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By J. P. Germiquet

"Rock properties have a material impact on mining processes, including drilling performance. An investigation using point loaded index (PLI) data converted to uniaxial compressive strength (UCS) has revealed that a direct relationship between grain size and UCS exists at Mogalakwena Mine. This correlation is best seen in unaltered rock, with lower correlations for altered rock types. Measurements from the new RockMa system installed on drill rigs can be used to obtain rock strength data to validate the current rock strength domains and create additional data for the next benches below. An investigation of penetration rates in different lithologies shows that rock composition plays an important role in determining drill performance. Additionally, there is an inverse relationship between rock strength and drilling penetration rate – a measure of how efficiently a hole is drilled.The domaining of grain-size-adjusted UCS at Mogalakwena Mine will allow more accurate scheduling of drill rigs through increased knowledge of rock strength in various areas. Successful rock strength domaining has the potential to be incorporated into blast indexing and predicting crushing/milling performance.IntroductionThe optimization of mining and processing through geometallurgical characterization of ore are key drivers of value realization (Deutch, 2013). Rock strength is one such property and is affected by, among other variables, composition, texture, and grain size (Ozturk, Nasuf, and Kahraman, 2014). Mogalakwena Mine is exploiting the intrusive Platreef PGE (platinum group element)-bearing orebody which forms part of the northern limb of the Bushveld Complex. This complex orebody exhibits areas of metasomatic alteration, metamorphism, and sporadic mineralization of the footwall and hangingwall (Nex et al., 2006). Understanding this variability is paramount due to the implications for rock strength and hardness, which in turn affect crushing, milling, and liberation efficiency. These variables must be known prior to blasting in order to optimize mine and plant processes using in-situ variables. This necessitates predictive modelling (Deutch, 2013). Geological and geotechnical data was sourced from the Overysel (OY) exploration database for the study. Point load testing was done for each borehole and the results converted to uniaxial compressive strength (UCS) (Akram and Bakar, 2007). The relationship of lithology, texture, and grain size with UCS revealed an inverse relationship between grain size and UCS in unaltered rock. The relationship was not present in altered rock types. A comparison of mean strength and hardness results indicated that Bond work index and UCS may be related. Drilling performance is affected by UCS (Bourgoyne et al., 1986), and this was proven using recent measurements obtained during drilling. Lastly, grain-sizeadjusted UCS values were applied to a 3D model for the OY property."

Jan 1, 2016

The aim of this research was to study the absorption characteristics of thermally dried fine coal from South African collieries. After milling to ?150 µm and pressure filtration, the samples were subjected to either air drying or thermal drying at 150°C. The samples were then put into a climate box at 28°C and at three different relative humidity levels, namely 30, 60 and 94 per cent. It was found that the equilibrium moisture content of thermally dried coal at a specific relative humidity was lower than that of air dried coal. The relationship between the equilibrium moisture content and relative humidity is described by 1 ? RH = exp (-KTMen). There was no relationship between the volatile matter content and equilibrium moisture content, but there was an increase in the equilibrium moisture content of the coal with an increase in mineral content. The moisture uptake rate increased with an increase in temperature and a decrease in particle size. A model is discussed that fitted the experimental data and gave a good prediction for changes in the conditions. There was no evidence of greater moisture absorption by thermally dried coal. Keywords: Fine coal, thermal drying, drainage, South Africa, drying

Jan 1, 2002

By R. A. Williams

Electrical impedance tomographic methods have been applied to a variety of mineral and chemical processes in the laboratory and on plant. This review paper surveys technical developments in measurement methods to enable quantitative extraction of key process information in the form of mapping of concentration profiles, mixture homogeneity and suspension velocity. The methods for determining velocity are summarized, since this is of especial interest when applied to opaque systems where most conventional optically based measurements fail. A recent significant development is the use of ultra-high speed measurement that now allows velocity vectors to be extracted for fast moving mixtures and fluids (up to several metres per second). New data are reported pertinent to low and high solids concentration flow in pipelines. Use of the methods offer improvements to design of such systems but also points to the use of tomographic electrical sensor as online flow measurement and fault detection. This offers new opportunities for applications and benefits in the design and monitoring of mineral slurries and sludges.

Jan 1, 2008

By J. Morkel

During research on mainly the weathering of kimberlite, it became evident that its mineralogical composition is an important factor in the complex process of physical and chemical disintegration. The mineralogy of tuffisitic kimberlite breccias from two localities, the Cullinan and Venetia mines, is compared with special reference to the occurrence of associated clay minerals. The clay mineral composition influences the engineering properties of these rock types. It is illustrated how the presence of swelling clay components can be confirmed by ethylene glycol treatment and chlorite minerals by heat treatment using X-ray diffraction. Smectites are present in both tuffisitic kimberlites, dominant at Venetia while chlorite is more frequent at Cullinan. More tuffisitic kimberlite breccias samples from venetia were also characterized. It was found that kimberlite disintegration is correlated with the presence and abundance of smectite.

Jan 1, 2006

The use of a time series variogram as an aid in controlling the quality of a product was pioneered by Pierre M. Gy and is described. The ability to analyse and interpret covariance relationships time series data is possible using the variogram. The concept of stream heterogeneity allows sources of variability in process streams to be identified and isolated. Principally this is distributional heterogeneity that is due to a short range effect of segregation in the process stream related to size or composition distribution of the material on a local scale and due to a long-range change in the size and grade of the material stream. The variogram is simply a tool for representing these sources of variability in a way that is explicit, allowing identification of the source and providing important insights to temporal continuity between samples. This paper describes the chronologically related large-scale variability in an iron ore process stream (%Fe), and illustrates the control and mitigation of variability at various stages within the process using a variogram. Three main sources of variability are identified including the random variability V[0], the process variability V[1], and the variability due to cyclical phenomena V[cyclic], arising from human routine or mechanical defects. These sources of variability can be represented on the control chart that provides the plant superintendent with insights as to the sampling capability of the systems in place. Maintaining levels of variability within customer specification limits requires that production systems be controlled without overcorrecting for the trends in changing quality. This can be done only by representing the limits of control relative to the limits of specification on a control chart. Where the specification limits encroach on the control limits, one or the other, or both, may need to be changed; specification limits that constrain the control limits lead to reactive decision making that is expensive and stressful for plant operators.

Jan 1, 2008

By D. G. Krige

For the purpose of determining confidence limits for ore grade estimates, an extensive simulated database was used, which included 1728 ore blocks with ?actual? grades and the corresponding estimates based on ordinary and simple kriging. The practical results show that conditional unbiasedness is essential and that acceptable confidence limits can then be set using Normal theory for the simulated error distribution based on the logarithms of the ratios of ?actuals?/estimates with a variance related to the kriging variance. The mean of the data used to prepare the variogram and the estimated block grade are to be used properly in this approach. A practical analysis was also done of the actual point and block data from a very large mined out Carbon Leader area. The distributions of the actual grades for two levels of block sizes with different levels of variability were fitted using three models, ie. two three and compound lognormal. The trends of tonnages, grades and relative profits for a range of pay limits, as well as the usual tonnage-grade curves, show a practical insensitivity for the choice between the three lognormal models considered.

Jan 1, 2004

By W. A. Naismith

On 16 July 2004, at 07:10 a collapse of about 1.8 million m3 (about 4 ½ million tons) took place on the north wall on Nchanga Open Pit. This collapse was the result of a developing instability that was first identified when the benches in this area were exposed during September 2002. The NOP geotechnical and survey departments closely monitored the development of the failure. Control measures were implemented to reduce risk to men and equipment. These measures were continually improved and adjusted in reaction to observations and changing conditions. The purpose of this paper is to describe in detail the monitoring results that were obtained both by traditional methods and the novel slope stability radar system (SSR). Difficulties encountered in establishing critical deformation levels and deformation rates that can be used to predict the onset of collapse are described. Details of the monitoring and control measures, which led to the successful completion of mining in the area, are also described in this paper.

Jan 1, 2005

By G. A. Craig

The Moon, asteroids, and planets of the solar system represent the most distant caches of wealth that humanity has ever considered recovering. Yet, in addition to the potentially recoverable values represented there, harvesting off-Earth resources has a second, almost incalculable sustainable benefit in that they can be retrieved with absolutely no damage to Earth. Previous research mostly assessed the potential of asteroids and the Moon for mining purposes from a theoretical and scientific point of view. These studies investigated drawbacks that could be experienced in this type of operation, but no detailed economic evaluation that is meaningful for mining project management has been conducted and the parameters that are most likely to make an operation feasible are unknown. This paper provides a preliminary economic and sensitivity analysis of a possible off-Earth mining business extracting minerals from an existing asteroid.

Jan 1, 2014

By D. C. Oliver

Paper written on project work carried out in partial fulfilment of B.Sc. (Eng.) (Metallurgy and Materials) degree Corrosion in exhaust systems can occur on both the interior and exterior surfaces. Chloride-containing de-icing salts on the roads in colder countries greatly increases the rate of corrosion on the exterior surfaces. This paper investigates the relative exterior corrosion resistance of three alloys?two ferritic stainless steels( AISI Types 409 and 441) and an aluminized mild steel. The exhaust system is split into two categories?the hot end and the cold end. A test for each of these ends was designed?the standard ASTM G85test was modified to create a simulated driving cycle. The cold end test samples were exposed to ten driving cycles, and the hot end test samples were exposed to five driving cycles. A driving cycle constitutes the car being started from cold, driven until the operating temperatures are reached, and switched off and allowed to cool. Pitting corrosion is the primary corrosion mechanism occurring at the cold end of the exhaust system. The aluminized mild steel was the most resistant alloy in this test, and Type 409 the least. However, once the protective aluminium layer degrades, corrosion will occur rapidly. At the hot end of the exhaust system, spalling of the surface oxide layer is the primary corrosion mechanism occurring. Type 441 was the most resistant in this test, and the aluminized mild steel the least resistant. Potentiodynamic tests were performed on the alloys?the results agreed with the results obtained in the exposure tests.

Jan 1, 2003

By C. van Tonder

Paper written on project work carried out in partial fulfilment of B Tech (Engineering Metallurgy) degree This investigation relates to a multi-purpose electrolytic system. Its primary purpose is to electrowin gold from high or low concentration gold cyanide solutions and/or from gold sludge, and to convert the recovered gold into a gold (alloy) electroform or electrode at the gold mine itself. These operations are carried out sequentially and in situ in the same electrolytic cell. Electrorefining of the gold recovered may also be done in the cell. The system applies to silver as well, and may be adaptable to base and platinum group metals. It could also be used in environmental applications, to remove undesirable metals present in aqueous solution at very low concentration. The work to be discussed forms part of recently filed patent applications. Subsequent and future developments of the system are briefly outlined. This paper, in part or in full, has been published by the Metallurgical Mine Managers Association (MMMA), with permission from the authors.

Jan 1, 2006

By J. Gholamnejad

The aim of short-term production scheduling is to decide which blocks of ore and waste to mine in which time period (shift, days, weeks or months) so that several operational and geometrical constraints can be satisfied simultaneously. Since 1960s several mathematical programming approaches were developed for solving production scheduling problems that are based on a combination of various operational research approaches such as linear programming (LP), integer programming (IP), dynamic programming (DP), etc. A number of models have been developed in the past three decades but some models have limited application especially to geometrical mining constraints. One of the geometrical constraints is block accessibility. All blocks must be accessible to mining equipments on the same bench. In this paper a binary integer programming model is developed in order to incorporate block accessibility constraints in an efficient manner. This mathematical model insures that each block has been open and can be loaded and transported easily by shovels and trucks.

Jan 1, 2008

By M. Verri

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Jan 1, 2009

By P. C. Schutte

The objective of ergonomics is to enhance the effectiveness and efficiency with which human tasks are carried out. Furthermore, the objective is to improve desirable human values. This can be achieved by enhancing safety, reducing fatigue and stress, increasing comfort, increasing job satisfaction, having greater user acceptance and thereby improving the quality of life. Mechanization has influenced the prevalence of injury, mainly due to the application of human physical effort as the power source. With mechanization, the operator?s function is now essentially one of control rather than being an energy source, however, the risk of injury has not diminished. Mechanization in itself has introduced inefficiencies, health risks and physiological stress. The major objectives of ergonomics are discussed through examples of acceptable and less successful implementation of ergonomics within mechanized mining. The influence of the machine system on the human is addressed and practical solutions to improve and optimize the interaction of the human and the machine are outlined. Furthermore, practical examples of control and display integration, anthropometric and biomechanic influences on design, orientation, posture and stereotypes are used to accentuate the advantages of the application of sound ergonomics principles to the specialized area of mechanized mining.

Jan 1, 2002

By A. Boniface

The International Tunnel and Underground Space Association (ITA) has a number of working groups (WG) that meet at least once a year. One of these is WG12, ?Use of Shotcrete?, of which the author is a member. The purpose of this paper is to draw attention to a number of topics that were discussed at the WG12 meetings held in April and September 2008; and also to a number of other matters that arose from the presentation of thirty-four papers at the 5th International Symposium on Sprayed Concrete held in Lillehammer, Norway between 21 and 24 April 2008.

Jan 1, 2008

By M. Visser

Keywords: Pyrometallurgy, furnace, ferrochrome, Samancor, ferrochrome process Samancor Chrome has been, and continues to be, a major player in ferrochromium production. The company has a proud history and possesses benchmark technology and operations. Currently five business units are operating: two sets of mines and three smelter plants. Samancor Chrome produces around one million tons of charge chrome annually. Chrome ore, intermediate-carbon ferrochrome, and low-carbon ferrochrome, form part of the portfolio. Electrode paste is also manufactured through a joint venture with Highveld Steel and Vanadium. Samancor Chrome has a balanced approach towards operational strategy, and has entered into a number of joint venture partnerships. Through its access to quality raw materials, knowledge, and experience of various production technologies, and its strategic abilities, Samancor Chrome is well positioned to reap the benefits from opportunities in the current and future industry context.

Jan 1, 2006

By R. M. Goktan

Rock brittleness plays an important role in the cutting action of picks on rock surfaces. It controls the ease with which cracks can propagate through the rocks. Although rock brittleness is known as a property that contributes to the cuttability of rocks, despite considerable research effort, there is still much uncertainty about the relation between rock brittleness and rock cutting efficiency. This fact can be attributed to the lack of a universally accepted brittleness concept and a brittleness measurement method. The existing publications of some researchers have, in a way, tended to confuse the understanding of brittleness in the general field of rock excavation where it is expected that the energy consumption of cutting should decrease with increasing brittleness of rock, other conditions being equal. However, this sometimes conflicts with the brittleness concept commonly used in rock mechanics, where the more brittle the rock the higher its mechanical strength. The ratio of rock compressive strength to tensile strength is considered by many authors to give a valuable brittleness index for drag pick operations. Hence, in this contribution the ratio of uniaxial compressive strength to tensile strength BI is considered as an index of rock brittleness, and a new methodology is proposed for its use in rock cutting efficiency analyses of drag tool operations. Validation of the suggested approach is supported by available experimental data in the literature. Contrary to the conclusions reached previously by other authors, it is shown that an increase in rock brittleness is accompanied by an increase in the cutting efficiency, other conditions being equal. Keywords: brittleness index, rock brittleness, cutting efficiency, specific energy, rock excavation.

Jan 1, 2005

By D. M. Walters

To achieve safe and healthy working conditions in shaft sinking operations, ventilation, and where necessary cooling, must be provided. These requirements are considered for sinking vertical, sub-vertical and decline shafts. Regulatory requirements, determining air volumes and amount of cooling required, the various ventilation methods used such as force, exhaust, twin columns, air reversal using four gate systems and the equipment required to achieve this, are discussed. Consideration is also given to the sinking of single and twin declines using diesel equipment, calculating the air volumes required to dilute pollutants and the various methods for achieving this. Also discussed is the importance of having early ventilation design input to the overall design of the mine. In many cases ventilation can be the prime determinant for the size and configuration of the shafts or declines that have to be sunk.

Jan 1, 2009

By D. M. Walters

To achieve safe and healthy working conditions in shaft sinking operations, ventilation, and where necessary cooling, must be provided. These requirements are considered for sinking vertical, sub-vertical and decline shafts. Regulatory requirements, determining air volumes and amount of cooling required, the various ventilation methods used such as force, exhaust, twin columns, air reversal using four gate systems and the equipment required to achieve this, are discussed. Consideration is also given to the sinking of single and twin declines using diesel equipment, calculating the air volumes required to dilute pollutants and the various methods for achieving this. Also discussed is the importance of having early ventilation design input to the overall design of the mine. In many cases ventilation can be the prime determinant for the size and configuration of the shafts or declines that have to be sunk.

Jan 1, 2009

By Nicholas Adrian Barcza

"What affects and influences one’s perspective of the mining and metallurgical industries?One’s perspective of the industry we work in changes over time as a function of our experience as well as from the interaction we have with colleagues locally and probably even more so with those internationally. Furthermore, the ever-changing environment continues to impact the context in which one sees things. Living mostly in South Africa through its changes in the past fi fty years but also having the opportunity to travel extensively and work on projects abroad adds an invaluable richness to this more global perspective. One of the greatest challenges is how best to use this experience to endeavour to support the many potential opportunities in southern as well as sub-Saharan Africa. However, one has also to face the realities of how the best interests of the country and its peoples are sadly often not well served for various unfortunate reasons. Investment, education, regional stability, and good governance are some of the most critical considerations for the prosperity and survival of the region.The mining and metallurgical industry in southern and sub-Saharan Africa changed significantly during the post-colonial and apartheid eras as a result of global and regional developments that have impacted the ownership of businesses, the technologies used, and products produced in a manner that was not envisaged even fi fty years ago. Southern Africa’s mining and metallurgical industry has progressed from one based mostly on diamonds and gold in the late 19th century to a much more diverse one that involves the production of a variety of other precious, base, and ferrous metals and minerals as well as coal and industrial minerals. The infrastructure and manufacturing capacity was largely developed to meet the needs of this industry during its growth phases, but even though the dynamics have changed there is still a need for more efficient and effective support systems in the region."

Jul 1, 2019

By D. C. Panigrahi

Extensive field studies have been carried out to investigate the pillar fire problems in one coal mine in India. A Thermal IR gun and a Thermovision camera have been employed for thermal scanning to assess the state of heating in selected pillars. Special sampling set-ups have been designed to collect gas samples from the holes drilled into the selected pillars and the multigas detector is used to analyse the composition of samples in situ. In order to predict the spontaneous heating in coal pillars, different gas ratios have been calculated and it has been observed that some of the established gas ratios, viz. Graham?s ratio, Young?s ratio etc. have resulted in negative values in samples containing high amounts of methane. The modified gas ratios have been proposed which will be useful for predicting the pillar fires. These ratios may also be used for assessing the condition of fires in sealed-off areas.

Jan 1, 2004