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Abstract
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Sulfate rocks are considered as problematic rocks due to their high solubility and deformation potential, when present in hydraulic structure’s foundation. In this paper, the effect of mineral composition on the dissolution rate constant ( Kc) of these rocks has been studied. For this purpose, sulfate rock blocks were collected from the sulfate rock layer outcrops of Gachsaran Formation at the three under construction reservoir dam sites in Iran, and by preparing cylindrical core samples, dissolution simulation experiments were performed. For the purposes of the pressure (P) phase, a special pressure vessel was designed and manufactured to accommodate the simulation of dissolution in the static to water circulation at the desired pressures. The experiments were performed at pressures of 1 to 7.5 atmospheres. The water flow velocities ( Vw) were set to a range between 0 and 0.008 m/s. The pH of the solution was maintained between 6.5 and 7 and a temperature of 25 °C. The results of this study confirmed that, firstly, there is a direct relationship between pressure and Kc. Secondly, as the water flow increases, the amount of dissolution and the Kc increase. Thirdly, sulfate rocks with different mineral composition experience different dissolution behaviors. One important outcome of this study is that, despite changes in P, Vw, and mineral composition the solubility of sulfate rocks at 25 °C in ionized water is about 1.9 g/l. Furthermore, all of considered factors affect only on the time of reaching the dissolution electrolyte to saturation or equilibrium condition.
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