Stability Analysis of an Unsaturated Silty Slope under Nonisothermal Conditions

Thota, S. K., Cao, T. D., Vahedifard, F., & Ghazanfari, E. (2019). Stability Analysis of an Unsaturated Silty Slope under Nonisothermal Conditions. Geo-Congress 2019. Philadelphia, PA. DOI:10.1061/9780784482124.085.

Natural and man-made unsaturated soil slopes can be subjected to different temperatures due to soil-atmospheric interaction, thermally-active earthen systems, and human-induced activities. Such nonisothermal conditions can affect the stress state variables, leading to changes in the soil strength and stability of slope. The main objective of this study is to investigate the stability of unsaturated soil slopes under elevated temperatures. For this purpose, Bishop’s effective stress expression for unsaturated soils is extended to account for the effect of temperature on matric suction and effective degree of saturation. The effective stress expression includes a nonisothermal soil water retention curve model to consider the thermal effects on the surface tension, soil-water contact angle, and adsorption by the enthalpy of immersion. The proposed effective stress model is then incorporated into an infinite slope stability analysis of a hypothetical silty soil under no-flow (hydrostatic) condition. The formulations are used to monitor matric suction, suction stress, and factor of safety of slope for different temperatures. The results suggest that the effects of temperature on slope stability can be significant. It was found that by increasing temperature from 25°C to 40°C and 60°C, the matric suction decreases by approximately 24% and 39%, suction stress increases by approximately 30% and 45%, and the FOS decreases approximately by 5% and 11%, respectively.