Experimental study on heat and moisture coupling migration behavior of unsaturated bentonite buffer materials for high-level radioactive waste repository

This paper independently developed a set of experimental equipment that can approximately simulate the service working environment of unsaturated bentonite buffer. By conducting heat and moisture transfer experiments on unsaturated bentonite under the combined action of heating-cooling path and water erosion conditions, the evolution laws of temperature, humidity, electrical conductivity at different locations away from the heat source, as well as the heat and moisture coupling migration behavior were studied. The results show that during the heating-cooling process, the temperature evolution laws is similar at different positions away from the heat source. Although the temperature of the heat source reaches 100°C, its impact range is relatively small. The evolution law of humidity varies greatly at different positions, and is significantly influenced by the temperature field, as well as the coupling effect of hydraulic field. The change in electrical conductivity is basically consistent with the change in humidity, and is also subject to the combined coupling effect of temperature field and hydraulic field. Under the condition of no water erosion and increasing heating/cooling rate, the amplitude of temperature change decreases, and humidity and electrical conductivity show a trend of migration away from the heat source throughout the heating cooling stage.