Gypsum Dissolution Study Under Confined and Unconfined Conditions

Abstract

Gypsum is a soluble rock, which when exposed to underground flowing water, may dissolve and cause the development of karst features. Prolonged exposure of gypsum to underground circulating water can lead to subsidence or collapse of the overlying ground. The Emirate of Abu Dhabi has large deposits of gypsum in the bedrock within 30m from the surface. This poses potential threats to infrastructure development, thus investigating and understanding the dissolution process of these rocks is crucial. In this work, experimental tests on the dissolution of gypsum are performed using specimens made from artificial gypsum powder (Plaster of Paris), as analogues to the natural gypsum present in Abu Dhabi. The specimens are subjected to flow through tests under different conditions; 1- unconfined stress conditions, 2- confined stress conditions. Concentration of the water flowing through the specimen is examined along with the changes in its mechanical properties. The results show, for both test conditions, an initial stage of high concentration of solutes, followed by a steep decline before a second stage of constant concentration and finally a steady increase with time. In addition, tests under confining pressures, show an increase in the dissolution of gypsum as water flow increases. Finally, it is observed that varying the confining pressure at low levels does not have a significant impact on the dissolution process.

Date of Award	Dec 2016
Original language	American English
Supervisor	Rita Sousa (Supervisor)