3D joint elements and relevant numerical analysis for simulating coupled thermo-hydro-mechanical processes

Considering the influence of temperature and pore pressure, the stress-displacement relationship of a 8-node isoparametric space joint element with a constant thickness is expanded, so the momentum equilibrium equation, the continuity equation for water and the energy balance equation are established correspondingly for analysis of the coupled thermo-hydro-mechanical processes in saturated-unsaturated rockmass with discontinuities. Combining the joint elements with the solid elements, a relative 3D FEM code is developed. Against an assumed model of geological disposal of nuclear waste, numerical analyses are carried out for the cases with and without joints. The computed results show: compared with the case without joints, the existence of joints causes obvious changes of the distributions and the values of temperature, stresses and velocities of water flows in the near-field rockmass, and especially some cooling effects of water flows and stress concentrations to a certain extent in the rockmass near the joints, and the stresses in other parts of the rockmass also increase.