Gypsiferous Soils: An Engineering Problem

Karstic terrain constitutes one of the most difficult grounds to be explored and assessed by engineers due to its unpredictable geometry and the voids that lie in the subsurface. This geological formation is normally associated with soluble rocks, of which one of the most typical representations is calcium sulphate. Calcium sulphate was found to extend over more than 20% of the land surface on the earth. It exists in various forms, the most common ones are gypsum (CaSO₄·2H₂O) and anhydrite (CaSO₄). The existence of gypsum terrains under construction zones is dangerous due to the collapsible nature of gypsum with the presence of water. Remarkable evidences are available on failures in dams, highways and some other structures constructed above gypsiferous soils or rocks. In this paper, some of the physical and chemical properties of gypsum are reviewed. Then the authors present the gypsum-anhydrite transition phenomena and the existing techniques for stabilizing gypsiferous terrains.