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1. Book review . Fundamentals of fracture mechanics, by J.F. Knot. London, Buterworths, 1981 (reprint). Reviewer: G. Leadbeater The present reviewer approached the above book as a relative novice on the intricate details of fracture mechanics. Thus, the review is based to a great extent on how easily the information presented can be assimilated and understood, and how the book's format and content facilitate this. Note was taken of the preface comments about jumping ahead, in chapters, to ease understanding, and this was found to be a common occurence. 2. New publications Mechanical testing. London, The Institute of Metals, 1988. 357 pp. £25 Mining potential in northern and southern Canada: Guidelines for regional development policy, by Leo J. Verleun and Brian W. Mackenzie. Centre for Resource Studies (Queen's University, Kingston, Canada K7L 3N6), 1988. 225 pp, $20 Pricing of metals, by Margaret E. Slade. Centre for Resource Studies (see previous item). 149 pages, $20 CRS Perspectives, no. 29.Nov. 1988. Issued by the Centre for Resource Studies (see previous item) Introduction to the modern theory of metals, by Sir Alan Cotrel. London, The Institute of Metals, 1988. 456pp. £18 Mine winding and transport, by S.C. Walker. Amsterdam, Elsevier, 1988. 546pp. Dfl. 275.

Jan 1, 1989

By J. M. Stewart, C. H. Wyndham

Suggested thermal stress limits for safe physiological strain in underground environments by J. M. STEW ART M.Sc. (Eng) (Witwatersrand) (Visitor) and C. H. WYNDHAM M.B., D.Sc. (Witwatersrand), F.R.C.P. (Land) (Fellow) A comparison of safe temperature limits, based on Mitchell and Whillier's equations for specific cooling power (SCP), with similar limits determined experimentally shows the SCP-based limits to be unnecessarily conservative. It is argued that, while a small part of this conservatism may be attributed to an erroneous extrapolation of the heat transfer dependence on wind speed, the major part is probably due to the use of too Iowa limiting mean skin temperature in the calculation of SCP. A combination of Mitche/l's basic data with results available in the literature permits the derivation of modified heat transfer equations based on data that fully cover the range of wind speeds of interest. These equations, using a mean skin temperature of 36°C as the basis for the calculation of safe temperature limits, are then shown to agree favourably with those determined empirically. Furthermore, values of SCP based on these equations are shown to correlate reasonably well with wet kata readings, giving positive support to the wet kata thermometer as a heat stress meter.

Jan 8, 1975

There are presently no suitable underground mine production scheduling optimisation models available for application to sublevel stope mining. Scheduling underground production for maximum return is therefore still a manual process, which generally involves scheduling production from the next available highest cash flow stope within the operational constraints of the project. In most mining operations, the scheduling problem is too large and complex to guarantee truly optimal results through manual scheduling. This paper reviews some general optimisation studies that have been proposed for underground hard rock mining. Furthermore, an example of a mixed integer programming model is presented for a small conceptual sublevel stoping operation. Comparative results of a schedule generated by a mixed integer programming (MIP) production scheduling model and a manually generated model on a nine stope example is presented. Results indicate that the potential benefits of the MIP production scheduling model for the purpose of maximising NPV are significant. Finally, a new constraint was formulated to limit multiple exposures of fill masses for use in an existing MIP production scheduling model. Testing of the formulation took place on the central stope of the nine stope example, which showed that the formulation performed its task without breaking other operational constraints.

Jan 1, 2007

By N. J. Alderman, R. Haldenwang

Flumes are ubiquitous throughout the mining and minerals processing industries as well as being used in the polymer processing and pulp and paper industries. With the increased demand for the transport of highly concentrated slurries in rectangular open channels, there is an impetus for a better understanding of the role of rheology in flow hydraulics. Until recently, design of such channels has been based on either the Chézy or Manning equations used for modelling open channel flow of Newtonian fluids. This has been done for modelling turbulent flow of low concentrated slurries with some success. However, this is not the case for highly concentrated slurries where the flow in the channel is no longer turbulent. Unlike Newtonian fluids, work carried out on flow of pseudo-homogeneous, non-Newtonian fluids in open channels is somewhat limited. Moreover, these results have been published in a variety of sources. This paper attempts to give a critical review of the work carried out on Newtonian and non-Newtonian flow of pseudo-homogeneous non-settling slurries in rectangular open channels. A comparison is also made of the models based on power law, Bingham plastic and Herschel-Bulkley fluids for laminar and turbulent flow in rectangular open channels.

Jan 1, 2007

By R. Banda

This paper describes the decision to implement and then the implementation itself, through trials, of electronic ?Smartdets? over previously used shock tubes. It concludes that Mufulira Mine has become the first mine in Zambia to convert 100% of its stoping to ?Smartdets?, because the Mine?s management was prepared to look beyond the unit cost of product and were ready to look at the broader picture of cost effectiveness and increased productivity.

Jan 1, 2005

By F. M. C. C. Vieira

There are many uncertainties that a mine designer should consider when selecting an optimal layout. Even though the inherent variability in the design parameters indicates that single-values are not representative of mining conditions, risk estimators such as ERR are often used without considering their statistical distributions. A probabilistic methodology has been developed to assess the influence of the extraction sequence and layout geometry on the rockburst risk associated with four ultra-deep mining layouts. The statistical distributions of incremental energy release rates and excess shear stresses at face elements are used as indirect estimators of rockburst risk in stopes, and the statistical distribution of the rock condition factor (RCF) is used as an indirect estimator of rockburst risk in tunnels and service excavations.

Jan 1, 2002

By J. Arzuúa, U. Castro-Filgueira, L. R. Alejano, F. Malan

"Pillar design for underground mining is typically done using empirical formulae or numerical modelling. Practical experience and recent literature, nevertheless, illustrate the shortcomings of these design approaches. Ongoing monitoring of pillars is therefore recommended to minimize the risk associated with these designs.In a mine where a large number of pillars are cut, different pillar strengths can be expected owing to variations in rock mass strength from area to area. This problem is compounded by the fact that in mining environments the pillars are not always cut according to the prescribed dimensions. Although the original design using either empirical methods or modelling may predict stable pillars, unstable pillars will be encountered in reality. Very conservative designs with large factors of safety may circumvent this problem, but this approach is uneconomical.A possible solution to localized stability problems may be to enhance the strength of a few unstable pillars. It may even be hypothesized that reinforcing a few critical pillars may prevent ‘pillar runs’ on a much larger scale. Rockbolting, strapping of pillars, and pillar shotcreting have occasionally been used in the past as possible solutions. It appears that these have not been successful in all cases and large collapses have occurred in spite of the pillar remedial work.The authors investigated the strapping of pillars by conducting laboratory tests on cabled rock specimens. The results were qualitatively compared to actual attempts of pillar reinforcement available in the literature, as well as additional observations in an old haematite roomand- pillar mine in Spain. Based on these results, the value of steel cabling and mesh wrapped around pillars to improve stability is demonstrated. Some cases where this approach will not be successful are also discussed."

Jan 1, 2017

By L. A. Cisternas, A. Lopez-Valdivieso, Y. L. Botero, L. Cortes

In the processing of sulfidic ores, pyrite is usually depressed and ends up in the tailings. However, pyrite is the most common species responsible for acid mine drainage (AMD) due to its spontaneous oxidation. This AMD affects the tailing chemical stability by dissolving some toxic or heavy metals species such as As, Cd, Co, Pb, and Zn, which can migrate into the surrounding ecosystems. Therefore, the strategies to reduce pyrite’s environmental impacts are a crucial point to produce more chemically stable tailings. Consequently, numerous studies have been made to find procedures that could inhibit or restrain AMD. This work aims to develop a procedure for designing conceptual flotation circuits that can produce tailings with low content of pyrite and to assess this type of circuit with traditional flotation circuits. The method consists of applying optimal flotation design where three products are considered: metal concentrate, pyrite concentrate, and tailing with low content of pyrite. Two approaches are considered; in the first, a flotation circuit is designed to generate a concentrate rich in all sulfide minerals and to obtain a tail with low pyrite content. Then, a second flotation circuit is designed for the selective separation of the bulk into metal concentrate and pyrite concentrate. This is called fractional separation design. In the second approach, a flotation circuit design is realised that generate the three products simultaneously. This is called integrated separation design. Both fractional separation design and integrated separation design are assessed in this paper. This methodology is focused on cleaner production (waste prevention and resource minimisation) rather than end-of-pipe technology (treat existing waste). The methodology was applied to a copper sulfide ore from a local company in the Antofagasta region (Chile). This ore contains chalcocite, covellite, iron oxides, and pyrite. Keywords: Flotation, tailing, pyrite, cleaner production

Jan 1, 2020

By H. Von Michaelis

The world is rapidly becoming more ?green? i.e. energy conscious. Since mining and mineral processing are massive energy users, the mining industry is seeking ways to reduce its energy footprint. In mining and mineral processing operations, energy is often the most expensive cost item. Comminution, i.e. grinding, is frequently the most energy-intensive step between mine and metal. High pressure grinding rolls (HPGR) are being installed in a rapidly growing number of ?hard rock? mineral processing operations. In the energy conscious cement industry, HPGR grinding has been standard practice for decades. HPGR is known to be energy-efficient; the question is how energy efficient? How can the energy efficiency of HPGR be enhanced? This paper reviews recent HPGR applications for the processing particularly of copper, gold, platinum, PGM-Ni-Cu and iron ores. HPGR technology is discussed with respect to energy efficiency. The harder the ore the greater the energy savings are likely to be. Typical energy savings of 10?20% can be expected when installing HPGR vs. a SAG mill. Wipf(2005) showed why conventional Bond Work index tests on HPGR product is likely to under-estimate the energy savings that can be achieved by installing HPGR. Energy efficiency of HPGR is, however, ore-specific. The biggest energy savings of HPGR tested thus far is 9.5 kWh/tonne claimed for Vista Gold?s Mt. Todd gold ore from Western Australia, a savings of over one-third of conventional SABC comminution energy. Several commercial scale iron-ore pellet feed plants install HPGR for fine-grinding of concentrate to increase the surface area of pellet feed in a manner that reduces overall energy consumption. Energy-consumption in comminution is, however, only part of the energy savings benefit story. HPGR typically also reduces the amount of steel lost through wear of mill liners and media. Marsden(2008) showed that when the energy that would have been consumed to produce the steel that is saved by applying HPGR is factored in, then the overall energy savings of HPGR is considerably greater. Johnson et al.(1988, 2005) tested HPGR in a flowsheet in which energy savings of around 50% can be expected if HPGR product screen oversize is recirculated to the HPGR. Innovative flowsheets have been proposed by Rule et al.(2008) and by Morley (2008) which are expected to result in significantly increased energy savings. HPGR applied in flowsheets in conjunction with coarse ore separation devices, e.g. ore sorting or DMS to remove barren waste from HPGR feed promises significantly greater energy efficiencies. Fine-grinding and ultra-fine grinding of ore or concentrates in conventional ball mills results in energy consumptions that increase exponentially with product fineness. Wipf (2009) presented a flowsheet in which he proposed the installation of HPGR ahead of the Aerosion ?Disintegrator? for ultra-fine grinding of ores and/or concentrates. This dry grinding arrangement is expected to achieve ap80 = 7 µm using up to 100 kWh/t less energy than could be achieved by wet ball milling. Using conventional comminution, an ore might require grinding to p80 = 45µm (? 325 mesh), for example, to liberate the valuable components, e.g. magnetite, from gangue, e.g. silica. Inter-particle comminution in HPGR may break some ores along grain boundaries thereby liberating valuable minerals from gangue at a much coarser particle sizes. Early magnetic separation rejection of silica gangue liberated from magnetite by HPGR at coarser grain sizes could further reduce downstream comminution energy consumption.

Jan 1, 2009

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 A. F. van der Merwe, R-D. Taylor, M. Jacobs, F. H. Conradie

Total bound moisture (TBM) is a typical quality indicator of industrial-grade gypsum. This gypsum is comprised of three distinct phases, namely anhydrite, dihydrate, and hemihydrate, of which only the latter is of much industrial use. TBM analysis is a lengthy laboratory procedure, and an artificial neural network (ANN) TBM inference measurement is proposed as a fast and online alternative. An ANN inference model for gypsum TBM based on plant data was developed. The inputs to the network were primarily focused on the plant's calciner, and different network topologies, data divisions, and transfer functions were investigated. Furthermore, the applicability of the TBM value as a quality indicator was investigated based on a gypsum phase analysis. A strong correlation between TBM and the gypsum hemihydrate and anhydrite content was found, validating the plant target TBM of 5.8% as a quality indicator. A network topology consisting of one hidden layer with logarithmic-sigmoid (logsig) and pure linear (purelin) transfer functions showed the best performance (R > 90%).

Oct 3, 2023

By A. Melkumyan, K. Silversides

Chemical assays collected from blast holes have the potential to greatly improve the local accuracy of grade models. Assays must be assigned to the correct domain or they will introduce errors. Boundary surfaces created from the widely spaced exploration holes (~50m) do not provide sufficient resolution to correctly delineate domain boundaries between closely spaced (3-5m) blast holes. This paper demonstrates a probabilistic method for classifying production blast holes near domain boundaries. Gaussian processes models are applied to identify the assays and assay ratios most suited to distinguishing particular domains. These models are combined with the exploration based surfaces to classify the blast holes that can be confidently assigned to a particular domain. A reiterative method is used, where information from the blast holes closest to the exploration holes is used to label blast holes further away. This is tested on two domain boundaries in a banded iron formation-hosted iron ore mine.

Sep 1, 2021

By M. Kumral, S. Li, M. Balci, Z. Shao

Main haulage roads play an important role in the performance of underground mines because of the cost of transportation of the extracted ore, equipment, and workers. During mine development, these roads are designed through manual tools or CAD-based software. However, the optimisation of these roads is still a complex problem due to some constraints such as minimum turning radius and maximum gradient. By utilising Dubins path theory, three elevation cases; namely low, medium and high are defined, considering gradient constraint as well as the minimum turning radius in a three-dimensional space. The shortest path between two points can then be found by the three-dimensional Dubins path algorithm with elevation constraint. As a further step, a three-dimensional Dubins path algorithm with elevation constraint for multiple points is also developed for multi-point cases. The effectiveness of these algorithms is tested through case studies in order to determine the optimal path between different points.

Sep 1, 2021

By S. Marx

More than twenty years ago Sasol, ISCOR, and some parastatals played a major role in ensuring that South Africa had sufficient technical skills. When the economy became tight and business and government were pressurized to decrease costs, the first budgets that were reduced were the training budgets. It seemed to be too expensive and too time-consuming to train apprentices. According to Stacey2, this is a major strategic issue facing the mining industry in South Africa. Two factors added to the shortage of skills challenge: ? Skills erosion and job losses ? Artisans ? currently the economy produces 5 000 but the need is 12 500 ? Level of mechanization in South Africa less than 10 per cent ? Average age of operators and artisans is 50 ? Greater awareness of occupational health effects of hand-held drilling. ? Workplace challenges ? The impact of HIV/AIDS and other employee wellness issues ? Changes and challenges in workplace environment i.e. the mining industry.

Jan 1, 2012

By F. Nakhaei, Z. Pourkarimi

Tailings produced from the iron ore industry present many challenges due to the high economic and environmental impacts involved with their disposal. However, the relative scarcity of high-grade iron ores has driven manufacturers to recover and recycle these valuable tailings (secondary sources). This study aimed at the purification of ultrafine tailings with high sulphur content from an iron ore concentrator via reverse flotation to produce pellet feed fines. A specially designed flotation column featured with a nano bubble generator and a conventional bubble generator were employed to assess the effects of nano bubbles on the desulfurisation performance of iron ore concentrate under different operating conditions. Results obtained from this study indicated that the sulphur content of iron concentrate could be reduced from 1.2% to 0.22% in the presence of nano bubbles. Also, the results showed that use of nano-micro bubbles increased sulphur recovery 20% more, in comparison to micro bubbles. Keywords: Column flotation, iron ore, tailings, slime, nano bubbles, desulphurisation

Jan 1, 2020

By Ri McCrindle

"Analytical Chemistry is moving rapidly towards a concept where technicians have to do no more than press a button and print the result from an instrument that is a featureless ""black box"". In this environment we must ask how much traditional ''wet chemistry"" is still required for undergraduate students.Methods that can be fully automated will become increasingly important. An example of such a method is that of the slurry nebulisation and ICP-OES analysis of precious metal concentrate. Grinding the sample and adding Triton X100 as dispersant, complete analysis time is in the order of 90 min as apposed to the traditional Carius tube method which could take as long as 24 h. For most of the elements studied, the results using ""in-house"" reference material for calibration and as samples as well were within the 95% confidence level. Elements of low concentration in the sample (As, Bi and Se) were not within that level."

Jan 1, 2014

By R. L. Machunda, A. M. Rugaika, D. D. Mdachi

Sedimentary and igneous rocks are the two primary sources of phosphate that are mined and beneficiated to fertilizer. During the beneficiation process, phosphate is lost into the tailings. We investigated phosphate concentrations in tailings dumps at Minjingu mine, Tanzania using energy-dispersive X-ray fluorescence spectrometry to quantify the chemical compositions. The phosphate content in the tailings varied from 12.91% phosphorus pentoxide (P2O5) in Tailings 2 to 19.61% in Tailings Dump 1. The naturally occurring phosphate concentration in rocks ranges from 3% to 35%, and phosphate tailings from various locations with P2O5 concentrations as low as 6.46-12.65% have been beneficiated to commercial fertilizer. Our investigation revealed that phosphate concentrations in Minjingu tailings may be sufficient to be recovered for commercial applications. Suitable recovery methods are discussed, and we recommend that beneficiation should be performed to minimize the loss of phosphate into tailings. Further research is needed to identify the optimal beneficiation methodology.

Aug 8, 2024

By HORNICKA OSTRAVA

The Czechoslovak Scientific-Technical Institute has arranged the international conference 'Hornicka Ostrava' for four or five days at the end of October, 1969, as part of the preparation for the international 'Miners' Congress' on deep coalextraction in 1970. The keynote of the conference is 'New Techniques in coal mining,' and will be covered by five groups dealing mainly with: 1. New trends in the opening of mines, optimal parameters, projections, equipment, utilization of computers for economic analyses, etc. 2. Increase in efficiency of coal extraction in deep mines, technology, concentration, pressure control, optimization of material and coal transport. 3. Modernization of devices for increased safety and working conditions, new trends in explosives, new techniques for reducing environmental diseases. 4. Innovations in deep level coal extraction, mechanization, rationalization, automation, etc. 5. Other topics about modern techniques in mining. Address your enquiries to: Ing. Karel Kalas (Secretary of the Conference), Dum Techniky Cs YTS, Ostrava 1, Jesenkiho 7-9, Czechoslovakia.

Alexander Sutulov. Mineria Ghilena 1545-1975 (Mining in Chile 1545-1975). Santiago, Centre of Investigation of Mining and Metallurgy, 260 pp. (In Spanish). G. B. Rothenburg. Speciality steels. D.S.A., Noyes Data Corp., 1977. 270 pp. Witbank Middelburg Branch A General Meeting was held at the Wit bank Golf Club on 20th April, 1977, at 17h30. Treatment of waste water An International Research Symposium on New Processes of Waste Water Treatment and Recovery is to be held in London from 6th to 8th September, 1977. It NIM reports Report no. 1708 An examination of the suitability of various reducing agents for the production of ferrochromium. (27th Feb., 1975; re-issued May 1977). Report no. 1724 The preparation and reduction of chrornite pellets containing a reducing agent. (14th Apr., 1975; re-issued Mar. 1977). Report no. 1854 The interaction of pyrite, oxygen, and xanthate. (8th Mar., 1977). Report no. 1876 The ultrasonic determination of the mud level in a thickener and the resin level in an ion-exchange column. (6th May, 1977). Report no. 1878 The electrochemical dissolution of galena in aqueous solutions. (5th May, 1977). Report no. 1881 n-Octylaniline, a new extractant for noble metals.(28th Mar., 1977). Report no. 1883 The determination of iron, chromium, titanium, and tungsten by X-ray-fluorescence spectrometry. (31st Mar., 1977). Report no. 1889 Entropy relations in the formation of complexes of silver (1), mercury (II), and cadmium (II) with llwnodentate liyaruls. (5th May, 1977). Mechanics of granular materials A conference on the above subject is to be held in London on 8th and 9th September, 1977, under the auspices of the Institute of Mathematics and Its Applications.

Jan 1, 1977

With the advent of the First World Conference on Sampling and Blending (WCSB1) in Denmark in 2003 and the subsequent biannual meetings, together with other sampling conferences held on a regular basis, the central tenets of sound sampling practice and theory are spreading throughout the minerals industry. End-users and project houses, or groups who execute the projects, are all now better-informed about the principles of ?correct? sampling and preparation. To support this, many large mining companies now have their own in-house champion who will advise and ensure that the supply of sampling equipment is correct in terms of design and application, which further contributes to improved metallurgical accounting. The presence of a sampling champion also ensures that consistent and acceptable standards in regard to sampling practice are maintained throughout the group. This has, in turn, placed a greater degree of responsibility on the shoulders of sampling equipment suppliers, in terms of their equipment designs and product offerings, as well as applications knowledge for effective installation of equipment on client plants. This paper attempts to highlight the significant challenges that sampling equipment manufacturers often face with regard to complying with the newly understood requirements of best practice and sampling equipment design. Manufacturers invariably face issues with end-users or project houses, including project cost control, restricted headroom for samplers in plant layouts, and a lack of knowledge in certain quarters. These all have a potentially negative effect on the final outcome of a proposed sampling solution or implemented project. In reality, what is intended by all parties and what is ultimately installed are at times very different, with undesirable consequences for all concerned. Against this challenging background, there are, however, a number of instances where intent and implementation are complementary, with very satisfactory results. Keywords sampling, mechanical samplers, design, installation, sampling theory.

Jan 1, 2014