Experimental study of the mechanics of gypsum seam hazard for Abu Dhabi

Abstract

Abu Dhabi is predicting a huge growth in population over the next 20 years (Plan Abu Dhabi 2030); further, it seeks to become an international destination for tourists, businesses, and investment while protecting its cultural heritage. A crucial aspect of achieving this goal is the development of large integrated transportation system, underground, and above ground, to ensure Abu Dhabi becomes a sustainable city on a global scale. The presence of gypsum rocks that occurs within Abu Dhabi’s bedrock is a major threat to underground construction and understanding the phenomena is of paramount importance. They are persistent quasi-horizontal bands, at different levels (top level between 10 and 15 m and bottom level between 15 and 25 m), prone to volume change by dissolution or swelling, due to changes in the stress regime and water chemistry and flow. The dissolution of gypsum is also a cause for cavities that can be found within this formation in greater Abu Dhabi. In this paper, the description and results of an experimental study aimed at obtaining a better understanding of the gypsum dissolution process, as well determine factors affecting it, are presented. Tests on the dissolution process of gypsum rock were performed using artificially created intact and fractured gypsum samples which are a representative of the collected in situ fractured gypsum rock samples obtained from Abu Dhabi. The samples are subjected to flow-through tests. Results obtained show that for an initially saturated gypsum specimen, there is a sharp decline in concentration with time (Stage I), followed by a constant concentration (Stage II) before a slight gradual increase is observed (Stage III) with time. This is a fundamental study-part of a larger set of experiments studying the gypsum dissolution process in Abu Dhabi. Using the data collected from the field and the experiments mentioned above, gypsum geohazard risk-related maps which reflect subsidence, swelling, cavity collapse, and cavity flooding associated with Gypsum Karst shall be developed using Geographic Information Systems.