Saturation Procedures of Soluble Rocks (Emphasizing on Gypsum-Anhydrite Rocks)

To identify natural behavior of rocks under the similar moisture conditions, two saturation methods of under atmospheric pressure conditions or vacuum pressure are usually used. In the method of vacuum pressure, the values of vacuum pressure Pvac as well as the time of applying this pressure Tvac are two effective parameters. In this study, the saturation method of rock, especially soluble ones such as gypsum and anhydrite, have been studied. The results of the experiments were analyzed in terms of sensitivity for four parameters of dry vacuum pressure Pvac(dry), wet vacuum pressure Pvac(wet) and the time of applying each one (Tvac(wet), Tvac(dry)). The results showed that by increasing Pvac(wet), the percentage of water absorption has been increased and the samples generally gain more than 95% of their increased weight after 4 days of applying wet vacuum and they can be practically assumed to be saturated. Applying dry vacuum Pvac(dry) before wet vacuum Pvac(wet), increases the weight of most samples after applying Pvac(wet). In case of gypsum-anhydrite rocks, the experiment showed that applying dry pressure equivalent to -0.5 atmospheres (atm) and to 5 hours (Pvac(wet) = -0.5 atm, Tvac(dry)) = 5h) propose ideal results.