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By Jackson S

An investigation into different aspects of importance in the understanding of explosibility of hybrid mixtures of coal dust, air and gases potentially found within mine workings through a comprehensive laboratory program of explosibility tests was conducted. Plotting of test results revealed that conditions of potential explosibility could be described using two dimensional flammability limit surfaces- for coal dust/oxygen; methane/oxygen; and coal dust/methane mixtures. From these plots, the three dimensional flammability envelopes defining the explosibility of the coal dust/methane/oxygen mixtures can be defined and illustrated for a coal sample. The surfaces of the three dimensional envelope describe limits which separate inert mixtures of coal dust and methane at varying oxygen levels from those concentrations which are ignitable under defined conditions. It is considered appropriate to generalise that the geometric shapes of these limit regions are applicable to all type classifications of coal dust. There are practical applications of these results to the underground environment.The action of free radical initiators in the propagation of a methane gas explosion was examined for its applicability to the flammability of coal dust/gas/air mixtures. The oxides of nitrogen or NO x radicals have influence upon the lean limits of flammability of hybrid mixtures and this is illustrated by use of three dimensional coordinate geometry. Gases can be introduced to the underground environment through the exhaust gases of diesel equipment. It is concluded that radical species can substantially increase the flammability of gas and dust flames and as a consequence raise risk of mine atmosphere explosibility.

Jan 1, 1998

By Raczej I, Defant M

Pre-Miocene igneous rocks from the Phili pine island arc are characterised by 87Sr/86Sr and 143Nd/144Nd ratios typical for intra-oceanic island arcs where sediment involvement in the magma genesis was minor. Lead isotopic ratios are similar to Indian Ocean MORB (Mukasa et al., 1986a,b). Pliocene to recent volcanics, however, have more radiogenic Sr and Pb and less radiogenic Nd, except for the volcanics of the Bicol Arc, which have similar isotopic signatures as the Pre-Miocene rocks. We suggest that Pre-Miocene magmas and Bicol-Arc magmas have been generated in response to the subduction of the Philippine Sea Plate, their isotopic characteristics reflecting the composition of Philippine Sea crust. The Bataan arc magmas may reflect the larger amounts of sediments available for subduction in the South China Sea, while magmas of the Mindoro Arc, which are characterised by the most radiogenic Sr and least radiogenic Nd, may have been contaminated by slivers of the Mindoro-North Palawan terrane, which have been carried down to mantle depths after the collision of this terrane and the Philippine arc in Miocene (McCabe et al., 1982). This interpretation implies that Nd (and by inference other REE) can migrate from the subducted slab to the mantle wedge. Thus, variable Nd-isotopic ratios in island arc magmas (e.g. Sunda, Lesser Antillas) may not he a primary feature of the mantle wedge but a consequence of the release of Nd from the subducted slab.

Jan 1, 1987

The south-east Missouri cobalt-copper-lead-zinc district is the worldÆs largest lead producer and a significant producer of by-product zinc, copper, cobalt, silver and cadmium. Current production in the district comes from six or seven mines in the Viburnum Trend. Most ores in the Viburnum Trend are characterised by a small number of minerals with simple compositions. Portions of some orebodies contain ores that exhibit greater variations in mineralogy, and these include shale-hosted lead- copper ores, bornite ores and nickel-arsenic sulfide ores. Ore textures include both replacement and open space filling textures, and the paragenetic sequence for the ores is characterised by repetitive periods of deposition of all of the ore and gangue minerals. Ore microscopy is an effective tool for not only the identification of the minerals and textures shown by the ores, but also to determine the mineralogy and textures responsible for beneficiation problems. An interesting variety of sedimentary and structural ore controls have determined the locations of individual orebodies in the district. Based upon the positions of orebodies with respect to Precambrian ridges and knobs, together with areal patterns of mineral/metal zoning, it is interpreted that the ore fluids came from diverse directions to form the deposits in the district. It is concluded that the Old Lead Belt subdistrict was mineralised by fluids that flowed from the north-east and north-west, the Fredericktown area by fluids from the north-east, the Indian Creek subdistrict by fluids from the north-west and the Viburnum Trend by fluids from the north-west and west.

Jan 1, 2008

By K Biegaj

The paper describes challenges the author has encountered on Australian underground gold and nickel mines over the last eight years, when recovering high-grade gold/nickel bearing mine floor material with a mobile supersucker/giant vacuum cleaner and other equipment. Whilst for a number of years the mine floor vacuuming and other mine floor clean-down technologies have been accepted/adopted and are working well in other parts of the world and on the South Australian opal mines, regrettably, they have not yet gained acceptance of mining executives and mine managers of gold and metal mines in Australia, who still elect to leave the never to be recovered gold/metal behind or to put it plainly - waste it.For reporting purposes during the mining process, the portion of gold/metal included in calculation of ore reserves prior to obtaining capital funds for their development, continues to be camouflaged in various reconciliation and call factors. This approach, ie wasting of capitally developed and already broken ore stocks should be viewed by the shareholders as totally inappropriate to say the least, especially with the current gold and other metals prices.The author attempts to provide answers as to why the technology referred to above has not yet been accepted on Australian gold and metal mines and outlines the way forward.CITATION:Biegaj, K, 2012. Why do shareholders and mining executives allow mine managers to leave behind high-grade broken ore underground?, in Proceedings Narrow Vein Mining 2012 , pp 197-206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By Heidecks C

Sub-level stoping with consolidated rockfill is the main method for mining steep dipping baryte and fluorite veins in Germany. Drifting is fully mechanised using drill jumbos, LHD units and shotcrete support. Stopes have heights up to 50 m with sub-level distances up to 15 m. Winning of the pillars between sub-levels is done by longhole blasting in slices of 3-5 m length on strike. Mucking is done on the lowermost level by LHD units. After each blast rockfill with binder (cement and/or fly ash) is dumped into the scope from the uppermost level. Economic success depends on both geological and technical parameters and factors, eg vein thickness and dip, ore grade, size and distance of sub-level drifts. Of particular influence are ore loss in pillar winning and dilution both in drifting on vein and in pillar mining. A comprehensive computer program has been developed for calculating the total cost per tonne run-of-mine ore respectively per tonne of concentrate for a single stope. The cost model includes development, longhole blasting, mucking and haulage to the mill, milling and ventilation. All costs (labour, energy, supplies, maintenance, depreciation and capital cost) are taken into account. Dilution and recovery are both considered. The program can be used to estimate the cost of mining a particular stope. It can also be used to investigate the influence of relevant parameters and factors on the economic result. By this way it should be possible to optimise the technical design of a stope.

Jan 1, 1995

By Hll J. K, Zhang Y. G

The wear mechanisms of impregnated diamond drill bit matrices are complex and believed to be the key point in solving drill bit self-sharpening problems. A method has been developed to find the change in c,, the wear rate of matrices having different fracture toughness K_ at the increment of drill pressure P. The worn surfaces of specimens were placed under a scanning electron microscope to examine the wear patterns and wear mechanisms at different pressures, and were compared with the worn surface of a practical drill bit. A model is proposed that within a wide range of pressures there exist two different wear mechanisms and three wear regions for cemented car- bide matrix materials. In region one (linear region), at low pressure, the major wear mechanism is plastic deformation in which the preferential wear of the binder phase of the matrix results in the loss of WC, tung- sten carbide particles. Wear rate is controlled by hardness, H as Archard's formula predicts. Wear enters region two and three (non-linear region) simultaneously as pressure is being increased. Consequently, wear transfers to fracture mechanism in which micro-fracture occurs at the root of wear grooves and the material is removed mainly in piece and mass. It has been shown fracture toughness K,, plays a more important role than hard- ness H. It is concluded that for a specific drilling condition, the pressure on the matrix should be carefully controlled and a balance between hard- ness and toughness of the material is essential for a steady drilling Condition.

Jan 1, 1989

By T J. Sheer

The removal of airborne pollutants from underground ventilating air is discussed. The work concentrates on the removal of CO, CO2, NOx, SO2, radon gas and respirable carbon particles. The investigation combines techniques for multiple contaminant removal using forced chemical absorption and oxidation. Both dry and wet scrubbing techniques are employed. Mixed success has been achieved in the tests carried out and this paper is seen as a progress report on the work done to date. The interference and interaction of the gases on the individual removal efficiencies is a very important factor in the finalisation of a macro air conditioner (MAC) design for treating underground ventilating air. This necessitates a specific sequence of contaminant removal. Efficiencies are discussed and recommendations made. Wet forced chemical absorption and oxidation processes, though efficient in terms of removal efficiencies, cannot be employed in the confined underground environment due to safety and health risks. Impacts on the internal water reticulation systems of the mine have been analysed to determine the effect of future large-scale macro air conditioning practices, including blow-off liquids discharged into the water circuits. To engineer the safety and health risks out of such designs can be costly and it is for these reasons the research now concentrates on dry scrubbing of the contaminants from the underground ventilating air. The paper concludes with statements on the benefits of macro air conditioning in deep hot mines, in both recirculating and series air ventilation distribution strategies. These benefits include reduced re-entry times after blasting and increased production rate opportunities.

Jan 1, 2005

An account of milling "methods and costs at Mount Isa Mines Limited up to the year 1938 has been published. The present paper outlines the methods since adopted in the milling of lead-zinc ores and presents a description of the equipment now being provided for the milling of copper ore.The programme approved for the mining, milling and smelting of both lead-zinc and copper ores involves the milling 9f 50,000 tons of lead-:-zinc ore and 35,000 tons of copper ore per month.The crushed ores will be delivered to the surface from alternate levels through No. 2 Ore shaft and conveyed to their respective crude ore bins at the crushing plant. The ores will be crushed and milled in separate circuits in common buildings and the tailings will be stored on a common tailings dump. The water services to the two circuits will be separate.LEAD ZINC PLANTCrushing PlantThe crushing plant described in the previous paper was located adjacent to the Urquhart shaft. The crushing plant had grown considerably over the years by the addition of a 4ft. BY-mons shorthead crusher and a set of Traylor 72 in. x 20 in. crushing rolls and, whilst operating satisfactorily, was difficult to maintain and cramped in many places. As a satisfactory layout for the new copper crushing plant could not be made in the vicinity of the, existing plant, it was decided to construct a new plant on the western side of theconcentrator building and provide identical equipment in...

Jan 1, 1953

By Xaykhamphoune, Ward B

Draglines have been used exclusively for primary overburden stripping at the German Creek Mine complex in central Queensland, where coal has been extracted from a series of ten open cut pits working seams of the German Creek Coal Measures. Due to the dip of the seams, most of the pits have now reached the limit of current economic viability and the emphasis has switched to underground extraction using longwall methods and to a new area of open cut reserves in the nearby Rangal Coal Measures at German Creek East. This area is characterised by weak Tertiary overburden, relatively steep dips and low strength intraformational shear planes at the top and bottom of the coal.The first pit, with a maximum depth to coal of 15 m at the low wall, avoided any major slope failure through use of scrapers to excavate the boxcut and dump the spoil away from the low wall. However, this method was not considered economically viable for the second pit where low wall depths reached 44 m. Following geotechnical investigations the boxcut was divided into a number of zones depending on depth of cover, dip and thickness of Tertiary clay. Slope stability was assessed for each zone using several analytical techniques to ensure that dragline mining would be acceptable. Slope design parameters incorporating various stabilisation techniques, notably an updip trench backfilled with competent spoil to form a low wall buttress prior to excavation of the boxcut panel, were successfully integrated into the mine plan after careful consideration of the complex scheduling to minimise rehandle.

Jan 1, 1992

From 1980 to February 1991 the Rosebery concentrator purchased ore from Aberfoyle's Que River Mine. Following the termination of the contract the concentrator reverted to treating Rosebery ore alone. Since that time it has become apparent that the circuit configuration employed was no longer optimum for zinc metallurgy. The circuit was designed to treat a difficult, slow floating sphalerite; however, the opposite was now found to be true. The sphalerite is fast floating and the circuit was cumbersome. During 1992 extensive circuit changes led to the provision of a simple open circuit flow sheet. The circuit is now easier for operators to understand and lends itself to improvements in process control. Middlings streams have been minimised, which produces a far more stable circuit. Significantly, it must be noted that the key to achieving potential results must lie in reducing variations within the process. A significant ore characterisation program has been undertaken, providing an insight into the metallurgical compatability of the ore to be mined. Using the information collected in this program, metallurgical recoveries and grades can now be predicted with a geater accuracy. Ore characterisation data suggests that an improvement from a 54 per cent zinc concentrate to a 57 per cent zinc concentrate should be achievable. By understanding the size-by-size mineral assemblage, a strategy for concentrate grade improvement has been developed. The requirements of the customer must in all cases determine the quality of the product. Pasminco is a fully-integrated zinc producer and as such significant gains can result by tailoring the concentrates to suit the Smelters.

Jan 1, 1993

By Sowerby BD

The CSIRU Division of Mineral Engineering is developing various techniques for the on-line determination of moisture in coal and coke, and some instruments are now commercially available. These techniques permit accurate and rapid determination of moisture in materials directly on conveyor belts or in bins. The most promising techniques for direct on-belt measurement of moisture in coal are capacitance and microwave transmission. A non-contacting under-belt capacitance and gamma-ray backscatter technique has determined moisture in coal to better than 0.5 wt'/. in field tests at BHP Stockton Borehole Colliery, NSW. Mineral Control Instrumentation Pty Ltd have been licensed to manufacture the capacitance gauges and have installed five commercial units in the coal industry and other industries. Microwave transmission techniques have an advantage over the under-belt capacitance technique in that they are not sensitive to vertical segregation of moisture in coal on the conveyor belt. A laboratory prototype of a microwave transmission gauge has been constructed and tested. Microwave techniques, based on a measurement of attenuation and phase shift, are under development and are expected to be field tested in 1987. These new techniques will enable a wide range of thickness changes to be accommodated. Capacitance and microwave transmission methods are unsuitable for materials of high electrical conductivity, such as coke. CSIRO is therefore developing a fast neutron and gamma-ray transmission technique, which is proving very accurate in laboratory tests. This technique overcomes many of the limitations of thermal neutron moisture gauges and it is expected to be field tested in 1987.

Jan 1, 1987

Most publicity about the copper industry nowa- days is focused on the adequacy of ore reserves and on excessive mining capacity. These concerns, stemming from public awareness of actual and poten- tial shortages and oversupplies, relate to production rather than consumption. Perhaps the reason for this one-sided view is that copper is thought of as a commodity which is conspicuously traded in world markets, rather than as one of many industrial materials that serve today's rapidly changing tech- nology. Copper differs from other widely traded com- modities in that its real cost of production has pro- gressively increased since World War II. The reasons for the increase are identifiable by analyzing operations in one of the world's large producing centres, the copper province of Arizona. Another respect in which copper differs from some other com- modities is that increases in demand occur less auto- matically in the case of copper than they tend to in commodities whose consumption is more directly related to population growth. The copper industry's current inability to generate and attract needed investment capital is attributable to these differences between copper and other com- modities; it suggests that the concept of copper purely as a commodity is outdated. The key to the problem is better integration between the activities of copper producers and users. Depending on cir- cumstances, integration takes various forms- for example, investment tied to long-term sales con- tracts between producers in developing countries and consumers overseas; common ownership of pro- ducing and manufacturing facilities in industrialized

Jan 1, 1978

Address by the President (Mr B T Loton) in presenting the Institute medal for 1981 to Charles Wooller Marshall AO. Address by Charles Wooller Marshall AO after accepting the medal.

Jan 1, 1982

High sulphur volcanic-hosted hydrothermal environments are favourable geological environments for gold mineralisation. Numerous world-class gold deposits including Pueblo Viejo (Dominican Republic), Goldfield (Nevada), EI Indio (Chile), and Wa

Jan 1, 1994

By C M. Côte, P Bolz, R Chrystal

The design of final landforms is an integral part of mine closure plans in Queensland and aims to ensure the rehabilitated land is safe, stable and non-polluting. Landform stability in this context is commonly assessed using Landscape Evolutions Models (LEM) which are physical models simulating sediment erosion and deposition around individual landforms over long timespans (up to thousands of years). The most used LEM for assessment of rehabilitated landforms in Queensland is SIBERIA (Willgoose, Bras and Rodriguez-Iturbe, 1991; Tucker and Hancock, 2010). SIBERIA models are complex, require very detailed input data and simulate erosion and deposition over time frames that extend decades beyond closure. They are not suitable to assess erosion risks during the operational phase of a mine and to support the development of erosion and sediment control plans. Other types of erosion models, such as the Revised Universal Soil Loss Equation (RUSLE, Wischmeier and Smith, 1978) or Water Erosion Prediction Project (WEPP, Nearing et al, 1989) calculate soil loss on a monthly or yearly basis and are much better suited to erosion management during the operational phase. They are simpler to implement and can support the design of control measures. For instance, designing a sediment basin requires quantification of sediment loads, which can be produced by these models. In Queensland, the legislation around sediment and erosion control for open cut mines is currently tightening. Soil erosion remains a major concern due to potential impacts on the receiving environment. It requires management during operation and for closure consideration alike and it is critical that erosion and sediment control plans are developed with the most appropriate tools. Globally, RUSLE is the most widely used soil loss model (Borrelli et al, 2021). This is because it is an empirical model with relatively simple input requirements: biophysical data such as soil properties, vegetation cover, topography and rainfall variability, which can be directly measured or derived from regional or national databases and/or spatial data sets that are available in most parts of the world. The second most used model is WEPP (Borrelli et al, 2021) but compared to RUSLE, there is a large drop in the frequency of its use. This is because WEPP is physically-based and has more complex data requirements. WEPP integrates hydrology, hydraulics, erosion mechanics and land cover to predict soil erosion and sediment transport on hill slope profiles and small watersheds (Stolpe, 2005). It requires some biophysical parameters in formats different from those of RUSLE, as well as detailed hydrologic and catchment data. Nevertheless, it has been used in landform design for mines across Australia to determine final landform stability (eg Howard and Roddy, 2012; Costin, 2020). In this study, we assess which tool would be the most appropriate to support development of erosion and sediment control plans from operation to closure. We use RUSLE and WEPP to predict soil loss from a mine site, compare the results from both models and outline the advantages of each method.

Aug 2, 2023

By C Hertle

GHD-Black & Veatch (GHD-BV) have completed design and specification of the ash thickening plant at Tarong Power Station, including operation of a pilot plant. Construction of the plant is in progress and commissioning is planned for early-2004. The objective of the new plant is to convert the low concentration (lean phase) ash slurry currently generated by the power station into concentrated slurry which will then be pumped to the existing ash dam. Water recovered from the lean slurry will be returned to the power station for reuse. The drivers behind this project are to extend the life of the ash dam and to reduce water pumping costs. A maximum flow of 1000 litres per second is expected in the thickening plant. The process involves a screening phase, which removes large material that could cause blockages or equipment damage. A 50 metre diameter thickener then concentrates the screened lean ash slurry to 55 - 60 per cent w/w solids. In addition, the thickener plant will allow the harvesting of floating cenospheres (hollow, spherical ash particles) from the lean slurry. Cenospheres are currently collected from the surface of the ash dam and drained on a pad adjacent to the dam. The new system will use a surface skimmer to remove the cenospheres from the thickener and transfer them to settling ponds for further classification. The settling ponds simulate the detention on the existing ash dam, and allow entrained fine ash and slow settling cenospheres time to settle. As settling occurs in ponds, the slow settling cenospheres can be completely recovered whereas when they settle in the dam, the opportunity for recovery is lost. Cenospheres are a valuable by-product produced during the combustion process, and recycling of this material reduces the waste generated by the power station. Water recovered from the thickener drains to a three megalitre reservoir. Water is drawn from the reservoir for thickener plant service water and various other uses in the power station. The bulk of the water is used to sluice ash from the power station to the thickening plant. In the current configuration, surface water from the ash dam is reused but must be pumped several kilometres back up to the power station. The dam also holds an inventory of several thousand megalitres of water and has significant evaporative losses. Therefore the current raw water make up demand is substantial. In addition, some areas of the power station traditionally using raw water will be modified as part of this project to allow the use of recovered water, further reducing the raw water demand. The design incorporates many features of sustainable water management. By more effectively recovering water from the lean ash slurry, the amount of raw water make up required by the system will be significantly reduced. This method of water recovery provides a more sustainable and energy efficient ash-transport mechanism.

Jan 1, 2003

By J Brisebois

The Wisemans Creek derelict mine site is located in native forest approximately 150 km west of Sydney. Mean annual rainfall at Bathurst, 20 km to the north, is 634 mm and reasonably distributed throughout the year, with slightly more rain falling in the summer months. Evaporation is 1350 mm per annum and considerably exceeds rainfall in all but the winter months (May to August). This results in a water deficit for much of the year. Groundwater is relatively deep, as it has not been intercepted in the shallow open cut workings. Investigation of the groundwater regime was beyond the scope of the current study. Mining has taken place on the site for almost 100 years, during which copper, talc and gold have been sequentially extracted from surface and shallow underground workings. The site is now characterised by the presence of small open pits, unprotected shafts and adits, mullock heaps and an unconfined tailing deposit from a small cyanidation plant. From a distance, the mine area is visible because of two distinct steep bare slopes below the relatively small mine workings and mullock heaps. The mining area was characterised in terms of its environmental, safety and heritage issues. Mullock from the early copper mining was found to be acid forming and leachate from this, combined with clearing of timber, has most likely resulted in death of vegetation below the heaps. The mullock also contains elevated concentrations of heavy metals. The gold tailing is apparently benign and not acid forming, although there are indications of oxidation and acid formation in the derelict gold open cut. Oxidation of the acid forming mullock still appears to be taking place even after being exposed to the atmosphere for at least 50 years, resulting in continued contamination of the slopes below the heaps with heavy metals. The concentrations of metals decreases with distance below the mullock heaps and also is confined to the ground surface the further away from the mullock, providing further evidence to support the theory that the mullock is the source of contamination. Despite this continuing contamination, its spread beyond the immediate mining area appears to have been limited because of the relatively dry climate, with only intermittent rainfall and stream flows. Irregular storm flows in the nearby creek could also have washed any contaminated soil some distance from the site and beyond the area investigated in this study. Remediation of the site and restoration of vegetation on the bare slopes will therefore depend on elimination of the source of acid and metals. Options for remediation, focussing on minimising cost by retaining the materials on or close to the site, are identified. The volume of the open cuts would appear to be close to that required for burial of the acid-forming mullock, thereby removing the source of surface contamination while keeping it above the groundwater table. However, implementation of this remediation plan will depend on the availability of funds to undertake the work through the New South Wales GovernmentÆs Derelict Mines Program.

Jan 1, 2003

By Johns AS

Comissioning of a new residue disposal tcluding upgraded classification for none backfill preparation, new variable speed pumps and a new residue dam took place in 1¦76. The system is described.

Jan 1, 1978

Ore petrology will fundamentally determine the types of metallurgical processes employed for ore treatment, their operational efficiency and the nature of processing problems encountered. It is therefore paramount that the petrological charact

Jan 1, 1998

Mackenzie (1968, p. 167) inferred that amphibolitelayers grade into and may be correlated with footwall Potosi gneiss where it is thin under the thickest development of the "lead lode" in the New Broken Hill Consolidated mine, Broken Hill. This gradation from amphibolite to Potosi gneiss is tacitly assumed in many of the constructed crosssections of the southern end of the orebody, where amphibolite and Potosi gneiss, defined in hand specimen, are correlated in adjacent drill holes. The basis for such correlations is the observation that some amphibolites in drill core lighten in colour from black to grey along the core and grade into an unlayered rock containing conspicuous pink garnets, which resembles Potosi gneiss (for descriptions of Potosi gneiss see Andrews, 1922; Gustafson, BurreIl and Garretty, 1950; Carruthers and Pratten, 1961;\Ternon, 1969).Average chemical compositions of "footwall" Potosi gneiss and "upper" amphibolite (Hawkins...

Jan 1, 1972