A temperature-dependent model for tensile strength characteristic curve of unsaturated soils

Abstract

Tensile strength is a key parameter controlling the formation of desiccation cracks in soils. Desiccation cracks are triggered in unsaturated soils due to drying imposed by natural processes or engineering applications mainly involving elevated temperatures. However, there is no closed-form model in the literature to capture the effect of temperature on tensile strength. This study presents a temperature-dependent model for the tensile strength characteristic curve (TSCC) of unsaturated soils. The model employs the suction stress characteristic curve (SSCC) to represent the uniaxial tensile strength of unsaturated soils at different water contents and temperatures. The model incorporates the effects of temperature into adsorptive and capillary suction stress components. The temperature-dependent adsorptive suction stress is obtained by accounting for thermal induced changes in suction stress at dry state through the Hamaker constant and the density of water. The temperature-dependent form of capillary suction stress is derived by employing temperature-dependent forms of surface tension, contact angle and enthalpy of immersion. Upon comparison, results from the proposed TSCC exhibited a very good agreement against laboratory-measured tensile strength data for two clayey soils tested at different temperatures ranging from 20 to 60 °C. The presented model can improve the analysis of desiccation cracking in unsaturated soils.