Effective stress incorporating osmotic suction and volume change behavior of compacted GMZ01 bentonite

Investigation of osmotic suction effects on the volume change behavior of clay is of great importance in evaluating the performance of engineering barrier in deep geological repository for the disposal of high-level radioactive waste. From the effective stress principle point of view, the linear relationship between the concentration of salt solution and osmotic suction described by the common van't Hoff equation is not consistent with the experimental results, because the salt solution (or osmotic suction) effect on the swelling behavior and compressibility became insignificant when the concentration of salt solution was higher than 2.0 M. Meanwhile, the osmotic suctions described by Lang (Aust J Chem 20(9):2017-2023, 1967), Rao et al. (Geotechnique 56(10):707-713, 2006) and Witteveen et al. (Geotechnique 63(3):244-255, 2013) are also not consistent with the effective stress principle. In this study, the influence of osmotic suction on swelling behaviors was explained from the crystalline swelling and the double-layer swelling for specimens with a void ratio higher than 0.5. According to the experimental observations, a new effective stress equation was proposed with consideration of osmotic suction effects for the compacted GMZ01 bentonite specimen with a void ratio higher than 0.5. Finally, the proposed equation was verified based on the observations of the swelling and oedometer tests conducted on as-compacted GMZ01 bentonite specimens.