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By Vernon PN

The Eossing Uranium Mine is a high tonnage low grade open pit operation using acid leaching for uranium extraction and ion exchange and solvent extraction for solution purification. Advanced technology, much of it computer based, has led to major economies that have contained operating unit costs over the last four years in the face of double figure inflation. An improved ore reserve block model and mine planning system have achieved a considerable reduction in the stripping ratio. Drilling and blasting costs have decreased some 25%, mainly by the introduction of heavy ANFO explosive. A centralised computer control centre for the metallurgical plant has increased labour productivity resulting in improved process control. The all-staff workforce is united with management in the objectives of creating a safe, healthy, working and living environment and a prosperous company, capable of contributing to the wellbeing of the nation and the shareholders. This situation has been brought into being by an equal opportunity policy coupled with a management system emphasising open two-way communication through all levels in the organisation. The success of this policy is highly apparent in the morale and productivity of the workforce.

Jan 1, 1986

By Howarth W. J, Sowerby B. D, Watt J. S

On-line analysis systems have found widespread application in the metalliferous mineral and coal industries. The continuous analysis and rapid response of these systems has led to improved control of mining, processing and blending operations, with increased recovery of valuable minerals and coal combustibles.The paper reviews developments in on-line analysis by CSIRO and Mineral Control Instrumentation Ltd which led to the award of the Australia Prize 1992. These commercialised systems analyse mineral and coal slurries; determine the ash and moisture contents of coal on conveyors, and the moisture content of coke on conveyors; and determine the carbon content of fly ash. These gauges are estimated to have resulted in productivity increases valued at $50 million per year to Australia.

Jan 1, 1993

By G W. Scott, H M. Lukey

The Lake Superior Region has been a producer of iron ore for over 150 years. Early mining operations concentrated on direct shipping ores, which are the result of post-depositional upgrading principally by deep weathering. As direct shipping ore reserves became depleted, the focus changed to the production of iron ore pellets from taconite. The post-depositional processes responsible for upgrading taconite are regional metamorphism, contact metamorphism and hydrothermal processes (Clout and Simonson, 2005). While these processes are important in iron ore genesis they can also contribute to liberation problems and in some instances reduced pellet quality (Han, 2004). Low-grade metamorphic mineral assemblages can negatively impact liberation and pellet quality. Low-grade iron formation may contain a suite of carbonate minerals including ankerite, dolomite, kutnohorite, siderite and magnesiosiderite. Variation in the distribution and composition of siderite and magnesiosiderite makes controlling the MgO content of pellets difficult. Carbonate minerals also require calcination in the pellet induration process, which requires additional heat to be added to the system, slowing down the induration process and reducing throughput. Prediction of carbonate mineralogy and carbonate mineral chemistry is an important goal of ore characterisation for pelletising properties. Contact metamorphism causes changes in mineralogy and grain size (Klein, 1973; Gunderson and Schwartz, 1962). Increasing the grain size of magnetite should improve its liberation characteristics. However, plant grinding targets may not allow the coarse-grained, more easily liberating magnetite ores to increase throughput and can actually result in decreased throughput due to recirculation. While magnetite and martite ores are well understood (Lukey, Johnson and Scott, 2007) late open-space filling microplaty haematite ores are not. These ores, while composed of similar minerals, have a unique genesis that results in fine grain size and complex textures that present liberation challenges and often make interpreting laboratory metallurgical test results more difficult.

Jan 1, 2007

By Wilson AC

Permian coal from Western Australia's only producing coalfield at Collie is the dominant fuel used in generating electricity for the State's interconnected grid. Collie coal is sub-bituminous, non-coking and has a low ash, medium volatiles and high moisture content. The seams were laid down in a fluvial basin which extended beyond the Collie Basin and included the Wilga and Boyup Brook Basins at least. Adjacent parts of the southwest Yilgarn Block are prospective for Collie-type basins. In the past few years significant deposits have been delineated within the Perth Basin, specifically on the Vasse Shelf and in the Hill River area. In the former area high quality steaming coals are correlated with the lowest coal bearing member at Collie. The seams are amenable to underground mining and because of their high quality, the coal may have export potential. Sub-bituminous coal deposits of Jurassic age are present in the Hill River area. Exploration has down-graded the prospectivity of the Carnarvon and Canning Basins for sub-bituminous near-surface coal deposits. Tertiary lignite deposits are present in palaeo-drainage systems in the southern part of the State and their potential for development is being evaluated.

Jan 1, 1986

By Romanovsky N. P

The Pacific Mobile Belt (PMB) is characterized by old origin and complex evolution both in time and space. As the global structure, the PMB is a narrow tectonic region dividing two plan-etary hemispheres, viz. the Pacific and IndoAfro-Atlantic ones, the relative shifting of which defines the character of many geodynamic processes in this belt. The PMB features inhomogeneity of structure, special matter composition characteristics, sharply broken-out topography, and intensive fields. Generalized anomalies of the gravitational field closely correspond to the PMB boundaries defined by the real features, i.e. the andesite line and distribution areals of Mesozoic-Cenosoic granitoids. The belt boundary position is controlled also by seismic velocity anomalies at a depth of down to 200 km. The modern PMB deformation is defined by the left-hand equatorial shift and rotation of the Pacific Ocean counterclockwise. This rotation is non-uniform in time and of an oscillating character. The motive forces of the phenomenon are considered.

Jan 1, 1990

By Heyer T, Wasmuth H-D

The concentrator plant of Fahrica Mine, that started production in 1977, was using nine Jones wet high intensity magnetic separators (WHIMS) of the standard type DP 317 with a 1.5 mm gap width for the production of pelletfeed concentrate. These WHIMS units were operating in parallel with a feed rate of 110 t per hour, with about 47 per cent Fe in the feed, and with a maximum of only 0.8 per cent magnetite. The field strength was about 1.2 Tesla. From 1986, the mine has adapted its production facilities to mine and concentrate larger amounts of lowgrade itabintes to maximise the use of the available iron ore reserves. An increase of up to three per cent magnetite in the magnetic separator feed, resulted in a reduction of capacity. This was due to partial clogging of the separation boxes at high field intensities, which were required for the recovery of the very fine hematite. Even by lowering the feed rate and the field intensity the problem could not be resolved. After extensive testwork in a pilot plant, with a Jones separator model DI' 90, the commercial WHIMS plant was modified into a two stage process using the existing nine Jones separators. The gap of the first stage with four machines was increased to a width of 3.5 mm, corresponding to a maximum field intensity of 0.7 Tesla. This first 'medium intensity scalping stage' is followed by a second 'real' high intensity WHIMS step with five machines operating at the original settings with 1.5 mm gap width and 1.0 Testa maximum field intensity. Feed rates of up to 320 tons per hour in the first and up to 240 tons per hour in the second stage could be achieved. The design concept of the concentrator at Fabrica mine is described using the old and new flowsheets. Details of the pilot plant testwork as well as actual performance data of the new plant section are presented.

Jan 1, 1993

By Ooms M, Scott OJ

This paper is concerned with the design and operation of storage and discharge facilit- ies for bulk solids handling. It presents an overview of the basic design philisophy emphas- ising the influence of bulk solid flow propert- ies and bin geometry on the flow patterns developed and how these, in turn, affect the reclaim efficiency and the bin structural in- tegrity and wear characteristics of both bins and chutes. The salient aspects of feeder design and operation will be discussed and the need to consider feeders as integral parts of the bin discharge system will be stressed.

Jan 1, 1978

By Hematian J

A high horizontal stress field has significant effect on the stability of underground roadways and influences the design of a support system in this environment. The high horizontal stresses at E1lalong Colliery, NSW, Australia provided the environment for this study. Samples of coal measures 'rock were collected and tested to determine their mechanical properties. The lithology, stress state, geometry and conditions prevailing in particular areas of the mine were obtained from geotechnical reports available at the mine and by field observation. The results of a series of finite element models constructed and tested under various conditions provided a basis for comparison with field observations. Analysis of the results indicated sufficient correspondence to provide a basis for the proposed design of an optimum support system. It is not suggested that finite analysis provides 'exact answers', but it does show the relative importance and interaction of various parameters.

Jan 1, 1995

The major coalfields of Australia are almost unique in the occurrence in some areas of CO partly or almost completely replacing CH4,t1e normal seam gas from metamorphism of coal due to time and depth of burial. This CO2 situation has some benefits but mostly it introduces particular safety problems result- ing from the high density of CO2 relative to air, magnifying problems of gas dilution in ventilation, and the greater affinity which coal has for CO2 than for CH4 increasing proneness to gas-dynamic phenomena. The occurrence of most CO2 seam gas can be directly related to igneous intrusion and to its associated pneumatolytic injections. Whilst intrusions locally increase the rank of coal by their contact metamorphic effect, normal coal metamorphism due to time and depth of burial continues after intrusion and injection together with the ongoing metamorph- ic production of CH . This new CH slowly displaces any CO to leave some present-day intruded coals with seam gas with reduced CO2 or even without any significant CO2 associat- ions. The seam gas maps of the Bowen and Sydney Basins and more detailed maps of specific areas exemplify these situations. Mining progress, plus more searching studies of igneous-coal relationships provide improved understanding of the factors involved.

Jan 1, 1986

One of the most difficult places to ventil ate in any mine is the working face area of an advancing mine heading. With an ever changing configuration, continual modification and extension to the ventilation system is necess- ary to maintain an adequate supply of fresh air and to control mixing and recirculation. Methane emissions and high dust levels as coal is broken and removed from the face area can produce unhealthy and dangerous conditions if ventilat- ion is not adequately monitored. An understanding of the air flow patterns which develop through use of different face ven- tilation systems can be reached by undertaking underground measurements or through observations using physical models. Tests undertaken by the author to determine the adequacy of different system-configurations are discussed together with approaches adopted by others working in the United States. Various new methods have been proposed for improving face ventilation beyond that sustained using conventional brattice curtain or tubing systems. The adequacy of some advances adopted by mining companies to improve ventilation while maintaining output efficiency is discussed.

Jan 1, 1983

By Morris B. J

Soil air samples taken from the top one metre of the soil profile, were measured for C02 and 02 using portable field analysers at a number of sites of known sulphide mineralisation in South Australia. Carbon dioxide anomalies were detected over actively oxidising sulphides during autumn and winter following recent rainfall. Anomalies were not detected where no oxidation was occurring, where seasonal conditions had been very dry, or where the sulphur content of the ore was low (

Jan 1, 1993

By Ward B

Central Colliery was developed to exploit large underground reserves in the German Creek lease. It was planned from the outset as a retreating longwall operation and is the first longwall mine in Queensland. Longwall mining is not new to Australia but all previous experience has been confined to the coalfields of New South Wales. There was no precedent for longwall extraction in the markedly different geological setting of the Bowen Basin in Central Queensland. Various investigations were thus carried out during the initial development of Central Colliery, prior to the installation of the longwall, to ascertain the geotechnical characteristics of the coal seam and the adjacent strata and to predict the performance of the heading and pillar design as mining proceeds to depth. Laboratory tests showed the coal to be weak with an unconfined compressive strength of 9.6 MN/m2. Site inspection and geophysical correlation revealed a shear zone and extensive intraformational shear planes in the seam. The latter were found to exert a controlling influence on rib reaction in the headings. This behaviour was predicted by finite element modelling of the development headings which indicated that mining induced stresses in the coal would be relieved by block movement of the ribs. A chain pillar width versus depth curve was established for yielding pillar design based on empirical and computational methods. This gave pillar widths from 25m to 48m over the proposed depth range of 150m to 300m. Finite element modelling of the 25m pillars chosen for the first gateroads confirmed the overall stability of the design but suggested that rib spall could be significant in the adjacent tailgate. (1) Chief Mining Engineer, Capricorn Coal Management Pty. Ltd., German Creek Mine, Queensland (2) Senior Engineering Geologist, Coal Division, The Shell Company of Australia Limited, Melbourne

Jan 1, 1986

Long-range side-scan sonar and conventional geophysical data for the Peru Trench region (8`S-15¦S latitude) have been analysed. The data show that the Peru Trench is a site of sediment subduction where bending-induced normal fault-ing of the Nazca plate plays a key role. The sediments are continually removed from the trench axis region by their inclusion in normal fault-defined void spaces, such as grabens. In the process of subduction, the sediments are often offscraped, folded arid kneaded temporarily at the base of the shoreward trench slope. The subduction complex comprising such sediments is narrower than 20 km and its volume remains more or less constant due to regular removal of its contents along with the down-going plate. Addi-tionally, morphology of the subducting Nazca plate is responsible for subduction erosion of the South American plate, where the horst blocks cause tectonic erosion by abrasion and the grabens provide a mechanism for removal of the eroded material.

Jan 1, 1990

By Hermulheim W

In the Federal Republic of Germany hard coal is mined underground only. The coal mines reach down to 1 500 m deep, recently having an average depth of 900 m. The commonly used winning system is long- wall mining with face lengths up to 250 in. The gate roads, which separate the seam into single panels, have an average length of one kilometre with a cross- section up to 20 m2. These single entries are usually supported by yielding steel arches. The installation of steel arches can hardly be mechanized. The choice of heavier support, caused by increasing depth and roadway cross-section, results in high cost for labour and material in gate roads. Furthermore, the heavy steel arch is acci- dent-prone, not only during installation but also during transportation and ship- ment. Rock bolts combined with a suitable lagging offer a way of mechanizing support work in headings. The aim is to decrease cost and to increase mine safety and pro- ductivity. Over the last ten years, 50 km of gate roads have been reinforced by a combination of rock bolts and weld mesh. Nevertheless, there are still differing opinions on the feasibility of rock bolting in gate roads. In Germany a long tradition and experience with steel arch support exists, whereas the function of an anchorage is a closed book to miners, preventing this new technique from spreading more quickly. Advantages and shortcomings of both steel arch support and rock bolting are compared. The experience with rock bolting up to now is reported. Possible improve- monts arm discussed.

Jan 1, 1986

The Escondida Porphyry Copper Deposit, located in Chile's II Region 160 Km to the southeast of the city of Antofagasta, is currently owned by Minera Escondida Limitada, a company comprising The Broken Hill Proprietary (57.5%), Rio Tinto Zinc (30%) a group of Japanese companies represented by Mitsubishi Corporation (10%), and the International Financing Corporation of the World Bank (2.5%) (Fig.l)By 1983, most of the reconnaissance drilling was completed and prefeasibility studies were regularly updated as new drilling results were reported and project concepts re-evaluated (Fig.2). In October 1982 the project was transferred from Exploration Management to Operations. By the end of 1984 project pre-development activities, including inpit development drilling, geological exploration, water resource definition, an underground bulk sampling program and the initial project feasibility report, were completed.

Jan 1, 1990

During induration of iron ore pellets produced from magnetite concentrates, there are many reactions occurring simultaneously. While the magnetite is being oxidised to hematite, carbonate fluxes are being calcined, leading to the formation of complex oxides. Calcination of fluxes and the formation of calcium and magnesium ferrites and silicates during the preheat stage can influence the magnetite oxidation process. As the calcination reaction proceeds quicker than oxidation at temperatures experienced during the preheat stage (700 - 1200¦C), the bulk flow of CO2 emanating from within the pellet should disrupt the diffusion of O2 to the magnetite reaction as the gas fluxes are similar in magnitude. This increases the time required for the oxidation of the pellet. Using an infrared rapid heating furnace, experiments were performed on heating individual magnetite green balls in an air atmosphere. These experiments showed that time played an important role in the extent of oxidation and calcination and temperature significantly influenced the initial evolution of high temperature phases such as magnesioferrite, calcium ferrites and calcium silicates. Understanding the kinetics of all these reactions for a particular pellet feed, and their interaction, is important for optimising the design of the induration furnace.

Jan 1, 2005

The author describes 1. The classification and characteristics of various thick seam mining techniques in various Japanese coal mines. 2. Practices of thick seam mining methods experienced in Taiheiyo Coal Mine. Currently, thick single lift, simultaneous multi lift and non simul- taneous multi lift mining methods are adopted as underground flat thick seam excavations in Japan. These are now reliable and effective in increasing the extraction ratio. At Kushiro Colliery of Taiheiyo Coal Mining Co., these three thick seam mining methods have been used. According to the results, if solidification of the top lift goaf is essential, the non simul- taneous multi lift mining method is the most effective in increasing the extraction ratio without minimising productivity of each lift and it points out that further development of this method is necessary.

Jan 1, 1976

By Barber S

The Golden Cross Mine is located within the Waitekauri Valley near the southern end of the Coromandel Ranges, eight kilometres north-west of Waihi, North Island, New Zealand. The mine is owned and operated in a joint venture by Coeur Gold NZ Ltd (80 per cent) and Viking Mining Ltd (20 per cent). The underground mine produces gold and silver from low sulphidation epithermal quartz veins which developed in the shallow parts of a meteoric water dominated system during the Upper Miocene (7.36 - 6.67 Ma). The Empire Vein System is hosted within a dilational structural environment which developed at the lithological contact between acid intrusives, rhyolitic-dacitic tuffs and reworked pyroclastics, and undifferentiated andesites. The formation of the Empire Vein System was controlled by the rheological properties of the host rocks and variable displacement along a series of normal, right lateral, easterly-dipping faults. These faults represent sub-parallel zones of master shearing within a Riedel shear model. Underground mining extracts ore from the steeply dipping hangingwall and the complex footwall veins of the Empire Vein System. Initially sills are driven along the hangingwall vein on ten to fifteen metre sublevel intervals. In the footwall zones where significant mineralisation adjacent to the hangingwall sill drives has been identified, a series of cross-cuts and footwall drives (sub-parallel to the hangingwall sill) are also developed. Where continuity of mineralisation and ground conditions permit a combination of post pillar flatbacking and AVOCA longhole benching methods are used. Detailed underground mapping of lithology, quartz veining and major structures provides the information for designing ground support and footwall pillars, planning mine development and ore extraction sequencing. Sectional interpretation displays the vertical extent of faults, fractures and the vein system. The mining methods used underground at the mine have evolved through a thorough understanding of the structural complexity and the systematic geological mapping of the Empire Vein System.

Jan 1, 1997

By Parker C. J, Mikula P. A

The excavation for the Sydney Opera House Parking Station comprises a large donut shaped underground cavern with a central sandstone pillar. The maximum effective roof span is about 19 m and the rock cover is between 7 m and 8 m. Permanent support for the roof and the various services tunnels consists of a combination of tensioned anchors, and untensioned dowels, and mesh with shortcrete and fibrecrete as the final lining. Steel sets were installed at main intersections.Fundamental to the design philosophy for excavation of these spans at such shallow rock cover was the use of monitoring to check on the adequacy of the installed support. Prior to excavation, extensometers, inclinometers, piezometers and surface settlement survey stations were installed. Underground survey stations, anchor load cells and shotcrete pressure cells were installed as excavation proceeded. Excavation commenced at the crown using an initial heading and three widening stages. Geological mapping during excavation confirmed borehole expectations, namely sandstone beds 1 to 4 m thick interbedded with thin shale units. Bedding plane contacts varied over short distances from tight partings to thick brecciated seams. Jointing was subvertical and joints tended to be bed-limited.

Jan 1, 1993

By Barnett DW

Financial risk analysis provides the tools to examine the uncertainty of capital decisions in new mining ventures. This paper explores the methodology by which financial risks can be studied and quantified. The most commonly used risk evaluation methods, such as sensitivity analysis and discount rate adjustment, are presented as an introduction to a more comprehensive discussion of stochastic methods of discounted cash flow analysis using Monte Carlo sampling. The discussion is illustrated with examples of a stochastic discounted cash flow. The advantages of Monte Carlo sampling in risk analysis are discussed together with its problems, particularly those originating from the correlation amongst the variables that determine the economic output of a mining venture, and the difficulties created by insufficient data, imperfect knowledge and complexity. The paper also surveys the most commonly used software used in risk analysis.

Jan 1, 1994