Influences of salt solution concentration and vertical stress during saturation on the volume change behavior of compacted GMZ01 bentonite

• Oedometer test was conducted on specimen swollen under vertical pressures.
• Swelling strain decreases as the concentration or vertical pressure increases.
• Compressibility decreases as the concentration or vertical pressure increases.

Investigation of the effects of salt solution concentration and vertical stress during saturation on the volume change behavior of compacted bentonite is of great importance for the assessment of the behavior of engineering barrier in deep geological repository for disposal of high-level radioactive waste. In this study, oedometer tests were conducted on densely compacted GMZ01 bentonite specimens with an initial dry density of 1.70 Mg/m3, which experienced swelling under different vertical stresses with infiltration of de-ionized water or NaCl solutions at different concentrations. The effects of salt solution concentration and vertical stress during saturation on the volume change of GMZ01 bentonite specimens were investigated in terms of swelling strain, elastic compressibility parameter, plastic compressibility parameter and yield stress. Results show that as the concentrations of salt solutions increase, the swelling strain, the elastic compressibility parameter and the plastic compressibility parameter decrease, while the yield stress increases. However, the vertical stress during saturation can only affect the swelling strain and the yield stress. Based on the test results, empirical equations with consideration of salt solution concentration and vertical stress during saturation effects were proposed allowing the prediction of swelling strain, plastic compressibility parameter and yield stress. The calculated results are in good agreement with the experimental ones.