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By L. Dison, J. A. Hahn, G. E. Blight

A system of artificial support for shallow mines is described, analysed, and evaluated. The system can be designed rationally to support a predetermined overburden load, and tests have shown that the design theory gives accurate predictions of strength. The support system, consisting as it does of two basic materials, reinforced granular material and reinforced cemented material, is flexible and can be varied to suit changing requirements of height and load. The system of preloading to the design load by jacking off the roof ensures that the walls are both stiff and prooftested.

Jan 1, 1982

By G. J. Kringe

The results of a series of measurements of accelerations and guide-roller loads made on mineshaft conveyances are given, together with the predictions of these accelerations and loads based on a computer programme. The analysis of the measurements is described, and the results of the measurements and computer predictions when compared show reasonable agreement. Some parameters that increase the guide-roller loads are identified, and their effects are studied, together with some comments on the total loads. Finally, a possible format for a design specification is discussed, and some tentative design values are given.

Jan 1, 1986

By P. Maais

This paper gives an account of the development of a plant for the differential flotation of mixed sulphide ore, special reference being made to the separation of copper and zinc sulphides. The uniqueness of the geology, mineralogy, and metallurgy of each complex ore-body is stressed. Consideration is given to the scale-up of laboratory data, and to some of the factors involved in the design of milling and flotation plants for this type of ore. Process control and development are discussed, as are the human requirements for the optimum operation of a concentrator.

Jan 1, 1980

By D. T. Jordan, L. C. Coetzee, G. Kalenga, T. Mahlangu, W. J. Shipman

Although online free cyanide analysers are widely available and used in gold leaching operations worldwide, reliable automated free cyanide concentration control is not consistently achieved in many of these operations. Effective cyanide concentration control is complex owing to amongst others, the long residence times and ore feed variations. Model Predictive Control (MPC) has been proven to provide superior cyanide concentration control over traditional proportional-integral-derivative (PID) control, leading to savings in operational costs and reduced leachable gold losses. In the first example reported in this paper, MPC has improved control of the free cyanide concentration by keeping it within the required range 73% of the time during testing, compared to the previous PID controller that only achieved this target 30% of the time. This represents a 143% improvement. Another example demonstrates a 22% reduction in cyanide usage as a result of using MPC. MPC functionality is rarely available on the programmable logic controllers (PLCs) and control systems installed at gold plants, hence it is implemented on a personal computer (PC) networked to the cyanide analyser and plant infrastructure. Mintek has developed an embedded MPC that installs into the Mintek Cynoprobe analyser, adding MPC functionality without the need for additional PC and network infrastructure, reducing installation costs. This allows plants to minimise their expenditure on additional infrastructure while gaining the benefits of superior MPC technology for multiple cyanide dosage points. This paper will present results showing that the embedded MPC performs as well as Mintek’s existing PC-based StarCS MPC controller, making it a viable alternative for infrastructure-constrained gold plants. Keywords: Model predictive control, gold cyanidation

Jan 1, 2020

By H. Gumede

The challenges of noise emission in the mining industry are well known. These challenges are exacerbated by the increasing trend towards mechanized mining, and there is general consensus that an effective industry-wide Buy Quiet initiative (BQI) will significantly assist in reducing noise-induced hearing loss by minimizing noise at its source. In its endeavours to improve the health of workers, the MOSH Noise Team has facilitated development of a proposed strategy and structure for a BQI. Extensive consultation with stakeholders resulted in support for the initiative. The MOSH Noise Team was advised to solicit the contributions of consulting mechanical and electrical engineers (CM&EEs), whose support is viewed as critical for realization of the initiative, since elimination of noise at source is an engineering challenge, and most procurement standards and specifications are set and managed by engineers. A workshop with CM&EEs and their representatives, as well as group environmental engineers (GEEs), confirmed the urgent need for the initiative and provided valuable insights. The workshop used obstacle based planning techniques to identify the factors on which the success of this BQI will depend. Most potential obstacles to the implementation revolved around proper scoping, leadership commitment, and companies? adherence to the initiative. Lack of involvement by the relevant stakeholders and economic issues were also identified as potential obstacles. Delegates at the workshop felt that the successful implementation of the industry-wide BQI, will depend on the mining industry addressing the specific obstacles. The most critical and urgent issue was identified as the formation of a properly constituted industry-wide BQI task team that includes representatives from critical stakeholder groups and which is mandated and empowered to drive the initiative.

Jan 1, 2014

By E. Dadzie

This paper will review some methods used to manage geotechnical risk at Damang Pit Cutback. The pit depth is designed up to 250m with push back on the eastern and western walls of the existed and depleted Railway Cutback (RCB) pit. The geotechnical design was presented by SRK Perth, focussing on the optimisation of the bench face angle which finally evolved with ?steep slope strategy?; 24m at 800 and 24m at 750 on the eastern and western walls respectively. The east wall was designed strategically to optimise the proximity of the tailings dam to the final pit crest of the push back. The pit has experienced failure in the weathered profile transgressing through the transitional material into the fresh rock at different location of the east wall since development in July 2005. To ensure stability and to minimise ore loss, the east wall has been redesigned using 700 batter angles and reduced berm width of 4m compared to 800 and 8.5 berm width of 24m bench height. The paper will also discuss how slope failures to the east wall had been sustained, managed and monitored to enhance production. Emphasis is placed on slope management at Damang which includes the principles of wall control blast, visual inspection, slope depressurisation and the state-of-the art of slope monitoring using Autoslope automated prism monitoring. Future slope monitoring is considering the use of 3D Laser and Radar to provide early warning so that evacuation could be effected. The intension is to provide mine personnel the means to identify risk areas during mining activities.

Jan 1, 2008

By J. A. L. Napier

The evaluation of stress distributions and deformations in the vicinity of tabular mine layouts has been carried out routinely for many years using the displacement discontinuity boundary element method (DDM). In this approach, mine layouts are approximated as irregular shaped planar cracks (or slits) where the ?width? of the crack, corresponding to the excavation height, is assumed to be negligible compared to the in-plane, lateral dimensions. Early implementations of this approach have employed square element tessellations with constant displacement discontinuity component values. This is generally restrictive when considering the analysis of irregular pillar layouts or the intersection of fault planes with excavations. This paper describes a general revision of this approach in which triangular or quadrilateral element shapes are introduced in conjunction with higher order variations of the displacement discontinuity shape functions. This facilitates an accurate evaluation of detailed stress and displacement components close to excavation surfaces and allows the investigation of local damage and failure behaviour associated with particular geological structures such as weak parting bands or weak layers. A method to embed these features in an efficient and accurate multi-level solution scheme is described. This formulation can be extended to allow the analysis of shallow-depth pillar layout problems, facilitating the assessment of the interactive response and stability of shallow depth pillar layouts. A simple deformation model is introduced to facilitate the assessment of pillar failure and bursting potential in shallow mine layouts. The computational techniques described here have been implemented in a computer code called TEXAN (Tabular EXcavation ANalyser) and are illustrated by the simulation of a particular multiple reef pillar mining problem in a shallow depth platinum mine.

Jan 1, 2007

If an orebody has been drilled to achieve some level of regulatory compliance, then a number of associated geological databases will exist, representing 10 000 to 100 000 m plus of core intervals. The databases usually contain data about assays, lithology, mineralisation and geophysical attributes. They will also include location information such as collar positions and downhole surveys. Obviously this data is collected by geologists for, predominantly, geologists and mining engineers. However, from a process design viewpoint process engineers usually ignore the geology where possible and rely on a small number of metallurgical test samples. Typically these test samples are sourced from convenient and available cores or from a small number of specially drilled metallurgical holes. One of the worst instances known to the author was the design of a SAG mill using only two SAG specific test results (one for each of the major ore types) while, geologically, the orebody was defined by more than 30 000 m of drilling. This paper sets out a philosophy to maximise the use of the geological data, both for process design and in preparation for the commissioning phase of projects. Geological data is used in the identification of preferred locations for metallurgical test samples, for checking the metallurgical validity of the geological ore-type definitions, where necessary developing new ore-type definitions (geometallurgical domains) and developing mathematical relationships for the estimation of important metallurgical factors across the geological database. If the estimation of factors (for example ore competence) is considered reliable enough then there is also the possibility of feeding calculated data back into the block modelling process to allow the generation of metallurgically relevant outputs in the mine plans.

Jan 1, 2007

By A. Koursaris, J. B. See

An investigation is described in which the resistivities of Mamatwan manganese ore, Delmas coal, and Iscor coke, at temperatures or up to 1400°C were determined, as well as the resistivities of mixtures of ore of a constant size range with Delmas coal or Iscor coke of three different size ranges. The resistivities of the ore and the coal were characteristic of those for semi-conducting materials, were strongly influenced by temperature, and decreased by several orders of magnitude between room temperature and IOOO°C. The resistivity of the coke changed only slightly between room temperature and 1400°C, and the resistivity of the coal approached that of the coke at I300°C. This provides support for the theory that the resistivity of carbonaceous reducing agents is primarily a function of heat treatment, and not of the rank and composition of the coal. Above 1200°C, the resistivity of mixtures of ore and coke fell steeply owing to an increase in the volume fraction of coke in the mixture and to the formation of slag. The results were similar for the three different size ranges of coke. The extremely high resistivities of ore-coke and ore-coal mixtures at Iow temperatures indicate that there is unlikely to be much conduction of current in the higher regions of a furnace. Thus, the resistance of a furnace is governed mainly by the conditions at the electrode tips and in the molten regions. To explain the very Iow resistances of furnaces, usually, about I m£?, it would be necessary for investigations to be conducted under conditions similar to those in the active zone of a furnace.

Jan 1, 1980

By L. W. Helle

This paper summarizes the investigations carried out into a defect involving the corners of billets rolled from continuously cast blooms, which broke open during the rolling process. As it was believed that the defect must be connected with the formation of subcutaneous blowholes in the bloom, the investigations were directed towards an understanding of the roles of the three gases involved in the process. In an extensive trial programme, samples were taken from the heat at all stages of processing, as well as from all the raw materials and alloys. The main sources of nitrogen were found to be re blows, pick-up from the alloys added to the ladle (especially graphite), and open-stream casting. The major source of hydrogen was moisture in the alloys, especially high-carbon ferromanganese and silicomanganese. Further, it was established that the moisture content of the alloys is closely related to the appearance of the defect in steels with a carbon content of less than 0,20 per cent; 72 per cent of all the defects were present in this type of steel. Most of the remaining defects were found in steels with a carbon content of more than 0,60 per cent, where the nitrogen content was substantially higher than in the lower-carbon steels. It is suggested that the defect arises from the combined effect of oxygen. nitrogen, and hydrogen. Its occurrence in low- and high-carbon steels is triggered by the formation of subcutaneous blowholes when the critical oxygen level for carbon monoxide blowholes is lowered by the presence of excessive amounts of hydrogen and nitrogen respectively.

Jan 1, 1984

By D. A. J. Ross-Watt

Right now the South African mining industry is a high-profile, vital contributor to the nation just as it has been for the past one hundred and twenty-six years since the discovery of diamonds-perhaps even further back if the mining of copper, iron ore, tin, and other minerals in earlier centuries is included. The media in 1995, as has been the case over the years, bear testimony to the complex interactions between the industry and its stakeholders: shareholders, government, employees and their unions, training and educational institutions, researchers, markets, the public, and suppliers of goods, services, and infrastructure. The pressures and challenges that the industry continues to face can be summarized as safety and health, competitiveness, and social and environmental responsibility. There are no surprises here. The motivation for the industry to perform well in these areas is clear; the focus I intend to bring is on the most important tool required for success-that of good mining engineering. This Address sets out - to review the mining aspects that have been discussed in South Africa during the first five years of the decade, a discussion that shows the return of the country as an important mining forum, confirms the role of professional institutes and associations in the development of mining engineering, and brings current relevant issues into focus - to highlight the vital role of mining engineering in the industry, and to identify priorities for the remainder of the decade - to provide the prospective mining engineer, the mining-engineering student and trainee, and the practising mining engineer and mine manager with a better appreciation of the mining-engineering discipline. institutes and ssociations

Jan 1, 1995

By M. J. A. Leal-Gomes

There is a set of settled ideas in the field of the mechanics of rock mass joints, that need a deep revision, after the last experimental works of several authors. In this paper, this theme is approached under several viewpoints, like the following ones: the essential influence of the mating or mismatching of rock joints on their strength (different strength models are applicable to these two situations, one leading preferably to normal scale effects, and the other to inverse scale effects); Patton's model is a bad formulation of the joint strength, whenever there is a dilation effect in the slidings (actually, the essential consideration of the amplitude of the roughess isn't made by any limit equilibrium model, like Patton's model); the joint strength increases as the width perpendicular to the sliding direction is reduced (previous works of other authors suggested the independence of the strength on that width); the reduction of the anisotropy of the roughness, as the sample symmetry and sample dimensions increase; there is no scale effect in the discontinuity mechanics, if there is no roughness heterogeneity; when only the same roughness and undulation orders are involved in the tests, shorter samples have larger peak displacements and lower shear stiffnesses than larger samples (usually, the contrary is admitted). For all these reasons, there isn't an easy correlation between the small scale tests and the natural large joint scale. Only "in situ" large scale tests have some representativeness. All the above mentioned questions are correlated to each other. Es gibt eine Menge eingewurzelter Ideen im Gebiet der Mechanik von Felsklüften, die, nach den letzten experimentellen Arbeiten von mehreren Verfassern, eine tiefe Überprüfung benötigen. In dieser Mitteilung, wird dieses Thema unter mehreren Blickpunkten angegangen, wie die folgenden: der wesentliche Einfluß des Zusammenpassens oder nicht Zusammenpassens von Gesteinsklüften auf ihre Festigkeit (verschiedene Festigkeitsmodelle sind auf diese zwei Situationen anwendbar, eins, das vorzugsweise zu normalen Maßstabseffekten führt, und das andere, das zu umgekehrten Maßstabseffekten führt); Pattons Modell ist eine schlechte Formulierung der Kluftfestigkeit, immer wenn es einen Dilatationseffekt in den Verschiebungen gibt (in Wahrheit, wird die wesentliche Berücksichtigung der Rauheitsamplitude von keinem Grenzgleichgewichtsmodell beachtet, wie Pattons Modell); die Kluftfestigkeit wächst wenn sich die Breite senkrecht zur Verschiebungsrichtung verringert (frühere Arbeiten anderer Verfasser suggerierten die Unabhängigkeit der Festigkeit von jener Breite); die Verringerung der Rauheitsanisotropìe, wenn die Probekörpersymmetrie und Probekörperabmessungen zunehmen; es gibt keinen Maßstabseffekt auf die Trennflächenmechanik, wenn es keine Rauhheitsheterogenität gibt; wenn nur die gleichen Rauheits- und Ondulationsgrößenordnungen in den Versuchen verwickelt sind, haben kürzere Probekörper größere Spitzenverschiebungen und geringere Schersteifigkeiten als größere Probekörper (gewöhnlich, wird das Gegenteil angenommen). Wegen aller dieser Gründe, gibt es keine einfache Korrelation zwischen den Versuchen im kleinen Maßstab und dem natürlichen großen Kluftmaßstab. Nur "in situ" Versuche im großen Maßstab sind einigermaßen repräsentativ. Alle die oben erwähnten Fragen hängen miteinander zusammen. Il y a un ensemble de des bien établies arrière-pensées idées dans le champ de la mécanique des discontinuités en massifs rocheux qui ont besoin d'une profonde revision, après les derniers travaux de divers auteurs. Dans cet article cette matière est abordée sous divers points de vue, comme les suivants: la signification essentiel de l'ajustement ou du désajustement des discontinuités dans leur résistance. Des différents modèles sont applicables à ces deux situations, une conduisant de préference à des effets d'échelle normaux et l'autre à des effets d'échelle inverses; le modèle de Patton est une mauvaise formulation de la résistance des joints quand il y a effet dilatant dans les glissement. En effet la contribuition essentielle de l'amplitude de la rugosité n'est pas consideré par aucun modèle d'équilibre limite comme le modèle de Patton; la résistance des joints croit au fur et à mesure que la largueur perpendiculaire à la direction de glissement est réduite. Des travaux antérieurs d'autres auteurs suggéraient que la résistance était indépendant de cette largueur; la réduction de l'anisotropie de rugosité au fur et à mesure que la symétrie et les

Jan 1, 2003

By S. Tu, Y. Yuan, H. Wei, Z. Chen, M. Jia

"To reduce production costs and increase efficiency in ageing coal mines, a system that utilizes two shearers in a fully mechanized longwall working face is proposed. Using theoretical and engineering experience, three issues pertaining to the system were determined: (a) the two-shearer mining technique; (b) matching and modifying the equipment; (c) and coal-cutting task allocation for each shearer. Two mining processes are proposed, with the two shearers travelling in either the same or opposing directions. To avoid breakage of chains and pan extrusion of the armoured face conveyor (AFC), the length of the AFC ‘snake’ was controlled. To ensure continuous cutting and transporting of coal, the cross-sectional dimensions of the AFC were checked and the shearer closer to the head drive was modified. Based on the assumption of equal cutting times for each shearer, the meeting position of the two shearers was obtained by using a theoretical model of mining task allocation. Application of this technique at No. 2 Jining Mine, China, has shown remarkable benefits: daily production capacity was increased by 54% and personnel efficiency was improved by 33 t/d per person. IntroductionAll coal mines aim to increase the unit output of the working face to reduce mining costs and improve the economic efficiency of the operation. To achieve this goal, a production model known as one mining face of the mining area has been adopted by most Chinese coal mines (Hu, Meng, and Zhu, 2008; Zhang, Zhang, and Wang, 2000). Under these conditions, the main technical approaches to maximize the output are increasing the width of the working face (Qu, Xu, and Xue, 2009) and accelerating the advancing speed (Robbins, 2000). In coalfields with shallow seams, the width of a fully mechanized face exceeds 300 m (Ju and Zhu, 2015; Fu, Song, and Xing, 2010); in coalfields with deep seams, the width of the face is usually greater than 240 m (Liu et al., 2016; Li et al., 2013). The term ‘super-long working face’ was proposed to describe working faces with a width of over 240 m (Zhao and Song, 2016; Xu et al, 2007) in China. To support these long working faces with rapid advancing speeds, high-powered mining equipment is required (Kulshreshtha and Parikh, 2001, 2002; Tu et al., 2009; Mishra, Sugla,and Singha, 2013). This is easily achieved in newly built mines, but is not a good choice for ageing mines because of the low return on a high investment on account of the limited remaining resources. It is therefore difficult for ageing mines to significantly increase their unit output with the existing mining equipment. This study focused on this problem: two shearers were applied to a longwall fully mechanized working face (LFMWF) to achieve increased unit output."

Oct 1, 2018

By T. Gibson

It is generally accepted that South African coal mines have gone through the mechanization of most of its underground mines, and while there certainly were a lot of productivity improvements, the lack of visibility on these machines operating underground still leave vast areas for improvement. The average actual cutting time still remains very low, in the 30 per cent area, which leaves significant improvement possible. Currently all analysis is carried out using hand-written reports. Unfortunately this is subjective and often inaccurate because of human interpretation. In addition in order to avoid costly component failure, a monitoring system is required to warn of eminent failures and condition monitoring. The challenge faced was to supply and install a system that was ‘Open’ and could be retrofitted to existing machines in operation because of the current standard of communication links to the underground sections. In addition it was intended to use, existing ‘off the shelf’ software and hardware and adapting this for the harsh underground mining conditions wherever possible in order to reduce costs. As development occurred, as with all technology, doors opened to other opportunities such as, remote access data logging and Internet based reporting. We focused on the Voest Alpine Bergtechnik (VA) range of continuous miners, as need arose to achieve the desired cost improvements because of the strategy of service contracts the subsidiary company, Voest Alpine Mining & Tunnelling (VAMT) offer the mining industry in South Africa. This paper describes a data logging system that has been installed on various continuous miners that provides data in real time, on line, and that could be expanded to any electrically supplied underground mobile or stationary mining machine.

Sep 1, 2001

By H. G. Mosenthal

In any mining enterprise, the extraction of the ore from the orebody is of vital importance. This activity is stoping. The gold mines of the Witwatersrand and its extensions in the Klerksdorp, Welkom, and Evander areas form the most extensive goldfield in the world. This address reviews stoping technology and improvements in this technology since the end of the Second World War. Although the reefs that make up the Witwatersrand orebody are uniquely extensive, they are not suited to mechanized mining. This is due to a number of factors such as the depth of the orebody, its narrowness, and the hardness and abrasiveness of the quartzite forming the orebody. The most notable improvements in stoping technology have been brought about because of our beter understanding of rock-engineering problems. This has resulted in beter layouts, stoping geometry, systems of aleviating rock stresses, and support systems. It has enabled the industry, at ever-greater mining depths, to maintain and even increase productivity. These improvements, based on rock engineering, have significantly reduced the accidents due to rockbursts. There are many diferences between today's stoping and that practised forty years ago. Panels are shorter, concentrated mining has superseded bench mining, and the support systems are certainly better. Yet the face scraper is still used extensively, as are pneumatic rock drills. Some innovative stoping systems that have given rise to improved productivity are discussed. Explosives technology has shown spectacular advances during the period under review. Sadly, our local industry has had little to do with this research and development, but has been most adaptive in using the new products on offer.

Jan 1, 1990

If an orebody has been drilled to achieve some level of regulatory compliance, then a number of associated geological databases will exist, representing 10 000 to 100 000 m plus of core intervals. The databases usually contain data about assays, lithology, mineralisation and geophysical attributes. They will also include location information such as collar positions and downhole surveys. Obviously this data is collected by geologists for, predominantly, geologists and mining engineers. However, from a process design viewpoint process engineers usually ignore the geology where possible and rely on a small number of metallurgical test samples. Typically these test samples are sourced from convenient and available cores or from a small number of specially drilled metallurgical holes. One of the worst instances known to the author was the design of a SAG mill using only two SAG specific test results (one for each of the major ore types) while, geologically, the orebody was defined by more than 30 000 m of drilling. This paper sets out a philosophy to maximise the use of the geological data, both for process design and in preparation for the commissioning phase of projects. Geological data is used in the identification of preferred locations for metallurgical test samples, for checking the metallurgical validity of the geological ore-type definitions, where necessary developing new ore-type definitions (geometallurgical domains) and developing mathematical relationships for the estimation of important metallurgical factors across the geological database. If the estimation of factors (for example ore competence) is considered reliable enough then there is also the possibility of feeding calculated data back into the block modelling process to allow the generation of metallurgically relevant outputs in the mine plans.

Jan 1, 2007

By G. P. L. van der Linde

EVERY OREBODY IS UNIQUE [ ] GEOLOGY AND MINERALIZATION DIFFERENT [ ]

Jan 1, 2005

By Z Bagheri, E Moosavi

Identifying the exact borders of geological domains and assessing the uncertainty of these borders are crucial steps in resource estimation. This potential field method was designed to build 3D geological models from data available in geology and mineral exploration, namely the geological map and a digital terrain model, structural data, borehole data, and the geologist’s interpretations. The resource evaluation of a copper ore deposit is often performed in three steps: (i) delimitation of the boundaries of the units corresponding to the various geological formations or ore types; (ii) estimating densities; and (iii) estimation of grades within each unit. In simple cases (e.g., a series of sub-horizontal layers), the geometric model can be built using 2D geostatistical techniques (kriging or co-kriging of the elevations or thicknesses of the various horizons) which also quantify the uncertainty of the model. A 3D model of Cu grade is generated using ordinary kriging; however, the indicator kriging method is run to design a 3D model of rock types by incorporating the drilling results. Block models of geophysical and geological characteristics are included in a similar 3D mesh to investigate their relationships in copper mineralisation.

Sep 1, 2021

By P. Beukes, D. Bessinger, R. Glenewinkel

High titania slag is produced by the smelting of ilmenite and a suitable carbonaceous reductant in electric furnaces. Currently liquid slag is cast into large blocks, which take about 10 days to cool down before they can be crushed, milled and classified into two final products. The two products, chloride and sulphate grade slag, are differentiated according to their size. Granulation of titania slag has been identified as a possible alternative to the conventional block route. This paper discusses some of the work carried out at Exxaro Research and Development to investigate both wet and dry granulation of titania slag.

Jan 1, 2007

By M. K. Matthews

The use of backfill has important environmental control implications which, although frequently overlooked, can be both beneficial and problematical. Where backfill is widely used, the reduction in stope heat load and improved air utilization influence the overall mine ventilation and refrigeration requirements significantly. A programme of work examining in detail all the environmental consequences of backfilling is currently underway at the Environmental Engineering Laboratory of the Research Organization of the Chamber of Mines. This paper gives an overview of the work and presents some findings. In so doing, the environmental implications to be considered when backfilling are highlighted.

Jan 1, 1988