Mining In South Africa Research Articles

Coal Moisture Variations in Response to Rainfall Event in Mines and Coal-Fired Power Plant Stockpiles—Part 1: Runoff, Infiltration, and Drainage

Excessive coal moisture leads to a lower heating value and power plant efficiency, and increased transportation costs. Therefore, coal stockpile management and moisture control are particularly important in regions with heavy precipitation. This paper and Part 2 address factors influencing moisture retention and migration in coal stockpiles. Part 1 of this paper series simulates phenomena of runoff, infiltration, and drainage in a stockpile after a rainfall event. Part 2 reports the effect of coal particle size and climate conditions on the rate and depth of moisture evaporation process within a coal stockpile. To perform this study, two coal samples were collected from the Witbank mine in South Africa. The results of the present study showed that smaller interparticulate void spaces because of the compaction or fines particles (−0.5 mm fraction) inhibited infiltration, leading to increased runoff volume. An increase stockpile slope increased the amount of runoff due to coal–water contact time reduction. The ability of heavy rainfall to destroy near-surface structures (erosion) happened more readily at stockpiles with high slopes and high fine content. The fine content significantly influenced the dewatering efficiency of drainage. Coals with higher ash contents had stronger moisture retention ability than that of other coals even though coals with low ash contents had a high fine content. This was ascribed to the contribution of the clay minerals, such as kaolinite, in the high ash coal. The results of this paper can be used for the effective management of coal stockpiles to prevent excessive moisture in stockpiles for the best possible utilisation of coal in power plants.

COVID Roundtable

COVID Roundtable

‘We are surviving well’: Adaptive strategies applied by women in an underground South African mine

Purpose: Research into women working in mines in general is limited, and less so for their presence in underground mines. This study explores the adaptive strategies women employ to navigate harsh physical and perceived threatening interpersonal contexts in an underground mine in South Africa. A contexulalised framework and guiding heuristic contructs (structuration and agency) were adopted to identify and discuss women’s adaptive strategies for navigating challenging underground mining environments and to propose interventions. Design/methodology/approach: A contextual, qualitative descriptive design was used. Twenty-one women in an underground gold mine in the North-West Province in South Africa were purposively selected and participated in semi-structured interviews ( n = 18) and an informal group discussion ( n = 3). Data was analysed thematically, using ATLAS.ti 8 (a qualitative data analysis and research software programme). Findings/Results: The women identified challenges on three levels: intrapersonal, relational and systemic and adaptive strategies on four levels: intrapersonal (adopting a different perspective and questioning traditional beliefs), behavioural (self-defence, solution-focused actions, working hard); relational (supportive same-gendered groups, support from working teams, and safe interpersonal spaces for debriefing); and broader systemic support (approachable human resources (HR) department, supportive close relationships, and external stakeholder resourcing). Practical implications: Interventions are proposed to support and strengthen the adaptive strategies of women working in mines. Originality/value: Identifying and supporting adaptive strategies applied by women in the workplace can benefit women individually and their work-teams, as well as informing best mining practices and society more widely.

A Comparative Study of Sulfur Isotope Variations within the Flatreef and Merensky Reef of the Bushveld Complex, South Africa

ABSTRACT The Flatreef, a down-dip, sub-horizontal extension of the Platreef, which underlies the Turfspruit and Macalacaskop farms, represents the future of platinum mining in South Africa. The stratigraphic connection between the Platreef, located at the base of the northern limb of the Bushveld Complex, and the Merensky Reef in the western and eastern limbs of the complex, was disputed for many years due to the heterogeneous nature of the Platreef along strike. However, the discovery of the Flatreef led to a new perspective on the Platreef as the former allowed for the study of a magmatic stratigraphy less affected by footwall interaction. Here, we report whole-rock S isotope (δ34S) compositions across the stratigraphic units of the Flatreef and its footwall and hanging wall as intersected by boreholes UMT-276 and UMT-393, as well as stratigraphic units of the Merensky Reef at Two Rivers Platinum mine in the eastern limb. The units of the Flatreef containing platinum group element mineralization, namely the Main Reef and Upper Reef, have δ34S values that overlap with the range recorded for the Merensky Reef in the western and eastern limbs. In UMT-393, Main Reef δ34S values range between 0.2 and 1.5‰ (with the exception of three outliers, 9.7‰, 11.1‰, and 7.9‰), and 0.52‰ and 11.2‰ for two Upper Reef samples. However, in UMT-276, Main Reef δ34S values range between –0.96 and 2.24‰ and 3.19‰ was recorded for an Upper Reef sample. The S isotope compositions recorded for the Merensky Reef pyroxenite at Two Rivers Platinum mine are relatively higher with δ34S values ranging between 1.24 and 4.83‰. The top unit of the Flatreef, which is a transition zone below the Main Zone, as well as the Footwall Cyclic Unit have heavier S isotope compositions with δ34S values ranging between 6 and 17‰ for the former and 0.7 and 18.6‰ for the latter. At Two Rivers Platinum mine, the hanging-wall anorthosite has a δ34S value of 2.9‰ in contrast to the 5.7‰ measured for the footwall anorthosite and 3.27‰ for the footwall feldspathic pyroxenite. The consistent near-mantle S isotope signature and accompanying metal enrichment in the Main Reef of the Flatreef may be explained by extensive interaction of sulfide minerals in a Lower Zone conduit/pre-Platreef staging chamber with large volumes of uncontaminated magma. The δ34S values of the Merensky Reef at Two Rivers Platinum mine are slightly higher compared to that of the Main Reef at Turfspruit and Macalacaskop possibly due to interaction with underlying carbonate rocks.

Assessment of asbestos contamination in soils at rehabilitated and abandoned mine sites, Limpopo Province, South Africa

Prior to its termination, asbestos mining in South Africa was centred on the large crocidolite fields of the present day Northern Cape, the amosite (grunerite)-crocidolite fields of Limpopo, and chrysotile fields of Mpumalanga provinces. The legacy of these activities continues to affect surrounding communities in contemporary South Africa. The asbestos fields of Limpopo host two important former mining areas at Penge and at the Bewaarkloof near Chuenespoort. A large abandoned site is located southeast of Penge at Weltevreden, where there is no evidence of any rehabilitation. Two former mines, Lagerdraai and Uitkyk, are rehabilitated sites in an extensive string of closed mines that operated in the southern Bewaarkloof. Samples from the abandoned and rehabilitated mine sites were studied using semi-quantitative X-ray powder diffraction (XRD) to determine asbestos contamination levels in soils, and to assess distribution patterns of asbestos mineral species in the surrounding soils. Only where below detection (typically 1–3 mass%) from XRD, samples were assessed optically. The Weltevreden site, with no observable rehabilitation efforts, contrasts with the rehabilitated sites at Lagerdraai and Uitkyk. The predominant asbestiform mineral species at each site were successfully identified, with underlying geological asbestos mineral distribution trends recognised in the soils at the Bewaarkloof. Trace amounts of asbestiform minerals were identified in soils downstream of the Weltevreden mine, as well as in surrounding hillsides. The results indicate that XRD is a potentially useful tool for benchmarking sites yet to be rehabilitated as well as monitoring the effectiveness of previous rehabilitation efforts. The method is also a suitable first-pass for target areas that may require more detailed, time-consuming, and costly analysis.

Predicting standard threshold shifts for occupational hearing loss among miners at a large-scale platinum mine in South Africa

Occupational noise-induced hearing loss (ONIHL) is associated with various risk factors in South African mines. We investigated the association between standard threshold shifts (STSs) and exposure to noise and platinum mine dust (PMD), using demographic data, five years of annual audiometry screening results, and noise and dust exposure data. Miners' age, sex, percentage hearing loss (PLH), and dust and noise exposure data were gathered, and a linear mixed effects regression model used to predict STS. Average occupational exposure levels to noise and dust were calculated from recorded measurements. A total of 12 692 records were analysed. Most miners were male (89.6%) and more than 50% were younger than 41 years. More than 70% were exposed to > 85 dBA noise and 58% were exposed to 1.5-2.99 mg/m3 PMD. Changes in hearing levels ranged from 8.3 dBHL at baseline (2014/2015) to 10 dBHL in 2016 (STS), with no changes thereafter. The model showed that the estimated effect on STS for males was 27% and 21% higher than for females, for the left and right ear, respectively The estimated effect of age, PLH, noise exposure and years of exposure on STS was < 10% for each variable. There was no statistically significant association between PMD and STS. The combined effects of age, sex, years of exposure to noise, and noise exposure levels, and strength of associations can be used to predict STS for this group of miners. Our findings may be used to measure the efficacy of the mine's hearing conservation programme.

Performance evaluation and monitoring of the tunnel excavation with a Mobile Tunnel Borer

The use of Tunnel Boring Machines (TBM) for tunnel excavation is widespread around the world for its capabilities and great advantages against the traditional tunnel excavation method, but sometimes this technology can be difficult to manage, requiring huge spaces for the assembly on the job site and involving complex installations at the tail of the machine.Aiming at creating a versatile and compact tunnel borer, TunnelPro and Master Drilling designed the MTB (Mobile Tunnel Borer) that is built on crawlers, easy and fast to assembly with no need of special equipment. This prototype MTB is currently excavating a Platinum mine in South Africa, being tested in very hard rocks.The study here presented, carried out by GEEG srl, startup of Sapienza University of Rome, compares the actual values of thrust, torque, penetration and cutter wear recorded during the trial excavation monitoring with those estimated with models commonly used in TBM performance prediction. The aims of this study, still ongoing, are a better comprehension of the MTB operation in terms of efficiency, work of the excavation tools, load distribution, and the evaluation of the adequacy of the most known methods when applied to this prototype machine.

Hydrothermal Carbonization of Searsia lancea Trees Grown on Mine Drainage: Processing Variables and Product Composition.

A 12-year-old planted woodlands Searsia lancea tree, grown on acid mine drainage for phytoremediation of polluted groundwater on gold and uranium mines in South Africa, was used in this research. The research describes the fuel-related characteristics and the influence of different operating conditions on the hydrothermal carbonization of the biomass and the combustion profiles of discard coal/biomass hydrochar pellets. The raw biomass was treated at temperatures ranging from 200–280 °C and residence time of 30–90 min. The hydrochar produced at 280 °C and residence time of 90 min had the highest calorific value of 29.71 MJ/kg compared to 17.23 and 16.73 MJ/kg obtained from the raw biomass and discard coal, respectively. Regression equations developed using the central composite design (CCD) indicated that the values obtained experimentally agree with the predicted values from the models for mass yield, calorific value, and ash content. The reactivity tests showed that the 100% hydrochar pellet had the highest reactivity and lowest ignition and burnout temperature compared to biocoal pellets and discard coal. The process water contained relatively low concentrations of major elements, and the study had shown that different high-grade biocoal pellets can be produced from the S. lancea tree.

Artisanal and small-scale mining activities as post-mining land use in abandoned mine sites: a case of Giyani and Musina areas, Limpopo Province of South Africa

South Africa has many artisanal and small-scale mining (ASM) activities that some are registered and others informal and illegal. This paper presents an overview of ASM operations in the vicinity of abandoned mine sites found in Giyani and Musina areas, Limpopo Provine of South Africa. It looks at the mining processes, environmental problems, and health and safety risks of ASM in the area. It also provideds a discussion of practical ways of dealing with the problems of artisanal and small-scale mining operations in a harmonized way with the rehabilitation of the abandoned mine sites. The exploitation of waste rock dumps for aggregate production in Musina demonstrated that formalized ASM activities can be the best alternative uses of the abandoned mine sites. However, artisanal gold mining around Giyani revealed the health and safety risks and environmental problems of these operations. The artisanal gold mining activities worsened the health and safety and the environmental problems of the abandoned mine sites. Therefore, this paper recommends that the efforts of coming up with strategies to formalize and regulate artisanal mining in South Africa be deepened for these activities to be accepteble as sustainable as post-mining land-uses in abandoned mines.

SIMULATING THE SENSITIVITY OF UNDERGROUND VENTILATION NETWORKS TO FLUCTUATING AMBIENT CONDITIONS

The weather directly impacts ventilation systems, especially large industrial systems found in underground mines. Underground mine ventilation systems have high cost implications that add to the financial strains and uncertainties of future mining operations. In addition, the dynamic nature of underground ventilation systems makes the accurate prediction of underground conditions extremely difficult using traditional steady-state methods. Therefore, improved prediction methods of dynamic underground environmental conditions are needed to ensure cost-effective ventilation systems. This paper investigates simulating the sensitivity that underground ventilation systems have to fluctuating ambient conditions. Simulation software was applied to a case study on a gold mine in South Africa. The results showed that transient software can now be applied to entire mine ventilation systems, and can improve predicting the underground environment because of fluctuating ambient conditions.

Research on South Africa Mining and Labor Force

As a country rich in mineral resources, South Africa has abundant gold reserves and large mining amount, which effectively promotes the national economic development. However, as the pillar industry, the mining industry also encountered some problems in the process of development, especially the dissatisfaction and protests caused by the long-term development of the mining industry. More and more workers hope that the state will improve the laws and regulations as soon as possible to truly realize the protection of their own rights and interests. By analyzing the development of the mining industry in South Africa, this work first discussed the shortcomings of the labor force in South Africa, and then put forward suggestions on safeguarding the legislative construction of workers' rights and interests.

The Relationship between Activity and Durability of Surface Area and Catalyst Loading of IrOx Anode Catalyst in Proton Exchange Membrane Water Electrolysis (PEMWE)

The R&D of highly active and durable anode catalysts for the oxygen evolution reaction (OER) is very important for high efficiency Proton Exchange Membrane Water Electrolysis (PEMWE). The reason is that the high overpotential of OER reaction is the main factor of the energy loss. At present, the use of highly active and durable iridium catalyst is one of the resolutions for reducing overpotential. From the perspective of iridium production, not only is limited the producing area, but production amount is limited because iridium is by-product of PGM mine in South Africa. Therefore, in order to popularize hydrogen production by large-scale PEMWE, it is necessary to to achieve the high performance with the minimum amount of iridium material. In this study, we report the activity and durability of catalysts coated membranes (CCMs) based on the IrOx catalyst surface area and loadings.High surface area IrOx catalyst (SA100) and a low surface area IrOx catalyst (SA5) from Tanaka Kikinzoku Kogyo K.K. were used for OER catalysts in this study. These catalysts were characterized by ICP-AES analysis, powder XRD, N2-BET, and SEM images. CCMs were prepared by spray-coating and hot-press with IrOx catalysts at the anode and carbon supported platinum at the cathode (TEC10E50E, Tanaka Kikinzoku Kogyo K.K.). Single cell electrochemical analysis including initial polarization curves, cyclic voltammetry, and durability tests (at 50℃, 2A/cm2) and SEM cross section images was studied for all CCMs.The SEM images of the CCMs microstructure near the catalyst layer were shown in Figure 1-A and 1-B. The particle size of IrOx (SA100) was found to be ca.5nm. For IrOx (SA5), the particle size was less than 2nm. The cell voltages focused on the iridium loadings were confirmed in Figure 2-A and 2-B. Although there was significant difference in SEM cross section images of catalyst layers, the trend obtained for the SA100 was consistent with the trend in the SA5. The IrOx loaded from 0.1 to 0.3 mg/cm2 range exhibited a gradual increase in cell potential. Furthermore, the catalytic durability and CV studies using single cells at 2A/cm2, 50℃ will be discussed. This report will be one of the valuable source of information for CCM design for general PEMWE. Figure 1

Synthetic Rock Mass Modelling and Geotechnical Mapping: An Open Pit Mine Case Study in Anisotropic Rock

ABSTRACT Most pit boundaries at Sishen Mine in South Africa consist of Banded Iron Formation (BIF), which exhibits anisotropic behaviour on a rock mass scale. A generally applicable approach is to apply Synthetic Rock Mass (SRM) modelling to characterise rock mass anisotropy. To characterise the rock mass for slope stability analysis, the persistence of bedding planes is very important. Subsequently, a sensitivity analysis on the effect that bedding persistence has on rock mass strength, was performed. Results indicate that bedding plane sizes less than the sample dimensions, produce higher strengths due to the influence of rock bridges. SRM modelling therefore demonstrates that persistence is a critical factor in rock mass strength analysis and subsequent slope stability analyses. The definition of SRMs is completely reliant on data provided by high quality, bench-scale structural mapping. The importance of geotechnical mapping is discussed, as it is currently the only way to accurately determine persistence. The Sishen study is a case in point that geotechnical mapping remains an essential function to obtain the appropriate rock mass characteristics for slope design. Routine mapping exercises, performed by well-trained geotechnical engineers, will therefore remain critical to acquire the necessary input parameters to advance the cutting edge SRM approach.

The toxicity of respirable South African mine tailings dust in relation to their physicochemical properties

Introduction Decades of mining in South Africa has given rise to hundreds of tailings storage facilities (TSFs) and several tonnes of waste. These TSFs have contributed to air pollution due to the lack of proper rehabilitation measures. Currently, it is not known whether tailings emissions could be the cause of respiratory-related ill effects. In addition, the physicochemical properties that may govern their toxicity have not yet been identified. Aim The aim of this research was to determine the toxicity of tailings dust and identify the physicochemical properties likely to govern toxicity. Methods Dust samples were collected from five TSFs in the Gauteng and North West Provinces of South Africa and sieved to enrich the airborne particle fraction more likely to be inhaled. Thereafter, their physicochemical characteristics were assessed i.e. size distribution, specific surface area, shape, surface elemental composition, mineral composition, total elemental composition and surface activity. In addition, the toxicity and cellular internalization of the particles were assessed using the BEAS-2B epithelial and U937 monocytic-macrophage cell lines. Results: The results showed that all tailings dusts showed toxicity, particularly in the BEAS-2B cell line. This toxicity could have been governed by either their elemental composition, e.g. high transition elements e.g. Fe, Cu, Cr and V in the dusts from TSF 4, or a combination of other physicochemical properties, e.g. higher quartz content, lower size and higher surface area in the dusts from TSF 1. Conclusion These results provide mechanistic evidence to support future epidemiological studies attempting to link tailings dust exposure to adverse health effects.

Natural Radioactive Environments as Sources of Local Disequilibrium for the Emergence of Life.

Certain subterranean environments of Earth have naturally accumulated long-lived radionuclides, such as 238U, 232Th, and 40K, near the presence of liquid water. In these natural radioactive environments, water radiolysis can produce chemical species of biological importance, such as H2. Although the proposal of radioactive decay as an alternative source of energy for living systems has existed for >30 years, this hypothesis gained strength after the recent discovery of a peculiar ecosystem in a gold mine in South Africa, whose existence is dependent on chemical species produced by water radiolysis. In this study, we calculate the chemical disequilibrium generated locally by water radiolysis due to gamma radiation. We then analyze the possible contribution of this disequilibrium for the emergence of life, considering conditions of early Earth and having as reference the alkaline hydrothermal vent theory. Results from our kinetic model point out the similarities between the conditions caused by water radiolysis and those found on alkaline hydrothermal systems. Our model produces a steady increase of pH with time, which favors the formation of a natural electrochemical gradient and the precipitation of minerals with catalytic activity for protometabolism in this aqueous environment. We conclude by describing a possible free-energy conversion mechanism based on protometabolism, which could be a requisite for the emergence of life in Hadean Earth.

A compliance driver tree (CDT) based approach for improving the alignment of spatial and intertemporal execution with mine planning at open-pit mines

The sustainable economic success of open-pit mines depends firstly, on the degree of integrity of the mine planning process and secondly, on the extent to which both spatial and intertemporal requirements of approved mine plans are executed. Accordingly, an open-pit mine meeting short-term production targets may fail to achieve planned spatial targets at the detriment of delivering on its long-term mine plan requirements. Therefore, this paper presents a new approach or framework, embedding compliance driver trees (CDTs) to improve the alignment of spatial and intertemporal execution of mine plan requirements, to the mine planning process. A case study application of the CDT-based approach to an open-pit iron ore mine in South Africa showed that when using a spatial mine-to-plan (M2P) index to measure compliance, the spatial mine-to-plan compliance improved from 74% in 2013 to 92% in 2018. The spatial M2P index plateaued at above 90% in the three years 2016–2018, indicating the implementation maturity of the CDT-based approach. The approach enables improved measurement and management of the spatial mine-to-plan compliance to ensure sustainability of the mining operation by maintaining planned levels of mining operational flexibility. The CDT-based approach can be adapted for practical use by the broader open-pit mining industry for economic sustainability of their operations.

Systematic Framework toward a Highly Reliable Approach in Metal Accounting

ABSTRACT Metal accounting is becoming an area of growing focus because of the requirement for the resulting data to feed directly into financial reports. It is vital in the fulfillment of best corporate governance practices and to provide assurance on metallurgical processes. The current metal accounting practices deliver a number of important measures, but an essential change in the approach toward data integrated and auditable metal accounting system is an indispensable need. This work aims to present a systematic framework toward a highly reliable method in metal accounting. The proposed approach introduces a novel mining to product metal accounting scheme and conceptualization of an intelligent metallurgical and metal accounting information management system (MMAIMS). An open cast gold mine in South Africa is presented as a case study. Based on the results and discussions that we have presented in this study, it has been shown that the proposed intelligent MMAIMS will result in improved plant process control, transparent financial reporting, and a suitable understanding of interrelationships between different process activities. The intelligent MMAIMS approach will eradicate data security risks related to multiple-user environment spreadsheets, create reliability in data used for decision-making and operation data synchronization. End to end metal accounting process visibility across the whole process will advance the audibility and transparency of metal accounting from mine to product, and enable good corporate governance and financial reporting of the salable metal product concerning smart mining and mineral processing concept.

Appraisal of Strategies for Dealing with the Physical Hazards of Abandoned Surface Mine Excavations: A Case Study of Frankie and Nyala Mines in South Africa

In order to improve the safety status and the quality of the landscape affected by surface mining, it is important that practical strategies for dealing with the excavations are identified. The aim of the work presented in this paper was to carry out an appraisal of the strategies for addressing the physical hazards of abandoned surface mine excavations in two mines in the Limpopo Province, South Africa. The method used involved carrying out field characterization of the current state and uses of the excavations, as well as their physical hazards of the surface mine excavations in the study area. The characterization took into consideration. Possible strategies for addressing the physical hazards of the excavations are identified, and their strengths, weaknesses, opportunities, and threats (SWOT) analyzed. The Quantitative Strategic Planning Matrix (QSPM) was performed on each of the identified strategies with the purpose of determining their attractiveness based on their SWOT factors. The results of the study showed that using a combination of strategies to deal with the physical hazards of the abandoned mine excavations was the most attractive approach followed by the grading of the slopes of the excavations to improve their stability, while promoting their safe alternative uses. The no-action option and backfilling of the excavations were the least attractive strategies for dealing with the abandoned surface mine excavations. The study demonstrated how semi-quantitative tools, such as the SWOT analysis and QSPM could assist in finding practical approaches for dealing with the problems of abandoned mine sites or features.

Ambiguous Repositories: Archives, Traders and the Recruitment of Mineworkers in the Eastern Cape: 1900–1946

ABSTRACT South Africa’s system of migrant labour is widely accepted as being an exploitative system that was based on the degree to which the Chamber of Mines could derive a profit from cheap labour. The exploitation and suffering that mine labour and recruitment produced, however, tells us only part of a story. Why were people so willing to become migrant labourers – particularly on gold mines – in the first place? This is all the more important because it has been shown that African peasants responded very positively to market forces in the last third of the nineteenth century, and thus would have all the reason more to remain in their rural homes. As in the Caribbean, the Chamber of Mines in South Africa realised that active recruitment was required to launch large-scale migration from one region of Africa into another. But what did this active coercion involve? This paper primarily uses archival and pictorial records to explore how workers could sell their labour so cheaply at the expense of their families and rural homes. Extensive use has been made of the Witwatersrand Native Labour Association (WNLA) and Native Recruiting Corporation (NRC) archives at the University of Johannesburg, as well as personal accounts of ex-traders in the Transkei. These have been used to inform an exploration of how the larger phenomenon of migration was propped up by false advertising, debt and extortion of mineworkers in the Eastern Cape.

Monitoring the development of artisanal mines in South Africa

Monitoring the development of artisanal mines in South Africa