A water retention curve model describing the effect of temperature

Abstract

Properly simulating multiphase flow involving non-isothermal processes in unsaturated soils requires the development of water retention curve (WRC) models with temperature effects. However, the majority of the existing WRC models are developed for isothermal conditions. This study aims to develop a new WRC model describing the effect of temperature on suction. Based on an assumption of an isotropic and homogeneous porous medium at the macroscopic scale, the formulations of non-isothermal suction account for the temperature effects on the surface tension of the water–air interface and air bubble shape. The tension of the water–air interface is expressed as a function of temperature, and the air bubble shape becomes a function of temperature and saturation degree. The suction formulations are then used to extend the van Genuchten equation to non-isothermal conditions. The final equation of the proposed model is a function of suction, and effective degree of saturation and temperature. A laboratory test was also designed to measure the WRCs of a loamy sand at different temperatures. The proposed model was validated against the measured results as well as experimental data of clayey-silt sand, Boom clay and FEBEX bentonite reported in the literature. The very good agreements show the capability and feasibility of the model to predict the temperature dependence of water retention behaviour with a wide range of soils. Highlights: A new WRC model was developed for non-isothermal conditions. The model considers temperature effects on water surface tension and air bubble shape. We tested the model against measured and literature data, with very good agreements. The model is applicable to predict non-isothermal water retention behaviour of unsaturated soils.