Closed-Form Solutions for Temperature-Dependent Suction Stress under Transient Infiltration in Unsaturated Soil: An Application for Stability Analysis of Strip Plate Anchors

Abstract The soil layer up to a certain depth below the ground surface exists in an unsaturated state, where factors such as precipitation, evaporation, and prolonged subsurface heat waves control the state and material properties of soil. The suction stress that contributes to the resistance of the soil mass governs the stability of geostructures and depends on the thermal and hydraulic interactions in unsaturated soil. No solutions are available to determine the suction stress in soils subjected to transient flow conditions at elevated temperatures. This study develops closed-form expressions for temperature-dependent suction stress under transient flow conditions using the one-dimensional transient flow equation and a temperature-dependent soil–water retention curve. The developed equation was implemented within the framework of stress-based finite-element limit analysis to evaluate the stability of strip plate anchors in terms of their uplift capacity embedded in unsaturated sand, silt, and clay under transient flow conditions and varying temperatures. The critical role of thermal and hydraulic interactions in different types of unsaturated soils (clay, silt, and sand), specifically regarding matric suction, effective degree of saturation, and suction stress over time, has been discussed in detail. Additionally, a comprehensive parametric study has been conducted to evaluate the effects of transient flow and elevated temperature on the uplift capacity of shallow strip plate anchors. The results indicate that the behavior of plate anchors in unsaturated sand and silt is distinctly different from that in clay.