Stress and pore pressure in saturated clay subjected to heat from radioactive waste: a numerical simulation

Some effects of temperature increase due to the emplacement of radioactive waste on the mechanical and hydraulic behavior of saturated clays are studied numerically. A mass-transfer model is adopted which simulates a possible degeneration of adsorbed water into bulk water at temperatures up to 150 °C. In contrast with a previous paper by the authors the heat output decreases with time to realistically simulate the effect of nuclear waste. Numerical results show that in the vicinity of the line heat source, a much lower value of excess pore pressure and faster propagation of the excess pore-pressure front are obtained because of the substantial increase in permeability arising from the adsorbed water degeneration at elevated temperatures. Moreover, the adsorbed water degeneration accelerates the water flow around the heat source. It is also concluded that over a long term the thermally induced degeneration of absorbed water into bulk water mitigates the possibility of thermal failure of clays surrounding t...