The Effect of Pore Solution on the Hysteretic Curve of Expansive Soil under Cyclic Loading

Abstract

A dynamic triaxial instrument was used to study the effects of different concentrations of sodium chloride and stress amplitudes on the dynamic properties of an expansive soil under cyclic loading. In particular, four parameters were considered in such a parametric investigation, namely, hysteresis curve morphology characteristic non-closure degree εp, the ratio of the short and long axis α, the slope of the long axis k and the enclosed area S. The results show that with an increase in the sodium chloride concentration, the soil particle double electric layer becomes thinner, the distance between soil particles decreases, and the whole sample becomes denser. The εp-N, α-N and S–N relation curves all show a decreasing trend. The ratio of plastic deformation to total deformation grows with increasing the dynamic stress amplitude, and the curves show an upwards trend. The k-N relationship curve displays an increasing trend with the concentration and a general downwards trend as the dynamic stress amplitude is made higher. This also indicates that sodium chloride solutions can improve the engineering properties of expansive soil to a certain extent. With an increase in the vibration times N, the shape of the hysteretic curve becomes narrower, and the whole soil exhibits a cyclic strain hardening. With the help of an exponential function, a model is introduced to predict the relationship between the concentration and the hysteretic curve.