Effect of hydrothermal path on swelling pressure and hydraulic conductivity of compacted bentonite

As a buffer material in a high-level radioactive nuclear waste repository, bentonite is subjected to the decay heat released by nuclear waste and the infiltration of groundwater from the surrounding rock. The sequential effects of temperature and water saturation are still unknown. The functional barrier effectiveness of the buffer layer is partly dependent on whether the hydrothermal path affects bentonite’s self-sealing. Thus, the swelling pressure and saturated hydraulic conductivity tests were carried out with three hydrothermal paths to investigate whether the hydrothermal path affected the barrier function of bentonite. The results revealed that the sequential effects of temperature and water saturation had little influence on the swelling pressure and hydraulic conductivity of bentonite. However, a high-temperature history can cause a significant deterioration in the swelling pressure and increases in hydraulic conductivity, which are mainly due to losses of exchangeable cations and the cementation formed between clay particles. Therefore, the temperature history should be taken into account for investigating the long-term performance of the buffer layer bentonite.