Correlation between permeability, swelling, and plasticity of sodium bentonite

Abstract:

The chemical compatibility study between salt solution and sodium bentonite plays an important role in evaluating the service performance of the antifouling barrier. Effects of different concentrations of NaCl solution and CaCl₂ solution on the permeability, swelling characteristics, and plasticity of sodium bentonite were studied by hydraulic conductivity test, free swell test, and water ratio limit test. Experimental results show that as the concentration of the cations in the solution increased, the hydraulic conductivity of the sodium bentonite increased, the swell index first increased and then decreased, and the plasticity index decreased. At the same concentration, the hydraulic conductivity of the sodium bentonite in NaCl solution was lower than that in CaCl₂ solution, and the swell index and plasticity index were both higher than those in CaCl₂ solution. Within the consolidation pressure range of 12－800 kPa, the hydraulic conductivity had a strong correlation with the swell index and plasticity index in CaCl₂ solution; in NaCl solution, when the solution concentration exceeded the critical concentration (200 mmol/L), the hydraulic conductivity also had a strong correlation with the swell index and plasticity index. Therefore, it is feasible to replace the hydraulic conductivity test with water ratio limit test and free swell test.