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Poorly designed sampling protocols generally result in high project risk by artificially increasing grade variability (ie the nugget effect). Sample collection, preparation and assay protocols that suit the ore type, together with QA/QC systems, will reduce this risk. All reporting codes (eg JORC, 2004) require the Competent Person to consider the quality and implication of sampling and assaying programs. High sampling errors beget higher project uncertainty; despite this fact, sampling does not receive the attention it deserves. The case studies presented show that many sampling issues frequently go unrecognised or unaddressed, resulting in poor project decisions during exploration through to feasibility and production. The overall conclusion is that correct sampling is critical to mining project success and that there is often a need for its optimisation.

Jan 1, 2007

By M. Soleymani Shishvan

"Continuous mining systems containing multiple excavators producing multiple products of raw materials are highly complex, exhibiting strong interdependency between constituents. Furthermore, random variables govern the system, which causes uncertainty in the supply of raw materials: uncertainty in knowledge about the reserve, the quantity demanded by the customers, and the breakdown of equipment. This paper presents a stochastic-based mine process simulator capturing different sources of uncertainties. It aims to quantify the effect of geological uncertainty and its impacts on the ability to deliver contractually defined quantities and qualities of coal, and on the system efficiency in terms of utilization of major equipment. Two different areas of research are combined: geostatistical simulation for capturing geological uncertainty, and stochastic process simulation to predict the performance and reliability of a large continuous mining system.The process of modelling and simulation in this specific production environment is discussed in detail. Problem specification and a new integrated simulation approach are presented. A case study in a large coal mine is used to demonstrate the impacts and evaluate the results in terms of reaching optimal production control decisions to increase average equipment utilization and control coal quality and quantity. The new approach is expected to lead to more robust decisions, improved efficiencies, and better coal quality management.IntroductionContinuous coal mining systems containing multiple excavators producing multiple products of raw materials are highly complex and exhibit strong interdependencies between constituents. A network of conveyor belts is used for transportation of the extracted materials to different waste dumps or the coal stockpile.Optimal decision-making in short-term planning and production control are impacted mainly by geological uncertainty associated with incomplete knowledge of the coal deposit represented in the reserve block model. These uncertainties cause deviations from expected process performance. For more robust decision-making, understanding the impacts of these stochastic elements plays a key role."

Jan 1, 2016

By M. D. G. Salamon

It has been noted in recent years that the pillars in some bord-and-pillar workings scale or spall. In due course this process may result in the collapse of the affected panels. This paper presents a methodology for assessing the long-term behaviour of such workings, employing a simple model of pillar deterioration by scaling. It is assumed that scaling causes a gradual reduction in pillar width, hence the safety factor of pillars reduces in time. It is also postulated that the process of scaling will be arrested if the coal rubble around the pillar reaches a critical height. The probability that the pillars will survive for a certain period of time, or indefinitely, can be estimated. This can be accomplished by using the log-normal distribution proposed by Salamon and Munro4todescribe the distribution of the apparent safety factor values at failure. If an estimate of the rate of scaling is known, it is also possible to quantify, using a Monte Carlo technique, the expected life of the pillars. The method also facilitates pillar design by specifying a probability of survival for a given number of years or, alternatively, for an indefinite period. Using the limited pool of available data, analyses show that the proposed model does not appear to be inconsistent with observed behaviour of pillars in the Vaal Basin. The crucial parameter is the rate of scaling. Back calculations from eleven cases suggest that the rate of spalling in the Vaal Basin is about 0.2 m/year. It is noteworthy that two further cases in the same area give significantly higher rates (0.85 m/year). Some underground observations in the Witbank area indicate considerably lower rates in the order of 0.02?0.04 m/year. Further areas for study are recommended. These include a study of old workings to determine the extent and rate of scaling in the various coal fields, an investigation into the possible relationship between scaling and the chemical composition of the coal. In addition, model studies will be required to assess the practical impact of the research findings.

Jan 1, 1998

By W. U. Reimold, R. Armstrong, R. G. Charlesworth

For many years rockbursts have plagued the mining industry. Although much research has gone into studying this phenomenon only a small proportion of it has been on the actual source mechanism. A study was recently carried out to compliment the previous work done on the micro-structure of these features and to compare it to the micro-structures seen on shatter cones, from meteorite impacts. Both optical and electron-microscopy were used during the study. Samples were collected from rockburst sites by the CSIR Miningtek Rockburst Investigation Unit, and from the collar of the Vredefort Impact Crater. In the optical-microscopy study, the pinnate fractures observed in previous studies were seen in the shatter cones, through all the material. In the rockburst samples, the fractures were observed only in the quartz grains. Quartz micro-crystals were present in the rockburst samples and appeared to be the product of comminution rather than crystallisation. Cataclasite was present on rockburst and shatter cone fracture surfaces. The observations of the shatter cone surfaces with the scanning electron microscope are in agreement with previous work, including the observed presence of melt features, spherules and spheroidal material. The deformation in the rockburst samples is concentrated in the quartz grains, highly complicated with brittle features like sub-conchoidal structures and step structures present. A quartz spherule was identified on one rockburst sample and rhombic-dodecahedra type micro-crystals were present and seen fracturing off quartz grains. It is clear that the rockburst and shatter cone fracture surfaces are quite different; the shatter cone deformation is equally distributed across the sample and involves plastic-deformation, while the deformation in the rockburst material is concentrated in the quartz grains and, with the exception of spherule formation, is brittle. This study agreed with the current explanation for the formation of the rhombic-dodecahedra, and disproved the possibility of it being coesite or fine-grained meta-chert. Although there is no definite evidence of the mechanism of formation of the spherule, it is believed to be the product of vaporization and condensation, and the presence of this material indicates the extreme conditions under which this event occurred.

Jan 1, 2003

By K. Liddell

Current practice for the recovery of platinum group metals (PGM) from flotation concentrates is by energy-intensive smelting processes followed by separation and refining of the base and precious metals. Energy costs are rapidly increasing in South Africa and this trend is forecast to continue in future years. Moreover, the smelting operations are highly susceptible to deleterious constituents, particularly chromite; and the increasing tonnages of UG2 chromititic ore being mined results in an increasing chromite content of smelter feeds. Hence there is a substantial incentive to assess and implement alternative processes to smelting for the treatment of PGM concentrates. The Kell process is a patented hydrometallurgical alternative to smelting that is totally insensitive to the chromite content of the feed concentrate and comprises three commercially proven unit operations (pressure oxidation leaching of base metals and sulfur, roasting and chlorination of precious metals). The Kell process provides the opportunity for existing and new PGM producers to significantly reduce their energy consumption, and in particular their consumption of electricity, by removing the need to smelt PGM concentrates. Energy costs, greenhouse gas emissions and installed power requirements are also much reduced. Compared with smelting and refining these reductions are calculated as: ? Total energy consumption-50% reduction ? Electrical energy consumption-84% reduction ? Energy consumption costs-76% reduction ? C02 emissions-70% reduction ? Installed power requirement 92% reduction. The data obtained from simple laboratory batch amenability testing can be readily applied to the Simulus mass and energy balance simulation procedure to determine energy and reagent consumptions, equipment selection and process optimization. The applicability of Kell to treating low-grade 'dirty' concentrates with high UG2 content as well as to polymetallic concentrates containing base metals as the major payable metals with subordinate PGM means that these savings can also be expected when the process is used for treating a range of concentrate types and grades. Keywords PGM,UG2, Merensky, smelting, chromite, electricity, hydrometallurgy, Kell Process, Eskom.

Jan 1, 2011

By A. D. Engelbrecht

An investigation was undertaken to ascertain the suitability of four selected low grade, South African coals for gasification in a bubbling fluidized bed for production of synthesis gas and for the development of integrated gasification combined cycles (IGCC). This study consisted of the characterization of the coals, laboratory evaluation of intrinsic reactivity, and experimentation with a pilot-plant fluidized bed gasifier. Results of the characterization experiments show that the selected coals are high in ash, rich in inertinites, very dense (low porosity), with low caking indices and high ash fusion temperatures. Reactivity measurements with a thermogravimetric analyser (TGA), under reaction rate controlling conditions with carbon dioxide, showed that the reactivity of the coal chars decreases with increase in rank of the coal, as expressed by the vitrinite random reflectance and carbon content of the parent coals. The fixed carbon conversion achieved in the fluidized bed gasifier also correlates well with the rank parameter of the coal, with higher conversions being obtained with the lower rank coals. Thermal shattering and attrition of the coal particles produce significant amounts of fines, which correlate with the grindability indices, and no agglomeration (non-caking) was observed. It is concluded that fluidized bed gasifiers are able to utilize typical low grade, high ash South African coals for synthesis gas production and for inclusion in integrated gasification combined cycles for power generation.

Jan 1, 2010

By S. G. Ercelebi

In surface mining operations, truck haulage is the largest item in the operating costs, constituting 50 to 60% of the total. In order to reduce this cost, it is necessary to allocate and dispatch the trucks efficiently. This paper describes shovel and truck operation models and optimization approaches for the allocation and dispatching of trucks under various operating conditions. Closed queuing network theory is employed for the allocation of trucks and linear programming for the purpose of truck dispatching to shovels. A case study was applied for the Orhaneli Open Pit Coal Mine in Turkey. This approach would provide the capability of estimating system performance measures (mine throughput, mean number of trucks, mean waiting time, etc.) for planning purposes when the truck fleet is composed of identical trucks. A computational study is presented to show how choosing the optimum number of trucks and optimum dispatching policy affect the cost of moving material in a truck-shovel system. Keywords: Open pit mine, equipment selection, dispatching, linear programming, closed queuing network theory

Jan 1, 2009

By A. H. Onur

Many factors govern the size and shape of an open pit, and these must be properly understood and used in the short and long-term planning of any open pit and quarrying operation. The importance of each factor will depend on the particular project, but the geology, grade, and localization of mineralization, extent of the deposit, topography, property boundaries, production rates, bench height, pit slopes, road grades, mining costs, and cut-off grades are key elements of open pits. This paper discusses the work done on the above parameters in order to provide an optimal production plan for a limestone quarry and clay deposits that provide raw material for a cement factory in Turkey. Soke cement factory has 1 400 000 tons of clinker capacity and is located on the western part of Turkey, in the province of Aydin. It is one of the largest facilities in the cement sector in terms of capacity, and it has a large advantage over facilities because the location of the factory was chosen to obtain the raw materials necessary for cement production within very short distances. However, the old reserves that supplied limestone to the factory had been reported to have run out, and therefore new limestone reserves in the same province have been investigated over the years by experienced geologists. From surface samples, high MgO content was reported in the neighbourhood of limestone formations with high dolomatization; hence, other alternatives were taken into consideration. One alternative with better chemical composition had been found 24 km away from the factory, but the haulage cost of limestone was unacceptable for the factory due to high diesel prices in Turkey. The maximum allowable MgO content in the pre-mix feed to a rotating furnace is 2.5% MgO content in pre-mix from both limestone and clay deposits. The clay deposits belonging to the cement factory have higher MgO content than the limestone deposit, and therefore this quality problem was taken into consideration first, instead of transporting material from 24 km away. This study gives the details of work done to evaluate both the clay and limestone deposits, statistical analysis performed on core samples taken from drill holes, mathematical modelling for both sites, and most importantly of all, in-pit homogenization work that reduced the pre-mix MgO content. As a result of this study, the profitable limestone quantity has been improved in order to serve the cement factory over a projected 25 additional years without using any material from the close deposit.

Jan 1, 2008

By F. P. Hassani

Today, mine backfilling has become an integral part of mining operations, both from a local and overall ground control point of view, and as regards mining techniques and environmental considerations. During the past decade, substantial research has been carried out to contribute to the better understanding of the mechanisms involved in mine backfill behaviour. This work involved analytical, experimental and numerical studies at different scales. Accordingly, this work has been aimed at developing backfill design guidelines for actual working conditions. Backfill design for deep mining conditions is complex and requires understanding of various elements. The most important of these elements are: backfill inherent strength parameters, backfill placement method, stope geometry and interaction between backfill and host rock. The mobilization of backfill strength parameters controls the backfill behaviour and thus, its failure mode. It is believed that the governing boundary conditions and backfill-rock interaction influence the backfill strength mobilization significantly. Accordingly, the interaction between backfill and host rock is an influential factor in overall backfill behaviour under applied loads. The focus of this research is to investigate the backfill-rock interaction, considering a nonlinear behaviour for both backfill and rock mass. Assuming typical stope geometry, the FLAC code was used to model the complex boundary condition associated with narrow vein mining conditions and to simulate the backfill behaviour. A comprehensive numerical study was conducted and the results obtained were compared against field observations. The analysis of findings provides qualitative results, which can be used for backfill design. Keywords: Numerical modelling, backfill, deep mining, non-linear behaviour, rock mechanics, backfill behaviour, narrow vein mining.

Jan 1, 2008

By Philippe Dumont

?Lay out of the tunnel section ?General ?Geology ?Tunnels methods ?Stations constraints ?Impacts on tunnels ?Design ?Programs

By T. P. Williams, M. B. Rydzewski, B. Corner

Konkola Copper Mines (KCM) plc is an integrated copper producer operating on the Copperbelt in Zambia. KCM has numerous mining operations located in the towns of Chililabombwe (Konkola Mine), Chingola (Nchanga Open Pit and Underground operations), Lusaka (Nampundwe Mine), with a smelter located in Kitwe (Nkana Smelter) and an SX-EW plant in Chingola (Nchanga Tailings Leach Plant). [ ]

Jan 1, 2005

Comminution is a vital part of minerals extraction, and therefore of the South African economy. The high cost and throughput-limiting nature of comminution forms a strong motivation for research directed at improving the efficiency of the process. Building on a ten year background of fundamental charge motion research, a new formal UCT flotation and communication group has been formed. The group is also moving strongly into the field of milling circuit modelling and simulation, based on close links formed with the Julius Kruttschnitt Mineral Research Centre (JKMRC) of Australia, and an international collaborative research programme.

Jan 1, 1998

By B. L. Eggers

This study investigates the application of computed order tracking with subsequent rotation domain averaging and statistical analysis, to the drag gearbox of a dragline used in a mining environment. Computed order tracking is a fault detection method developed to deal with the varying speed conditions often found in industry and has been proven effective in laboratory conditions. Its application to real situations, however, requires some adjustment to deal with issues such as inadequate speed data and the fact that the drag gear rotates in two directions. This provides a unique opportunity to observe the performance of the order tracking method in a bi-directional rotating environment, allowing an investigation of the relationships between the results obtained from each operating direction. A monitoring station was set up aboard the dragline and data was captured twice daily for a period spanning approximately one year. The data captured consisted of accelerometer and proximity sensor data. The key on the shaft triggers the proximity sensors, allowing speed and direction to be measured. The measured speed is interpolated by using various speed interpolation techniques. Then the interpolated speed is used to complete the order tracking procedure that resamples the vibration data with reference to the speed. The results indicate that computed order tracking can be successfully employed in real environments. Furthermore it is shown that the rotation direction that opens the gear-tooth crack gives a better indication of incipient failure. It is therefore important not to disregard either direction when monitoring rotating machinery of this kind.

Jan 1, 2007

Tunnelling under squeezing ground conditions poses significant challenges. There are fundamental differences in the choice of support for mining as opposed to civil engineering. This paper reviews ground support strategies that have been used to control large deformations in mining excavations based on field data from five different mines in Australia and Canada. Recommendations are made for improved ground control strategies in squeezing rock conditions.

Jan 1, 2008

By D. C. Andersen, G. L. Smith, J. Pearson-Taylor

Following a restructuring of Anglo Platinum Limited in 2004 the strategic long-term planning function has been centralized. This paper describes the revised strategic long-term planning process covering aspects of the planning cycle, systems and methodologies, categorization of capital expenditure, corporate governance and planning tools.

Jan 1, 2006

The 108th Annual General Meeting of The South African Institute of Mining and Metallurgy was held at The Country Club, Johannesburg, Napier Road, Auckland Park on Thursday, 11 August, 2005. Welcome The President extended a special welcome to the guests and representatives of our sister institutes and other associations, also to recipients of awards, senior members of industry, Honorary Life Fellows, past-presidents, our members and other guests, among them the following: Dr Con Fauconnier, President, Chamber of Mines of South Africa Prof. Jay Barton, President, The Geological Society of South Africa V. Townshend, President, Institute of Certificated Mechanical and Electric Engineering, South Africa M. Livingstone-Blevins, President, Institute of Certificated Mechanical and Electrical Engineers, South Africa Prof. B. Lacquet, President, South African Institute of Electrical Engineers Dr F. Malan, President, South African National Institute of Rock Engineering

Jan 1, 2005

The influence of varying amounts of magnesia, silica, and alumina in iron ore sinter on its mineralogy, reducibility index (RI), reduction disintegration index (RDI), physical breakdown (AI and TI), and production properties (coke breeze rate) were examined. It was found that the mineralogy of iron sinter can more easily be predicted from its chemical composition than from the RI, RDI, AI or TI. Anticipating the consequence that varying amounts of MgO and SiO2would have on sinter properties is complex, and not necessarily predictable. High concentrations of Al2O3in the sinter result in high concentrations of the SFCA phase, but with drastically deteriorated properties. This study also confirmed that the form in which fluxes are added to the raw material sinter mixture affects the mineralogy and properties of the produced sinter.

Jan 1, 2010

By V. S. S. Yadavalli, J. Hager, R. Webber-Youngman

"This article investigates the complex problem of a budgeting process for a large mining operation. Strict adherence to budget infers that financial results align with goals. In reality, the budget is not a predetermined entity but emerges as the sum of the enterprise’s operational plans. These are highly interdependent, being influenced by unforeseeable events and operational decision-making.Limitations of stochastic simulations, normally applied in the project environment but not in budgeting, are examined and a model enabling their application is proposed. A better understanding of budget failure in large mines emerges, showing that the budget should be viewed as a probability distribution rather than a single deterministic value.The strength of the model application lies with the combining of stochastic simulation, probability theory, financial budgeting, and practical scheduling to predict budget achievement, reflected as a probability distribution. The principal finding is the interpretation of the risk associated with, and constraints pertaining to, the budget.The model utilizes a four-dimensional (space and time) schedule, linking key drivers through activity-based costing to the budget. It offers a highly expressive account of deduction regarding fund application for budget achievement, emphasizing that ’it is better to be approximately right than precisely wrong’."

Jan 1, 2015

By C. -J. Rick

By implementing a converter downstream of the reduction furnace it is possible to broaden the product range significantly. The converter can also successfully be used to strip furnace slag from chromium oxide. Some process alternatives and their economical, practical and environmental implications are studied using process models developed based on UHT?s long experience in stainless steelmaking, stainless steel process control and charge chrome refining. Keywords Charge chrome, converter refining, ferrochromium products, process design.

Jan 1, 2010

By H. P. Kritzinger, T. C. Kingsle

"Rotary kilns are used for a variety of mineral processing operations. Hatch makes use of a kiln model developed from first principles to evaluate designs for its clients. This tool has been applied to a variety of pyrometallurgical applications, including ferrovanadium, nickel carbonate, nickel laterite, iron ore reduction, and spodumene (lithium) production.This paper illustrates the application of numerical optimization techniques in combination with the kiln model in the interrogation of a generic iron ore reduction process. The fundamental modelling concepts are explained, followed by a description of the optimization approach. The results show how the combination of the two methods, with modern computing power, can generate a large number of viable design and operating candidates."

Jan 1, 2015