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By J. Kortnik

Mining has always been, and still is, an activity which is vital for the development of mankind. This is because a predominant proportion of industrial products and energy is produced from raw materials that are excavated using mining methods. The need for environmental protection and the close proximity of urban settlements and mines in Slovenia have necessitated ever stricter requirements for the excavation of raw materials and the introduction of more environmentally-friendly mining methods. This is achieved by implementing a closed eco-technological cycle of raw material excavation within the scope of mining methods. In surface mines, this means prompt reclamation of the degraded surfaces, and in underground mines the use of methods with minimized impact on the surface and on underground water. In underground mines, mining methods with backfilling installed according to the multi-barrier disposal system are the only ones that allow the possibility of implementing a closed eco-techno-logical cycle of excavating raw materials. Various industrial waste materials are also included in the backfilling material in order to improve its strength properties. Backfilling consisting of several different waste materials is produced in the form of a composite. Before backfilling consisting of waste material composites can even begin to be used in mines, an environmental impact assessment of its suitability for mines needs to be made. In order to make such an assessment, a pressure leaching cell and an open diffusion cell were made, i.e. a pressure leachate test and a sorption test were developed. The two cells and the developed tests will enable the study of the influence of backfilling on the environment if installed in an underground mine. The pressure leachate test performed with the use of the pressure leaching cell simulates leaching from a consolidated backfill during the seeping of underground water into the backfilling material under pressure. The sorption test performed in an open diffusion cell simulates the flow of eluate leached from the backfilling material through the rock/geotechnical barrier. The two tests were developed in such a manner that they are performed either in succession immediately after one another, but they can also be performed separately at a certain time interval. The paper presents an assessment of the suitability of backfilling made of different waste material composites. Keywords: environmental impact assessment, multi-barrier disposal system, waste material composites, pressure leachate test, sorption test, pressure leaching cell, open diffusion cell, eco-technological cycle, mining methods with backfilling.

Jan 1, 2003

By André de Jager, Henk Ludik

Navachab Mine experiences difficulties with pit wall stability in certain areas of the mine. The main reason for the instability is the fact that the geology comprises many joints and faults. Blasting, without impacting negatively on the stability of the pit walls, poses a major challenge. The mine has installed a technologically advanced seismic monitoring system with monitoring sensors positioned at various locations and depths throughout the pit. The electronic data recording system records all relevant information on a continuous basis with early warning signals in cases of potential danger. From the information recorded by this micro-seismic system it was established that the energy release into the high-wall is predominantly influenced by the mining rate, water content and mining tempo and to a lesser extent by the blasting operations. To limit the negative effects of blast vibrations, the use of Electronic Delay Detonators (EDDs) was introduced. The optimal delays were determined through signature trace analysis. The vibrations obtained during blasts initiated by means of electronic delay detonators were monitored and compared to those traditionally obtained when standard pyrotechnic delay detonators had been used. The measured vibration data indicated an improvement of 25% to 100% drop in vibration amplitude compared. The accuracy and programmability of EDDs presented huge potential for blast optimization in terms of limiting the vibrations without compromising fragmentation. The whole project was conducted over a twelve week period with some 4000 EDDs. The average size of a blast was in the order of 350 holes using about 40kg explosives per hole, which equates to 14,000 kg explosives over 12 different blasts. The paper deals in detail with the blast optimization process with regard to: - determining the rock response time; - establishing the signature traces; - analyzing the wave interference patterns; - predicting the direction of constructive and destructive wave interferences; - optimizing of the inter-hole and inter-row delay periods; - measuring the ground vibrations. The results obtained during electronic blasting are compared to those obtained during pyrotechnic blasting. Comparisons are being made with regard to the following: - ground vibration measurements; - pit wall stability measurements; - blast safety.

Jan 1, 2006

By H. A. D. Kirsten

Shotcrete has become a strategic component of support in underground mines. The ductility of reinforced shotcrete makes it a safe and economic means of surface support under adverse static and dynamic loads. The ability of ductile shotcrete to sustain load at large deflections enables excavations in squeezing conditions to be stabilized and the safety in excavations subject to rock bursting, to be assured. A Shotcrete Working Group was formed to find the configurations of fibre reinforcement that would give shotcrete the same ductility as when reinforced with mesh. Beams and panels reinforced with various types and lengths of fibre were accordingly tested. A single mix design consisting of river sand, ordinary Portland cement, fly ash, condensed silica fume and gunite dust and segregation suppressant was used. Steel and polypropylene fibre varying in length from 25 to 50 mm were used in nominal contents of 5 % and 0.5% by mass respectively. Beams, panels and control specimens were shot into specially made formers. Suitable mixing procedures were developed for the different types of fibre. The test specimens were shot in a semi-dry mix process. The shotcrete was cured until tested 28 days after shooting. The fibre contents and uniaxial compressive and Brazilian tensile strengths of the shotcrete were determined from the control specimens. The beams and panels were tested in bending in specially manufactured test rigs. The beams were examined for simple supports and fixed ends. The panels were fixed in a manner that simulated underground conditions and were loaded statically under uniform pressure. The beams were loaded and the corresponding deflections measured up to failure. The panels were loaded up to mid-span deflections of 150 mm. The results are presented in the form of load-deflection graphs. The peak loads and ultimate deflections for the fixed end beams were considerably larger than for the simply supported beams for the various types of fibre considered. None of the beams tested, however, were able to sustain load at relatively constant value beyond the peak load. The panel tests showed that 40 mm and 50 mm long steel fibre and 30 mm, 40 mm and 50 mm long monofilament polypropylene fibre reinforcement gave shotcrete the same ductility as mesh.

Jan 1, 1998

By J. Little

It is common practice for underground mine plans to be created sequentially, where results from one planning process form the input data for another. While this is practical for manual methods, computerized optimization techniques should consider an integrated approach to creating the global mine plan. This is because optimizing an individual mine planning process, such as stope layouts, introduces a likelihood of increasing costs or decreasing revenues associated with other areas, such as production scheduling, as harmful decisions must be balanced. Considering the interaction and influence that individual underground mine planning processes have on each other during optimization will provide more profitable results than if these are ignored. Optimization techniques for stope layouts and production scheduling are reviewed. An integer programming model is proposed that allows for either integrated or isolated optimization. Both approaches are separately applied to a block model. The results demonstrate the model?s ability to produce optimal long-term sublevel stoping mine plans and the benefits of using an integrated approach. Keywords underground mine optimization, stope layouts, underground production scheduling, integer programming, mathematical programming application.

Oct 1, 2013

By R. Dass

Paper written on project work carried out in partial fulfilment of B. Sc Eng (Extractive Metallurgy) degree Screening is an industrial process that splits material at a specific cut size into one fraction of particles larger than the cut size and another fraction of particles smaller than the cut size. Particles are vibrated to increase the probability of them being accurately classified and to move the oversize particles off the screen surface. In conventional screening, the screen mesh vibrates with a single frequency and the particles on the screen are all exposed to this same frequency. The Ultimate Screener (see Figure 1) is a new screen technology that imparts multi-frequency vibrations to the screen mesh so that different parts of the screen surface vibrate at different frequencies. The Ultimate Screener incorporates an additional deck that holds the multi frequency adapters as shown by Figure 2. These special adapters can transform single frequency vibrations into multi frequency vibrations. When the screen motors are switched on they begin to vibrate. This vibration is transmitted to the adapters via the body of the machine. The adapters then modify the vibration to have multiple frequencies, which are transmitted to the screen surface via resonating rings.

Jan 1, 2004

By G. S. Maré

Tin plating operations are of a complex nature due to the many operational variables that need to be controlled in order to create a product of required quality. The work in this report lays the basics for the control of a halogen plating operation based on the DuPont tinplating set-up with regard to the chemical make-up of the plating solution, as well as operational variables such as temperature and current density. To evaluate these aspects of the process, a rotating cathode Hull-cell set-up was used. This allowed for a laboratory scale plating arrangement that simulates industry closely with regard to chemical and hydro-dynamic considerations. Typical industry accepted standards were obtained for the values of operational variables and a ?baseline? test was conducted employing these standards. All subsequent tests conducted were benchmarked against this baseline result. A large suite of results was obtained in which it was found that changes could be made to the industry accepted norm which would improve on the stability of the operation and therefore the quality of the final tin-plated product. Examples of these results are: an increase in stannous tin concentration, an increase in sodium chloride concentration and a slightly elevated plating temperature. In addition, conditions were found that must be avoided to prevent instability and poor product quality.

Jan 1, 2010

By H. Jang, Y. Kawamura

Unplanned dilution and ore loss directly influence not only the productivity of underground stopes, but also the profitability of the entire mining process. Stope dilution is a result of complex interactions between a number of factors, and cannot be predicted prior to mining. In this study, unplanned dilution and ore loss prediction models were established using multiple linear and nonlinear regression analysis (MLRA and MNRA), as well as an artificial neural network (ANN) method based on 1067 datasets with ten causative factors from three underground longhole stoping mines in Western Australia. Models were established for individual mines, as well as a general model that includes all of the mine data-sets. The correlation coefficient (R) was used to evaluate the methods, and the values for MLRA, MNRA, and ANN compared with the general model were 0.419, 0.438, and 0.719, respectively. Considering that the current unplanned dilution and ore loss prediction for the mines investigated yielded an R of 0.088, the ANN model results are noteworthy. The proposed ANN model can be used directly as a practical tool to predict unplanned dilution and ore loss in mines, which will not only enhance productivity, but will also be beneficial for stope planning and design.

Jan 1, 2015

The current methodology to design stope support systems in South African gold and platinum mines is based upon the tributary area concept. The discontinuous nature of the hangingwall rock is not adequately addressed, and mechanisms leading to rock mass failures between adjacent support units are poorly understood. The work reported here aims to formulate a basis for quantifying support mechanisms and gain insights into the influence of rock discontinuities on stable hangingwall spans. Numerical models are used to qualitatively investigate the stress transfer from the support units to the discontinuous hangingwall. Stable hangingwall spans are quantified by considering two failure mechanisms, namely (i) beam buckling, and (ii) shear failure due to slip at the abutments. The output of the proposed design methodology is appropriate site specific support spacing, based on discontinuity spacing and orientation. The method is particularly suited to mines at intermediate and great depth, where typically the hangingwall is highly discontinuous due to face parallel mining induced fractures. Results of parametric studies show that with increasing in situ compressive hangingwall stress, beam thickness and friction angle, hangingwall stability is increased, leading to wider stable hangingwall spans between adjacent support units.

Jan 1, 2000

By R. T. Jones

"SynopsisScientific progress relies on the publication of ideas and experimental results that can be replicated, tested, and improved over time. The first printed book on metallurgy to have been published in Europe is considered to be De la Pirotechnia, written in Italian by Vannoccio Biringuccio, and published in Venice in 1540. Together with De Re Metallica, written by Georgius Agricola and published in Latin in 1556, this can be considered to mark the start of scientific and technical literature in this field. Scientific publishing of journal papers has been in existence for 350 years, since the world's oldest and longest-running scientific journal, the Philosophical Transactions of the Royal Society, was first published in London in 1665.The nature of scientific societies has changed significantly since the early days when regular meetings were held to discuss science and conduct experiments, and the reading of scientific papers took place, and publication of papers was undertaken to record the proceedings of meetings, often including rather robust debate. In today’s world, there is a plethora of publications, and it is close to impossible for anyone to keep up with the vast flow of information. International conferences with hundreds of presentations have taken the place of the local meetings that used to discuss a single paper or experiment. In this frenetic environment, it is essential that researchers are able to trust the material they read.The system of peer review is used to maintain standards and to improve the quality of papers. This vital system is, however, significantly flawed. There is little incentive for reviewers to invest sufficient time in picking up all errors in publications, and any ineptitude on their part is usually protected by anonymity. It has reached the point where some reviewers have mistakenly permitted the publication of hoax papers deliberately presented with a complicated scientific facade. In light of such astounding inadequacies, perhaps a more open review process would be an improvement. Electronic publishing allows errata to be linked to the original papers.There is an increasing trend towards open access for papers in scientific journals and conference proceedings, which helps to reach as wide an audience as possible. This also supports the statement in the Universal Declaration of Human Rights, which says ‘everyone has the right freely to … share in scientific advancement and its benefits’."

Jan 1, 2015

By R. W. Ottermann, N. D. L. Burger, A. J. von Wielligh, P. R. de Wet, J. L. Steyn

A low noise blast hole drilling system was developed to limit the risk of noise induced hearing impairment in mining operations. Noise induced hearing loss has been identified as a major occupational health risk in SA mines. The noise generated by pneumatic percussion drills is a major contributor to such noise induced hearing. This motivated the South African Safety in Mines Research Advisory Committee (SIMRAC) to commission the development of a low noise rock drill system. The system had to be designed, manufactured, tested and demonstrated in a simulated underground mining environment. The specification required noise levels below 90 dBA. Other important design considerations were ease of manual transport, setting up and operation. The primary design concept was to encapsulate a standard Seco S215 pneumatic rock drill in a composite material tube. The tube is pushed onto the rock face by a pneumatic cylinder and is sealed at the rock face by an elastic seal. The drill is pulled towards the rock face by a rope and pulley mechanism fitted inside the tube. This mechanism is powered by a second pneumatic cylinder. The actions of moving and setting the drill require two persons. However, the team can carry out the drilling function itself on several drills simultaneously because of the self-thrusting design. The drill is supported by two camlocks. The exhaust (air containing dust, water, rock shavings, oil and grease) is removed from the encapsulating tubes via exhaust tube to the end of the stope. In this way exhaust noise and air pollutants are disposed of away from personnel. Tests were conducted in a test stope. Noise levels of under 90 dBA were achieved, thereby attaining the primary design specification. This was achieved without materially compromising ease of handling. Penetration rate was somewhat improved compared to that of the standard drill, so that productivity could be maintained. Keywords: Drill, rock drill, quiet, noise, mine, underground.

Jan 1, 2003

By M. Stephton, L. A. Cornish, R. Süss, N. B. Maledi, J. H. Potgieter, L. Chown

In today?s gas turbines, the emphasis is on saving energy and reducing the amounts of pollutants emitted. This can be attained only by designing alloys with higher melting points and the capability to retain mechanical integrity at increased temperatures. The development of nickel-based superalloys (NBSAs) has reached its limit, as the alloys are operating at critical temperatures close to their melting points. Further increase in the operating temperatures will result in dissolution of the strengthening phases and even melting. Recent trends are towards developing materials that are adequately strong but have much higher melting points and corrosion resistance than the NBSAs that are currently in use. Studies conducted on Pt alloys with similar structure to the NBSAs have presented mechanical results that are promising. This has led to further development of these alloys as a replacement for NBSAs. The operations of gas turbines are usually limited by hot corrosion, which could lead to catastrophic failures. Increased temperatures have an adverse effect on the corrosion of the alloys by making the environment more aggressive. Hence, during a material selection process, the corrosion behaviour of any selected material for a highly specialized application such as gas turbines needs to be assessed. Generally, coatings are applied to combat degradation by salt deposits, hence coated and uncoated NBSAs were selected as benchmark alloys. Corrosion mechanisms and kinetic studies of the Pt alloys were conducted. High temperature hot corrosion (HTHC) tests were conducted at 950°C for540 hours. Analysis of the corrosion products was conducted using a Raman spectrometer, scanning electron microscope with energy dispersive X-ray spectroscopy (EDS) optical microscopy, and X-ray diffraction study of the phases that formed. Both coated and uncoated NBSAs failed under the test conditions. Samples were covered with a porous non-adherent greenish layer which is characteristic of NiO. Pt alloys displayed superior corrosion properties compared with the benchmark alloys.

Jan 1, 2006

By M. Dworzanowski

The physical beneficiation of iron ore that has a wide particle-size distribution is problematic, regardless of the process applied, whether dense medium separation, gravity concentration, magnetic separation, or flotation. The problem of particle size is further compounded when there is a significant -10 µm fraction. Generally the approach to a wide particle-size distribution is to split into narrower size ranges and treat each separately. More often than not the -10 µm fraction is not treated but discarded. This approach results in a more complicated and expensive flow sheet and the loss of any potential value in the -10 µm fraction. Wet high-intensity magnetic separation (WHIMS) bench-scale test work was conducted on a haematite-rich material with a particle size of -200 µm. What made this material different was that it contained a 60% -10 µm fraction, hence discarding the -10 µm material was not an option. The objective of the test work was to determine how to maximize the recovery of the haematite across the full particle size range. Given the unusual particle size distribution, it was concluded that WHIMS would be the only practical beneficiation route. The -200 +10 µm and -10 µm fractions were treated separately and together under varying WHIMS conditions. For a given concentrate grade, the mass yield obtained was greater when the total particle-size distribution was treated. The inferred optimum conditions, using the same material, were tested on a pilot-scale WHIMS and similar results were obtained.

Jan 1, 2014

By R. Ribacchi, P. Tommasi, C. Consorti, P. Campedel

The runout of dry blocky rock avalanches produced by planar rockslides affecting a limestone formation with clayey interbeds is analysed by means of distinct element modelling. Numerical analyses are validated by means of the back analysis of a historical rockslide occurred in the investigated area and physical aspects of the phenomenon evidenced by modelling are discussed. On analyse par la méthode aux élements distincts la distance de parcours des avalanches rocheuses sèches produites par des glissements plan interessant une formation de calcaire à intercalaires argilleux. Les analyses numeriques sont validées à l’aide de la back-analysis d’un glissement historique survenue dans le site en examen. On décrit les aspects physiques su phénomène mis en évidence par la modélisation efféctuée. In diesem Beitrag wird die Reichweite von Steinlawinen besthend aus trockenem blockhaftem Fels mittels der Distinct Element Methode untersucht. Die Steinlawinen werden erzeugt von Rutschungen in einer Kalkstein-Formation mit tonhaltige Schichten betreffen. Die numerischen Berechnungen wurden anhand einer Simulation einer historischen Bergsturzen verifiziert, der sich auf den untersuchten Gebiet ereignete. Auf der Basis der erhaltenen Ergebnisse wurden die physikalischen Aspekte der untersuchten Steinlawinen analysiert.

Jan 1, 2003

By M. A. Hermanus

This paper examines the occupational health and safety performance (OHS) of the South African mining sector against the backdrop of changes in the composition of the sector, international trends in OHS performance, and the agreement on OHS milestones and targets by mining stakeholders at the Mine Health and Safety Summit of 2003. Although OHS performance has improved, progress is slow and there is need for significant rather than incremental change if the targets are to be realized. Since 2003, fatalities and injuries are 20?25% short of annual milestones and not all commodities show consistent improvement. Statistics on occupational health impacts are unavailable, but noise and respirable dust levels are known to be high in mines, with much work lying ahead to address exposures at source. Trends in regulating and addressing OHS hazards are discussed with reference to the notion of ?systems-thinking? and the targets. Efforts to improve OHS and to respond to changes in the sector are constrained by a lack of training and consistency in risk management, guidance for junior, small and artisanal miners, and holistic approaches to risk. For example, treating risk holistically would involve taking proper account of contractors and women in the workplace, and attending to human factors and ergonomics.

Jan 1, 2007

By H. E. Bartlett

In the operation of some flotation plants treating platinum ores it was found that there were imbalances between the inputs and outputs. The inputs and outputs were sampled as slurries and it was determined that the imbalances arose from biases in the sampling, despite the samplers having been designed according to well-established rules. The launders feeding the sample cutters, and the sample cutters themselves were redesigned using finite element analysis to model the flows. A new set of design rules were formulated. The application of a Components of Variance Analysis, to determine the variance of primary and secondary sampling and of analysis in the lab for a concentrate is presented to illustrate the need for frequent sampling of process streams.

Jan 1, 2002

By J. de Villiers

Through the application of the Rietveld method, X-ray diffraction analysis has developed into a fully quantitative method for phase analysis. The Rietveld method itself has progressed from an unstable method that required constant operator intervention to a stable and robust method suited even for routine analysis. The method, however, requires a good initial calibration and periodic checks on its precision and accuracy. Several examples from minerals processing, pyrometallurgy, and materials science show the strengths and applicability of the method. The limitations and sources of error are also discussed.

Jan 1, 2007

By P. J. Bartlett

Premier Diamond Mine exploits a kimberlite orebody using cave mining methods. A drilling level is established at the base of a block of ore to effect undercutting that leads to caving of the overlying ore. A second level is developed some 15 metres below the undercutting level to allow extraction of the ore once it has caved. As much as 45 per cent of the rock is removed on the extraction level creating a series of pillars. Undercutting creates abutment stresses, as high as 3 times the virgin stress, which affect the rock mass to a distance of 20 metres from the undercut face on the undercut level and on the extraction level 15 metres below. If the extraction level is completely developed prior to undercutting, where stress levels exceed 20 percent of the rock mass strength, extensive rock mass and support damage occurs as the undercut passes overhead. Rock mass damage takes the form of movement along existing joints and minor shear failure through intact rock. Support damage takes the form of cracking in rigid concrete linings. Where induced stresses exceed 50 per cent of the rock mass strength it is often impractical to keep excavations on the extraction level open. Rock mass damage takes the form of extensive failure of the rock in shear which evidences itself as propagation of the fracture zone around tunnels and footwall heave. Support damage results in destruction of shotcrete linings and concrete footwalls. As the interbolt support fails, badly fractured rock ravels around the steel tendons. Observation and monitoring at Premier Mine and on other cave mines has shown that induced stress levels and consequent damage are a function of :?the extraction ratio on the undercut and extraction level prior to undercutting ?the shape of the undercut face ?the rate of undercut advance ?the distance of leads and lags between adjacent tunnels on the undercut level. To ensure the stability of excavations, all of the above parameters must be carefully planned and the planned mining sequence rigidly enforced. The minimum of development is completed on the extraction level prior to the undercut passing overhead. Required development is then rapidly completed once the area has been de-stressed. Support is installed in three phases: ?Rockbolts are installed as soon as excavations are developed ?Wire mesh, steel tendon straps and a layer of shotcrete sufficient to protect the mesh and straps from damage by blasting and LHD loading is installed as soon as practical thereafter. Inevitably the shotcrete lining has to be replaced once the undercut has passed overhead.. ?Rigid shotcrete linings and concreted footwalls are completed only after the undercut has passed overhead and the area has been de-stressed.

Jan 1, 2000

By Yijun Caoa, Xiuxiang Taoc, Zhongbo Hub, Yinfei Liaoa

A new preparation scheme for a difficult-to-float coking coal from the Kailuan Mine, Tangshan, China was investigated. The results showed that grinding followed by column flotation was beneficial for obtaining products with low ash content. The positive effect of grinding on the coal floatability is attributed to the liberation of intergrowths and coal surface improvement. Tests indicated that 10 minutes was the optimum grinding time, and over grinding resulted in a deterioration in flotation performance. With a grinding time of 10 minutes, conventional flotation had potential to yield a product with around 12.42% ash content and 69.15% combustible recovery. Column flotation can reduce the product ash content to 11.15%and increase combustible recovery to 74.47%. Consistently better flotation results reveal that column flotation is more efficient than conventional flotation for such fines.

Jan 1, 2015

By G. G. le Roux

The purpose of the investigation was to assess various options for increasing the efficiency of the conveyor belt transporting system used at 4 Belt Shaft at Lonmin?s Marikana operations. The reason for the investigation was to prevent the occurrence of a ?bottleneck? at the main ore passes delivering ore to the conveyor belt system, thus creating more fluent operational conditions. The options assessed for increasing the efficiency of the conveyor belt transporting system were: ?Variation of the conveyor speed ?Concurrent tipping from two ore passes on the belt ?Increase the available drive unit power ?Increasing the feed rate from vibratory feeders ?Change in belt width/belt specifications The report shows that the most preferable option to the current situation at 4 Belt, Lonmin, would be the option of concurrent tipping from two ore passes to the belt.

Jan 1, 2008

By D. Schreuder

Conditions in the South African market relating to atmospheric emission control has changed dramatically over the last 10 years. Companies have become more responsible, environmentally aware, and have to comply to more stringent environmental limits set by legislation. This paper describes briefly the current best available atmospheric pollution abatement technologies relating to particulates, acid gases, NOx, acid mists, aerosols, mercury, dioxins and furans. Mention is also made as to the best practices for product work-up and waste product disposal.

Jan 1, 2006