Abstract: Expansive soil is a special kind of soil, which inevitably involves infrastructure construction such as roads and railways. However, the change of pore solution environment has a comparatively great impact on expansive soil. In this study, a cyclic load test on expansive soil in NaCl solution was carried out by using GDS true/dynamic triaxial instrument. The dynamic characteristics of expansive soil under the change of pore solution concentration were studied, and the cumulative deformation and damping ratio of expansive soil in NaCl solution with different concentrations under different dynamic stress amplitudes were analyzed. The results show that as the concentration of NaCl solution increases, the cumulative deformation of expansive soil decreases; and as the amplitude increases, the cumulative deformation gradually increases. According to the vibration frequency-accumulative deformation curve of expansive soil under different concentrations and amplitudes, a single exponential function is used to fit and judge it. The damping ratio curve of expansive soil under different NaCl solution concentrations gradually separates with the increase of the amplitude; the damping ratio gradually decreases with the increase of the concentration, and gradually increases with the increase of the amplitude. A model of the relationship between concentration and average damping ratio is established to provide reference for actual engineering.

Key words: expansive soil, NaCl solutions, cyclic loading, electrical double layer, cumulative deformation, damping ratio