Abstract:
Over the past decade, there have been 45 tailings storage facility (TSF) disasters worldwide resulting in fatalities, serious environmental
damage, and the destruction of entire ecosystems. These failures often stem from substandard design or operational
practices. Many TSFs are constructed in regions associated with intrusive mafic rocks such as gabbro, norite, pyroxenite,
and anorthosite, which are commonly found alongside platinum group metals in areas like the Bushveld Igneous Complex in
South Africa and the Great Dyke in Zimbabwe. The stability of these structures can be significantly influenced by the residual
soils present at the construction sites. Residual soils, both cohesive and non-cohesive, contain varying quantities of different
minerals, which can impact the compaction characteristics and, consequently, the stability of the TSF foundations. Cohesive
soils rich in clay minerals, such as kaolinite and smectite, exhibit properties that can hinder effective soil compaction. The
expansive nature of smectite due to its ability to absorb large amounts of water and host free exchangeable cations counteracts
the compaction process, reducing soil stability. Soil compaction is a complex process influenced by several factors,
including compaction effort, method, water content, particle size distribution, and mineralogy. This study aimed to analyse
these factors using a series of laboratory tests, including foundation indicators, MOD AASHTO compaction testing, and
X-ray diffraction analysis, on residual soils from two TSF construction sites. The findings revealed that soils with high clay
content tend to retain more water and have a higher optimum water content, adversely affecting their compaction properties.
This study highlights the critical need to consider the mineralogical composition and weathering effects of residual soils in
the design and construction of TSFs. By improving our understanding of these factors, we can enhance the stability of TSF
foundations, reducing the likelihood of future failures. The insights gained from this research highlight the importance of
thorough geotechnical assessments in the successful design and maintenance of TSFs.
