Effects of chemical composition on the solubility and geomechanical characteristics of gypsum rocks from Gachsaran Formation, Iran

摘要

Evaporite rocks of the Gachsaran Formation make the reservoirs and foundations of several important dam site in southwest Iran. The solubility of these rocks is the main cause of instability and leakage problems usually observed in these dam sites. Therefore, investigation and consideration of engineering geological characteristics of these rocks, including their solubility, is crucial. In the present study, 10 gypsum rocks of the Gachsaran Formation were selected from Masjed-Soleyman, Haftkel, and Ramhormoz areas in southwest Iran. The chemical and mineralogical compositions of the samples were determined through optical microscopy, XRD, and XRF analyses. Different characteristics of samples including physical and mechanical properties, solubility, and solution rate were determined. Then, the effects of the chemical composition of gypsum rocks on geomechanical characteristics, solubility, and solution rate were assessed. Results showed that the proportion of two main gypsum components of CaO and SO3 and the CaO/SO3 ratio has a significant effect on gypsum strength and solubility. Also, an increase in the abundance of minor oxides of Al2O3, Fe2O3, SiO2, and K2O leads to a decrease in the solution rate.