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By Johnson M, Wooltorton B

A programme of hydraulic fracture stress measurements conducted in surface drill holes along the alignment of the King River Power Tunnel has provided information of importance to the assessment of the extent of steel lining requirements for the tunnel. A significant horizontal stress field has been detected at a location remote from the power station site, with a corresponding absolute minimum stress magnitude approximating the overburden pressure based on depth of cover. Measurements made closer to the power station site (located toward the bottom of a valley) have revealed an apparently relatively destressed region with minimum stress magnitude less than overburden pressure. The implications of these results are discussed.

Jan 1, 1987

By M Dixon, T OÆShannessy

Melbourne Water (MW) is responsible for a section of existing gravity trunk sewer servicing the Melbourne central business district, Docklands, Port Melbourne and other adjacent areas, known as the Melbourne Main Sewer (MMS). MW has determined that the 2.2 km long 110 year old sewer will not adequately service these areas into the future or provide the level of reliability needed. The Melbourne Main Sewer Replacement project (MMSR) involves the replacement of the MMS with a new gravity sewer main and six key manhole shafts, known as the Melbourne Main Reliever (MMR).The majority of the MMR sewer tunnel is situated south of the Yarra River and will be constructed using an earth pressure balance (EPB) tunnel boring machine (TBM) and will be lined with precast concrete segments. The tunnel will be 2.4 m internal diameter and will have a 1.8 m diameter glass fibre reinforced plastic (GRP) sewer pipe positioned within it. This project represents the first large-scale, modern, mechanised tunnel project in MelbourneÆs Yarra Delta Quaternary sediments. There is little precedence known to the authors of similar scale tunnelling projects in these particular geological units. During the recent detailed investigation and design stages of the project, significant effort has been spent on characterising the geotechnical conditions along the alignment and predicting the effects of the new tunnel on the existing environment. Some of the key design issues that have been identified and managed through the design process include short-term surface settlement due to tunnel excavation and the predicted effects on surface infrastructure, potential spalling of the steel fibre reinforced concrete segments under full TBM ram loads and tunnel lining design in geological units with highly variable stiffness.Construction of the new MMR sewer tunnel is expected to commence in mid-2008 with a capital cost of approximately $160 million. Sewer system commissioning is scheduled for completion by early 2012.

Jan 1, 2008

By Warner RE

SINCE 1952, when Elliott et a/ first applied the Sherwood correlation for flooding in chemical absorption towers to blast furnaces numerous investigators throughout the world have followed their example and much research effort has been spent to tighten the correlation and recently to extend investigation of flooding to side gas entry conditions. The widespread use of the Sherwood concept of flooding has been such that even the word itself has become an integral part of blast furnace nomenclature. The evidence for the applicability of Sherwood's relationship has been that the flooding limits calculated from blast furnace parameters lie approximately on the Sherwood line. However, the values of many of the variables for the blast furnace calculation are only estimates and at first sight one may wonder at such 'close' coincidence when some of the estimated parameters entering the Sherwood correlation are raised to the power of three or more, as for the bed porosity and the liquid surface tension. It is felt that the explanation of this result lies in the logarithmic: nature of the plot and/or the fortuitous can- cellation of the errors of the estimates in the calculations coupled with the fact that blast furnace fluid ratios lie within a very narrow range of values. The foregoing considerations should in their own right place doubt on the correctness of the Sherwood type flooding correlation applied to the blast furnace. Additional doubt regarding the existence of the Sherwood type flooding in the furnace has been cast by the results obtained in the Tokyo University experimental blast furnace. From the reasoning of both Standish and Colquhoun (p. 20) and Warner (p. 23) it is deduced that flooding in the traditional sense will only normally occur in the upper bosh (somewhere near the mantle), following softening as discussed by Palella et a/ on p. 75, and flooding in that zone is likely to result in furnace irregularity. On the other hand, the concept developed by Warner of slag hold-up above the raceways as a stable phenomenon not affecting furnace regularity is a process unique to the blast furnace and is not described by the Sherwood flooding theory. Recognising the considerable practical implications of slag hold-up above the raceways, this note further explores the physical process of slag hold-up. We envisage that bed of coke above the raceways in almost all blast furnaces would contain some slag held up by the gas pressure gradient. In general the slag would be contained in a ring and gas would bubble through in its ascent through the furnace. The force supporting this slag is the pressure gradient and obviously -much of the blast pressure is dissipated in supporting this structure.

Jan 1, 1975

By J Zhang, O Ostrovski, C Zhang D Cai, Q Wang

The conventional CaO-SiO2-based mould fluxes are not suitable for high-Al steel casting because of the strong reaction between silica in the flux and aluminium in the steel strand. In the process of casting of high-Al steel, flux composition changes; with the decrease of the silica concentration and increase of alumina. Knowledge and understanding of the effect of the Al2O3/SiO2 ratio on flux structure and properties are useful for flux design for the high Al-steel continuous casting. This paper investigated the effect of the Al2O3/SiO2 ratio on structure, viscosity, phase composition of fluxes quenched at different temperatures and heat transfer of CaO-Al2O3-SiO2-B2O3-Na2O-Li2OMgO- F fluxes. It was found that flux melting temperature increased with the increase in Al2O3/SiO2 ratio. Viscosity of the flux melts increased significantly with the increase of the Al2O3/SiO2 ratio from 0.7 to 1.2, reaching the maximum value, and then decreased with further increase of the Al2O3/SiO2 ratio. Raman spectroscopy analysis revealed that the change of the Al2O3/SiO2 ratio led to the change of aluminate and silicate structural units. The turning point for viscosity was attributed to the change in the degree of flux polymerisation. X-ray diffraction (XRD) analysis showed that increasing Al2O3/SiO2 ratio increased crystallisation tendency of the fluxes. Heat transfer measurement by infrared emitter technique (IET) revealed that increasing Al2O3/SiO2 ratio led to the decrease in heat flux which is correlated well with the increased crystallinity of the flux. The results suggested that the flux with Al2O3/SiO2 ratio 4.3 is the best candidate among the studied CaO-Al2O3-based mould fluxes for casting of high-Al steel.

Aug 21, 2024

By O Tiili, A Dixon

Many minerals processing plants need to have greater efficiency in current times and optimise their process performance in order to maintain high profitability. This is even more so in the current economic climate. In the case of large flotation cells, such as TankCell«-300 with over 300 m3 active capacity, ensuring consistent operation and optimal flotation conditions is particularly critical, given the high impact on overall process and throughput of such cells. As there are fewer cells to control and monitor, there is also a lower initial capital cost for instrumentation - the requirements, however, are higher. Despite such compelling reasons, instrumentation and basic control in flotation cells has not changed much in recent years. The standard is still to use traditional feedback (PI algorithm) controls for slurry level and flotation air. A new advanced instrumentation and control package for large flotation cells has recently been developed by Outotec and has been installed at Macraes.In addition to the standard basic instrumentation and control, the new system at Macraes consists of a froth image analysis system, a froth velocity control, and a level control system which utilises adaptive feedforward compensation. There are three TankCell«-300 cells in operation at Macraes since November 2007 and the new control system was commissioned in December 2007.The paper will include comparative data from pre- and postsystem installation and discusses benefits including optimised recovery, improved performance, as well as ease of operation.

Jan 1, 2009

By B Andrew, L Krois

Ground control systems, including ground control management, play an integral role in the effective and efficient extraction of copper ore at the Xstrata Copper û Mount Isa Copper Operations (MICO). Rock mechanics engineers and support technicians at Xstrata Copper have undertaken a wide range of investigations and actions over the past few years. Outcomes from this work have resulted in the evolution of ground control management practices on the site. Specific areas of improvement include the installation of efficient one pass ground control systems, greater application of sprayed concrete for areas requiring rehabilitation and the addition of new improved products, the removal of obsolete and less efficient products used in standard ground control practice. In some areas underground, the most effective methods to manage ground control hazards continue to be a variation on proven methods that have been in use for many years in the MICO. Ground control systems for developing through the basement contact zone are very similar to that developed in the late 1980s. Similarly, ground control systems have gone through repetitive evolution, whereby some systems fall in and out of favour subject to perceived costs. For example the pouring of concrete shuttering around drawpoints in poor ground conditions has recently been re-accepted as an effective means to manage this poor environment û despite having been previously cast aside as too expensive. Ground control management systems continue to evolve towards the goal of creating a workplace that is free of rockfall-related injuries and provide for higher levels of efficient and effective techniques by which ore is extracted from the ground.

Jan 1, 2005

By T Sirinawin, R H. Murfitt, W Shywolup

The Bong Mieu Project lies within the Pre-Palaeozoic Kontum Craton near the southern margin of the regional Phuoc Son û Tam Ky Suture. The Suture and accompanying Truongson Fold Belt of Indosinian age host significant gold and base-metal bearing districts including OlympusÆ other project at Phuoc Son to the west of Bong Mieu and OxianaÆs Sepon project in Laos. The Bong Mieu Project is located some 90 km south of Da Nang and some 30 km south-west of Tam Ky, the provincial capital of Quang Nam province in central Vietnam. The project area is covered by an Investment Licence of some 30 km2 which was granted in 1991 and a mining permit of some 365 ha granted in 1992. Several mesothermal, gold-silver deposits with assigned resources are present on the property. Deposits with assigned resources contain some 615 000 ounces of gold in situ. These are at Ho Gan and Ho Ray which are potentially exploitable by open-pit mining and Nui Kem which is potentially exploitable by underground mining. Newly discovered extensions to the known deposits at Ho Gan, Ho Ray and Nui Kem, and several other new prospects, are currently being investigated by drilling. The Ho Gan mineralisation is of mesothermal, shear and shear breccia quartz vein, as well as intrusive breccia hosted style. Nui Kem mineralisation is of mesothermal, shear and shear breccia quartz vein style. The Ho Ray mineralisation is of skarn (gold-bismuth-tungsten) and lesser quartz vein style. The deposits straddle and flank the east-west trending Bong Mieu Anticline which trends through the central portion of the Investment Licence. In this paper the geology of the deposits, details of resources, results of recent exploration on the Investment Licence and recent engineering and mining studies at Ho Gan are briefly reviewed.

Jan 1, 2004

By R T. A MacGillivray, S B. Curtis

Bacteriophage (phage) are viruses that infect bacteria. Protein coatings on the surface of the phage particle can be genetically engineered so that they bind to inorganic molecules. The filamentous phage particle is about 930 nanometres in length and 6.5 nanometres in diameter and consists of a single-stranded molecule of DNA surrounded by five different coat protein molecules denoted P3, P6, P7, P8 and P9. Peptide sequences in the P3 coat protein that bind to sphalerite and chalcopyrite have been identified. The binding is selective; phage with specific P3 peptide sequences bind to minerals but do not bind to silica or to pyrite. Two peptide sequences in the P8 coat protein that bind selectively to chalcopyrite and pyrite have also been identified. The amino acids in the P8 binding sequences are hydrophilic and thus a coating of a mineral particle with phage having these peptide sequences may render the particle hydrophilic. Experiments are underway to confirm this. Phage are relatively easy to grow and are not living organisms requiring an energy source to maintain life. Phage can also tolerate a range of pH and temperatures. Given this, and the ability to indentify phage coat proteins that bind selectively to a variety of inorganic molecules, phage have the potential to be useful tools in mineral processing and waste treatment.

Jan 1, 2008

By B Dunstan, F Wirfiyata

PT Newmont Nusa Tenggara (PTNNT) operates the Batu Hijau copper and gold mine and process plant on the island of Sumbawa, Nusa Tenggara (Barat)  NTB, Indonesia. The plant consists of a nominal capacity 120 000 t/d conventional semi-autogenous ball milling crushing (SABC) circuit followed by sulfide flotation to produce a bulk copper concentrate for sale. Process control is effected by a plant wide distributed control system that overlays an extensive integrated programable logic controller (PLC) framework. The system is enhanced by a supervisory expert control system.Since plant commissioning in September 1999, over US$4 million has been expended as part of a systematic continuous improvement approach to optimise plant control performance. Works completed to date include: redesign and upgrade of architecture of the control system to ensure long-term system reliability, security and upgradeability and to provide a suitable platform for advanced control; integration of supervisory and advanced control tools, techniques and instrumentation; and implementation of sound network communication and plant data reporting tools. This paper outlines the evolution of process control and associated systems and tools that contribute to successful operation and ongoing performance optimisation at Batu Hijau.

Jan 1, 2009

By R Morrison, P Owen

Particle breakage is an essential part of mineral processing. The aim is to reduce run of mine mineral ore to an optimal size for liberating target minerals and for subsequent recovery by separation processes such as flotation. This size reduction is typically accomplished in a series of stages in a grinding circuit tailored to the properties of the particular mine ore. Commonly this involves two or more classes of equipment starting with crushers, followed by SAG mills and then sometimes ball mills. Occasionally, high pressure grinding rolls or other novel devices are substituted. Broadly, energy consumption increases and energy efficiency decreases with the fineness of the material produced by each piece of equipment. For many operations, up to 50 or 60 per cent of total greenhouse gas emissions from a plant arise from the operation of the comminution circuit with the majority produced by the finest grinding parts, such as the SAG and ball mills. Wear of mill liners and grinding media also add to greenhouse gas emissions generated by their manufacture. The need for continual cost reduction and increasing regulatory and social pressure relating to greenhouse emissions create a strong need for improvements in comminution energy efficiency. Traditional experimental and modelling approaches are not well placed to create the required insights into comminution fundamentals or facilitate radical step changes in performance. This paper discusses the role that advanced modelling (based on coupled DEM and CFD) can play in improving the energy efficiency and performance of existing mainstream grinding equipment and in the development of new ones with radically superior performance. Achieving this goal will also require an improved understanding of ore breakage and methods to include sufficiently realistic breakage models within the DEM models. Developmental issues for the modelling and the critical need for validation of the advanced model features are highlighted.

Jan 1, 2004

Results from current NERDDC funded research into the geotechnology of highwall trench mining methods have clear implications for mine planners in the areas of blast design, trench shape, location of the surcharge spoil and remnant coal pillar design.Adoption of successful smooth wall blasting techniques not only removes safety hazards from the trench face, but limits development of bedding partings at the seam contacts that interrupt the smooth transition of stress across the coal seam.

Jan 1, 1992

The City of KalgoorlieBoulder is situated approximately 600 kilometres to the east of Perth, and as the major regional centre of the Eastern Goldfields, supporting a population of approximately 25 000. The formation of Kalgoorlie Consolidated Gold Mines in 1989 brought the existing operating entities adjacent to the city under common ownership and management. The Joint Venturers forming the management company are Homestake Gold of Australia and Gold Mines of Kalgoorlie (a Normandy/Poseidon company).This traditional underground mining centre has been worked since 1893, yielding 40.5 million ounces of gold ore with an average head grade of TEN grams per tonne. Historically the heart of the operation has been the famous Golden We located on the Eastern perimeter of the city, in the area known as Fimiston. The other significant operations that form KCGM are the Mt Percy Open Pit and the Mt Charlotte Underground Operation.

Jan 1, 1992

By J Bartlett, P Quigley

Historical research has played a significant role in the rebirth of the Bendigo Goldfield. The historical research undertaken by the company has been directed to specific areas such as verifying the total gold production of the field, the gold production from defined blocks on each of the major anticlines, the extent of workings of each mine which exceeded 200 m depth, the size and style of reefs mined in each shaft and also within specific domains of the field. Application of this data has assisted in the determination of possible dimensions of different reef styles and the location of mineralisation within each reef system. Description of grade variation, percentage of quartz and the amount and species of accessory sulphide minerals, as well as early geotechnical observations accompanying stoping methodologies, provides valuable analogues for reef structure being defined in the current program. Historical information on shafts on the two anticlines the company is exploring has allowed the postulation and recognition of repetition of reef development within the same stratigraphy in the hinge zones of the adjacent folds. The similarities of mineralisation styles across the field within both specific lithological units and structural setting has had important implications in respect to exploration drill targeting and the estimation of grade and tonnes.

Jan 1, 2003

By V K. Singh, G Sural

The problem of spontaneous heating/fire is very common in coal mines all over the world. The coal industry faces many problems day by day due to the occurrence of spontaneous heating in the open pit coal mines. Presently, about 70 per cent of total coal production in Indian mines is being carried out by open pit mining. Fire in coal, particularly in open pit mines not only causes irreparable loss of natural wealth but also damages the surface structures and pollutes the environment. It is well known that 75 per cent of the fires occur due to the spontaneous combustion of coal. Spontaneous heating is a very common occurrence in coal mines and is a major factor contributing to mine fire. The liability of coal to spontaneous heating causes many serious problems before, during and after mining. In opencast mines, coal immediately oxidises and catches fire due to the intrinsic characteristics of coal, such as low rank, high moisture, high volatile matter, presence of sulfur in the form of pyrites, low crossing point temperature (CPT) and ignition point temperature (IPT) value and less incubation period. In opencast mines, when the coal benches are left idle for a longer time, heat accumulation takes place in favourable conditions and sometimes leads to fire. The purpose of this paper is to present the different successful case studies regarding the safety management of open pit coal mines from occurrences of spontaneous heating/fire.

Jan 1, 2007

By F R. M Pires, Y Hasui, A Schrank

The iron ores of Alegria mine are composed of itabirites enclosing minor bodies of high-grade ores. The itabirites are classified according to mineralogical composition in five types: martite-rich, goethite-rich, specularite-rich, magnetite-rich and anphibolite-rich ores. The hematites are martite-rich, magnetite-rich, specularite-rich and more rarely, amphibolite-rich. Other classification criteria of the ores are based on the physical properties and the degree of compaction. As such, the itabirites and hematites can be classified as hard, friable and soft types. The mineralogical/textural evolution of the ores is linked to the pressure and temperature conditions that accompanied the tectonic processes in anphibolite facies and the different degrees of subsequent surficial weathering processes. Petrographic and microstructural studies indicate that the magnetite and amphibole bearing itabirites represent the parent rocks that created the other itabirites and that the specularite itabirites and the hard martite types are related to silica dissolution and redeposition in zones of high and low strain. Most of itabirites ores correspond to chert oxide facies banded iron formation, except the goethite and amphibole bearing itabirite that resemble a silicate or oxide-silicate facies with minor carbonate impurities. The great mass and pods of soft martite itabirites are probably shaley oxide facies BIFs with little volcanic contribution. Trace element contents of the AlegriaÆs itabirites show strong dissimilarities with BIFs associated with volcanism (Algoma type), but closely ressemble to the Lake Superior type, with high content in Cr, Co and low V, Ni, Cu and Zn. Although the absolute contents of REE present in the AlegriaÆs itabirites are, in general very low, the pattern when normalised by NASC is similar to the great majority of the Archean and Paleoproterozoic BIFs elsewhere in the world, and characterised by positive Eu anomaly.

Jan 1, 2002

By D Wallace, H Guo, B Shen

Appropriate management of the ground subsidence induced by coal mining activities is essential. To assess the effectiveness of grout injection for mining subsidence control, time-lapse ground penetrating radar (GPR) imaging data were collected before and after grouting. The pregouting subsurface responses were interpreted to have changed after grout injection. The changes were caused by injecting the grout materials (flyash and water) into the delaminated strata and permeable fracture zones. The largest distance of the observed GPR event changes at the right end of the main profile is 132 m away from the injection borehole. Although the GPR images could not easily tell if the image changes were caused by the injected ashes or the water, it does suggest that the injection materials had been pushed at least 130 m away from the injection borehole. This is consistent with the borehole scan monitoring, which confirmed that the grout has travelled more than 90 m from the injection borehole.

Jan 1, 2006

By G Yeowart, P D. Munro

The Prominent Hill copper-gold concentrator of OZ Minerals Limited in South Australia was built in 2008 and commenced commercial production in early 2009. It has a design ore throughput of eight million tonnes per year (Mt/yr). While the flow sheet has many items in common with other plants treating ores from iron oxide-hosted copper-gold deposits, the Prominent Hill concentrator also has some unique features. Plant design has been based on a 'template' of the very successful Ernest Henry concentrator. Initial options considered for processing Prominent Hill copper-gold ore are briefly examined as well as potential complications arising from the presence of a considerable tonnage of 'gold-only' material present in the deposit. Metallurgical test work and the subsequent decisions leading to the selection of a conventional crushing, semi-autogenous grinding (SAG) and rougher flotation circuit is discussed. One particular difference with other plants treating this ore type is that metallurgical tests and mineralogical studies identified that rougher concentrate had to be reground to a P80 of 20 - 25 microns or finer for adequate liberation of fluorine-bearing minerals. Subsequent satisfactory separation of fluorine-rich gangue material from the valuable copper sulfides requires highly efficient cleaner flotation to make a commercial quality copper-gold concentrate. Xstrata Technology's IsaMillÖ and Jameson Cell technologies developed to meet similar taxing fine grinding and flotation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province were selected for regrinding and cleaner flotation. Plant design has features aiding ergonomics for ease of operation and maintenance not commonly seen in recent projects with large sulfide flotation concentrators.

Jan 1, 2009

By A Radici, M Attwill

The Dampier Port Upgrade Project (DPU) involves an upgrade to Hamersley IronÆs Parker Point iron ore port facility at Dampier, Western Australia. The $US700 million DPU Project will increase Hamersley IronÆs shipping capacity at Dampier from 72 million tonnes per annum (Mtpa) to 116 Mtpa. The DPU Project comprises a new car dumper facility and rail spur, an upgrade to the existing stockyard and conveying system, a new screen-house and a 450 m wharf extension with two new shipping berths and a new ship-loader. This paper discusses the innovative design and construction of the new car dumper facility, which is capable of automatically unloading 240 car iron ore trains at a rate of 10 000 t/h. The facility design is unique compared to more conventional designs currently in operation, and greatly improves operation and maintenance functions.

Jan 1, 2005

By R L. Brathwaite, R Carver

The REGCHEM (Regional Exploration Geochemistry) database of open file mining company data, managed by GNS Science, has recently been upgraded with the compilation of additional data, especially for the Otago region (see http://maps.gns.cri.nz/website/minmap). In June 2007, data compiled for the Otago region included more than 2000 stream sediment samples from 19 surveys, more than 800 BLEG (bulk leach extractible gold) samples from 12 surveys and a few pan concentrate samples. The stream sediment samples were typically analysed for Au and As, and in many cases for other elements including Cu, Pb, Zn, Sb, W and Mo. The BLEG samples were analysed for Au and in some cases also for As. The main exploration target was mesothermal gold deposits in the Otago Schist, although one survey of the Otago Peninsula targeted potential gold deposits associated with the Dunedin volcanic complex. Geochemically, the mesothermal gold deposits are characterised by anomalous As and Au, with some also characterised by anomalous W and Sb, and these four elements are the best pathfinders in stream sediment geochemical surveys. The introduction of lower detection limits in Au analyses in the more recent stream sediment surveys and in the BLEG surveys enables the use of this element as the primary pathfinder for mesothermal gold deposits.

Jan 1, 2007

By De Broglio R

The Mae Moh coal deposit was discovered some 60 years ago by villagers who noticed spontaneous combustion of coal outcrops. The first production began in the 1950's to fuel a fertilizer plant and a 12.5MW power station. During the period 1976 to 1979, three 75MW power station units were constructed on site. These have a total daily coal consumption of some 5000 tonnes and are served by a stockyard of approximately 60 000 tonnes total capacity. Stacked coal is reclaimed by means of a front end loader onto reclaim conveyors. During the years 1983 to 1986 four 150MW power station units were constructed east of the eastern seam subcrop, sons 2 km from the original power station complex. These have a daily coal consumption of nearly 12000 tonnes and are served by a stockyard of total capacity 270000 tonnes, equipped with two stackers and two bucket-wheel reclaimers for a totally mechanised system.

Jan 1, 1986