Search Documents

By Price B. D, Staunton W. P

The Mineral Science Laboratory of the Government Chemical Laboratories has recently investigated various procedures for the analysis of the platinum group metals (PGMs). This investigation covered a number of methods for the extraction and preconcentration'of the PGMs from a wide range of geological materials. The nickel sulphide extraction technique proved to be overall the most applicable procedure. Flame atomic absorption spectroscopy (FAAS), electrothermal atomisation atomic absorption spectroscopy (ETA-AAS), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) were examined for their suitability in analysing platinum group metals in solution. ETA-AAS and ICP-MS proved to be the instruments of choice due to their low detection limits.

Jan 1, 1987

By Rosentreter N

Difficulties with froth flotation recovery and vacuum de- watering equipment for the treatment of fine coal have been investigated. Mechanical alterations to cyclone desliming banks, and flotation cells are described. A large disc filter has been replaced by two drum filters for dewatering, and the improvement in plant. operation is discussed:

Jan 1, 1978

It is recognised by the current JORC (1999) code that resource classification involves the interaction of numerous qualitative and quantitative criteria such as data quality, geological continuity and grade continuity. No prescribed criteria and rules will work for all situations or even between different ore types within the same deposit. Also these criteria and rules are sometimes applied without a clear understanding of their appropriateness, accuracy or correct implementation. For these reasons case studies are useful to evaluate and compare criteria commonly used to assist in resource classification. In this paper blasthole data from a selected area of Joffre Member hosted ore of the Brockman Iron Formation at the Mt Whaleback orebody are used as the basis of a case study for the above-mentioned purposes. Iron grade, in per cent, is interpolated from a blasthole dataset into a block model using ordinary kriging. Samples are then removed from this blasthole dataset to produce a random sample grid, a semi-random sample grid and a regular sample grid. Using nearest neighbour, inverse distance squared, ordinary kriging and sequential gaussian simulation, block iron grades are estimated using these three blasthole data subsets as inputs. This provides four groups of estimates with the ordinary kriging estimate based on the complete blasthole dataset being considered to represent the true estimate of iron grades. Also generated during this process are estimates of the error for each block. These error estimates range from the simple, such as drill spacing, through to more advanced methodologies such as kriging efficiency and simulation. These estimates of grade and grade estimation error are then compared to the true estimate using graphs and statistics. In order of increasing accuracy the block grade estimation and simulation methods were nearest neighbour, inverse distance weighting, ordinary kriging and finally conditional simulation. The simulation in some instances doubled the accuracy of individual block grade estimates when compared to nearest neighbour and inverse distance weighting estimates. It was found that many methodologies for estimating the error of individual blocks performed equally well with only methods such as average drill hole spacing and classification by search ellipse pass number performing poorly. An approach on how to convert the abovementioned error estimates of individual blocks into a meaningful JORC classification is also discussed. Although advanced non-linear resource estimates are applicable, most iron ore mines are still using relatively straightforward methods. The use of blasthole data and some simple linear interpolation methods and simple linear based error estimates makes this study repeatable for most iron ore sites and their resource geologists. This style of investigation is recommended as a useful approach for the Competent Person to apply to their deposit and thus better select, implement and understand the criteria used for resource classification and provide more consistency and confidence in the resource classification process.

Jan 1, 2002

By P J. Colbert, P D. Munro

OZ Minerals' Prominent Hill copper-gold concentrator in South Australia was built in 2008 with commercial production commencing in early 2009. In addition to recovery of valuable minerals, the flow sheet for this iron oxide-hosted copper-gold deposit has to address the issue of producing a good quality saleable copper concentrate by high selectivity against non-sulfide gangue. Detailed mineralogical studies integrated with the metallurgical test work highlighted that liberation of fluorine-bearing minerals and subsequent very efficient rejection in cleaner flotation was necessary to produce a commercial quality copper-gold concentrate. Bench scale laboratory metallurgical tests and mineralogical studies identified the need to regrind rougher concentrate to a P80 of 20 -25 microns or finer for adequate liberation of the fluorine-bearing minerals. Satisfactory separation of the fluorine-rich gangue material from the valuable copper sulfides requires highly efficient cleaner flotation. This is done by a combination of washed froth cleaning and conventional dilution cleaning. Proven equipment developed to meet similar taxing liberation and separation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province have been selected. The combination of Xstrata Technology's IsaMillÖ and Jameson Cell technologies addressed both the liberation and separation issues in the Prominent Hill concentrator. The energy efficient IsaMillÖ technology both regrinds the rougher concentrate while its inert grinding environment prevents contamination of mineral surfaces with 'debris' ensuring subsequent optimum flotation performance. Heading up the cleaner circuit with a 'scalping' Jameson Cell followed by conventional flotation equipment allows this section to take advantage of the Jameson Cell's high intensity flotation environment and froth washing capability to achieve maximum concentrate grade (at minimum fluorine levels) while maximising recovery through the use of conventional flotation machines. This paper looks at the development of the Prominent Hill flow sheet from the initial mineralogical and laboratory test work to the design, scale-up and early operation of the Prominent Hill regrind and cleaner flotation circuits. The mineralogically-based approach of domaining metallurgical ore types combined with the axiom of size-by-size mineral particle behaviour by liberation class gave a clear understanding of the liberation and separation issues involved in the processing of Prominent Hill ore. Technologies developed to meet much more onerous liberation and separation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province were successfully used to improve concentrate quality by rejecting non-sulfide gangue containing impurities. An IsaMillÖ and a Jameson Cell are included in the circuit for fine grinding and for additional concentrate cleaning. Plant performance since commissioning has justified the approach for metallurgical test work and equipment choices for the flotation circuit.

Jan 1, 2009

By J Vann

The key functions of project evaluation are to assess potential profitability and to develop an effective operational design. For mining projects, design aspects include mining methodology, ore treatment methodology and production rates. All of these characteristics impact on project economics and overall value. Resource models, which form the ultimate basis of project evaluation, typically consist of tonnes above cut-off, grade above cut-off and the spatial distribution (connectivity) of tonnes/grade above cut-off, for one or more variables. Dilution, ore loss and metallurgical recovery are all modifying factors applied to the resource model during evaluation and determination of profitability. A key issue is: how is the value determined? In addition to traditional combination of in situ tonnes/grade, the following merit serious consideration: the concentration of deleterious elements, throughput rates, mining/processing costs and û importantly û metallurgical recovery. Geometallurgy is an emerging field targeted at integrating these issues by identifying either direct measures or proxies for throughput (hardness, grindability), recovery (liberation, mineral shape/texture, etc) and concentrate quality from easily collected macro-, meso- and microscopic data. These ægeometallurgical variablesÆ drive project costs and revenues in a fundamental way. For geometallurgical characterisation to have a real impact on business design, it must enable improved mine planning. When creating spatial estimates for such variables, it is preferable to find proxies that can be measured as close to the intact rock mass as possible. However, spatial estimation of proxies for geometallurgical properties and responses is complex and requires special consideration. Unlike grades, both proxies and absolute measures of geometallurgical variables are not necessarily linear or additive and therefore require very careful geostatistical consideration. In some cases, models must predict extreme values of geometallurgical attributes rather than averages. Incorrect characterisation of metallurgical recovery/throughput can (and has) led to misspecification of the scale of projects, and thus can be seriously value destructive. Aspects of geometallurgy have long been important in iron, bauxite, manganese and coal deposits and are increasingly on the radar for base and precious metal miners. However, as more metallurgically complex deposits are developed and mining of large-scale, low-grade deposits becomes more commonplace, the importance of characterising the metallurgical response in order to generate properly optimised projects will rapidly increase. It is possible that in many ætraditionalÆ (ie grades and tonnes) reserve models, the variables that drive the project are missing!

Jan 1, 2007

The quality of the external water source for a mineral processing plant may influence the extent to which the environmentally desirable practice of recycling of water from plant products is possible. This is particularly likely for froth flotation plants where the chemical quality of the water may affect the plantÆs performance. The quality of the external water source or the recycled water can be improved by a water treatment step, and in turn the extent of recycling which can be tolerated is able to be influenced. The quality of the external water can range from very high quality, soft water derived from melting snow, to poor quality, hard water (high levels of dissolved calcium and magnesium) from underground aquifers, and to even lower quality sea water (very high levels of dissolved species including sodium chloride). It can be noted that some underground water is more saline than ocean water as well as containing high levels of dissolved calcium and magnesium. Occasionally, a different source of water is utilised in the wet and the dry seasons. Increasingly, sewage water from cities is becoming a potential external water source with sustainability implications. If the initial quality of the external water is high, the scope for recycling of water from all the products is maximised. Such reuse or recycling of water from the products allows chemical species from oxidation of the ore and from other inputs to the process such as reagents to increase in concentration in the water returned to the plant. Such accumulation of species can have negative effects on the performance of a process such as froth flotation but instances of positive effects exist. Some reagents which are used in flotation plants such as lime or sodium carbonate also happen to be commonly used for independent water treatment plants. Hence, the flotation process may inadvertently provide some aspects of water processing. Where the quality of the water in the feed to a mineral processing plant (external water plus recycled water) is not an issue, more powerful solid-liquid separation processes can be considered to maximise the removal of water from the products and its reuse. Such processes may also have complementary benefits in a sustainable mineral industry by, for example, producing a tailing stream with a higher per cent solid value which is more suitable for safe storage on the surface or underground. This paper documents findings on the effect of water quality on the flotation process. It also considers current directions of change in the need for increased removal of water from plant products. It then considers the implications of these trends for maximisation of water recycling by such operations.

Jan 1, 2003

By R L. Verburg, R Johnstone

DeBeers Canada Mining Inc (DeBeers) recently submitted an Environmental Assessment (EA) for its proposed Snap Lake Diamond Mine located in Northwest Territories, Canada. As part of the EA process, a site water quality management plan must be developed. Plan development requires an integrated approach such that the key factors influencing water quality can be identified and managed to minimise potential impact. A system model was therefore developed to simulate the site-wide water quality conditions and mass loadings to the principal environmental receptor of concern, Snap Lake, during operations and post-closure. Requirements of the simulation included integrating hydrology, geochemistry, hydrogeology and site management practices in a dynamic way. A unique feature of the site was the need to accommodate a complex flow system that included a feedback loop between lake water and mine water. A system model was constructed using the GoldSim software package that integrated on-site water quality and flow measurements, as well as results from independent groundwater flow and geochemical modelling efforts. The GoldSim model simulated concurrently the movement of 39 solutes through the subsurface mine and surface facilities. Solute sources considered included four different waste rock and tailings types, explosives use in the mine, treatment plant discharge, and recycled process water for dust suppression. Separate solubility constraints were identified for different regions of the flow system (eg underground mine; treatment facility; surface water bodies). Kinetic test data were used to derive temperature-dependent rate constants for use in calculating mass inputs from surface sources such as waste rock piles. The model generated water quality estimates over time for a variety of management scenarios at several potential discharge locations. The integrated approach used by the model was effective in identifying the significance of key factors influencing overall water quality such as explosives use, mine water inflow rates, waste rock reaction rates, site/mine management options, and effectiveness of treatment. The model provides an example of an effective tool for comprehensive, integrated system evaluation and management.

Jan 1, 2003

By D Thomas, B Gallagher

Valuable data for geotechnical interpretation and integration into effective Australian underground mine planning may often be available, yet is not always fully appreciated or utilised, particularly in the early stages of mine planning or in due diligence studies. There may be considerable benefits associated with early prioritisation of geotechnical evaluation and impact on mine planning. Unidentified, misinterpreted, or ill-defined adverse geological and related geotechnical resource characteristics can pose significant business risk to underground coal projects and operations. Preliminary resource definition in the early conceptual mine planning stages attributes significant focus (entirely warranted) on resource quality and structural geology constraints. Yet detailed geotechnical data analysis and interpretation, which may have a substantial down stream impact and sensitivity with respect to future mine planning strategies, at times is given lower priority, or scoped and resourced in the later stages of a bankable feasibility study. Through extensive mine planning experience and observation of downstream process impacts, it has been found there is often data available for geotechnical analysis that does not readily stand out or is not adequately understood or utilised, available at the early (conceptual) stages of mine planning. Part of the issue may be that exploration geologists are not necessarily experienced geotechnical engineers and do not necessarily recognise or understand all important parameters. Subject to appropriate application of experienced professionals data can be manipulated to provide key geotechnical hazard assessment at minimal cost, and provide a framework for understanding and optimising the mine planning process. Although there is no single prescribed strategy for resource evaluation from a geotechnical perspective, potential business risks and mitigation approaches can and should be adopted at the conceptual mine planning stage. There has been a recent focus in the metals industry to provide a reporting framework for geotechnical classification of mining projects. This paper outlines the strategies and gives examples of key analyses adopted in mine planning and discusses the relative merits of adopting a reporting framework as a tool for geotechnical classification in mine planning.

Jan 1, 2005

By T Hausler

The pitfalls, pleasures and management issues associated with international and remote projects are diverse.However, no problem is insurmountable and if an engineering team chooses (by luck or good planning) to push through the difficulties, success can mean an extremely satisfying experience for individuals and a significant, positive result for an organisation.International projects are not for the faint hearted or inflexible. Working in foreign lands with people who may or may not speak English and who may not initially respect you can become mentally and physically tiring.Sometimes the challenges are not fully explained to individuals in advance. Individuals then often learn about the challenges ù and discover solutions ù on the job. While this initially puts great pressure on individuals, matters improve eventually, especially when the locals come to understand that you are on site to make a positive difference.This paper will discuss aspects of a recent international project including meeting international clientsÆ expectations, dealing with cultural differences, social reckoning, environmental issues, and personal challenges. Specifically, it will cover aspects of working within a Russian cultural setting and overcoming social barriers.The paper also presents coping strategies for long periods of time spent away from home in remote places with extremes in weather beyond the normal experience of most Australians. For example, dealing with the effects of the spring thaw and coping with temperature ranges of -45 to +45¦C.Lastly, and possibly most importantly, there will be a focus on the role of translators. They have the power to make an engineer everyoneÆs best friend or, on your behalf, to order cold chicken liver and heart salad for lunch. If an engineering team can establish a working relationship with translators, they can become an invaluable asset and both on and off site.CITATION:Hausler, T, 2013. Achieving success in large-scale, remote area metallurgical plant projects, in Proceedings MetPlant 2013 , pp 539-552 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By D C. Franklin, C T. Farrelly

The future of human exploration in space is intimately bound to the future of mining and energy production on Earth. By 2025, one or more manned bases will probably exist on the Moon, exploring the lunar landscape and geology, and acting as a learning platform, and possibly a resource platform, for expeditions to Mars and beyond. Unless the mining and space industries take an active and cooperative interest in the technologies required to exploit minerals and fuels in and from hostile environments, the necessary advances to support permanent extraterrestrial exploration will not be ready in time. With the notable exception of using lunar Helium-3 as a fusion power fuel, no other reason has been identified for the mining industry to take any direct interest in the exploitation of extraterrestrial resources for the benefit of its customers on Earth. Ample reasons exist, however, for the industry to take a direct interest in supporting technological development of the extraterrestrial resources necessary to support the economical exploration of space. The mining industry has critical experience in the development and application of technologies for the discovery, extraction and processing of natural resources; experience that the space industry will need to create a viable permanent presence in space. The industry also understands the end to end process of resource development and utilisation. On the other hand, the space industry can directly benefit the mining sector by helping mature and advance the extractive and processing technologies needed to economically and sustainably develop resources in hostile terrestrial environments, such as those available in low concentrations, at extreme depth and/or inconvenient geographic locations. We propose that strategic partnerships be created between the mining, space and allied industries and research organisations. Such partnerships would develop a joint capability for mutual benefit, targeting the most significant advances in the least time. The space industry will learn how to exploit essential resources off-planet, and the mining industry will gain access to technologies to help extend their activities on earth.

Jan 1, 2008

By S K. Michelic, M Schickbichler, A Kharicha, E Karimi-Sibaki

The requirements for the controllability of metallurgical processes are increasingly becoming the focus of both industry and research. Advances in this field of research not only impact the stability of processes but often also influence the quality of the final product. One important way to examine processes in-depth, and thus show potential for improvement, is to describe them using physicsdriven models. In metallurgy, thermodynamic and kinetic descriptions of interactions between individual components of a system are often used to describe and analyse important metallurgical phenomena across the entire process. However, for the creation of physics-based models, boundary conditions and process variables must be implemented to enable a description that is as realistic as possible. The collection and generalisation of boundary conditions and process variables is, therefore, an important step towards functional models. The focus of this study is the determination of mass transfer coefficients between all components in a steel/slag/refractory system. For this purpose, experimental and theoretical methods are applied. Laboratory scale experiments are carried out in an induction furnace, and the mass transfer coefficients of the defined steel/slag/refractory system are calculated from changes in the chemical composition of the various components. Additionally, a calculation of the mass transfer coefficients based on dimensionless quantities is carried out. By comparing the values of the mass transfer coefficients determined theoretically and those determined experimentally in the trials, the suitability of the calculation is examined. The collection of mass transfer coefficients provides essential findings for future kinetic descriptions of inclusion modification based on the effective equilibrium reaction zone (EERZ) approach.

Aug 21, 2024

By D H. Bell

The potential for extracting gravel materials from active floodplain and channel areas has been investigated for three West Coast rivers û the Grey, Inangahua and Whataroa. Studies have focused primarily on resource availability and replenishment, but there are clearly also environmental management issues associated with such a proposal. The potential uses for of extracted materials include roading and concrete aggregates, as well as railway ballast, whilst a major benefit would be in assisting with flood control and channel maintenance in a naturally aggrading system. Sediment movement in the rivers has been examined at three scales; long-term (>100 years), medium-term (10 - 100 years) and short-term (<10 years). Long-term sediment movement is based on geological and geomorphological information, such as cyclic fan development and down-cutting in the Whataroa River where sediment input appears to be largely controlled by Alpine Fault rupture events. Medium-term assessment relied on air-photo interpretations over a period of about 50 years, with the mapping of channel changes and bank migration. Short term changes were evaluated from gauging records and other hydrological data, and took account of the development of an armour layer in these gravel-bed river systems. It was concluded that sediment in the lower reaches of each river was suitable for most aggregate uses, although input of more weathered Greenland Group materials in the upper reaches (eg of the Mawhera-iti or Little Grey) resulted in product that was not satisfactory for sealing chip or railway ballast. Of greater importance was the fact that short-term studies showed that a minimum threshold of flow was required for gravel entrainment, and that significant sediment movement only occurred above the one-year return period flood. Ongoing monitoring of river profiles, with accompanying flow gauging, would clearly be necessary were a substantial increase in river bed extraction to be permitted by The West Coast Regional Council.

Jan 1, 2003

By M J M Cunningham, M Greentree, J H Liu

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Palaeozoic rocks of north-eastern Laos are an attractive target for gold explorers due to the complex tectonic history and lack of past exploration in the region. Alluvial workings along the Nam Xiang River and its tributaries have highlighted the potential for gold mineralisation in the Vieng Kham region. The Nam Xiang River follows a regionally-extensive NNE-striking thrust fault. Adjacent to the Nam Xiang fault, the dip of the main foliation steepens, and in many places the stratigraphy is overturned as a result of this faulting.United Minerals and Mining Company conducted a regional exploration program to explore for gold. This included stream sediment and rock-chip sampling, and airborne geophysics. Geochemical anomalies were followed up with more detailed exploration, including geological mapping and soil sampling. Despite the relatively deep weathering profile, gold mineralisation is associated with a low-level but well-defined gold-in-soil anomaly. Drilling has shown that gold mineralisation occurs on structures and fabrics parallel to the main Nam Xiang fault. The highest gold grades are associated with brecciated sandstones that have experienced strong carbonate alteration. This suggests that late-stage structures such as the Nam Xiang fault are the major control on gold mineralisation in the region.CITATION:Greentree, M, Cunningham, M J M and Liu, J H, 2015. Gold mineralisation along the Nam Xiang fault, Vieng Kham Project, North-east Laos, in Proceedings PACRIM 2015 Congress, pp 177–182 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By R Vleggaar

In addressing a short-term operational need for the relocation of a tailings storage facility reclaim pond, a mine has achieved a host of water management objectives. Through effective planning and adoption of a strategic æwhole of mine lifeÆ approach, the mine has achieved significant environmental, social and economic benefits. A review of all water management aspects across the site identified a host of other interrelated water issues and concerns which, if dealt with individually, would prove too costly for individual operational departments. When considered as a whole, however, the issues became opportunities and provided the stimulus for integration of the site water management system. The development of site water and solute balance models provided the tool by which a number of water management options/strategies could be evaluated. The conceptual design and costing of the proposed water infrastructure further facilitated the evaluation of the multiple benefits to be gained from each option. A business case could then be made to mine management for the preferred option. The recommended water management strategy finally recommended to the mine not only provided a tailings storage facility (TSF) reclaim pond, but also provided for:increased wastewater recovery from the TSF, the capture of all waste rock dump run-off, additional water harvesting from local creeks, increased wastewater reuse, improved environmental water management, infrastructure that could be used by the local community after mine closure, and overall cost savings. This paper illustrates how effective water management planning can provide both short-term economic and environmental benefits, as well as long-term social benefits.

Jan 1, 2006

Until 1937, the mining of ore was carried out by conventional methods, using pneumatic drills and standard drill steel. The adoption of the diamond drill, formerly used for exploration work, for blast hole drilling in stopes, was first developed by Noranda Mines Limited, Noranda, Quebec, although it had been used previously in Northern Ontario and Western United States, to remove weak pillars and ore remnants left by conventional methods. Previous to the adoption of the diamond drill method at Noranda, a sub-level benching system of stoping was used. Sub-levels were driven at 35 ft. intervals and the benches drilled off by pneumatic drills using sectional steel. Results were very satisfactory, in sulphide ore, where the drilling was comparatively easy, but in the harder rhyolitestopes the footage drilled per machine-shift was only half of that obtained in the sulphide stopes, and owing to the high gauge loss, there was often difficulty in drilling holes to the required depth. This led to trials with the diamond drill for this type of work. While the cost per foot was more than with sectional steel, an appreciable saving in development work could be made by increasing the sublevel interval from 35 ft. to 60 ft., and stope widths from 60 to 100 ft. This saving, together with the increase in blasting efficiency, resulted in a substantial reduction in overall costs.CONDITIONS FOR SUCCESSFUL APPLICATIONWhile long diamond drill blast-hole mining has widespread application, there are certain conditions which appear to be desirable, if not absolutely necessary, for its successful use.

Jan 1, 1946

During the course of an investigation into the fundamental chemistry of the cyanide process, it became evident that the usual method of determining protective alkalinity was not completely satisfactory. T.he routine method for the determination of protective alkali by first removing free cyanide by the addition of silver nitrate, followed by titration of alkali with dilute acid using. phenolphthalein as indicator, can be shown to give correct results only when the alkali is a strong base. For other sUbstances, the alkali so determined is not the protective alkali. In view of the complications associated with the presence of zinc in cyanide solutions the discussion will be restricted in the first place to solutions free from zinc. Until the chemistry of simple cyanide solutions is placed on a quantitative basis it will be difficult to elucidate the behaviour of complex mill solutions.By the use of physico-chemical theory, it is possible to treat certain aspects of 'the chemistry of cyanide solutions in a manner which not only illustrates the important variables involved, but which also shows the need for care in interpretIng results obtained by conventional methods.In the following, comparatively simple systems are discussed; the principles established should be of use in interpreting the behaviour of more complex solutions. The methods described are not intended for routine work, but may be regarded as supplementary to the usual analysis carried out for the control of plant solutions, or as alternatives to be used when the latter do not appear to be satisfactory.

Jan 1, 1948

Aspects and anomalies in the present Standard Specifications for Blended Cements which may have operated in Australia against the development of the greater use of Slag Blended Cements are noted. Estimates of slag and ash usage in Australia are given and the need for further research with local materials stressed.

Jan 1, 1979

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 Savidis G

The characteristics of 'Z' (Back-over run) and 'R' (Reverse) ventilation systems are dis- cussed in relation to their suitability for longwall mining. Experience in European mines has been described as a basis for comparison with Australian conditions. In assessing the merits of each ventilat- ion system, such factors as longwall layout (pillar design, number of headings and gateroad stability), the need for gas drainage and bleed- er systems, as well as the influence of seam dip have been considered relevant. The R system is generally applicable for single and two heading development in seams where gas emission is a less serious problem. In contrast, the lower extraction to development ratio of the Z system (which arises from using three or more heading layouts) is considered more favourable where high gas emission occurs. The Z system provides greater flexibility with respect to the provision of refreshing air at the tailgate end, access of men and materials, installation and retrieval of gas drainage systems and the ability to interchange main- gate and tailgate roadways in cases where roof strata loads are difficult to control, or where cpam in hac an influrnra

Jan 1, 1983

The far reaching consequences of designing pillars for coal mines, while retaining concern for safety and economics, are cause for the search for refinement of the existing engineering methods to continue. Coal pillars, while having various functions within the overall mine plan, are the basic structural elements that assure the stability of a mine. Reliable coal pillar design methods take into account criteria which the pillars should meet in specific applications. These applications include typical mining situations such as the partial extraction room and pillar method with and without subsidence considerations, high extraction rate room and pillar, longwall mining chain pillars, and barrier pillars. However coal pillars are onlyu one element of a three element roof-pillar-floor system, weakest element of which system usually determines the stability of the excavations; however, the mining engineer can ony change dimensions of a pillar, properties of the surrounding strata remain beyond his control. The state of the art approach in pillar design places emphasis on recent developments in research. A widely encountered problem in certain coal fields is where pillars are underlain by weak floor strata. The resultant pillar design constantly maintains the perspective of the reliability of the design.

Jan 1, 1991