The Engineering Characteristics of Silty Loess Contaminated with Natural Salts

Abstract

A considerable part of Golestan Province is covered by loess soils, most of which are of the silty loess type, which is one of the most problematic soils. The proximity of the Caspian Sea leads to salinity of the groundwater in some areas of the province. Due to high evaporation, salts reach the surface and cause salinization of the silty loess soils at the surface. The presence of soluble salts can lead to changes in the engineering properties of silty loess soils at the site of construction projects. It is therefore necessary to investigate the influence of salts on the geotechnical properties of silty loess soils. The aim of this study was to investigate the effect of sodium chloride or halite (NaCl) and calcium sulphate or gypsum (CaSO4.2H2O) salts, as the two most abundant natural salts, on the engineering properties of silty loess soils. For this purpose, silty loess soil samples were collected from Maraveh Tappeh city, Golestan province, Iran. Geotechnical tests including uniaxial compressive strength, shear strength and standard compaction tests were then carried out on soil samples in the natural state and with 3, 5, 7, and 9% NaCl and CaSO4.2H2O. Based on these tests, the variation in optimum water content (ωopt), maximum dry density (ρdmax), uniaxial compressive strength (UCS), cohesion (C), internal friction angle (φ) were evaluated. The results showed that these parameters increased with increasing both natural salts concentration. Finally, the reason for the changes in the engineering properties of the soil samples due to the presence of these two natural salts was discussed.