Modeling the combined effect of initial density and temperature on the soil–water characteristic curve of unsaturated soils

Abstract

The soil–water characteristic curve (SWCC) plays an important role in solving the stability and deformation problems of unsaturated soils. In many practical situations, soils are usually experienced by both deformations and thermal conditions. In this interest, the paper proposes a simple and effective model to predict the combined effect of initial density and temperature on the SWCC and to be able to quantify the changes in thermal-hydro-mechanical behavior of unsaturated soils. In the first step, an initial density-dependent SWCC model is presented using the translation principle between particle-size distribution curve and soil–water characteristic curve. In the second part, a non-isothermal model is proposed to predict the effect of temperature on the SWCC. The key to the non-isothermal model is considering five different temperature-dependent functions, which are surface tension, contact angle, particle-size expansion, void ratio, and water density. On the basis of 22 data sets of thermal volume change, this study also developed further a theoretical correlation between void ratio and temperature that is directly related to soil plasticity. It was observed that the value of the thermal void ratio increases as soil plasticity increases, and there is a nonlinear relationship between the plasticity index and the void ratio. Because of this, soils with high plasticity are more susceptible to volume changes caused by temperature fluctuations than soils with low plasticity. A coupled mechanical–thermal model is then produced which is capable to predict separately or simultaneously the effect of temperature and initial density on SWCC. The proposed model is validated against several test data sets available in the literature. The results show that the proposed model has a good performance in predicting the variation in SWCC with arbitrary temperature and initial density.

Experimental Investigation of the Soil-Water Characteristic Curves (SWCC) of Expansive Soil: Effects of Sand Content, Initial Saturation, and Initial Dry Unit Weight

“…However, significant variations in soil density can be introduced by external factors and stress conditions of the soils. This intricacy highlights how crucial it is to investigate how density affects the SWCC, making it an engaging and extensively researched topic of broad interest [32][33][34][35][36]. Chen et al [29] found that higher initial dry density led to increased water retention capacity.…”

Thermal Effects on the Soil Water Retention Curves and Hydraulic Properties of Benggang Soil in Southern China

“…However, it does not provide a complete explanation of the temperature-influence mechanism of the SWRC. Numerous studies have demonstrated that as soil temperature increases, additional variables, including soil air retention, the thermal expansion of water, alterations in the soil-water contact angle, and modifications to the soil pore distribution, also contribute to variations in soil hydraulic properties [16][17][18][19]. However, the investigation of temperature on soil hydraulic characteristics in the Benggang area is limited.…”