore-fracture media was degenerated into a model for single pore media; then this model and the gradient of rock dilatancy was introduced into the FEM code developed by the first author; also the Mohr-Coulomb yield criterion was used and the effects of dilatancy of plastic rock on porosity and permeability of rock mass were considered. Aiming at a model of hypothetical nuclear waste repository in a saturated porous rock mass with a laboratory scale, five computation cases with different values of rock dilatancy gradient were designed; then the corresponding numerical simulations for a disposal period of 4 years were carried out; and the states of temperatures, normal stresses, plastic zones, porosities and permeabilities, pore pressures as well as flow velocities in the rock mass were investigated. The results show that：compared with the case without considering dilatancy gradient, the distributions of normal stresses, porosities and permeabilities, pore pressures and flow velocities correspond to obviously the distributions of plastic zones, so some “shearing effects” are presented; all of the values of normal stress, areas of plastic zones, porosities and permeabilities, pore pressures and flow velocities increase with the raise of given dilatancy gradient.

Key words: rock dilatancy, porous media, elastoplastic model, thermo-hydro-mechanical (THM) coupling, finite element analysis