A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, in fulfilment of the requirements of the degree of Doctor of Philosophy in Engineering / The thesis describes the determination of the steady state line for the Merriespruit gold and Bafokeng platinum tailings by means of triaxial undrained compression tests. It shows that there are numerous steady state lines for the above mentioned tailings products and thatthe location oftheirsteady state lines in void ratio- mean confining effective stress space is influenced by the percentage fines (particles smaller than 0.075mm) present in the tailings, among other factors. As the percentage fines increases so the steady state line for the particular material shifts downwards in void ratio- mean confining effective stress space. The difficulty of defining a unique steady state line for a particular fines content tailings, due to errors in measurement of initial size, mass, etc. and changes in void ratio due to flooding, saturation and consolidation of the moist tamped triaxial test samples is illustrated and it is recommended that error bands be assigned to the steady state lines. The steady state lines determined for the Merriespruit gold tailings and the concepts of liquefaction are combined with evidence obtained from the post failure investigation into the Merriespruit flow slide failure to prove the premise that the flow slide was as a result of static liquefaction failure of the tailings. It is also illustrated that the notion of using a single steady state line to evaluate the liquefaction susceptibility of a tailings dam is insufficient due to the particle size distribution of the tailings varying along the beach length of the tailings dam and the location of the steady state line being influenced by the percentage fines content. Flume modelling using the Merriespruit gold tailings were carried to obtain a qualitative understanding of the behaviour of flow slides. Comparisons between the flume model tests and the Merriespruit flow slide (prototype) showed that it is difficult to obtain a correlation between the two due to the influence of scale, different dominating forces in the model and prototype and the inherent variability associated with such geotechnical phenomena- particularly in the preparation and deposition of the tailings in the flume model. Keywords: liquefaction, steady state line, flow slide, failure, flume modelling, Merriespruit, Bafokeng, gold, platinum, tailings / AC 2018

Contaminant release and transport in platinum tailings are poorly studied in literature. This study serves to characterise these processes. The tailings facility is located in Steelpoort, Mpumalanga, South Africa on Critical Zone rocks of the Rustenburg Layered Suite in The Bushveld Igneous Complex. Tailings material samples were collected by hand auger- and direct push probe drilling at specific locations to represent the different materials present in the tailings facility. Water samples were collected from monitoring boreholes as well as the Steelpoort River. The samples were analysed using XRD, XRF, ABA, NAG, Reflected Light Microscopy, Acid Leaching Tests and ICP scans. Using the collected data, a geochemical model was constructed for the interpretation of mineral phase dissolution and to trace the mineral phases releasing contaminants. Analysis-, test- and modelling results showed that alteration mineral phases formed within ten years in the tailings material and that the existing alteration phases viz. talc and chlorite, as well as sulphides, are the major contributors of contaminants. Elevated pH values as well as major cation and anion concentrations were found in the fluid discharging from the tailings as well as the in groundwater, with little to no heavy metals, which were traced directly to the chromite phase. This suggests that platinum tailings do not contribute to heavy metal contamination or acid rock drainage but may increase aquifer salinity and alkalinity. The flow through the tailings, underlying vadose zone and fractured rock aquifer was characterised using permeameter- and pumping tests. From the data collected, an unsaturated flow model was developed to characterise the flow through the tailings. From the model, discharge from the tailings was calculated to take place at 0.7m per decade into the underlying vadose zone with fracture flow in the aquifer ranging from 0.46-0.026m/d, as calculated from pumping test results. Contaminant migration into the Steelpoort River is possibly inhibited by the Dwarsriver Fault, based on the chemical data and hydraulic conductivities calculated. Therefore, groundwater is considered to be the major receptor in the system and groundwater users may be negatively impacted by increasing groundwater salinity and major ion concentrations. / Dissertation (MSc)--University of Pretoria, 2013. / Geology / unrestricted

A sustainable society is a society that satisfies its resource requirements without endangering the sustainability of these resources. The mineral endowment on the African continent is estimated to be the first or second largest of world reserves. Therefore, it is recognised that the African continent still heavily depends on mineral exports as a key contributor to the gross domestic product (GDP) of various countries. These mining activities, however, do introduce primary and secondary environmental degradation factors. They attract communities to these mining areas, light and heavy industrial establishments occur, giving rise to artisanal activities. This study focussed on satellite RS products as an aid to a mine’s operations and the monitoring of its environment. Effective operational mine management and control ensures a more sustainable and profitable lifecycle for mines. Satellite based RS holds the potential to observe the mine and its surrounding areas at high temporal intervals, different spectral wavelengths and spatial resolutions. The combination of SAR and optical information creates a spatial platform to observe and measure the mine’s operations and the behaviour of specific land cover and land use classes over time and contributes to a better understanding of the mining activities and their influence on the environment within a specific geographical area. This study will introduce an integrated methodology to collect, process and analyse spatial information over a specific targeted mine. This methodology utilises a medium resolution land cover base map, derived from Landsat 8, to understand the predominant land cover types of the surrounding area. Using very high resolution mono- and stereoscopic satellite imagery provides a finer scale analysis and identifies changes in features at a smaller scale. Combining these technologies with the synthetic aperture radar (SAR) applications for precise measurement of surface subsidence or upliftment becomes a spatial toolbox for mine management. This study examines a combination of satellite remote sensing products guided by a systematic workflow methodology to integrate spatial results as an aid for mining operations and environmental monitoring. Some of the results that can be highlighted is the successful land cover classification using the Landsat 8 satellite. The land cover that dominated the Kolomela mine area was the “SHRUBLAND/GRASS” class with a 94% coverage and “MINE” class of 2.6%. Sishen mine had a similar dominated land cover characteristic with a “SHRUBLAND/GRASS” class of 90% and “MINE” class of 4.8%. The Pléiades time-series classification analysis was done using three scenes each acquired at a different time interval. The Sishen and Kolomela mine showed especially changes from the bare soil class to the asphalt or mine class. The Pléiades stereoscopic analysis provided volumetric change detection over small, medium, large and recessed areas. Both the Sishen and Kolomela mines demonstrated height profile changes in each selected category. The last category of results focused on the SAR technology to measure within millimetre accuracy the subsidence and upliftment behaviour of surface areas over time. The Royal Bafokeng Platinum tailings pond area was measured using 74 TerraSAR-X scenes. The tailings wall area was confirmed as stable with natural subsidence that occurred in its surrounding area due to seasonal changes of the soil during rainy and dry periods. The Chuquicamata mine as a large open pit copper mine area was analysed using 52 TerraSAR-X scenes. The analysis demonstrated significant vertical surface movement over some of the dumping sites. It is the wish of the researcher that this dissertation and future research scholars will continue to contribute in this scientific field. These contributions can only assist the mining sector to continuously improve its mining operations as well as its monitoring of the primary as well as the secondary environmental impacts to ensure improved sustainability for the next generation. / Environmental Sciences / M. Sc. (Environmental Science)