Influence of salt solutions on the swelling behavior of the compacted GMZ01 bentonite

During the long-term operation of a deep geological repository, infiltration of pore fluids with different chemical compositions can influence the swelling behavior of the compacted bentonite. In this paper, using a self-developed swelling deformation apparatus, one-dimensional free swelling tests were conducted on densely compacted GMZ01 bentonite specimen with an initial dry density of 1.70 g/cm3, with infiltration of de-ionized water, NaCl, or CaCl2 solutions at different concentrations. Results show that the swelling strains of GMZ01 bentonite specimens infiltrated with salt solutions were significantly lower than that of those infiltrated with de-ionized water. In fact, the swelling strain decreased in a form of power function with the increasing concentration of infiltration solutions. For a given concentration, the one-dimensional swelling strain of specimens contacted with NaCl solutions was higher than that of the specimens infiltrated with CaCl2 solutions. However, the difference of the swelling strains decreased with increasing concentrations. This phenomenon could be explained by the impact of cation types on the microstructure of bentonite.