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By I. Ince, S. Kahraman

Preparation of suitable core specimens for physico-mechanical testing s not always possible, particularly for soft and clay-bearing rocks. Although several indirect test methods have been proposed to predict the properties of rocks, specimen preparation from soft rocks for some indirect tests is still difficult. For such cases, the needle penetration test has been developed. In this paper we present a study on the predictability of the physico-mechanical properties of pyroclastic rocks from the needle penetration index (NPI). The NPI, uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), density, and porosity tests were performed in the laboratory on specimens from ten different locations in Turkey. Correlations were established between the NPI values and the physico-mechanical properties. Strong correlations were observed between NPI and both UCS and BTS. General correlations were found between NPI and both density and porosity.

Sep 6, 2023

By T. R. Curr, W. A. Gericke, J. Basson

South Africa is a leading player in the international ferro alloys industry. Historical factors that have contributed to this dominant position include an abundance of natural resources and relatively low cost electricity. A number of relatively recent developments are potentially threatening this position. These include new legislation affecting the mining and minerals industry, a shortage of some types of suitable reductants, depletion of surplus electricity generation capacity with resultant threat of real escalation of electricity prices and pressure resulting from the recent strengthening of the South African Rand. The industry is addressing these challenges in a number of ways to ensure long-term viability. Some of these measures include investments in more efficient technologies that have economy of scale benefits and are less dependent on expensive reductants and electricity. Local macro-economic impacts include new legislation regarding ownership of enter-prises, mineral rights and royalties on mineral sales, development plans for port and rail infrastructure, as well as initiatives to expand electricity generation and coke production capacity. The fundamentals for being a successful ferro alloy producer are still largely in place for South African producers. Therefore the South African ferro alloy industry will remain competitive and is well placed for continued growth in line with the international growth in ferro alloy demand. The industry should emerge leaner, more efficient and ready to respond to any future demands of the industry. This paper will cover the present status of the industry, the factors that are impacting thereon and a view on its future outlook.

Jan 1, 2007

By D. Chetty

Process mineralogy forms an integral part of geometallurgy, with ore body characterisation being but one piece of the puzzle in optimising value derived from ore. This value is not only financial, but importantly speaks to sustainability from environmental and social standpoints. The reactive approach of traditional process mineralogy is increasingly being replaced by predictive methods in the geometallurgical sphere, for which mineralogical information must be timeously acquired on judiciously selected sample sets to understand ore variability and its impact on orebody processing. Such processes are not only metallurgical, but must incorporate mining and waste management protocols. Dwindling resources like water and energy also demand innovative approaches for lowering consumption and/or promoting recycling along the value chain. Addressing such challenges relies on appropriate characterisation of ore behaviour under different process regimes. Coupled with this, emerging characterisation tools are increasingly applied to understand the mineralogy of unconventionallypresented and difficult-to-process ores to meet societal and technology demands. Such tools are often accompanied by the generation of large, computationally intensive datasets, for which data management and storage are key requirements, particularly when deciphering temporal trends in ore and process variability. This paper will elaborate on these themes with examples that highlight the importance of process mineralogy throughout the minerals value chain. Keywords: Process mineralogy, ore characterisation, geometallurgy

Jan 1, 2020

By M. Z. Emad, N. Abbas, Y. Majeed

Room-and-pillar mining is commonly employed for the extraction of rock salt in undergroundmines. Pillar stress is a major concern in these mines as it is directly related to stability and mineralrecovery. In this study a flat jack method was used to measure pillar stresses in three undergroundrock salt mines in Pakistan. The field work included determination of in-situ stress, in-situ elastic modulus, recording of field variables (pillar length and width, height and width of opening, opening width to height ratio, extraction ratio, and overburden height) and collection of salt block samples. The geomechanical properties of rock salt (uniaxial compressive strength, Young’s modulus, Brazilian tensile strength, and density) were also determined to estimate overburden stress, pillar strength, and factor of safety (both estimated and actual). It was found that the measured pillar stresses are proportional to the overburden stress values, with their magnitude ranging from 6.05 MPa to 11.97 Mpa, and the pillars were found to be stable. Regression analysis was performed to develop statistical models for in-situ stress and in-situ elastic modulus. Finally a quick guideline chart was developed to determine the suitable length of pillar for a given span and required level of safety.

Jun 5, 2023

By C. J. Badenhorst

The primary focus of management today is safety, or preventing negative, generally irreversible, events of acute duration. The outcomes of safety-related events are usually visible and can evoke strong emotions if the results are severe. Experts now see that occupational illness and disease also result in significant emotional and financial toll to workers, their families and communities, and to their employers. Effective health and safety management must include acknowledging the importance of occupational health hazards and the proportionate application of resources to address those issues. Improvement in workplace conditions and decrease or elimination of illness and disability are due to actions within the workplace and result from the implementation of risk prevention and control measures. However, success may only be visible months or years later and may require interventions that have to be maintained over prolonged periods. This demands continuous, co-ordinated effort to ensure sustainability of diverse occupational health programmes and the relevant management systems. Too often occupational health is not seen as being part of the general management of business, but rather the function of a medical practitioner somewhere off site in a clinic. Integration of occupational health management systems with other management systems within an organization is essential for its success.

Jan 1, 2004

By E. Öğretici, S. Kahraman

The indirect estimation of intact rock properties is particularly useful for preliminary investigations in engineering projects. In this paper we examine the usability of electrical resistivity, a nondestructive measurement, for the prediction of physical and mechanical rock characteristics. Physico-mechanical tests (uniaxial compression, Brazilian tensile, density, and porosity tests) and electrical resistivity measurements were performed on specimens of 36 rock types. Before the resistivity tests, the specimens were completely saturated with saline solution. Evaluation of the test results showed that there are medium or strong correlations between resistivity and rock properties. There are also strong or stronger correlations between the two parameters for the rock classes. The regression equations developed were statistically tested, and their validity was confirmed. The results were also compared with previous studies. The conclusion is that electrical resistivity measurement can be used for reliably estimating physical and mechanical rock characteristics.

Aug 8, 2024

By B. O. Odera

The Pt-based alloys have a high potential for replacing some Ni-based superalloys (NBSAs) used in the highest temperature and most aggressive environments, and vanadium would be a beneficial alloying element. Six alloys of average compositions Pt-26.6Al-9.1V, Pt-23.1Al-17.8V, Pt-9.6Al-21.1V, Pt-17.4Al-6.4V, Pt-22.3Al-7.9V, and Pt-6.0Al-10.1V (all in at.%) were manufactured by arc-melting and examined in the as-cast condition using scanning electron microscopy and X-ray diffraction (XRD). Five samples were heat treated at 1 000°C for 1 500 hours and water quenched, then examined. The phases were identified using energy-dispersive X-ray spectroscopy and the identities were confirmed by XRD. In most of the samples, the phases existing in the as-cast condition were different from those at 1 000°C after ~1500 hours heat treatment. A solidification projection, an isothermal section and a liquidus surface projection were determined for the Pt-rich corner.

Jan 1, 2012

By T. E. Oates, W. Spiteri

In 2015, after amendments to the explosives regulations, stemming became a mandatory activity for all South African mining operations. There are, however, circumstances in which it is thought stemming has an adverse impact on the blasting outcome. Some of these circumstances include blasting in hot holes, in reactive ground, or when blasting a pre-split. In order to determine when stemming is necessary, its role in the control of adverse blasting phenomena and impact on explosive performance were reviewed. Stemming was found to play a significant role in the fragmentation process and burden movement. Additionally, stemming significantly influences the control of flyrock, air-blast, and toxic fume generation. The review of the literature indicates some motivation for not using stemming for presplit, trim, hot hole, and reactive ground blasting, provided the benefits associated with not stemming the holes outweigh the risks of stemming them. Best practice for stemming from the literature indicates a stemming length of 0.7 × burden is best for larger hole diameters, and 20 to 30 × Ø for smaller hole diameters. Crushed aggregate appears to be the most effective stemming material. The South African explosives regulations pertaining to stemming were found to be consistent with those of Australia and the USA.

Aug 1, 2021

By R. B. Ngenda

The ?Kolwezi Zinc Plant?, in French ?Usines à Zinc de Kolwezi? (UZK), has produced about 910 000 dry metric tons of residues during the hydrometallurgical treatment of calcines from sulphide zinc concentrates. The zinc hydro plant residues contain on average 19.47% Zn, 2.7% Cu, 2.1% Pb, 26.6% Fe, 0.12% Cd, 0.39% As, 157ppm Ag, 447.8 ppm Ga, 475.4 ppm Ge, etc. This material was dumped in five ponds in the vicinity of the plant. The high Fe content in the ore concentrates induced important conversion of some of zinc and copper into ferrites during the roasting process. Those ferrites are very stable compounds, which are difficult to leach with dilute sulphuric acid solution. Therefore, they mainly report to the leaching residues. Hot leaching has been successfully applied to the treatment of zinc hydro plant residues. The method, however, presents the disadvantage of simultaneously dissolving iron(Fe). It is then necessary to remove an important iron quantity from solution prior to zinc and other metals recovery.

Jan 1, 2009

By A. Tello

Variography was introduced by Dr. Pierre Gy to monitor a process, in the sixties. Later on, Francis Pitard extended this concept, building a complete system of variographic controls for different applications. Nevertheless, the existence of information about its use as a way to effectively control plants has been limited. There are infinite areas where variography and chronostatistics can be used. In this paper, two different cases related to gold and silver recovery, through well known but complex metallurgical routes are studied. The use of effective management of process variability software (EMPV) has shown to be a suitable solution to clarify problems at the plant and, consequently, a solution to the encountered problems has been proposed. Chronostatistics is like opening a new world to the metallurgist, making the process variability speak in a more comprehensive and in depth way. Once the ore has been extracted from the mine, sampling is necessary at each sequence of the metallurgical process involved. As a first example, leaching of the ore with cyanide in agitated tanks is another case of a complex metallurgy. The aim of the process is to know about residual values in the tailings in order to optimize process. As a second example, leaching of gold and silver in ore heaps, has to be optimized in terms of time, reagents consumption and, of course, in predicting a reasonable recovery. This last issue appears to be crucial. After cyanide leaching at the heaps, a carbon in columns process is involved, where there are a series of carbon loaded columns that are submitted to a dynamic process of load and unload, to finally deliver an enriched solution to the precious metal electrowinning plant. In both cases, variography has been a good approach to show metallurgists ways to improve the operation.

Jan 1, 2009

By J. O. Claassen

"A study conducted at 22 operating mines in the southern African region indicated that each mine employs about five management and improvement methods with roots in the manufacturing industry. All respondents reported the implementation of cost-saving initiatives, whereas 80% of the mines are affected by restructuring. TQM, Six Sigma, BPM, and TOC were found to be the most prevalent manufacturing management and improvement methods used. A mechanistic vs systemic evaluation of the suitability of these methods to bring about positive change in the industry suggested that complex, ever-changing mining systems are better served by a systemic flow-based approach, which is embedded in methods such as TOC, JIT, TPS, and Lean Production. These methods, however, lack industry presence, possibly because they do not effectively deal with the unique challenges associated with the mining environment. It is argued that successful mining business management and improvement depends on management’s ability to deal effectively with mining industry-specific requirements, the integration of the geologymining- plant system, and the implementation of systemic flow-based principles in all aspects of mining. IntroductionThe study aims to explore the use of manufacturing management and improvement methodologies in the southern African mining industry. Considering the unique challenges associated with mining operations, attention is given to the applicability of the most commonly used manufacturing methodologies in the tactical, operational, and strategic environments. The article endeavours to stimulate more research and debate in an unexplored field of study."

Jan 1, 2016

By K. C. Sole, M. E. Mitshiabo

Although surfactants have proven to increase metal extraction by improving solution flow in porous media, these reagents have not been widely adopted in heap leaching operations because of potential incompatibilities with downstream processes that are subject to surface properties. The BASF leaching aid, LixTRA 118, was previously found to have no significant effect on post-leach operations. This study evaluated its performance in ores of different particle size distributions and the impact on acid consumption and metal recovery. Column leach studies, carried out on a copper oxide ore and mixed oxide–sulfide ore, showed that the effect of LixTRA 118 was more pronounced in ores with wider particle size distributions than in those with more uniformly sized particles. Solution percolation rates increased by up to 18% in the presence of leaching aid, and increased copper recovery and acid consumption. Improved wetting facilitated the kinetics of acid diffusion at macroand micropore level. There was no significant effect on iron recovery

Jan 1, 2023

By G. Akdogan, I. J. Geldenhuys, Q. G. Reynolds

Efficient recovery of titanium from titaniferous magnetite ores continues to be a promising, yet unrealised opportunity, despite significant occurrences of titaniferous magnetite deposits worldwide and the existence of established industrial-scale practices. Current smelting processes only recover iron and vanadium, while the titanium is discarded in the waste slag. These slags are stockpiled and present massive environmental challenges, while still containing value as residual iron, vanadium and titanium. The complex mineralisation of these deposits does not allow for a significant opportunity to separate the titanium and magnetite minerals through normal physical upgrading processes. An upgrading process is therefore required to derive economic value. An efficient process technology could create an opportunity to unlock all three valuable commodities. South Africa’s Bushveld Complex, the largest known deposit of its kind in the world, is known for the high vanadium content but is also associated with relatively high concentrations of titaniferous magnetite. The quality of the Bushveld Complex was one of the drivers for the establishment of the Highveld Steel and Vanadium Company in the mid-1960s. The unfortunate demise of Highveld Steel and Vanadium created an opportunity to review current practices and evaluate the best available process for this complex ore in the context of the three elements of interest. Past and current processes, the nature of these deposits and the potential to recover titanium are assessed to highlight the potential of fluxless smelting of titaniferous magnetite to produce a titania-rich slag as feedstock to the pigment, titanium metal industry in conjunction with recovery of iron and vanadium. Ilmenite smelting practices are proposed as a suitable alternative to achieve the goal, namely sustainable processing. Keywords: Titaniferous magnetite, titanomagnetite, smelting, titania slags, comprehensive processing

Jan 1, 2020

By S. Dey, C. Bhar, S. K. Mandal

Loading and hauling of ore and waste are the key operations of an opencast coal mine and entail a high operational cost. The productivity of a mine can be increased by reducing the cycle time of loading equipment as well as utilizing dumpers optimally. In this paper we discuss the impact of rock type, bucket fill factor, rock fragmentation, the height of the cut, and angle of swing of the bucket on shovel performance. A time study is conducted on shovels in an opencast coal mine with experimental blasts of rocks to assess the impact of different factors on the performance of the shovel. Based on the data, the authors applied multiple regression (MR) and artificial neural network (ANN) techniques to develop different models for the prediction of the shovel cycle time. Developed models are validated by comparing the predicted data with actual field data. With the help of the best model, the plausible fleet size is determined in order to utilize the shovel and dumper optimally and to improve the performance of shovel–dumper operation.

Oct 1, 2022

By P. Saayman

The mining industry has much potential for automation. A great deal of work has been done on this subject and is still ongoing. With automation comes the possibility for optimization, because more information is available and actions can be repeated with more accuracy. This paper looks at possible solutions to the problem of optimizing the autonomous vehicle dispatch system in an underground mine. Possible optimization strategies are evaluated using a simulated environment. The majority of the results indicate that improvements on current methods are possible. Keywords: mining automation, simulation, vehicles, dispatching strategy, optimization.

Jan 1, 2006

By P. O. Osifo, K. Premlall, X. Goso, R. H. Matjie, M. R. Mulaudzi, J. R. Bunt, K. Mphahlele

This study investigates the transformation of pyrolytic spent tyre-derived char and crumb rubber into high-performance activated carbon chars for industrial wastewater remediation. Utilising an in-house macro-thermogravimetric analysis system under an argon atmosphere, spent tyre-derived activated carbon char were synthesised via physical temperature activation and aqua regia demineralisation. Comprehensive characterisation using x-ray diffraction, Raman spectroscopy, and scanning electron microscopy, revealed a predominantly amorphous structure with nanoscale crystallites (~1 nm) and active surface functional groups. Proximate analysis confirmed that both crumb rubber and leached tyre crumb rubber with aqua regia derivatives achieved favourable compositions (ash ≈ 9.6%; fixed carbon ≈ 84%), comparable to commercial activated carbon (AC). At an optimal activation temperature of 850°C, the char of tyre crumb leached with aqua regia variant exhibited a significant surface area of 300 m²/g. Crucially, the tyre crumb char produced at 850°C variant developed a pore volume of 0.8 cm³/g—effectively doubling that of commercial activated carbon (0.4 cm³/g)—facilitating the sequestration of large organic molecules. In application tests using high-strength starch wastewater, char of tyre crumb leached with aqua regia and tyre crumb char, both produced at 850°C, achieved total organic carbon removal efficiencies of 60% and 50%, respectively, bridging the performance gap between waste-derived and commercial adsorbents. These findings validate waste tyres as a viable, low-cost precursor for industrial-grade adsorbents, offering a sustainable circular economy route for tyre valorisation and reduced industrial disposal costs. Future research will focus on kinetic modelling and the recovery of zinc from spent tyre-derived activated carbon char residues.

Mar 30, 2026

By M. Z. Naghadehi, E. Emami, J. Sattarvand, R. Battulwar

In this paper, a methodology for a computerised recognition of joint sets on 3D point cloud models of rock masses is presented. The process starts with classifying joints on a 3D rock mass surface through training a deep network architecture and validated using manually labeled datasets. Then, individual joint surfaces are identified using the Density-Based Scan with Noise (DBSCAN) clustering algorithm. Subsequently, the orientations of the identified joint surfaces are computed by fitting least-square planes using the Random Sample Consensus (RANSAC). Finally, the joint planes are classified into different joint sets, and the dip direction and dip angle for each set are calculated. The performance of the proposed methodology has been evaluated using a case study. The results show that the presented procedure is fast, accurate, and robust.

Sep 1, 2021

By N. V. Moraka

In dealing with transformational aspects, the South African Constitution aspires for a balance between attempts to broadly represent the country’s demographics in the way in which organizations are structured and the need to maintain the necessary skills to ensure continual retention of skills for optimum and efficient organizational performance. Through the Mining Charter, government aimed to redress gender and racial imbalances in the mining industry as part of transforming the demographic representation of mining companies to include black people, women, and people living with disabilities in all job levels up to top management. While the Constitution calls for an appropriate balance between demographic representation and competency, this aspiration for mining poses challenges for companies due to the proficient and competent skills needed in this industry. To this end, the South African mining industry has been subjected to substantial criticism from government regarding the slow progress of transformation. The mining industry justifies its slow pace of transformation by pointing at inconsistent, varying legislation and definitions governing transformation, limited skills available from historically disadvantaged groups, and cautioning not to compromise the sustainability of mining companies by marginalizing white males and white youth with the objective of addressing racial imbalances. This lack of understanding between industry and the government has led to considerable confusion regarding the accountability of stakeholders in transforming the industry. This article presents the perspectives of ten mining executives on transformation in the South African mining industry. The theoretical description of transformation, as well as other mining stakeholders’ interpretations of transformation. is presented. Qualitative data from interviews with mining executives demonstrates their understanding of transformation through rich descriptions, interpretations, and implications in their contexts. The findings demonstrate that transformation in the mining industry is not simply about race and gender, but about cultural change, a change in mind-sets, embracing diversity, equalizing rights and opportunities, and attaining social justice. Moreover, transformation is clearly a gradual process. The article concludes with a recommendation for the definition of transformation to be corroborated with the views of mining executives and that of the Constitution of South Africa. This will create an overarching, simplified definition of transformation that can be accepted and interpreted by all stakeholders.

Jan 1, 2016

By M. Mokgohloa, T. R. Stacey

Boring of tunnels and shafts in hard rock under high stress conditions is becoming more common as mines and tunnels are developed at greater depths. Under the high stress conditions, fracturing of the often-brittle rock occurs in the walls, backs, and ahead of advancing faces of excavations. Fracturing can have a significant impact on boring activities: sidewall spalling, which affects machine gripper capacity, and fractures can also develop in the rock ahead of the face, leading to blocky rock conditions, which may have a significant effect on machine excavation. Fracturing may develop dynamically, leading to rock bursts manifesting in the form of strain bursts, which can be hazardous and destructive. In brittle rock, fracturing is commonly extensional in nature. The focus of this paper is on fracturing in the face of the excavation. Examples of such fracturing behaviour are described briefly in the paper. Numerical analyses were carried out to predict the initiation of extension fractures and their orientations ahead of excavation surfaces, and the resulting formation of rock slabs/plates, and the stability of these plates. The results should be beneficial for the evaluation of the conditions prior to, and during boring operations.

Nov 27, 2024

By R. H. Matjie, J. R. Bunt, A. C. Collins, J. C. van Dyk, C. A. Strydom

South African discard coal fines and K₂CO₃ blends were heated in a laboratory-scale rotary kiln to produce ashes for H₂SO₄ leaching tests. The optimized H₂SO₄ leaching conditions of 6.12 mol.dm³ (M) H₂SO₄, solid to liquid ratios 1:5 and 1:10, and 80°C for 8 hours were used. K₂CO₃ was added to increase the dissolution efficiency of K. The objective was to determine if the Al present in metakaolinite (Al₂O₃.2SiO₂), the Al, K, and Ti in the alumino-silicate glasses, and the Ti in rutile (TiO₂) in the ashes could be selectively dissolved in H₂SO₄. XRF results show that the ashes formed at 700°C dissolved more efficiently (87% Al, 89% K and 23% Ti) compared to the ashes formed at 1050°C. This can be attributed to the presence of Al₂O₃.2SiO₂, K₂CO₃ melt, K₂CO₃ remnants, KAl(SO₄)₂, and K-aluminosilicate glass in these ashes. XRD results indicate that the ashes prepared at 1050°C contained anorthite (CaAl₂Si₂O₈), microcline (KAlSi₃O₈), pseudomullite (Al₂O₃.SiO₂), and silicon spinel (2Al₂O₃.3SiO₂), which are either insoluble or only sparingly soluble in H₂SO₄. These minerals resulted in the lower dissolution efficiencies of Al and K. Based on the high dissolution efficiencies of Al and K for the ashes produced at 700°C, coal fines blended with K₂CO₃ could possibly be utilized as feedstocks for the production of aluminium(III), potassium(I), and titanium(IV) and a sulphate-containing leach liquor. Furthermore, the environmental issues and costs associated with the handling and disposal of large volumes of coal fines will also be resolved.

Aug 2, 2022