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By M. -H. Fillion

"Geotechnical stability analysis and design in open pit mines requires access to representative geological, structural, hydrogeological, and rock mass models. The quality and quantity of collected geomechanical data used to build such models can have significant implications in the design of safe and economically viable slopes. Data collection is a continuous process throughout the life of a mine. The process starts from exploration to conceptual/preliminary feasibility, feasibility, design and construction, operations (early production/late production), and mine closure.As geomechanical data is often limited at an early stage of a project, the estimated variability of the geotechnical factors may be larger than the actual data variability. This can potentially result in a conservative selection of the pit slope angle. Collecting additional geomechanical data at later stages of the mine development may contribute to reducing the uncertainty associated with the geotechnical properties and a steeper slope angle may be used for the design. This can result in significant economic benefits.This paper investigates the impact of access to new data over time, following a series of geomechanical data collection campaigns, on design decisions. This is illustrated by comparing the resulting slope design, at three stages of the mine project, at a South African open pit mine. To demonstrate this, a series of slope stability analyses were performed using limit equilibrium tools. For each project stage, the slope angle design was modified until a similar probability of failure of 5% or less was obtained. The corresponding factor of safety distributions for each project stage were then compared to evaluate the impact of collecting additional data on the resulting slope design.The results showed that data variability can differ significantly from one project stage to another. Data variability may be greater at more advanced project stages (i.e. a wider distribution of the factor of safety). Furthermore, the results showed that, even for the cases with greater variability, steeper slope angles were possible at more advanced stages for the proposed design requirement (probability of failure < 5%). In this investigation, as more data became available, the uncertainty associated with data variability could be sufficiently reduced to allow the selection of less conservative slope angles. This can be used as a managerial tool in developing data collection strategies and allocating the necessary funds, and can lead to important economic benefits to the mining operation."

Jan 1, 2016

By F. Dinter, S. A. C. Hockaday, Q. G. Reynolds

The thermal decomposition of carbonate minerals as pre-treatment before smelting reduces the energy requirement for smelting. It can also make the combustion of fossil fuels for heating unnecassary. Thermal decomposition may become important in reducing greenhouse gas emissions when producing ferromanganese alloys while simultaneously reducing electrical energy demand during smelting. A kinetic reaction rate model for the thermal decomposition of manganese ores is presented, based on published reaction rate kinetics for the decomposition of manganese oxides and calcium carbonate. The model was validated against thermogravimetric data for two carbonaceous manganese ore samples and one ferruginous manganese ore sample. The reaction rate model shows that carbonate minerals in the manganese ores are decomposed at temperatures above 900 °C while pyrolusite is decomposed at temperatures from 450 °C to 500 °C. Mn2O3 decomposes rapidly at 550 °C. Braunite decomposition at temperatures below 1000 °C was negligible. The presence of organic carbon in the samples led to further reduction of the samples during thermal treatment.

Aug 3, 2023

By M. Tangstad, J. D. Steenkamp

In April 2013 a 48 MVA submerged arc furnace producing silicomanganese was excavated in South Africa. Since the high shell temperatures recorded in the tap-hole area resulted in the furnace being switched out for relining, the tap-hole area was excavated systematically. A refractory wear profile of the tap-hole area with affected hearth and sidewall refractory was obtained in elevation. The carbon ramming paste in front of, above, andbelow the tap-hole was worn, as was the SiC with which the tap-hole was built. A clay mushroom formed but was detached from the refractories. Thermodynamic and mass-transfer calculations were conducted to quantify the potential for wear by chemical reaction between refractory and slag and refractory and metal in the tap-hole area. It was found that chemical reaction between refractory and slag or metal could offer only a partial explanation for the wear observed; erosion is expected to contribute significantly to wear.

Jan 1, 2015

By B. P. Watson, D. Hoffmann, D. P. Roberts

Potholes on the Merensky and UG2 reefs in the Bushveld Complex occur as near-circular to elliptical depressions or slumps on the reef horizon, normally presenting as severe disruptions which prevent economic extraction. Within the pothole, the reef and other strata may either be attenuated, absent, or highly deformed, this being the result of the overlying hangingwall strata having slumped down. The hypotheses for pothole formation involve several mechanisms, including downward erosion, upward fluid movement, or synmagmatic deformation. When potholes are exposed in mine workings, significant fracturing is often observed. This fracturing is particularly evident in anorthosite rock types. Stress measurements were conducted in a pothole on the Merensky Reef to determine if the fracturing was due to high stress conditions. The paper describes the measurement results and numerical modelling that was done to determine the influence of depth and mining on the stress condition at the site. The results show that high stresses do exist in at least some potholes, and that current formation theories do not adequately explain the measured stresses. In support of understanding the high local stress associated with the pothole, the study explored several rock engineering modelling processes to validate the conditions of the study site and enclosing excavations. A better understanding of the stress conditions in potholes with additional data could lead to more appropriate support design and avoidance of potential rockbursts in these structures.

Jan 1, 2021

By J. A. Maritz, D. F. Malan

Pillar strength is affected by pillar shape, but this has largely been ignored in past research studies. Bord-and-pillar layouts are typically designed using empirical strength equations developed for square pillars. Owing to the poor quality of pillar cutting, many hard-rock pillars have an irregular shape and it is not clear how this affects pillar strength. Furthermore, the strength of rectangular pillars in comparison with square pillars is also difficult to quantify. The ‘perimeter rule’ is widely adopted for rectangular pillars, but its applicability for pillars with irregular shapes has never been tested. We used numerical modelling in this study to investigate the effect of pillar shape on strength. An analytical limit equilibrium model of a square and a strip pillar also provided useful insights. For slender pillars, the strength of a long rib pillar is essentially similar to that of a square pillar. In contrast, for rib pillars with a large width to height ratio, there is a substantial increase in strength. The study found that the perimeter rule should not be used for irregularly shaped pillars. Displacement discontinuity modelling, using a limit equilibrium approach, is proposed as an alternative to determine the strength of these pillars.

May 3, 2023

By M. Kerr

Background- History The most significant change in mining since the late 1970?s has been the emergence of very large scale mining operations , which have been developed to ensure profitability with relatively low grade ores. These large tonnage operations have resulted in the development of larger unit sized machines in all operations of beneficiation, solid-liquid separation and dewatering. Often only a few flotation lines are installed and tonnages up to 25 ktpd and beyond are not uncommon. The increased throughputs have led to the development of circular, reactor type tank designs. The reactor cell system is the most up to date flotation cell design to utilise the principles of circular cell design. The Svedala DV mechanism was specially developed to suit the RCS machine giving good solids handling characteristics and excellent metallurgical performance. Development of UG2 ore type flotation equipment The equipment was developed and optimised by Svedala process from 1995. A higher energy specification was requested by industry. This amounted to 3kW/m3 for installed volume. Existing designs were at 1.5kW/m3. Hence various modifications were required to achieve the required power input. The first 50m3 machines were installed and developed at Impala Platinum?s UG2 circuit over a one year period. Once reliability and performance was achieved, over 300 large volume flotation cells were installed at Anglo Platinum and Lonmin operations as well. Pilot Plant Development The Impala Platinum High Energy pilot plant was commissioned in 2002 and had an installed power exceeding 5kW/m3. It was operated for over a year at the tailings dam booster station and was fundamental to the large scale scavenging plant design. All experience in overcoming mechanical and operational problems was applied in scale up design principles. A very robust mechanism was designed to accommodate the additional power input from installed motors, as well as the high SG (>1.5) of the feed source. The pilot plant flowsheet is shown in the figure below.

Jan 1, 2007

By G. C. Lindeque

"A downward trend in tyre life on haul trucks at an open pit iron ore mine prompted an investigation into the current tyre management strategy in order to improve tyre life. ‘Best practice’ was compared to the current tyre management strategy at the mine to determine aspects that could be improved. Aspects that showed significant room for improvement included employee tyre awareness, tyre pressure maintenance, and road conditions. For each of these aspects a plausible alternative was suggested.A new tyre management strategy was formulated as a step-by-step guide on how to implement the proposed changes. Each step introduces new initiatives but at the same time builds on the previous step’s success. A sensitivity analyses was performed to determine the impact of the proposed changes, with the variables being the reduction in the percentage of premature tyre failure, and the reduction of the site wear rate.The ‘most likely’ scenario showed an increase in tyre life of 41% for the Komatsu 730 trucks and 105% for the CAT 777 trucks if the entire tyre management model is implemented. This would result in a possible annual saving related to tyre usage of R9.2 million. OverviewThe study focused on the tyre life on the main haul fleet at an open pit iron ore mine. The haul fleet consisted of 17 Komatsu 730 (180 t) haul trucks and 12 CAT 777 (90 t) haul trucks.The haulage operation consists entirely of tyre-based haul trucks. Five per cent of the total mining budget is related to tyre costs. Since 2012 there has been a steady decrease in tyre life as measured in operating hours (Figure 1) due to the high percentage of tyres that fail prematurely. In 2014 a total of 41% of all tyres failed prematurely and 61% were classified as ‘worn out’."

Jan 1, 2016

By M. Matabane, T. Khati

"Accurate delineation of the contact between a kimberlite pipe and country rock at production level depths is a challenge due to limited geological data. Geological information is obtained from widely spaced diamond core boreholes which are drilled either from surface or from higher mining levels within the pipe. Kimberlite pipe/country rock contacts are notoriously irregular and variable, further reducing the confidence in contact positions defined by the drill-holes. At Finsch Diamond Mine (FDM), the opportunity arose to further improve the confidence in the contact positions relative to the planned slot (end) positions of each sublevel cave tunnel during the development stage of these tunnels. As a result, the accuracy of the 3D geological model has improved.The use of diamond drill core for this purpose is expensive due to site establishment requirements. The lengthy time taken during site establishment also delays the development of tunnels and support cycles, thereby extending the completion dates. FDM has reduced delays during development by adopting percussion drilling, in conjunction with gamma ray logging. The S36 drill rig is mounted on a moveable platform and does not require a costly and lengthy site establishment. The holes are generally drilled (0°/flat) on grade elevation, and these holes could also be drilled from the rim tunnels (developed in waste) into the kimberlite pipe. A single-boom production drill rig is normally used to drill holes about 20 m in length.On completion of the contact delineation drilling, gamma logging of the holes is conducted using the GeoVista geophysical sonde (or probe) to log the natural gamma signature of the dolomite/ kimberlite contact. The advantage of this tool is that the readings are continuous within centimetre intervals, and due to contrasting characteristics between kimberlite (rich in clay minerals) and dolomite, the contact position can be determined accurately. The better definition of contact positions also adds value to tunnel stopping distance in terms of developing the tunnel’s slot at the optimum distance from the contact (easier blasting of longhole rings, avoidance of contact overbreak and premature waste ingress, and other matters relating to extraction of ore from these tunnels). This method is highly successful and has reduced development costs (on-time completion), improved definition of the pipe’s contact position for geological modelling, improved blast design, and mitigated early waste ingress by maintaining the contact’s integrity."

Feb 1, 2019

By B. k. Kenzhaliyev, M. A. Naimanbayev, Zh. A. Baltabekova, N. G. Lokhova

In research various desorbents were used to desorb the following rare-earth metals from Purosorb 140 cation exchanger, i.e. ammonium chloride; ammonium sulfate; a mixture of nitric acid and ammonium nitrate; a mixture of hydrochloric acid and ammonium chloride; a mixture of sulfuric acid and ammonium sulfate. It was established that a solution containing 30 g/dm3 of H2SO4 + 300 g/dm3 of (NH4) 2SO4 is the most optimal desorbing solution to desorb REMs from macroporous Purosorb 140 cation exchanger impregnated with rare-earth metals from industrial dihydrate wet-process phosphoric acid. It was established that the residual REM content in the cation exchanger decreased from 0.89 to 0.10 wt. % with an increase in the ammonium sulfate concentration from 10 to 400 g/dm3. Technological desorption regimes for rare-earth metals from cation exchanger were developed. The optimal conditions were determined to desorb rare-earth metals from the Purosorb 140 cation exchanger, particularly temperature 25°C; L:S ratio = (0.8 ÷ 1.1):1; duration = 1.0-1.5 hours. Keywords: Rare elements, sorption, cation exchangers, wet-process phosphoric acid, desorption

Jan 1, 2020

By D. F. Malan, R. P. Els

The limit equilibrium model, used in displacement discontinuity codes, is a popular method to simulate pillar failure. This paper investigates the use of physical modelling to calibrate this model. For the experiments, an artificial pillar material was prepared and cubes were poured using the standard 100 mm × 100 mm civil engineering concrete moulds. The friction angle between the cubes and the platens of the testing machine was varied by using soap and sandpaper. Different modes of failure were observed depending on the friction angle. Of interest is that significant loadshedding was recorded for some specimens which visually remained mostly intact. This highlights the difficulty of classifying pillars as failed or intact in underground stopes where spalling is observed. The laboratory models enabled a more precise calibration of the limit equilibrium model compared to previous attempts. Guidelines to assist with calibration of the model are given in the paper. The limit equilibrium model appears to be a useful approximation of the pillar failure as it could simulate the stress-strain behaviour of the laboratory models.

May 3, 2023

By J. S. Contreras, E. Córdova, I. Gottreux, A. Anani, A. Ferrada

Cave mining is an underground mass mining technique. The largest projects, which are known as ‘super caves’, produce hundreds of thousands of tons of ore per day, which involves large footprints with considerable column height, and have a life of mine of over 20-40 years. These operations are typically located deep, under high stresses and in competent rock masses, making initiation and propagation of the caving process harder to manage. These challenges must be confronted by optimizing the fragmentation of the orebody to achieve smaller size blocks that will result in consistent caving and improved flow of the ore from the drawpoints. To achieve better performance from the drawpoints, preconditioning is applied to fragment and damage the material required to cave. We present a proposed design for preconditioning in underground mines, considering the challenges that these large-scale mines are already facing, based on a comprehensive analysis of current design parameters, case studies, and sensitivity analyses using numerical models.

Feb 2, 2021

By K. Sasaki, S. Kuroiwa, H. Miki, Y. Aoki, T. Hirajima, Y. Orii, G. P. W. Suyantara

Selective flotation to separate copper minerals from, for example, Mo- and/or As-bearing minerals is a continuing problem because the selectivity of current systems is imperfect. Selective Cu-As flotation is currently difficult, and the most common Cu-Mo selective flotation method uses NaHS; this must be done in an enclosed system because, under acidic conditions, this method produces hydrogen sulfide. In this paper, some novel alternative flotation processes that use redox reactions are discussed; these methods have a much lower environmental impact. Oxidation and reduction reactions can be used to make copper minerals more hydrophilic and Mo-bearing minerals more hydrophobic. X-ray photoelectron spectroscopy (XPS) analyses indicated that the copper minerals became hydrophilic because hydrophilic iron precipitated and several hydroxides covered the copper minerals’ surfaces, whereas the molybdenum minerals remained hydrophobic because their sulfide surfaces were not covered. Flotation experiments on these minerals after redox treatments indicated that excellent separation of Cu-minerals from Mo-minerals can be achieved. Possible mechanisms for this separation were investigated using detailed surface analyses and thermodynamic calculations. The additives used to initiate the redox reactions are easy to handle and make these new flotation procedures better than current processes because the new methods do not emit effluent gas and because they are commercially viable. Keywords: Flotation; chalcopyrite; molybdenite; oxidation; reduction

Jan 1, 2020

The Annual General Meeting of the South African Institute of Mining and Metallurgy was held in Kelvin House, Johannesburg, on Wednesday, 27th August, 1975. Professor R. P. Plewman (President) was in the Chair. There were present 45 Fellows, 37 Members, 8 Graduates, 3 Associates, 4 Students, and 45 Visitors, making a total of 142. The President declared the Meeting open at 16h00. OBITUARIES The President: Ladies and gentlemen, it is my sad duty to announce the death of the following members of the Institute : M. Barcza, an Honorary Life Fellow and Past President of the Institute; J. A. Boyd, F. E. Keep, and J. H. Taylor, Life Fellows ; I. D. B. Corner, C. O&apos;G. Deane, R. E. Gilmour, A. C. Hofmeyr, M. W. Howell, T. J. Robin, and F. S. Steinhobel, Fellows; J. J. Frankel, Member; and T. J. Higgs, Associate. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, I ask you to rise and observe a few moments&apos; silence. MINUTES The President: May we confirm the minutes of the General Meeting held on March 12th 1975 and published in the June issue of the Journal? Agreed. WELCOME The President: It is now my very great pleasure to welcome the many members of our Institute and all the distinguished guests who have honoured us with their presence this afternoon. In particular, I would like to welcome our Honorary President, Mr R. S. Lawrence, President of the Chamber of Mines, and also our Honorary Vice-President, Mr T. L. Gibbs, the Government Mining Engineer. Ons is ook besonder vereer dat dr. Naude, die Wetenskaplike Raad-gewer aan die Eerste Minister, en mnr. C. A. J. Borman, Direkteur van die Witwatersrandse Kollege vir Gevorderde Tegniese Onderwys, hier aanwesig is om die vergadering by to woon. We are also honoured by the presence of some 19 Presidents, Vice-Presidents, and Chairmen of our sister scientific and technical organizations. I would particularly like to welcome Mr Gericke of the South African Council for Professional Engineers, Professor Pretorius of the A.S. & T.S., and Dr Lloyd of F.S.P.E. And then, also the Presidents of the Institute of Welding, Professor Robinson; of the Electrical Engineers, Dr Troost ; of the Certificated Mechanical and Electrical Engineers, Mr Gibbs; of the Geological Society, Professor Maske; of the Land Surveyors of the Transvaal, Mr Course ; of the Assayers and Analysts, Mr Williams; of the Mine Ventilation Society, Mr Martinson; of the Chemical Institute, Mr Goodman; of the Association of Mine Managers, Mr Pretorius ; of the Institute of Foundrymen, Mr Attenborough; of the Production Engineers, Mr Duggan ; and of S.A.F.U.E.S., Mr Avalle. Then, the Chairman of the Council of the Institute of Metallurgists, Mr Snow; the Vice-President of the Town and Regional Planning, Mr Reinecke; the Vice-President of the Association of Consulting Engineers, Mr O&apos;Kell; and Mr Cronje, who is representing E.A.S.A. Finally, the Chairman of the Southern Transvaal Section of the Chemical Institute, Mr Bloom ; the Chairman of the Witbank-Middelburg Branch of our own Institute, Mr Hosking; and the Secretary-Treasurer of our O.F.S. Branch, Mr Bird. We also have with us Mr Trueman; the Deputy Manager of Kelvin House, Mr Mrost ; our Honorary Editor, Dr Glen; Mr Walford; and also some representatives of the Press. Finally, it gives me great pleasure to welcome those who will receive Honorary Life Fellowships tonight, and also the winners of our student prizes. MEMBERSHIP The President: Ladies and gentlemen, I have pleasure in announcing the names of the following candidates, which have been published in accordance with By-Law 5.2.5., and Council has elected them to membership in the following grades: Fellows: R. G. Boswell, R. W. Chadwick, D. R. Hardman, J. A. Holmes, T. J. B. Jones, and R. P. King. Members : M. A. Bridgeford, C. F. Bonney, H. E. Bartlett, L. G. Floyd, A. K. Haines, D. Hatfield, C. G. Heymann, M. J. Howes, J. B. See, E. van Greunen, and S. P. Swanepoel. Associate Members : J. Coetsee and R. P. G. Steyn. Graduates: J. J. de Villiers and J. C. King. Associates: B. J. Bucher, P. A. Combrinck, W. J. N. Gelderblom, L. S. Halasz, J. van Wyk, C. P. Visser, and A. Veress. Students: D. J. Claasens, P. C. Crous, D. H. Murchison, P. A. Rossouw, and J. P. L. Schultz. Company Affiliates: Airco Engineering (Proprietary) Limited and Deelkraal Gold Mining Company Limited. There have also been some transfers: Member to Fellow: J. B. Nangle. Graduate to Member: E. E. Eichenbergen, M. J. Hillbeck, L. A. Melis, P. J. Venter, and R. O. Wellman. Associate to Associate Member: B. M. Williams. I welcome the newly elected members to the Institute, and I congratulate those who have been transferred to a higher grade.

Jan 10, 1975

By B. Emwanu, R. A. Raju

The implementation of new technology in mining can be likened to a paradoxical situation or dilemma, where, on one hand, major mining projects are not able to solicit investor funding unless it is proven that the business cases were developed using tried and tested mining methods. On the other hand, new and innovative mining technology and mining methods need first to demonstrate and prove themselves under real production conditions over a reasonable period before they can be considered bankable feasibility studies in the mining industry. This dilemma locks new mining technology investments in a continuous cycle of underinvestment. Technological innovations are particularly relevant to the mining industry, which deals with the challenges of depleting access to resources, requiring new solutions to remain sustainable and competitive. In the last decade, the mining industry has come to realise that technological innovations can directly contribute to its sustained competitive advantage (Sanchez, Hartlieb, 2020), helping to reduce costs, lessen environmental impact, increase production, and improve mineral recovery. While understanding barriers and drivers for technology adoption is important for the success of technology implementation efforts and the sustainability of the mining sector (Muduli et al., 2013), this paper suggests strategies to exit the dilemma, proposing a preliminary framework.

Oct 24, 2025

By M. Grozdanovic, D. Marjanovic, M. Ilic

We present a framework for solving the problem of functional compatibility between process control equipment in control centres at underground mines and operator capabilities. The equipment incorporates displays of current ventilation, gas, and fire hazard data, status of alarm and early warning systems, a voice communication subsystem, and facilities for recording and printing ofdata and reports. The layout of the existing control panel is compared with a recommended design. The basic principles of ergonomic design and arrangement of the controls and indicators, as well as ease of use, type of operations carried out with these controls, and operators’ viewing angles are discussed. The objective is to improve the usability of control panels, display boards, and graphic screens so as to enhance the functioning of control centres and optimize control of technological processes in coal mines.

Jun 10, 2024

By E. C. de Beer

"SynopsisA number of important areas in nuclear fuel cycle, at both the front end and back end, offer ideal opportunities for the application of non-destructive evaluation techniques. These techniques do not only provide opportunities for non-invasive testing of e.g. irradiated materials, but also play an important role in the development of new materials in the nuclear sector. The advantage of penetrating radiation used as probe in the investigation and testing of nuclear materials makes X-ray and neutron radiography (2D) and tomography (3D) suitable for various applications in the total nuclear fuel cycle. The unique and different interaction modes of the two radiation probes with materials provide several opportunities. Their complementary nature and non-destructive character makes them most suitable for nuclear material analyses, analytical method development, and the evaluation of the performance of existing nuclear material compositions. This article gives an overview of the X-ray and neutron radiography/tomography applications in the field of nuclear material testing, and highlights a few of the success stories. Several selected areas of application in the nuclear fuel cycle are discussed to illustrate the complementary nature of these techniques as applied to nuclear materials.IntroductionDuring the development of new materials for the nuclear industry, materials testing and characterization are of the outmost importance to maintain safety standards and reliability. No compromise on safety in the workplace in any area within the total nuclear fuel cycle can be tolerated, and therefore most in-situ material characterization and testing is conducted by certified and qualified personnel schooled in destructive and non-destructive testing (DT and NDT) methods. Certification and qualification in NDT can be obtained through many training centres in South Africa in accordance with European, American, and other international standards (SGS, n.d.; SAIW, n.d.; African NTD Centre, n.d.)."

Jan 1, 2015

By W. C. Joughin

The science of soil mechanics is 100 years old, and rock mechanics is about 80 years old. While methods of analysis and design have been developed and have evolved over time, these are relatively young sciences. The rapid increases in computing power and new technologies have enabled more sophisticated modelling and monitoring. However, there are still many aspects of soil and rock mechanics that are not well understood. Geotechnical failures, which have major consequences, still occur. These consequences may include environmental damage, major production holdups and associated loss of revenue, damage to infrastructure, and loss of life. High-consequence events, which are rare, are more difficult to anticipate and to design for, because by their nature they involve extraordinary circumstances or conditions, often geological in nature. The risks are usually mitigated by conservative designs and monitoring. Detailed geotechnical investigations help us to understand the natural variability of soil and rock masses and identify unusual or unexpected conditions. Investigating and researching major geotechnical failures is essential to enable these unusual circumstances to be anticipated. In the past, severe unanticipated events may have been treated as natural events or ‘acts of God’. However, society now has much greater expectations and it is essential to have policies and procedures in place that enable appropriate management of these rare, high-consequence risks. A good example is the Global Industry Standard on Tailings Management (GISTM), which was introduced after the catastrophic dam collapse at Vale’s Corrego de Feijao mine in Brumadinho, Brazil. The address will explain the concepts of uncertainty and variability, and how they should be taken into account in geotechnical design. The challenges facing geotechnical engineers, mine owners, and managers will be discussed. referencing a number of real case studies.

Sep 6, 2023

By T. Dlokweni, M. Bester, C. Koegelenberg, I. Basson

Certain degrees of safety, economic, and financial risk are implicit in any mining operation. At Thabazimbi Mine, slope stability was one of the major sources of risk, largely due to data uncertainties. Consequently, a risk-based approach in slope design was followed. On 6 June 2015, a slope failure occurred in Thabazimbi Mine’s Kumba pit, involving approximately 65 million tonnes of rock failing into the pit and the valley below. Although the failed mass moved rapidly and resulted in a run-out distance of approximately 900 m, controls had been put in place to successfully evacuate all personnel. Risk assessment during the onset of failure supported the decision to not compromise the safety of personnel in any way, leading to unavoidable equipment loss. This contribution presents the failure as a case study in the context of a risk-based approach to slope design as well as the importance of implementing geotechnical controls to effectively manage slope instability risk. Furthermore, a comprehensive back-analysis was performed, on a fully constrained 3D model, utilising 3DEC software, to gain insights into the failure mechanism. In conclusion, lessons from the Thabazimbi slope failure are valuable as they demonstrate the importance of following a risk-based approach in slope design to effectively manage safety and financial risk in open pit mines.

Sep 1, 2025

By N. Baloyi, P. Popoola, M. Tlotleng, S. L. Pityana

"The advantages of using Nb and Ti-Nb coatings for improving the hardness and corrosion resistance of Ti6Al4V were investigated. It has been reported that Ti6Al4V used in orthopaedic implants tends to release toxic Al and V ions into the surrounding tissue. Thin layers of Nb and Ti-Nb were deposited on Ti6Al4V substrates using a laser metal deposition technique. The deposited material was analysed using optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, and X-ray diffraction. The corrosion behaviour of the deposited layers was investigated using a Metrohm Autolab PG Stat101 compact potentiostat at 25°C in simulated body fluid. A Vickers hardness system was used to study the mechanical properties. Both Nb and Ti-Nb coatings exhibited good metallurgical bonding with the substrate. The microstructure and the XRD analyses for the Nb system showed that the ??-Nb phase was most dominant, while the Ti-Nb system comprised a mixture of the ?? and ?? phases. The average hardness of the Ti6Al4V substrate was 350 HV0.3, with a slight increase for the Nb coating (363 HV0.3) and a much higher hardness from the Ti-Nb coating at 423 HV0.3. The corrosion results show that the deposited Nb was more corrosion-resistant in the solution than either the Ti6Al4V substrate or the Ti-Nb coating. IntroductionMetals such as CoCrMo, 316L stainless steel, and NiTi alloy are used for manufacturing biomedical implants because of their distinct properties, including low Young’s modulus and resistance to corrosion (Ryan, Pandit, and Apatsidis, 2006). These implants are required to remain in the body of the patient for many years. Due to a favourable combination of mechanical and corrosion properties, titanium (Ti) and its alloys have emerged as the material of choice for biomedical implants. Nevertheless, their use is not entirely without challenges. For example, in total hip replacement, surface degradation and release of metal debris from metal erosion caused by friction limit the service life of the implant (Oldani and Dominguez, 2012; Manivasagam, Dhinasekaran, and Rajamanickam, 2010). Ti6Al4V is generally regarded as the material of choice, but it has been found that over extended periods of time, the combination of surface corrosion and erosion releases toxic aluminium (Al) and vanadium (V) ions into the body (Khan, Williams, and Williams, 1996). This has led to the investigation of titanium alloys containing niobium (Nb), zirconium (Zr), tantalum (Ta), and molybdenum (Mo) as substitutes for the aluminium- and vanadium-containing Ti6Al4V (Okazaki et al., 1997)."

Apr 1, 2019

By W. Newcomen, G. Dick

"Effective management and mitigation of pit slope instability in open pit mines begins with a comprehensive slope monitoring programme. The ability to differentiate between non-critical pit wall movements due to rebound or relaxation of the excavated slopes and movements that may be indicative of slope failure is important for maintaining a safe working environment and maximizing production. Slope failure prediction methods using velocity, acceleration, and strain criteria have been introduced and put into practice over the past few decades. Forty-eight slope failures with surface monitoring data are presented and assessed using the strain-based failure prediction approach, with consideration of the quality of the rock mass and the potential failure mechanism. The results indicate that the strain-based approach can be used to provide general guidance regarding strain thresholds for pit walls for a variety of failure modes in diverse geological environments. The advantages and potential drawbacks of the strain-based and other slope failure prediction methods are discussed. The importance of implementing a pit slope monitoring and performance evaluation system early in mine development is also emphasized. IntroductionThe successful prediction of the Manefay Slide pit slope failure at Bingham Canyon at 9:30 am on 10 April 2013 (Engineering and Mining Journal, 2014) highlighted the importance of having a comprehensive slope monitoring system that provides an accurate prediction of the time of failure of an open pit slope. Using most of the geotechnical monitoring tools available, the time of the failure was predicted within hours and equipment and personnel were evacuated from the pit well in advance of the failure. From a time to slope failure perspective, the monitoring system in place was a success.There are two general groups interested in monitoring pit walls, with slightly different objectives in mind when the monitoring system is being set up. There are those at the mine site that have to implement the pit slope design, monitoring protocols, and the action response plans, and there are those designing the slopes (often consultants) who regularly visit the mine but may not be responsible for the day-to-day activities. was a success.There are two general groups interested in monitoring pit walls, with slightly different objectives in mind when the monitoring system is being set up. There are those at the mine site that have to implement the pit slope design, monitoring protocols, and the action response plans, and there are those designing the slopes (often consultants) who regularly visit the mine but may not be responsible for the day-to-day activities."

Jan 1, 2016