Prediction of Swelling Pressure of Compacted Bentonite with Respect to Void Ratio Based on Diffuse Double Layer Theory

Abstract

Compacted bentonite was chosen as the buffer and backfill material in high level nuclear waste disposal due to its high swelling pressure and low permeability. The estimation of swelling pressure is essential in design and construct the nuclear repositories. The swelling pressure model of compacted bentonite has been developed by former researchers based on Gouy-Chapman diffuse double layer theory. It is effective in predicting low swelling pressure (low compaction dry density), while it is invalidated in simulating high swelling pressure (high compaction dry density). Based on the published literature data of MX80 bentonite, the new relationship between nondimensional midplane potential function, u, and nondimensional distance function, Kd, is established. The new relationship is based on the Gouy-chapman theory by considering the variation of void ratio. The proposed equations are applied to compute swelling pressure of other bentonites (FEBEX, Bavaria bentonite, Bentonite S-2, FoCa bentonite and GMZ bentonite) based on the reported experimental data. Results show that the predicted swelling pressure has a good agreement with the experimental swelling pressure.