Experimental Study on Effects of NaCl Solutions on Soil-Water Characteristic Curves of Expansive Soil

Soil-water characteristic curve (SWCC) is an important characteristic of unsaturated soil. This paper investigates the total suction of the MX-80 bentonite, under different saturation and different concentrations of sodium chloride solutions. To create the soil-water characteristic curves for different amounts of NaCl, but same dry densities, the study used chilled-mirror dewpoint WP4 potentiometer. The experimental results show that the concentration of salt in pore water has significant influence on the bentonite. With the increase of the NaCl concentration, the samples total suction increased gradually and the matric suction decreased. When the soil saturation was greater than 50%, the pore solution’s addition led to the rapid increase of the soil’s total suction. The
low concentration of salt has relatively little effect on the matric suction of the MX-80 bentonite; while when the ion concentration is high, the solutions’ matric suction has a very significant impact on the soil matric suction.