Temperature-Dependent Models for Soil Water Retention Curve and Effective Stress of Unsaturated Soils

Vahedifard, F., Thota, S. K., Cao, T. D., & Ghazanfari, E. (2019). Temperature-Dependent Models for Soil Water Retention Curve and Effective Stress of Unsaturated Soils. Engineering Mechanics Institute Conference. Caltech, CA.

Many near-surface geotechnical and geoenvironmental applications involve elevated temperatures, which can affect the mechanical behavior of unsaturated soils. There has been an increasing interest toward fundamental and applied research to study the behavior of unsaturated soils under elevated temperatures. However, major gaps remain in the development of unified models that can properly represent temperature dependency of unsaturated soils behavior. The soil water retention curve (SWRC) and effective stress are critical factors controlling the strength and stiffness of unsaturated soils. This study presents closed form models for representing temperature-dependent SWRC and effective stress of unsaturated soils. A temperature-dependent SWRC model is developed, which accounts for thermal effects on the adsorbed and capillary water, two main water retention mechanisms in unsaturated soils. The capillary water formulations include the effects of temperature on surface tension, contact angle and enthalpy of immersion per unit area. The temperature-dependent functions of the SWRC and moist air pressure are then incorporated into a suction stress-based representation of effective stress originally developed using volume averaging. The validity of the models is examined by comparing predicted values against experimental data reported in the literature for various soils ranging from clay to sand. The models can be readily incorporated in numerical and analytical methods, leading to more accurate modeling of unsaturated soils subjected to elevated temperatures.