EVOLUTION OF BARRIER PROPERTIES FOR GAOMIAOZI BENTONITE UNDER CHEMICAL EFFECTS

In the high-level radioactive waste deep geological disposal,the properties of engineering barrier made up of bentonite are probably weakened under chemical effects originating from natural groundwater and possible leaked nuclides. This paper aims to summarize the latest researches about the evolution of barrier properties for Gaomiaozi(GMZ)bentonite under chemical effects. The basic physical properties of GMZ bentonite and the chemical environment in Beishan China are introduced first. Subsequently,the barrier properties involving hydraulic,mechanical and retardant under chemical effects are analyzed systematically. Results show that the chemical effects on the water retention and permeability relate to osmotic suction and diffuse double layer theory respectively. The attenuation of swelling pressure under chemical effects can be explained by the hydration mechanism of bentonite. The deformation properties under the chemical-mechanical coupling or chemical-hydraulic-mechanical coupling conditions would change owing to osmotic consolidation and chemical softening effect. The adsorption and diffusion properties of bentonite are affected by nuclide concentration,ionic environment,pH value and other factors. Finally,we summary the key research challenges and suggest directions for future works.