Investigation of the Effect of Different Factors on The Dissolution Rate and Single-Site Compressive Strength of Gypsum- Containing Materials (Case study: Marash Zanjan Dam)

Soluble rocks such as gypsum and anhydrite are problematic rocks in geological engineering and geotechnics. The presence of these rocks in the construction of water structures such as bridge piers, coastal walls, diversion dams and dams, etc. due to their solubility and behavioral mechanism and deformability of gypsum-containing materials poses serious challenges in terms of stability The construction of Marash Dam, which is located about 98 km from Zanjan city, has special complications due to the presence of gypsum and anhydrite materials along with marl materials. Due to the fact that the materials of the dam bed, which contain gypsum and anhydrite materials, are exposed to loading and moisture, as well as solubility at the same time, so it is very important to study the mechanism of solubility and final strength of these rocks at different humidity. The effect of moisture on the deformation of gypsum materials is quite obvious and can sometimes lead to a decrease or increase in the strength of gypsum materials in certain conditions, Hooka et. al. (2006). At high pressures and in the presence of moisture, the dissolution rate as well as the compressive strength of gypsum and anhydrite samples have complex behaviors and depending on the contact area of the materials relative to each other and the moisture content, the dissolution rate can decrease and increase resistance over time, Hasan F, Ibrahim A, (2021). Based on the explanations provided and others' research, in the present study, according to the site conditions, rock samples from different depths (10 samples) to perform uniaxial tests and determine the Young's modulus and other parameters including natural density, moisture content and Poisson's ratio. And the porosity was transferred to the laboratory. In addition to resistance tests, solubility tests were performed to determine the maximum solubility of materials containing gypsum and anhydrite under different conditions (Marash dam water and distilled water and water containing 1% sodium chloride). By performing statistical and graphical analyzes, the behavioral status of gypsum rock samples in relation to various parameters has been investigated and its results have been presented.