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By Steven Hoerger

Newmont Mining has a large, integrated gold-mining operation in northern Nevada with several mines, stockpiles and processing facilities. There are more than 90 defined metallurgical ore types and more than 60 defined gold-recovery process options. Newmont developed a mine plan and process model to take better advantage of the available synergies at its Nevada mines. This plan includes a mixed integer and linear programming optimization tool. This system is maintained and operated by a Nevada planning group. Standard in-house planning software tools and methods have been implemented at all mine sites. These changes have allowed a reduction in mine engineering staff and have increased the effectiveness of mine planning.

Jan 1, 1999

By H Bleuler

A new portal and access drift was constructed by Concrete Constructions for BHPÆs Elouera Colliery, south of Wollongong.The portal area at the base of the Illawarra Escarpment is in soft colluvium material, underlain by highly to moderately weathered sandstone. The area has a well documented history of slope movement or slope creep and one of the main criteria for the design was to minimise disturbance to the unstable slope by limiting the excavation for the portal establishment. This was achieved by incorporating a sloped headwall and gabion wingwalls to accommodate the anticipated creep and groundwater seepage.Main features of the design process also included the provision of both primary and secondary support in a single shell application and the use of canopy tubes to provide support ahead of the tunnel face.The active involvement of the designer during the construction phase and the flexibility of the design concept allowed changes to the support methodology to be carried out as excavation proceeded.This paper describes the design process undertaken for portal establishment and access drift to cater for the variability of the exposed ground conditions along the drift alignment.

Jan 1, 1999

By R. Sharma, S. Svoronos, S. Gupta, N. A. Abdel-Khalek

This paper presents the results of column flotation of a fine feed sample of Florida phosphate. A central composite design is used to study the main and interaction effects of parameters affecting column efficiency. The statistical design is also used to determine the optimum conditions. The results indicate that, depending on the experimental conditions, it is possible to achieve a concentrate of high grade and recovery. A concentration of 15 ppm of non-ionic frother is found to be enough to maximize the recovery at the pH of 9.5.

Jan 1, 1999

By J. Engelbrecht

South Africa?s re-entry into the fast moving and competitive global economy calls for some careful strategic planning and a good deal of co-operation between suppliers and end-users. The issues that need addressing are generally well known and include: ?South Africa was ranked 45th out of 46 i.r.o. productivity ?SMMEs contribute 1% to exports compared to 40-60% for the ?tigers? ?High unemployment ?Limited skills of the majority of workers ?Slow growth rate of the economy ?The vast majority of suppliers are not world-class ?The vast majority of suppliers are not export or marketing orientated. In order to survive, all parties, i.e. government, labour and business, will have to play their part.

Jan 1, 1999

By C. Patrick, D. Puckett

The feasibility of monitoring the locations and vital statistics of equipment and personnel in surface and underground mining operations has increased with advancements in radio frequency identification (RFID) technology. This paper addresses the use of RFID technology, which is relatively new to the mining industry, to track surface equipment in mine pits, loading points and processing facilities. Specific applications are discussed, including both simplified and complex truck tracking systems and an automatic pit ticket system. This paper concludes with a discussion of the future possibilities of using RFID technology in mining, including monitoring heart and respiration rates, body temperatures and exertion levels; monitoring repetitious movements for the study of work habits; and logging air quality via personnel sensors.

Jan 1, 1999

By G. C. Hall, B. E. Hobbs

Giant gold deposits are considered products of crustal-scale systems. Reduced fluids stored in mid to lower crustal reservoirs were discharged into mid to upper crustal sites of deposition. Elements of the architecture include crustal-scale structures, reduced packages of rock and regional seals. Gas-rich aqueous fluids were common but non-aqueous fluids may have been significant in the deeper parts of the systems. Fluid fluxes in over pressured domains were maintained by porosity waves. Abnormal heat input from the mantle may not be required once the systems were perturbed. Fluid-mixing and hypogene enrichment were probably the most significant precipitation processes.

Jan 1, 1999

By A E. Annels, I P. Hodkinson an, S P. Barr

Narrow vein systems represent an important source of gold, which have generally been exploited by small to medium sized companies. Their evaluation poses particular problems because of their grade and geological complexities. The determination of grade is arguably the most important activity in resource estimation, as it is generally grade and not tonnage that makes an orebody. This is particularly true of narrow vein-gold deposits whose resources are generally relatively small, though medium to high-grade (6 - 40+ g/t). They often display extreme grade anisotropy in all directions. Two grade populations are generally observed; 1) low, often subeconomic, background grades and 2) high-grades associated with discrete ore shoots. It is possible for gold to be distributed within the wallrocks as well as within the vein. Extremely high-grade values typify this style of mineralisation and require special consideration during grade estimation to determine if top cutting is valid or not. Estimation of both width and accumulation in 2D on vertical longitudinal projections or inclined planes have historically been used to evaluate narrow veins. Resource estimates based on traditional 2D methods is still widespread, but has in some cases been replaced by computer-based 3D modelling. Grade estimation methods are well-known, ranging from classical to geostatistical. Historically, classical methods such as inverse distance weighting have been used, though geostatistical indicator kriging methods are sometimes applicable. Geostatistical studies are driven by the production of reliable variograms, which in narrow gold veins is often problematic. It is generally difficult to define resources from drillhole intersections beyond the inferred and indicated categories with any confidence. In the majority of cases underground development is required to define measured resources and ore reserves. Trial mining/bulk sampling is often used to test estimated grades and also provides important data on ground conditions and the parameters relating to the proposed mining method required for ore reserve definition. Regular reconciliation should be undertaken between the estimated stope grades, grades indicated from stope/truck sampling and grades realised in the mill in order to determine whether correct evaluation strategies are being applied. The important feature of narrow vein-gold deposits is their strong geological controls; in response to this, geologists must understand the geology as best as possible.

Jan 1, 1999

By P. D. Navarro

The behavior and operability of LIX 1104SM extraction was studied at laboratory scale on the Solvent Extraction at Sb3+, from high concentration sulfuric acid. In order to evaluate the reactant batch tests were made at laboratory scale as well for extraction as for re-extraction of Sb3+. Experiences achieved were: extraction kinetics, temperature effects, selectivity tests and re-extraction selectivity. A extraction kinetics was found, reaching equilibrium in 2 min, high selectivity of Sb3+ extraction in front of Cue , existing As5+ co-extraction and Fe3+ At the re-extraction stage, equilibrium was reached in 3 min, getting high Sb3+ re-extraction efficiency with HCl concentrations within 6 and 8 M. A high selectivity was achieved on Sb3+ re-extraction in front of As+5, existing Fe+5 re-extraction.

Jan 1, 1999

By J. Drelich, M. Pawlik

An improved experimental procedure to measure contact angle has been consolidated with coal surface preparation involving polishing with abrasive paper, alumina powder, and a cloth, followed by ultrasonic and mechanical cleaning. Specifically, the captive-bubble measuring technique has been compared with the sessile-drop technique and the former has been recommended for the examination of the hydrophobic properties of coal surfaces. Results of the research program, which is currently under way, on the examination of the effect of the nature, amount, size, and distribution of mineral inclusions in coal, on its wettability are briefly reviewed.

Jan 1, 1999

By M. A. S. Siraa

A program of work was undertaken at the Kennecott Smelter and Refinery to model the complex. This effort contributed a total of eight models of the plant: flash smelting furnace, flash converting furnace, slag concentrator, anode furnace, offgas scrubbing system, acid plant, hydrometallurgical dust treatment plant, and the precious metals plant. Some of these models have been used in a variety of investigations ranging from offgas capacities for a steam generation analysis to an examination of impurities. The culmination of this enterprise has resulted in an on-line control scheme for the flash smelting and flash converting furnaces. These two process control schemes incorporate their respective steady-state heat and mass balances that are executed in response to feed changes while a feedback loop calculates when product grade and temperatures deviate from setpoints. This system has been put into place to improve furnace control and on- line time.

Jan 1, 1999

By Ing. E. h. Martin Herrenknecht, Werner Burger

In recent years, there has been a dramatic increase in the number of machine driven soft ground tunnelling projects. This increase is largely due to the technological development of slurry and EPB Shield systems. A new generation of soft ground tunnelling machines, markedly different from those of five years ago, now overcomes ground conditions that until now were too costly and impractical to undertake. The paper reviews the latest soft ground tunnelling machine developments in material transport, guidance and control, seismic surveying, soil conditioning, settlement control, cutting tool applications and variable mode operating systems. Specific projects where this technology has been applied will be highlighted.

Jan 1, 1999

By J. K. Neathery, T. X. Li, H. Ban, J. L. Schaefer, J. M. Stencel, X. K. Jiang

Pneumatic, triboelectrostatic processing of physical mixtures containing fine (-200 mesh) particulate may have significant application potential in the mining and energy industries. Such dry processing methods, especially for finely comminuted materials, have not been examined in as much detail as wet processing methods nor have been part of the training or education of mining and process engineers. We have examined fundamental and applied physical and engineering factors controlling triboelectrostatic beneficiation of fine-sized physical mixtures, one of which - combustion fly ash - has size, heterogeneity and mineral concentrations typical of those expected in mined minerals. The applicability of dry processing, however, cannot be readily evaluated because of the unavailability of standard procedures for process assessment.

Jan 1, 1999

By D Suppel, Y Miezitis, S Jaireth

The competition between various options for the use of land is ever increasing. Commonly in Australia large tracts of land were un-encumbered by sweeping land use option limitations, but this situation has been rapidly altering in recent decades as governments are obliged to maximise the utility of the land for a broad range of competing interests. While the interests of miners have always been considered, the effects on limiting access to land for exploration and possible mining have not always been effectively incorporated into decision-making processes. As a result the challenge for national and state organisations representing these interests has been to develop a transparent process to allow for the mineral potential of an area to be systematically assessed and for information to be presented for use by specialists and non-specialists. Government agencies are called upon to implement government policy but also to provide accurate and meaningful advice which can assist in policy and land use decisions. Commonly timeframes are short and information can be less than complete. Nevertheless on-going decisions are made based upon the best available understanding. It is in this operational framework that the methods described in this paper are set. The paper describes a process for quickly and systematically providing advice on mineral potential for use by government agencies and ultimately the community within tight time and resource constraints. It is a method of combining the accumulated knowledge about mineral resources and their potential and presenting this information in an easily accessible form which can be used in a negotiation and policy development environment. Development of the method was undertaken to meet the needs of the Regional Forestry Agreement process in Australia. The method has been applied to study areas in New South Wales, Tasmania, Western Australia and elsewhere. Examples in this paper are taken from north eastern New South Wales.

Jan 1, 1999

By R Bertuzzi

Permanent rock bolts in civil engineering are taken as having to serve their design purpose for at least 50 years. In many projects the design life is specified as greater than 100 years. A review of recent Australian tunnelling projects shows that substantial differences exist in the level of corrosion protection provided for permanent steel shafted rock bolts. This paper reviews the current state of practice and sets out what the authors consider to be appropriate requirements for corrosion protection.

Jan 1, 1999

By M. Matthias

A study, part of a doctoral dissertation (Matthias, 1991), was conducted during 1987 and 1988 to establish the means by which professionals assess and maintain their competence during the various stages of their careers. The study elicited responses from fifty-nine subjects representing engineering, pharmacy and medicine (twenty subjects from engineering, nineteen from pharmacy and twenty from medicine) on their perception and assessment of continuing competence. The findings revealed a wide variation of how professionals perceived their continuing competence and the means they adopted to keep current. The implications of the study are significant for adult education practice and theory building. The author strongly believes that now, more than ever, engineers must take ownership of their careers and professional development activities. While management and supervision have a key role to play, it is the engineer, who is ultimately responsible for the scope, planning and implementation of her/ his professional development needs. An example from one high technology company will illustrate these points.

Jan 1, 1999

By Ning Liu, Di Yin, Xuming Wang, Yongqiang Lu, Jan D. Miller

Air-sparged hydrocyclone (ASH) flotation technology has been evaluated for phosphate recovery from the central Florida phosphate deposits. As expected, it was demonstrated in pilot-plant tests that the ASH system has a specific capacity about 50-100 times higher than that of a traditional flotation cell. In the case of fatty acid flotation, single-stage ASH flotation produced a recovery of 75-77% in a rougher concentrate containing 24% P2O5 In reverse flotation with amine, the single- stage ASH system produced a phosphate recovery of 98% in a cleaner concentrate containing 31% P2O5. These results are comparable with those obtained at plant operations in the Florida phosphate industry. Based on these pilot-plant results, the effects of process variables are discussed in terms of separation efficiency. Subsequently, a 6-inch ASH system was fabricated and tested in a central Florida phosphate plant for reverse flotation in the amine flotation circuit. The high capacity of the ASH system was again demonstrated for the 6-inch ASH system. A single-stage phosphate recovery of 91% was achieved with a concentrate grade of 30% P205. During plant tests, it was established that porous tube plugging, the most significant engineering problem identified, was due to the poor quality of the plant water. Possible solutions to this problem are discussed.

Jan 1, 1999

By C J. R Hart, J K. Mortensen

The distribution of mineral deposits within northwestern North America (Alaska, Yukon, and northern British Columbia) allows for an in-depth examination of the metallogenic patterns of a growing continental margin. A more complete understanding of the tectonic evolution of this part of the Pacific Rim, achieved over the last 15 to 20 years, now allows for the placement of ore systems into a well-defined plate tectonic framework. Ore deposits older than about 185 Ma represent hydrothermal systems that were active in the platform/shelf environment of ancestral North AmericaÆs miogeocline or hydrothermal systems developed in oceanic arcs and continental fragments more distal to the craton. These include important SEDEX, VMS, and pre-accretionary porphyry deposits. In contrast, most mineral deposits younger than about 185 Ma were formed within the growing Cordilleran orogen, as terranes were accreted to the continental margin during interactions between the North America and Pacific/Farallon/Kula plates. Such syn- to post-accretionary mineralised systems include many large lode gold and porphyry/skarn systems.

Jan 1, 1999

This paper discusses the potential role of underground space and tunnelling in urban planning in Australia. The paper gives examples of the infrastructure and commercial applications of underground space which have been effectively used overseas but have been slow to be considered as a part of urban planning in Australia. In particular, the paper looks at underground quarrying and underground commercial development and their potential use in the urban environment. Existing sites and potential sites for quarrying and/or commercial use have been classified using a system developed by the author. Underground quarrying may provide some solutions for planning problems involving sand and aggregate supplies, waste disposal and other uses. Commercial development involving underground excavation may be accepted if the cost of underground commercial development can be shown to be equivalent to the cost of above ground development. The paper concludes that one role of the underground construction industry is to promote tunnelling and underground space amongst architects, town planners and planning decision-makers. The Australian Underground Construction and Tunnelling Association (AUCTA) and the Australian Society for Trenchless Technology (ASTT) should be instrumental in actively promoting the use of underground space in society.

Jan 1, 1999

By Toshihiko Emi

The quest for cleaner steel is driven by increasingly stringent requirements from the manufacturing and construction industries. Key issues are the occurrence and removal of inclusions; These are discussed in the context of the unit processes of deoxidation, refining, transfer and casting of molten steel. Process thermodynamics and kinetics are also discussed. Recent progresses achieved and problems yet to be solved are elaborated, and an integration of the unit processes into a system to produce extra clean, steels with better performance is presented.

Jan 1, 1999

By May Nyman

Due to the vast diversity of chemical media in which metal separations are executed, a wide range of ion separation materials are employed, This ,results in an ongoing effort to discover new phases with novel ion exchange properties. We present here the synthesis of a novel class at, thermally and chemically stable microporous, niobate-based materials. Ion exchange studies show these new phases are highly selective for Sr2+ and other bivalent metals.

Jan 1, 1999