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By Zhang S

A probabilistic approach is proposed for updating open pit slope sta- bility based on successful performance. The suggested approach is developed within the framework of Bayesian probability theory. In seeking solutions to geomechanics problems consideration must be given to inher- ent variability of shear strength parameters and to the errors in the esti- mation of these parameters. The latter can be significant and may lead to consistent overestimation or underestimation of the values derived from site investigation and testing. Conventional deterministic methods of slope stability analysis do not allow systematic modelling of uncertainties in applied loads or in shear strength parameters. Within a probabilistic framework indicators of stability may be calculated, e.g., the reliability index and the probability of failure. Based on observation of slope per- formance at any given stage of a project, the mean or the standard devi- ation (or both) of a shear strength parameter may be updated. Consequently the indicators of stability can also be updated. The appli- cation of such an approach is demonstrated by an illustrative example.

Jan 1, 1989

The growth in the nickel market and the price increases predicted in 1970 have not mat-erialized. Several plants have been construct-ed, particularly to treat lateritic ores. A spectacular increase in cost of energy and the escalation of capital costs have led to severe economic difficulties on the part of many nickel producers. Several of the nickel prod-ucers joined together to form a Nickel Develop-ment Institute in 1984 with the prime objective of improving nickel markets. Most producers have taken exceptional action to cut overall costs as well as unit costs. Another organiz-ation made up of nickel producers, NiPERA, was established in 1980, to study and take action on problems of nickel in the environment and especially in the workplace.Ion exchange, and particularly continuous ion exchange, has been developed into a reli-able commercial unit operation in the last dec-ade. An example of how ion exchange combined with hydrogen reduction can be integrated into a Caron type reduction roast ammonium carbonate leach process for the recovery of nickel from laterites is discussed.

Jan 1, 1985

By N J. Arunakumaren

A coal mine is proposed for an area where a major river traverses the project area. There were initial concerns that inflow of groundwater from exposures of high permeability alluvium associated with the river system could pose mine dewatering problems together with adverse impacts on surface water resources in the river. The project included collation and analysis of geological and hydrogeological data collected historically over a long period of project investigation and evaluation. The project also included establishment of additional groundwater monitoring points to provide a reliable groundwater contours. The groundwater level contours were produced to allow numerical models to be calibrated to support estimation of groundwater inflow. River bed cross sections were also prepared to assist study of the effect of river flow on the inflow. Two separate MODFLOW groundwater models were produced to simulate long-term groundwater inflow to the mine with an upper model consisting of the Quaternary and Tertiary alluvium lumped together and a lower, separate model consisting of Mesozoic coal measures. Analytical solutions were used to predict initial inflow from the alluvium and from the coal measures.

Jan 1, 2003

The major heavy industrial consumers of limestone are the cement, lime'and steel ind- ustries. Each of these requires large quantities of cheap raw material. Other ind- ustries such as glass and chemical manufactur- ing are significant consumers and agricultur- al and constructional activities provide additional demand which is usually more local in its occurrence. Limestone is widely dis- tributed throughout Australia but location in relation to major markets, and transport con- siderations render most deposits of no economic value. Among deposits which are sufficiently close to the major metropolitan markets many must be rejected as being unsuitable on grounds of quality, inadequate size for major.develop- ment, or other reasons such as environmental considerations. The major producing locations are sit- uated in a variety of geological environments. Most have limited reserves and require partic- ular attention to quality control. Planned extraction programmes based on detailed geo- logical investigations enable not only satis- factory grade control but also permit, by the adoption of appropriate quarry procedures, the use of sub-grade material, thus optimis- ing utilisation of the available reserves.

Jan 1, 1976

By Griffiths J. B

From its mining lease at the northern end of Cohens Reef at Walhalla in the North Gippsland Mountains, the Long Tunnel Extended Gold Mining Company produced 13,695 kg of gold, which at 1980 prices represents a value significantly in excess of $200 million. In the period 1885 to 1908 the mine was one of Australia's principal reef gold producers, being top Victorian producer in six of these twenty-four years. Prior and subsequent occupants of the lease produced an additional 160 kg of gold. The Extended and the other mines on Cohens Reef whilst contributing importantly to the financial resource of Victoria, were the sole important support for the substantial town of Walhalla that had grown up around them. When the mines closed, Walhalla gradually reduced from a bustling developed town to the present attractive mountain village so favoured by tuurriSts. To allow the visitor to obtain a better ;ri.icrstanding of Walhalla's mining past, important parts of the Long Tunnel Extended Gold Mine workings and site are being

Jan 1, 1981

By Ward S. C, Gardner J. H

In 1990, Alcoa of Australia Limited was elected to the Global 500 Roll of Honour of the United Nations Environment Program for the environmental management and rehabilitation of the bauxite mines in Western Australia. This award placed Alcoa in the international best practice category. The story of constant improvement spans more than 20 years from a 'trial and error' start to a strategically focussed and research driven program today. The main driving force has come from within the company, against a set of strong corporate values and a well publicised Vision based on 'excellence through quality'. Along the way public opinion, action group protests, increased legislative controls together with the professional competence of internal and external environmental resources have all played a part in arriving at the level of current environmental management and mine rehabilitation performance. There were numerous lessons learned here during the evolution and maintenance of best practice. These included: I . To work diligently in obtaining a vision or strategic intent on mine site rehabilitation and environmental management - don't be easily dissuaded.

Jan 1, 1995

The environmental and social responsibilities of the mining industry have long been recognized by the industry itself, but during the past decade it became one of the main targets for the more radical members of the community. This came as something of a shock to an industry which had always considered that it had acted responsibly within the standards of the day. As far back as early 1968, the Australian Min- ing Industry Council (AMIC) was clipping from newspapers the odd letter written by environmen- talists and critics of mining activities. In those days every such letter was carefully studied to ensure that AMIC, if not having the answers, at least had an understanding of the types of argu- ments then starting to be used against mining activity and in favour of environmental preserva- tion. Within 18 months, the infrequent letter to the editor had become a flood of such letters and feature articles, and the environmentalists' attack on mining activities had been launched in all its Vehemence.

Jan 1, 1978

By Kyle J. H, Misra V. N

The recovery of copper from a flotation concentrate using ferric chloride leaching has been investigated. The concentrate from the Horseshoe Lights Mine near Meekatharra, Western Australia, contained mainly digenite, pyrite and talc minerals. Over 95 per cent of the copper was dissolved in an acidified ferric chloride solution in one hour at 70¦C and ambient pressure. The pyrite and gangue minerals did not react. The leaching process was found to consist of four separate reactions and the shrinking core model was used to describe the process. The effects of particle size, temperature, concentration of FeCls, stirring speed and leaching time on metal dissolution were investigated. The apparent activation energies in the second, third and fourth reactions of leaching of copper concentrate were 28.8, 11.9 and 53.9 kJ/mol, respectively. The optimum conditions for the leaching of copper from the concentrate, within the range of conditions studied were: particle size 63 per cent minus 38 ¦m, a ferric chloride concentration of 1.48 M, a temperature of 70¦C, and a stirring speed of 800 rpm.

Jan 1, 1991

By Parker C. J, Mikula P. A

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

Jan 1, 1993

The major incentives for developing continuous processes for the production of formcoke are to achieve a wider range of coals which can be used, greater operating flexibility enabling the production of various coke qualities, and environmental improvements. The characteristics of a formcoke which must be considered when assessing its performance in the blast furnace are compressive strength, abrasion resistance, volatile matter, reac- tivity, porosity, density, size, shape, ash yield and sulphur content. Lurgi's development work in attempting to pro- duce a formcoke which meets the specified requirements has resulted in most current efforts being concentrated on the Bergbauforschung/Lurgi hot briquetting process. This process blends hot char produced from a non-caking coal with small quantities of caking coal in a special mixer in the plastic range of the caking coal. The material is subsequently briquetted hot, then subjected to a thermal after-treatment to produce a strong abrasion resistant formcoke. A 650 tonne per day plant for British Steel Corporation is now under construction. A study of the equipment requirements and the operating costs indicate that the economics of large scale formcoke plants compare favourably with those of conventional coke-making plants.

Jan 1, 1975

The effects of changes in sintering bed height, coke fuel, suction and basicity on sinter productivity, physical strength and mineralogy were determined. It was found that, for a given iron ore, there is a narrow -coke range which maximises sinter strength, irrespective of bed height (in the range 300 to 500 mm) or basicity (in the range 1.2 to 2.2). Increases in bed height, at a constant coke level, improved the physical strength of the sinter. Productivity increases were obtained by increasing the sintering suction but, at coke levels other than the optimum, these *ere somewhat offset by the decrease in sinter physical strength. At basicities higher than 1.2 (i.e. 1.6, 1.8 and 2.2) there was a narrowing of'the size range of product sinter, with a decrease in the percentage of top size material, and a decrease in the amount of fines produced. Changes in coke, bed height and basicity exert major effects on sinter mineralogy, while the Nagoya index was mainly influenced by cote and bed height Changes.

Jan 1, 1975

A great part of the research on froth flotation of gold ores deals with ores containing gold associated mainly with sulphides, resulting in a largely accepted view that what takes place with sulphides (eg pyrite) in a flotation cell also happens to gold particles. This paper is concerned with the influence of some inorganics (CuSO4, CaO and NaCN) on gold particles flotation, using ethyl or amyl xanthates as collectors. The bench-scale tests were carried out with ground quartz and gold particles mixtures. Some findings stemmed from this study: flotation of the gold particles of size 0.16 mm was efficient adding only frother; larger gold grains were better recovered by the use of stronger collector CuSO4 did not seem to be an activator for gold; the addition of NaCN up to 200 g/t or CaO up to 2000 g/t did not depress the gold grains when amyl xanthate was used as collector although with ethyl xanthate the gold depression was verified.

Jan 1, 1993

The implementation of the Mining Further Amendment) Act, 1970, and later the Coal Mining Act, 1973, placed a requirement on the Department of Mines to accept an initiative in relation to coal exploration and coal mine development which does not apply in the case of other minerals. It is necessary to consider the exploration of the total coal resources of the State when considering exploration rather than one individual basin or deposit. If the level of knowledge of the coal resources in these basins is considered in relation to their potential for development it is possible to allocate broad scale priorities to their assessment. Due to the enormity of the task which involves a conservative estimate of in excess of 400 000 m of drilling to reach a broad reconnaissance level of understanding the involvement of industry with the Department in the exploration programme is necessary. The development of the coal deposits by mining operations must give consideration to a number of constraints apart from the simple availability of the resources. Principal among these are aspects

Jan 1, 1976

This paper explains why the valuation of mining assets is often a very different exercise from the valuation of the shares in the mining company which owns those assets. The fundamental reason for this is that mining assets, and the shares of the company which owns those assets have different risks. In order to properly value mining securities it is essential to: ò ensure all the different risks and other factors which impact on the value of the mining assets and the value of the shares are taken into account; and determine the extent to which the different risks and other factors are addressed in the value of the mining assets and the value of the shares so as to avoid double counting or not counting at all. If the alternative, but far from consensus, view is accepted that the correct valuation methodology to apply to shares in mining companies should be based on option pricing theory then conventional valuation practice of both mining assets and shares in mining companies will need to be fundamentally reassessed.

Jan 1, 1994

Agglomeration Drum Selection and Design A model has been developed by for drum agglomeration which allows selection of geometry and power input. Specific aspects considered are: calculation of total operating volume, solids residence time based on drum geometry and operating parameters, selection of the drum aspect ratio, selection of proportion of critical speed, calculation of rotating power requirements. The model uses solids total residence time to calculate the required operating volume. The burden density is calculated from the solids bulk density, agglomerate packing and the fluid density. Power is calculated using a modified Liddell and Moys correlation for burden position and shape, and the operating drum speed. A further power allowance is made to allow for accretion drop off during drum rotation. Results from the model (especially power and per cent operating fill) have been verified from industrial installations of significant size. Predicted and observed power draws are within five per cent when burden slip and bypassing are not significant. When these are significant (at fills above 15 per cent) the actual power draw will be less than the model prediction. Under these circumstances the quality of the agglomerates will be poor.

Sep 13, 2010

The 250 metric tonnes of gold and 360 000 metric tonnes of copper recovered from the Mt Morgan Mine in Central Queensland justify its fame. The mine ceased operation before the advent of three-dimensional computer graphical modelling of orebodies became common practice in mine planning. The Mount Morgan Mine records however remain and are the database for this study. The Mount Morgan project takes ore deposit modelling one step further by examining the relationship between grade distribution within the orebody and key geological features, as a tool for exploration and development.The Mount Morgan gold and copper mineralisation is shown to be strongly lognormally distributed. The deposit has been split into three areas, using geological boundaries, each with different geostatistical characteristics. Important features include: the spatial relationship of near-vertical, high grade shoots with a ring dyke thought to be related to the North Dyke; separation of the high grade eastern stopes from the others along the Andesite Dyke; and lack of concentrated mineralisation along the Slide Fault.Recognition of these features is useful to those currently exploring the Mount Morgan district for similar style deposits, by stressing the importance, or lack thereof, of the geological features.

Jan 1, 1993

By Marshall GA

Structural fatigue damage of haul truck frames is a costly problem associated with the operation of large mine haul trucks. A monitoring programme is described which has been instigated to measure stresses in the frames of haul trucks under actual mine operating conditions. The instrumentation used and methodology employed in the computer analysis of the results is briefly described. The results of the monitoring programmes are reviewed, and the effects of various factors affecting structural fatigue damage of three common types of rear dump truck are considered. Factors discussed include the effects of haul route features (for example shovel, dump and crusher areas); the effect of operations such as turning, braking, loading and dumping; the influence of payload; the effects of malfunctions in suspensions; and the influence of haul route surface quality. It is shown that with respect to payload, while structural fatigue damage is increased with payload, the structural damage per unit of payload does not change significantly for moderate increases in payload above the nominal value. Finally, on the basis of these results, recommendations are made for haul route design and operational practices which will increase the structural fatigue life of haul truck frames.

Jan 1, 1986

By Moelle KHR

The successful operation of a longwall face depends significantly on the efficient actions by support systems and on the ability to form a supported beam for a limited time span.The mechanical action of the supports can set up complex stresses in the immediate roofstrata.The cyclic application of supporting loads to the immediate roofstrata of a longwall face creates a special type of fabric disintegration in the rocks -affected. The mode of application and the distribution of the supporting forces is thus severely modified in a number of cases.The occurrence of true fatigue damage in brittle sandstones has been identified by studying the subcritical crack growth and microcrack development in the fracture-tip region. Several mechanical effects peculiar to the cyclic fatigue process have been identified. These effects had not previously been widely recognized. Damage in brittle rocks subjected to cyclic loads is shown to be distinctly different from any other damage processes under either monotonic or sustained (creep) loading conditions. The face support systems will frequently support rockmasses with mechanical properties not identified in conventional monotonic or sustained load tests.

Jan 1, 1991

Dynamic hydrothermal modeling is a tool that can aid in studying problems associated with hydrothermal ore deposits and can help increase our understanding of the spatial distribution of ore within hydrothermal systems. Models are constructed by a sequence of steps involving development of a conceptual model, followed by its mathematical description in terms of governing equation with accompanying initial and boundary conditions. This equation is then solved either analytically or numerically. The four model types ò that fully describe a hydrothermal 'system are those for fluid flow, heat and ore solute transport, and deformation. At Renison, models have been used to help understand two major exploration problems. These are the controls on ore localisation in dolomite horizons and feeder faults respectively. The types of models used ò have simulated the distribution of all mineral zones, pyrrhotite, and temperature in the dolomites. This has allowed evaluation of the effects on ore localisation by physical and chemical heterogeneities within the dolomite host rocks, and allowed estimation of potential controls in different physical and chemical environments.

Jan 1, 1987

The Newmont Waihi Operations mill has undergone significant growth over its life. Initially designed as a single SAG mill operation, the circuit has been progressively upgraded since 1988 from a nameplate capacity of 600 000 tonnes per annum to the current rate of 1.3 million tonnes per annum. With future mining potential there is renewed interest to increase the processing rate even further. Over the next twelve months five sustaining capital projects will be undertaken and two major eco-efficiency projects will be completed. With the exception of the large grinding mills, most equipment on a gold treatment plant is replaced after 10-15 years. Waihi Gold mine has been operating for 14 years and has just recently received approval to replace equipment in five main areas; carbon elution, carbon regeneration, scats crushing, intertank screens and variable speed drives. Each project has been justified on improved process efficiencies and operating/maintenance cost savings. The two eco-efficiency projects involve a water balance model and a cyanide optimisation project, both of which are Corporate key performance indicators (KPI).

Jan 1, 2002