Abstract: Physical and mechanical properties of bentonite-sand mixtures have important influence on the stability and safety of a high level radioactive waste repository when they are used as buffer materials for high level radioactive waste repository, which may be affected by the decay heat released from high level radioactive wastes. Some heat conduction simulation tests for small samples with different dry density, water content, and sand content were carried out using a designed device in our study. The thermal-mechanical coupling process of buffer layer was simulated and analyzed, and variation and distribution of temperature, stress and strain of buffer layers were obtained with a focus on the influence of temperature. The results show that the increasing of dry density, water content and sand content can increase thermal conductivity and strain, stress is affected by temperature and reaches equilibrium earlier, and the temperature, stress and strain of buffer layer near heat source are the largest and decrease along the axial direction, with obvious change at the initial period.

Key words: bentonite-sand mixtures, thermal conduction device, buffer layer, thermal-force coupling, numerical simulation