Abstract:

Based on the differential control equations of the coupled thermo-hydro-mechanical processes of dual media, a three dimensional coupled model of dual media to research coupled thermo-hydro-mechanical(THM) processes of fractured rock masses, is proposed. In coupled model, the values of nodal displacement, water pressure and temperature in different media were solved. A three dimensional FEM code. for analysis of coupled thermo-hydro-mechanical processes of dual media is developed tentatively, in FEM program, 3D jointed elements with 8 nodes were used to simulate the crack elements during the stress analysis of discontinuities; and 2D isoparametric elements with 4 nodes were used to simulate discontinuities during seepage and heat energy analysis of discontinuities. So the different media can exchange water and heat flux, water head, temperature and displacement of nodes which are in the interface between two models were equal. Through the numerical computation for heat extraction in HDR; it is shown: that in the thermo-hydro-mechanical coupling process, discontinuous is in low stress state; the crack width increases nonlinearly with the heat extraction; in transient fluid flow stage, the water head in discontinuities was higher than equivalently continuous rock medinm; in steady fluid flow phase, the dominant effect of discontinuities on fluid flow would unconspicuous. Because of massive heat replenishment, the compact of discontinuities on temperature distribution was indistinctive.

Key words: discontinuities, dual media, thermo-hydro-mechanical coupling, jointed element, finite elements