On the Solubilities of Anhydrite and Gypsum

Abstract

Claystones containing finely distributed anhydrite swell due to water uptake. Experience shows that the swelling may cause considerable damage and lead to high repair costs. During tunnel excavation, a change in the field conditions occurs, causing the dissolution of anhydrite into its ions and the subsequent precipitation of gypsum crystals. The formation of the latter is (together with water uptake by the clay minerals) the cause of the swelling process. Identifying the conditions under which anhydrite or gypsum is the stable phase is crucial for understanding the process. The current paper presents a thermodynamic model for the individual assessment of anhydrite and gypsum solubilities by additionally considering the partial contact stress between the minerals. The model is verified with experimental and theoretical results from the literature.KeywordsGibbs Free EnergyClay MineralPore PressureVersus Versus Versus VersusVersus Versus Versus Versus VersusThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.