Swelling pressure and hydraulic conductivity of compacted GMZ01 bentonite under salinization-desalinization cycle conditions

Abstract : Compacted bentonite has been used as buffer material in radioactive waste disposal. Once compacted bentonite is emplaced, the chemical composition of site water is changed due to the long-term interaction between the bentonite, surrounding rock and the concrete facility; therefore the hydraulic mechanical behavior of compacted bentonite should be evaluated for the disposal safety. In this study, the swelling pressure and hydraulic conductivity of compacted GMZ01 bentonite were investigated under salinization desalinization chemical cycles using a newly developed apparatus. Results show that the salinization process leads a reducing of swelling pressure and the desalination process leads to an increasing of swelling pressure; the hydraulic conductivity increases in the salinization process while decreases in the desalinization process. The variation magnitude of the swelling pressure and hydraulic conductivity is related to the solution concentration applied. Meanwhile, the initial chemical condition and chemical cycle paths have a significant effect in the swelling characteristics and hydraulic properties. Since the salinization-desalinization cycle is expected to occur over a long time during the operation of the repository, the monitoring of the buffer materials will be important for the disposal safety.