Calculation of Osmotic Suctions for Bentonite in Saline Solutions

Bentonites are usually selected as the engineered barrier material of repositories for radioactive waste. The saline solution from surrounding rock fissures can affect the mechanical behaviour of bentonite for the reason that the osmotic suction in pore water can act as an additional total stress component on bentonite. The osmotic coefficient, as the key to calculate the osmotic suction, is usually obtained by measuring the vapor pressure of a solution and that of the pure solvent with a differential manometer in experimental method. Considering that the vapor pressure is affected by many factors such as solute type, concentration, and temperature, it is very complicated to obtain the osmotic coefficient by experimental method. In this paper, the osmotic coefficient is calculated according to the modified Debye-Hückel equations and the calculated results are validated by comparing with the experimental data in other literature. In this way, the osmotic suction for different solutions under different temperatures can be obtained by calculation.