Coupled thermo-hydro-mechanical-migratory model and fem analyses for dual-porosity medium

One kind of coupled thermo-hydro-mechanical-migratorymodel of dual-porosity medium for saturated-unsaturated ubiquitous-jointrockmass was established, in which the stress field and the temperaturefield are single, but the seepage field and the concentration field aredouble, and the influences of sets, spaces, angles, continuity ratios,stiffnesses on the constitutive relationship of the dual-porosity medium canbe considered, and also the corresponding two-dimensional program of finiteelement method was developed. Taking a hypothetical nuclear waste repositoryas a calculation example, the case in which the rockmass is unsaturateddual-porosity medium and radioactive nuclide leak was simulated numerically,and the temperatures, negative pore pressures, saturations, flow velocities,nuclide concentrations and principal stresses in the rockmass wereinvestigated. The results show that: (1) the negative pore pressures andnuclide concentrations in the porosity and fracture systems presentdifferent changes and distributions; (2) even though the saturation degreein porosity system is only about 1/10 of that in fracture system,the flow velocity of underground water in fracture system is about3 times of that in porosity system because the permeability coefficient offracture system is almost four orders higher than that of porosity system;(3) the value of nuclide concentration in fracture system is close to thatin porosity system in the medium.