|dc.description.abstract||In a final disposal site for radioactive wastes, the evolution of the near field is mainly controlled by the thermo-hydro-mechanical-chemical (T-H-M-C) effects. The coupling effects have a direct impact on the deterioration of the buffer material, and therefore the effects of various near field environmental factors on the swelling behavior of the buffer material must be analyzed.
In this study, SPV 200 bentonite compacted to a dry density of 1600 kg/m^3 was tested for one-dimensional swelling pressures, with considerations on simulation decay heat, groundwater chemistry, pH environment, and the vertical stress effect. Results from the study show:
(1) SPV 200 bentonite at 65℃ water - heat solution exhibited a rapid development of bentonite swelling pressures, and increases in temperature cause decreases in swelling pressure;
(2) in NaCl and CaCl2 solution, the swelling pressure of bentonite decreases with increasing cation concentration, and the effect of NaCl on swelling pressure is more pronounced;
(3) at solutions with pH < 13, no significant reduction on swelling pressure was observed;
(4) as illustrated by XRD and ICP analysis, SPV 200 bentonite in NaOH [1.0M] solution shows decreases in montmorillonite and quartz minerals, while the Si ions exhibits obvious increase;
(5) one-dimensional swelling tests showed that the amount of swelling is highly dependent on the vertical stresses applied on bentonite.||en_US|