ORIGINAL PAPER Investigating effects of water salinity on geotechnical properties of fine-grained soil and quartz in a sandstone case study: Ajichay project in northwest Iran Hadiseh Mansouri 1 • Zeinab Jorkesh 1 • Rassoul Ajalloeian 1 • Amir Hossein Sadeghpour 2 Received: 11 January 2016 / Accepted: 12 July 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract The effect of water salinity on the geotechnical properties of a CL soil and mechanical properties of a quartz sandstone has been studied using samples from the Ajichay project, located in the northwest of Iran. The purpose of this investigation is to investigate the feasibility of using saline water in processing the clay core of earthen dams in this area. One-dimensional consolidation, swelling, and uniaxial com- pressive strength tests were performed on the soil with distilled, half-saline, and saline water. To evaluate the effect of water salinity on the sandstones placed in the abutments of the dams, the slake durability index and uniaxial compressive strength were investigated. Results indicated that the compressibility index decreased, hydraulic conductivity decreased, and uni- axial compressive strength of the soil increased with increasing water salinity. The soil swelling percent with all three waters was less than 1 % after 24 h. However, swelling percent increased by 23 % with saline water and decreased by 32 % with half-saline water. Some damage in the rock texture such as disaggregation, weathering, and corrosion of the feldspars along with the dissolution of carbonate cement was observed in thin sections after 6 months of immersion in saline water. The strength of the sandstones exposed to saline water for 5 months decreased by between 5 and 13 %. Keywords Salinity effect  Fine-grained soil  Sandstone  Uniaxial compressive strength  Dam Introduction In this paper, the effect of water salinity on the geotech- nical properties of fine-grained soil and quartz sandstones was investigated. The soil and rock samples were taken from the Ajichay project. The Ajichay River is among the most important rivers in the northwest of Iran. This river begins on the southside of Sabalan Mountain and enters Urmia Lake 90 km to the west of the city of Tabriz (Fig. 1). Initially, the source of water was of good quality. However, due to the joining of saline water branches in the main stream, the quality of the water has gradually reduced. Since the Ajichay River is recognized as the only major water supply source of Tabriz, it was proposed to construct the Vanyar Dam. In order to improve the water quality of the reservoir, a number of small embankments would be constructed on the saline branch. This project has encountered two main problems: due to the large distance between the location of the saline controlling structures and the main fresh water river, the water needed for clay core processing of these dams would be supplied from the saline water. However, because of high hardness and TDS (Total Dissolved Solids) of the water, its effect on the clay core had to be evaluated. Moreover, stability of the dam abut- ments exposed to saline water should be investigated. In this research, water samples from the Korchay Branch and the Ajichay River were used as saline and half-saline water, respectively. Salt weathering is among the most important agent of damage in porous rocks (Benavente et al. 2007; Angeli et al. 2010). Several mechanisms such as crystallization pressure, hydration pressure, osmotic pressure, thermal expansion, and chemical weathering have been proposed to describe how salt impacts porous materials (Rodriguez- Navarro and Doehne 1999). Among these mechanisms, & Hadiseh Mansouri hadismansouri2000@gmail.com 1 Department of Geology, The University of Isfahan, Isfahan, Iran 2 Department of Architecture and Art, University of Kashan, Kashan, Iran 123 Bull Eng Geol Environ DOI 10.1007/s10064-016-0920-4