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 ε p , 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 ε p -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.

Effects of Drying–Wetting Cycle and Fines Content on Hysteresis and Dynamic Properties of Granite Residual Soil under Cyclic Loading

“…(2) Unlike the other three parameters, as shown in Figure 5b, k increases sharply in the early load stage and then increases slowly, and moreover, k approximately changes linearly with LogN. [32,53]. The ratio of the decrease under the first 20 loads to the total decrease can be found in Table 2.…”

“…As shown in Figure 4, it is observed that the higher the number of loads, the smaller the area and the degree of opening, while the larger the degree of tilt. [32,53]. The ratio of the decrease under the first 20 loads to the total decrease can be found in Table 2.…”

“…In the study on peaty soils, Huang et al [29] considered the effect of confining pressure and loading frequency on the hysteresis curve. Zhu et al [30] took into account the stress amplitude on this basis and the factors affecting the hysteresis curve of expansive soils, which mainly include the confining pressure and loading frequency [31,32]. Different test factors can greatly affect the dynamic elastic modulus E d and damping ratio λ.…”

Experimental Study of the Dynamic Characteristics and Microscopic Mechanism of Lightweight Soil Modified with Expanded Polystyrene and Sisal Fibre

“…Figure 2 shows soil specimens with different EPS doping levels after the test (from left to right: EPS doping levels are 0, 5%, 10%, 15% and 20%). The magnitude of the dynamic modulus of elasticity [18] expresses the magnitude of the stiffness and elastic kinetic energy of the soil at a given dynamic stress amplitude. It is expressed as the slope of the line connecting the two endpoints of each hysteresis curve and it is given by the following:…”

“…This is because EPS has a lower strength relative to the soil and reduces the strength of the clay cementitious structure. When the dynamic load is increased, the soil with a higher dose of EPS undergoes greater deformation, the cement structure starts to breakdown slowly, pores and cracks gradually penetrate and the tendency of its dynamic strain The magnitude of the dynamic modulus of elasticity [18] expresses the magnitude of the stiffness and elastic kinetic energy of the soil at a given dynamic stress amplitude. It is expressed as the slope of the line connecting the two endpoints of each hysteresis curve, and it is given by the following:…”