Influence of temperature on the water retention properties of compacted GMZ01 bentonite

Investigation of the temperature effects on the water retention properties of compacted bentonite is of great importance in the context of geological disposal of high-level radioactive waste (HLW) based on the multi-barrier concept. Gaomiaozi (GMZ) bentonite, collected from the Inner Mongolia Autonomous Region of China, has been selected as a potential buffer/backfill material for the construction of Chinese HLW deep geological repository. In this study, soil water retention curves (SWRCs) of both confined and unconfined compacted GMZ01 bentonite specimens with an initial dry density of 1.70 g/cm3 were investigated at temperatures 20, 40, 60 and 80 °C. Results indicate that the water content decreases as temperature rises, even though the temperature effects on the water retention capacity of compacted GMZ01 bentonite depend on constraint-conditions. The influence of constraint conditions is more significant at relatively low suctions. Under unconfined conditions, the temperature effect is insignificant. However, under confined conditions, the influence on the water retention capacity is found to be significantly suction dependent. The hysteresis behavior of unconfined compacted bentonite becomes less significant as temperature increases. Based on the corresponding results obtained, a modified model was developed for describing the SWRCs of confined compacted GMZ01 bentonite with consideration of temperature effects. It appears that the calculated SWRCs agree well with the experimental ones, indicating that the modified model can satisfactorily describe the effect of temperature on the water retention properties of confined compacted GMZ01 bentonite.