Study on swelling deformation of GMZ bentonite infiltrated with salt solutions considering temperature effects

Investigation on swelling deformation of bentonite infiltrated with salt solutions considering temperature effects is of great significance for design and safely operation of deep geological repositories for disposal of high-level radioactive wastes. In this study, one dimensional deformation tests are performed on GMZ bentonite specimens with infiltration of NaCl and CaCl₂ solutions at different temperatures. Coupled temperature and salt solution effects on the swelling deformation properties are investigated. Meanwhile, MIP tests and SEM tests are performed to find out the micro-mechanism of the effects of temperature and salt solution on swelling deformation. Results indicate that the time to reach the maximum swelling strain is reduced and the maximum swelling strain decreases with increasing temperature and concentrations. In high concentration of salt solutions, the thickness of the diffuse double layers decreases, the osmotic suction and effective stress increase; meanwhile, the increase of temperature causes the shrinkage of inter-aggregate pores and the lattice contraction, and also inhibits the expansion of the diffuse double layers. As a result, the pore density of inter-aggregate pores decreases, the inter-aggregate pores are filled and blocked during the hydration process, and the swelling capacity of bentonite decreases. Finally, a model for the time-evolution curve of swelling deformation considering temperature and concentration of salt solution is proposed.