Effect of road salts on the hydro-mechanical behavior of unsaturated collapsible soils

Hydro-mechanical behavior of unsaturated collapsible soils can be drastically affected by saline infiltrations. Saline infiltrations into the underlain soil layers of the urban transportation and lifelines due to deicing or existence of traffic pollutants has been a common issue of concern for years in many countries. Additionally, many reports have been published so far, indicating the construction of roads and railways on unsaturated collapsible soils. In this research, hydro-mechanical characteristics of an unsaturated collapsible loessial soil diluted with saturated solutions of three different salts that are frequently involved in transportation infrastructure (namely NaCl, CaCl2 and KCl) are investigated by conducting scanning electron microscopy (SEM), filter paper, uniaxial compression and oedometer tests. Obtained test results have been analyzed by simultaneous consideration of the matric and osmotic suctions in the soil texture and the applied stresses. Test results revealed that the soil texture and hydro-mechanical responses of the soil are considerably affected by the salt type, saline degree of saturation and applied loading paths. Results also imply that there is a critical saline degree of saturation (corresponded to each loading path and each mixing salt type), at which the magnitude and modality of the osmotic and matric suctions within the soil fabric are changed. In addition to experimental studies, empirical constitutive models are presented in this paper to predict the changes in strength, stiffness and yield stress of the tested collapsible soil subjected to different road salts. Comparisons show very good agreement between the laboratory test results and the model predictions. The achievements presented in this research can be directly implemented for better prediction of the behavior of unsaturated collapsible soils subjected to salinity. In addition, the result can be implemented in a suitable stabilization plan when the soil and salt involved in transportation infrastructures.