Abstract: In deep geological disposal of high-level radioactive waste (HLW), the thermal conductivity of host rock is a key factor in design because it has a direct impact on the repository layout and the optimization of distance between disposal elements. This study aims at investigating the thermal conductivity characteristics of Beishan granite treated with different temperatures ranging between 200 ℃ and 800 ℃. The influence of thermal treatment on thethermal conductivity of Beishan granite is analyzed, and the relations between thermal conductivity and other conventional physical parameters are also discussed. The effect of water saturation on the thermal conductivity is revealed as follows: 1) the thermal conductivity of Beishan granite specimens decays as treatment temperature rises, and the decay rate reaches peak value in the temperature range between 550 ℃ and 650 ℃; 2) as treatment temperature rises, the mass,dry density and P-wave velocity of specimens increase in general while the volume and porosity of specimens present an increasing trend; according to the relations between thermal conductivity and P-wave velocity, porosity, and dry density, respectively,models are established to predict the thermal conductivity of thermal-treated specimens; 3) before thermal treatment, the thermal conductivity values of saturated specimens increase by 9.7%-12.1% compared with those of dry ones,and the thermal conductivity of saturated specimens increases in an approximately linear trend with the increase of thermal conductivity of dry specimens; 4) on the other hand, when the thermal-treated specimens were saturated with water, the thermal conductivity shows a slightly decreasing trend as treatment temperature rises. We also found that the effect of water saturation on thermal conductivity increases with the increase of rock porosity, and this behavior can be described reasonably using a linear equation. The research achievements provide a theoretical basis for the design and optimization of deep geological disposal engineering.

Key words: Beishan granite, thermal treatment, thermal conductivity, geological disposal of high-level radioactive waste, water saturation effect