Analysis of embankment stability: a case study at Awaso mine, Ghana

Ghana Bauxite Company Ltd operates an open cast bauxite mine at Awaso in the western region of Ghana. As part of its mining activities, a 36 000 m³ water storage facility has been constructed to store water for use in the processing plant. The facility consists of a 4 m high embankment built across a valley on a silty sandy gravel foundation. Seepage forces and pore pressures in the foundation and embankment have raised some stability concerns. The principal objective of this study is to carry out an assessment of the stability of the water storage facility embankment and foundation and propose measures to improve it. The stability assessment procedures include: (a) investigating the geological, geotechnical and engineering properties of the embankment and foundation material, (b) evaluating possible failure factors such as piping, erosion, sliding and seepage; and (c) reviewing operational parameters of the facility. From the qualitative and quantitative assessments, it was concluded that the embankment of the facility was susceptible to failure resulting from inadequate compaction, seepages and overgrown tree roots. The foundation, on the other hand, was found to be susceptible to failure resulting from seepages. Recommendations for improving the embankment integrity include the construction of a toe drain, implementation of a vegetation cover management scheme and documented periodic monitoring.