The evaluation of water salinity effect on geotechnical characteristics of fine grained soils

In this research، the effect of water salinity on geotechnical properties of fine grained soil used in Korchay dam core have been studied. This dam is located in East of Tabriz. In order to the water samples were obtained from half saline water of Ajichay River and saline water of Korchay branch. In the laboratory، several tests such as Atterberg limits، compaction، permeability، compressive strength، direct shear، free swell and dispersion (cramb، double hydrometer and pinhole) were done with distilled، half saline and saline water. Since there are a few percent of active clay minerals in the soil، changes in geotechnical properties of the soil are not considerable. However the results showed the Atterberg limits decrease and permeability coefficient and shear strength parameters increase as pore water salinity increases. Water salinity has no effect on swell time and the soil primary swell finished after 180 minutes with three types of water. Swell percent decreased 32% and increased 23% with half saline water and saline water respectively. Since percent of divanlet cations in half saline water was more than saline water، swell pressure decreased with half saline water more than saline water. Although Na percent in half saline and saline water was high، but no dispersity behavior was observed with them. Most of obtained results have been attributed to increase attractive force between soil particles via salts in water and create flocculate structure in the soil