The present paper aims at investigating the effect of water salinity on engineering properties of fine-grain soil. Saline water used in this study was obtained from half saline water of Ajichay River (with TDS more than 1877 ppm) and saline branch of Korchay (with TDS more than 97000 ppm) located in Northwestern of Iran. Fine-grain soil studied is from Korchay dam core. Due to the high hardness of water in this river, the feasibility of using saline water as the water required in clay core of the dam process has been studied in this research. The experiments were performed including Atterberg limits, standard compaction, consolidation, direct shear and dispersion. These tests were performed by using distilled water, half saline water and saline water on reservoir materials. Due to low percentage of clay minerals in the soil, the changes in engineering soil properties as salinity increases are negligible. However, the use of saline water reduces Atterberg limits, compression index (Cc), swell index (Cs(, coefficient of compressibility (av), coefficient of volume compressibility (mv) and causes slight increase in soil shear strength parameters. Despite the high percentage of sodium in half saline and saline water, dispersion degree of soil is ND2 in pinhole test
