An insight into the swelling pressure of GMZ01 bentonite with consideration of salt solution effects

Investigation of the swelling pressure of compacted bentonite is of great importance in evaluating the performance of the engineered barrier system in deep geological repositories for disposal of high-level radioactive waste. In this study, three methods including Cui method (Cui et al., 2013), swell-consolidation method and constant-volume method were employed for determining the swelling pressure of compacted GMZ01 bentonite with infiltration of different concentrations of salt solutions. The swell-consolidation method gave higher value of swelling pressure, while the other two methods produced almost the same values. A critical void ratio was determined for separating the swelling induced by combination effects of double-layer swelling and crystalline swelling from that caused by the effect of crystalline swelling. Based on this, the salt solution effect on swelling pressure can be well explained. For specimens with a void ratio higher than this critical value, swelling pressure decreases with the increase of concentration of NaCl solution, due to the inhibition of the double-layer swelling and crystalline swelling. On the contrary, in case of void ratio near this critical value, the salt solution effects become negligibly. Conclusions reached on GMZ01 bentonite in this work are useful for determination of geological engineering parameters for construction of the Chinese deep geological repository.