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

Investigation on swelling deformation of bentonite infiltrated with salt solution considering temperature effects is of great significance for design and safely operation of deep geological repositories for disposal of high-level radioactive waste. In this study, one dimensional deformation tests were 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 were investigated. Meanwhile, MIP tests and SEM tests were 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 was reduced and the maximum swelling strain decreased with increasing temperature and concentrations. In high concentration of salt solution, the thickness of the diffuse double layers decreased, the osmotic suction and effective stress increased; meanwhile, the increase of temperature caused the shrinkage of inter-aggregate pores and the lattice contraction, and also inhibited the expansion of the diffuse double layers. As a result, the pore density of inter-aggregate pores decreased, the inter-aggregate pores were filled and blocked during the hydration process, and the swelling capacity of bentonite decreased. Finally, a model for the time-evolution curve of swelling deformation considering temperature and concentration of salt solution was proposed.