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By P O. Andersson

Mining of sill pillars is more difficult than the ordinary mining. The sill pillar mining is performed under more difficult conditions and the mining of the sill pillar itself produces more problems; failure of the rock due to high stresses, difficulties in controlling the fill above, overall stability of the stope and special requirements on the technique for backfilling. Altogether this makes sill pillar mining technically difficult and often not profitable. A project was therefore initiated with the aim to increase the mineable ore reserve by making sill pillars mineable, both technically and economically. The project aimed at developing technique for already existing sill pillars as well as planned sill pillars. For the existing sill pillars a technique would have to be developed for mining beneath unstabilised fill. For sill pillars that would be created in the future, the most suitable mining method and methods of supporting or stabilising the fill in the stope above was to be chosen within the project.

Jan 1, 1998

By M A. Gontalves, A F. D C Varajpo, S A. Stachissini

Clays from the Santa Elena Peninsula, south-east of the Ecuador coast, were investigated with a view to identifying their main mineralogical, physical, chemical and textural characteristics as well as their potential for industrial use as adsorbents. Identified as calcic bentonites, two representative samples from the Tosagua Formation (Oligocene to Lower Miocene) were selected for acid activation trials. The selection criterion was based on the greatest amount of clay fraction (<2 ¦m fraction) associated with the greatest content of montmorillonite. For the activation treatments, HCl and H2SO4 solutions of 4, 6 and 8 N were used in a stirred glass reaction vessel with the clay sample under reflux during four hours at temperatures of 70¦C for HCl and 85¦C for H2SO4. Mineralogical analysis by X-ray diffraction (XRD), chemical analysis by X-ray fluorescence (XRF), differential and gravimetric thermal analysis and measures of density, surface area and porosity indicated the changes occurred in the crystal structure of the montmorillonite. The acid treated clays were utilised in trials of purification and decolourisation of soybean vegetable oil in a ratio of 2:100 (clay/oil) at 90¦C for 30 min, under constant stirring. After centrifugation of the suspension, the wavelength of the bleached oil was measured by UV-visible spectrophotometer and the bleaching capacity of the clays was determined. The best bleaching capacity of the samples was obtained with 6 N H2SO4 acid-activated clays. The bleaching capacity was compared to Tonsil, a commercial acid-activated clay and similar results between them evidenced the potential industrial application of the Ecuadorian clays to bleaching of vegetable oil.

Jan 1, 2008

The accuracy of an ore reserve is only as good as the geologist's understanding of the deposit. The methods that are applied to resource and reserve estimation reflect that understanding. At the Olympic Dam copper-uranium-gold deposit in South Australia, evolution in the understanding of the controls on mineralisation coupled with the changing demands of the project have led to changes in the approach to reserve estimation. The project has moved into a phase where detailed stope mining reserves are now required as distinct from global ore reserves. The complex nature of the mineralisation and the large amount of data demand that all available information be readily accessible in a flexible format. To enable the selective manipulation of geological and assay information and its characterisation, a relational database has been developed. For reserve calculations themselves, initial computations were based on a system derived from that used for the Kambalda nickel orebodies. The Olympic Dam system differed mainly in the use of statistical analyses in the estimation of grade instead of the previous polygonal area of influence weighting method, Three dimensional weighting techniques are now being used for local reserve estimates. Flexible facilities for raw data handling combined with grade estimation techniques which are commensurate with the mine geologist's understanding, produce detailed gridded and contoured ore zone models suitable for reserve calculations and stope designs.

Jan 1, 1987

Leadership challenges for mine management over the next decade will be primarily about doing more with less labour. This will require a greater focus on people leadership and management, reducing uncertainty by evening out employment peaks and troughs, understanding and addressing our demographic destiny and its implications whilst identifying and holding onto our mission critical employees, managing creativity and accepting diversity whilst providing flexibility in employment for work-life balance. Greater emphasis will also be required on the non-technical social skills of complex interactions with community and education providers and finally a greater emphasis on forecasting and planning for the provision of future skills needs. Skills needs will become an ever increasing priority in risk management as retention starts with attraction and remember: SATISFACTION = REALITY                                EXPECTATIONS These are the challenges and opportunities for leadership and mine management of the 21st century to assist in better meeting and maintaining our human resources needs and thus contributing to the sustainability of the sector in Australasia.

Jan 1, 2006

By K Lee, K Fernando, S Rayner

Copper-gold ores have been technically difficult and uneconomical to process due to high consumptions of cyanide. Many copper oxide and sulphide minerals react with cyanide to form copper cyanide complexes, partly contributing to the high level of weak-acid dissociable cyanide in the tailings which is normally experienced during the processing of copper-gold ores. The cost for detoxification, if required for treating these tailings, would further inhibit the development of these copper-gold resources unless the cyanide used for leaching was recovered. Several technologies have been proposed to process copper-gold ores, aiming to recover copper as a co-product and cyanide for recycling in conjunction with the leaching process. A critical review of these processes reveals that a pre-concentration stage (solvent extraction or resin ion exchange) is required. Cyanide is recovered by the conventional Acidification-Volatilisation-Regeneration technique in most cases. A critical evaluation is also provided on technical aspects related to the use of Vitrokele Technology and a newly developed Elutech process in processing copper-gold ores, in particular with its application at May Day Mine.

Jan 1, 2000

Powercoal Pty Ltd operates eight underground coal mines in New South Wales and produces coal for both domestic power stations and the export market. Approximately 40% of total production is from continuous miners. Over the past five years, place change mining methods have been introduced to improve productivity from continuous miners. This has involved utilising the existing coal clearance system from the continuous miner to the ratio feeder using trailing cable shuttle cars.By late 1996 average productivity at Cooranbong Colliery using this system had plateaued at 800 tonnes per eight hour shift. A number of factors were identified to increase average productivity to 1500 tonnes per eight hour shift. An improved coal clearance system was one of the factors identified.

Jan 1, 1998

By Jingmin Xin, Wenhua Xing, Zongxin Huo, Hongzhang Chen

Drawing up the successive plan for mining and development is a very important and regular plan work. The expert system of the successive plan for mining and development drawn up by computer is developed on the basis of network, computer simula

Jan 1, 1998

By Fitzgerald DE, Taverner MG

The principles, fields of application and equipment design concepts of several new approaches to continuous vacuum treatments of molten metals and alloys are discussed. Partic- ular attention is paid to the results of pilot plant tests evaluating a launder-in-tube method of 1. continuous production of refined zinc from a zinc-bearing lead produced in the lead splash condenser of the Imperial Smelting Furnace (ISF), and 2. continuous refining of crude cadmium. The former trials were not sufficiently encouraging to justify consideration of the process for commercial development. The applic- ation to cadmium upgrading gave very promising results; metal of 99.99 per cent purity was produced continuously at pilot scale (120 lb per hour) from crude metal containing 5.0 per cent Pb.

Jan 1, 1972

Mining had a very considerable effect on the country's development. The visual evidence remaining is an integral part of New Zealand history. Early mining for manganese and copper in the 1840s was succeeded by alluvial gold rushes. These gave way to hard rock extraction, hydraulic elevation and dredging. Coal mining dating from the 1850s was fairly widespread. Other minerals were obtained on a small scale. Manufacture of mining' machinery stimulated industrial engineering enterprises. Schools of mines played a significant part in advancing technical skills and several remain as museums. Surviving mine structures and site relics are part of the industrial heritage signifying the technological and economic development of a small isolated nation. Some of these are described. Identification, recording and preservation where practicable is advocated.

Jan 1, 1990

The paper describes the reasons for the development and for the selection of systems which were finally adopted; further estima- tion and design engineering problems, as well as experience with large screens in operation. Advantages, disadvantages and the final li- mits of screen dimensions are indicated.

Jan 1, 1984

By Shihui L, Lianfu Z, Llanming J

The paper considers the essence of the multi-objective decision-making issues for selecting an optimal mining plan, and analyses the advantages and disadvantages of the multi-objective decision-making techniques commonly used for selecting an optimal mining plan. It presents the principle and practice of using a group-AHD with mixed factors to select an optimal plan.

Jan 1, 1995

By Bhattacharyya A. K

The current methods for predicting pillar strengths are reviewed. A two-dimensional model, based on the Mohr-Coulomb failure criterion, is proposed for determining the compressive strength across the width of a long pillar. The model can be used to determine pillar strength and the depth of the crushed (ie yielding) zone from the pillar edges. The values of the parameters in the model, namely the cohesion and internal friction angle of the coal seam, friction angles at the contact of the coal seam with the roof and floor are determined by matching the strengths predicted by this model with the Bieniawski pillar strength formula for pillar width to height ratios up to 5. It is found that the derived values of these parameters are quite close to the results from laboratory tests. Based on the model, a preliminary analysis of pillar stability is made.

Jan 1, 1995

Sample preparation for gold samples, where the distribution and size of gold particles is often irregular, usually demands that a relatively large sample weight is taken to produce a representative sample for analysis. Traditional sample preparation of gold samples incorporated multiple stages of coarse particle size reduction followed by subdivision of the sample prior to final fine pulverising. This technique developed because of the limited equipment options available to laboratories. As a result significant errors are introduced and the final sample size being pulverised is a small fraction of the original sample weight. Three significant developments have occurred in the last 25 years to significantly improve sample preparation of gold samples: 1.  large capacity fine pulverising,2.  fine jaw crushing, and3.  whole sample coarse pulverising. In the mid-1980s an Australian manufacturer developed large capacity pulverising bowls which had the ability to reduce samples with a mass of 1.5 - 3.5 kg to a nominal 0.075 mm product in approximately three to five minutes. Laboratories were able to produce a large homogeneous pulverised sample which significantly reduced the error in sampling. However, exploration and mine samples are usually 7 to 10 kg and the sample requires a subdivision stage following crushing to produce the 3.5 kg for the pulverising step, thus introducing potential for significant error. The development of fine jaw crushing allowed particle size reduction to -2 mm which reduced the subdivision error of the bulk sample prior to fine pulverising. Subdivision of the crushed sample at -2 mm still results in potential sampling errors, where the gold particles are not sufficiently liberated to be representatively sampled. Clearly the best option would be to reduce the particle size small enough to ensure a representative sample prior to final pulverising. Continuous mills offer a partial solution but are relatively slow and subject the sample to differential pulverising prior to subdivision. Clearly this does not provide the best solution for routine laboratory applications where high volumes of samples are to be processed. The recent development of a large capacity coarse pulverising system allows samples of up to 10 kg to be reduced to -0.25 mm prior to subdivision, and fine pulverised to -0.075 mm. Laboratories now have the necessary equipment to perform reliable large capacity sample preparation of gold samples. The exact choice of a sample preparation scheme may still depend on particular ore types but the need for multiple crushing and subdivision stages is redundant.

Jan 1, 2008

The accurate determination of trace level gold in ores, metallurgical samples and process solutions is required because of the value of gold, the efficiency of the cyanide leach process and because of the high gold recovery from these cyanide solutions. It is thus necessary to routinely analyse geological and metallurgical samples with gold concentrations of 3 g tonne (ug g- 1ppm) and process solutions with a gold concentration of 0.01 mgL 1 (ppm) preferably with sufficient accuracy to quote at least two significant figures. Several techniques have been reviewed for their suitability for the routine gold analysis of these samples which also contain signif- icant concentrations of other ions. The classic fire assay technique has achieved the respect and confidence of mining personnel because of the results achieved by very experienced assayers. Other extraction and concentration techniques have now been shown to be equally effective. The use of instrumental analytical techniques particularly atomic absorption spectrometry have shown that cheaper procedures, which are as reliable, are now available to gold producers for the routine analysis required to maintain an efficient gold recovery process.

Jan 1, 1982

A number of suggestions have been made to improve the design of cells used for electro winning and electro refining of metals. Most of these designs have been aimed at increasing the current density used in order to improve cell capacity, although the purpose of some has been to produce electro deposited metals in a continuous manner. Improvements in the electrolyte flow pattern in conventional cells have resulted in an increase in the rate of mass transport of metal ions to the electrode surface; giving rise to lower concentrat- ion polarization and an improvement in the nature of the product obtained, Other cell designs are based on a moving electrode, usually a rotating disk, and these may include provision for removal of the product in a continuous manner, The maximum current density which can be used in an electro- lytic deposition process is determined by the limiting diffusion current, the physical nature of the, product, the purity of the product required and by the increase in power costs which result from the higher cell voltages, This paper examines the properties of an agitated bed of particles as an electrode system when used for a metal deposition Process,

Jan 1, 1969

By M Heidari, M Ataei

Today, the selection of a mining method is a multi-criteria decisionmaking process, with many factors in this process connected to each other. These trends do not have a high degree of confidence. In this study the analytical hierarchy process was used to select the suitable mining method for anomaly No 3 of Gol-Gohar iron mine of Iran. The results of this study show that gathering all existing information from the exploration stages and using AHP technique, the open pit mining method is the mining method for this anomaly.

Jan 1, 2003

There are two main challenges in analysis of spectral data: to output as accurate an interpretation of the sample mineral assemblage as possible and to then use the spectral data to map out trends (downhole, across section or traverse) that will assist the exploration geologist to target drilling and further exploration. This paper will discuss methods of extracting the maximum amount of information from spectral data and examples of plotting the information downhole, in section and plan view to assist in exploration and mining. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By G Johnson, S Michalek, N Redman

As the modification of the 2009 Mill OperatorsÆ Conference theme from æmilling through the boomÆ to æthe boom û experience gained and lessons learnedÆ exemplifies, comminution practitioners are facing a series of challenges in the dramatically changing mining environment. One of the main problems plant managers have been facing during the boom times has been the severe metallurgy skills shortage and high staff turnover, both factors that can cause difficulties in mill liner management. Many of todayÆs mill managers are now also more than ever faced with the need for cost-cutting in order to continue operating viably. Amongst other potential target outcomes such as maximised throughput, MillMapperÖ, a tool for mill condition monitoring and mill performance optimisation, can be utilised to address these issues. This paper demonstrates how MillMapperÆs quantifying decision making tools can serve to be in control of managing mill liner and production issues, and how it can form the basis for mill cost savings without the risks normally associated with conventional methods or the lack of using any condition monitoring methods. MillMapperÖ is currently being referred to at a rate of approximately 150 surveys and associated reports per annum at processing plants in Australasia, South America and Africa. Examples throughout the paper provide insight into how the presented sample set of users have extracted benefits that could have otherwise not been safely or at all achieved.

Jan 1, 2009

By E M. Rykaart

The design of soil covers as part of the remediation initiatives for mine waste facilities is common practice and more and more engineers are faced with designing these facilities. The design issues associated with these soil covers are complex and requires a good understanding of unsaturated flow. More engineers are making use of numerical models to predict how cover designs would perform, and this has been necessitated by the high non-linearity associated with solving unsaturated flow problems. There are numerous numerical models available to the prospective users and they are all simplifications of reality using different assumptions. The users of these models often do not understand the limitations of the models but rather select a model based on ease of use, and that lends to increasingly erroneous designs being proposed for construction. This paper describes a comparative evaluation of a cover design using four different codes available today; SoilCover, SWIM, HYDRUS-2D and HELP. The paper does not propose to measure these codes up against each other and make statements about which is better than the other but rather illustrates how the assumptions in each code affect the outcome. The data set used for the comparative study is a well calibrated data set that that has been collected over a long period in time and that has been collected according to strict controls. The authors present the pitfalls of numerical modelling of the surface flux boundary conditions, as well as present guidelines towards appropriate use of these modelling tools.

Jan 1, 2003

By Smith E. L

The Ore Reserve/Exploration System implemented at Mount Isa for M.I.M. Holdings Limited is a comprehensive computer system designed to process assay, geological, structural and survey data input via special purpose logging sheets from daily activities at Isa Mine, Hilton Mine and various Carpentaria Exploration Company prospects. The system performs two basic functions; (1) data acquisition, validation and file maintenance to prepare the data for retrieval, and (2) generation of routine and optional reports. The types of reports available range from masterfile detail printouts and retrieval of data by key items to survey computations, structural analyses, cutoff calculations, statistical analyses and ore reserve calculations by the polygonal, inverse square or moving average techniques. The use of various optional reports available through the system is illustrated by several examples, and planned future development is discussed.

Jan 1, 1973