Slope Stability Analysis for the Phosphogypsum Stockpiles: A Case Study for the Sustainable Management of the Phosphogypsum Stacks in Aqaba Jordan

Abstract

The process of making phosphates fertilizer involves taking the soft rock phosphate and mixing it with sulphuric acid. This process creates a gypsum by-product (phosphogypsum). Although gypsum is a widely used material in the construction industry, most of the produced phosphogypsum is not processed around the world and is stacked into large piles over the land, especially near coastal areas, which raised concerns about their stability. Such a disposal scheme creates man-made slopes in the surrounding areas which are prone to failure, which represents a common challenge for engineers. A slope failure will lead to a significant risk not only to human lives and activities but to the topographic and geological location of the stacks. In this paper, the geotechnical properties of the phosphogypsum in Aqaba, Jordan are determined and embankment stability analysis is carried out, as the purpose of this study is to evaluate the phosphogypsum stockpiles’ stability, and therefore, avoid any possible environmental disasters. Limit equilibrium methods and finite element methods were utilized in the analysis of this study. The required topographic and geological characteristics were obtained during the site visits and the contour plot of each phosphogypsum pile was produced by the Jordan Phosphate Mines Company (JPMC). Several laboratory tests were conducted to estimate the geotechnical properties of the stacked material due to the limited information on the Jordanian Phosphogypsum characteristics. Based on the results of this study, the above-ground slopes for the stacking of Phosphogypsum in Aqaba were found to be stable under both static and earthquake loading. Therefore, this study proved that the disposal process of the current stockpiles in Aqaba is sustainably managed for providing stable stockpiles and that the process has a generally low environmental risk.