JWSS - Journal of Water and Soil Science

Gypsiferous soils are one of the problematic soils which, due to solubility and contact with water, are a threat to various civil structures, especially water structures. Various factors affect the rate and amount of gypsum particles solubility. Gypsum types, the soil texture, the amount of gypsum in soil, the hydraulic gradient, and temperature and flowing water from gypsum soil are the major factors affecting the quality and quantity of the gypsum solution. In this research, the effects of some peripheral conditions including water temperature and hydraulic gradient on the solubility of gypsum soils were studied. To this aim, samples of gypsum soils were provided artificially by adding various rates of the natural gypsum rock including 0, 5, 10, 20 and 30 percent by weight of clay soil. Then, all gypsum soils were leached under five hydraulic gradients levels including 0.5, 1, 2, 5 and 10. The results indicated that the rate of Gypsum in the soil had a direct effect on the rate of solution in a way that by increasing the percent of Gypsum, the rate of solubility was increased. Also, the rate of leaching (the rate of the derived Gypsum from soil to the primary rate of Gypsum) was decreased by increasing the rate of Gypsum. In addition, by increasing hydraulic gradient, the speed of water and its amount in soil environment within a specified time were raised; further the rate of gypsum was increased too. Also, it was found that the rate of the solubility was increased directly by the temperature. The solubility rate of the gypsum soil at 50 C⁰ was found to be 2.5 and 1.6 times greater than that of the soil at 5 and 20 C⁰, respectively.