The measurement of hydraulic conductivity of unsaturated bentonite is verydifficult because of the fact that the bentonite volume would expand and shrink with the increase and decrease of water contents, respectively.In this study, following instantaneous profiling method, a new multi-ring wasapplied in wetting apparatus to ascertain water diffusivities of Kunigel-V1bentonite with different dry densities. Hydraulic conductivities of unsaturatedKunigel-V1 bentonite were calculated combining water diffusivities and soilwater retention curves (SWRC). The SWRC was determined by immersing the 5mm-heightKunigel-V1 bentonite for different durations. Then, the total suction of the Kunigel-V1bentonite was obtained with WP4C dew-point potentiometer. Then, the SWRC wasfitted with VG model and the fitting parameter was used for the calculating of hydraulicconductivity during saturation. The results from this study can be concluded as:1) It is found that water diffusivity decreases with the increasing watercontent; 2) The SWRC obtained by using the 5mm-height specimen can fitted well withthe VG mode; 3) In the saturated state, the degree of saturation of Kunigel-V1 bentonitecan exceed 100%, which can be explained as the water density in bentonite exceeds1 g/cm3; 4) The hydraulic conductivity increases firstly with increasingwater content and then decreases with the rise of water content; 5) The hydraulicconductivity of unsaturated Kungel-V1 decreases with increasing dry density.

Addressing issuesrelated to high level radioactive waste(HLW) from nuclear power industry is an important task for researchers. Deep geological disposal method, which intends to seal HLWdeeply underground, was chosen by many countries to deal with HLW. In a Japanese deep geological disposal project,a multi-barrier system, including vitrified waste, stainless over-pack containers, buffermaterials, and hostrock, is planned to be constructed more than 300 munderground to prevent the leakage of HLW. As indicated by numerous studies, bentonites and theirbased materials were selectedas candidate buffer materials because of their low permeability. Pelletedbentonite has recently been considered as a candidate buffer material. Thepurpose of using pelleted bentonite as a buffer material is to avoid thechallenges identified in the full-scale mock-up study, such as improvedworkability during barrier installation. Bentonite pellets can be installedusing pneumatic projection techniques, which makes backfilling operationseasier and potentially robotic.In addition to low permeability, anotherimportant characteristic of bentonite is its highself-healing ability. As important ingredients for evaluating self-healing capacity, swellingpressures (ps) duringsaturation, including pressures at peak (ppeak),valley (pvalley), re-peak(pre-peak) and equilibrium(peq) points in swellingcurve had beenstudied by experiments. Amongthose swelling pressures, most scholars examined peq instead of ppeak,pvalley, and pre-peak. However, experimental conditions strongly affect ppeak, pvalley and pre-peak.Meanwhile,findings from the study of ppeak,pvalley, and pre-peak can elucidate the swelling mechanisms duringsaturation. Devoting greaterattention and making greatereffort to assess ppeak, pvalley, and pre-peak are necessary.In this study, swelling pressure tests were conducted at25, 50, and 80 °C to elucidate temperature effect on swelling pressures at peak, valley, re-peak andequilibrium points (ppeak,pvalley, pre-peak and peq) in swelling pressure evolution curve. A pellet bentonite, Kunigel-GX,was used to investigate ppeak,pvalley, pre-peak, and peqat different temperatures. Experimentallyobtained results were the followings: 1) ppeak, pvalley, pre-peak, and peq of Kunigel-GX decreased as temperature rises and increased as dry density increases; 2) Kunigel-GX was found to have larger values of (peq-pvalley) at higher dry density and lower temperature conditions.