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Optimisation and sensitivity analysis of final pit limits is now an accepted procedure for open pit planning studies. Tools to assist the design engineer in an underground metalliferous mine to make optimal choices for the selection of major development, stope geometry and cut-off grade analysis have not been available. The engineer has had to rely on experience and a limited analysis of design alternatives. A new tool called the `floating stope' has been developed to define the optimal (boundary) limit for material that can be economically extracted by underground stoping methods. The method is analogous to the `floating cone' method of open pit optimisation. The geology and mineralisation are modelled as a regular or subcell block model. Included in the model are structural and geotechnical features, and any previously mined out areas. Inputs to the procedure include the minimum stope dimensions, cut-off grade, stope head grade, and the way in which dilution is to be calculated. The optimisation procedure can be directed to maximise ore tonnes, grade, contained metal or the economic (dollar) value of material mined. The procedure can be applied at each stage of mine evaluation and design to assist with preliminary resource appraisal, selection of stoping methods, and detailed mine design. As with open pit optimisation procedures, manual intervention by an experienced engineer is required to produce practical and detailed designs. This practical design should follow the optimised design as closely as possible. The paper outlines the algorithms used in the definition of the stope envelope, and describes the analysis and results of several case studies where the optimisation procedure has been applied.

Jan 1, 1995

By L E. Setiawan

The mining and milling groups at Batu Hijau are tasked with increasing SAG mill throughput by approximately ten per cent. Avenues used for this process are blasting and crushing optimisation, ore blending and predicting SAG mill throughput in relation to the geological model. This is in line with traditional æMine to MillÆ studies. At Batu Hijau, mill and mine sequencing cannot readily be configured to perform the surveys traditionally required by a æMine to MillÆ study while meeting the daily production target of 140 000 tonnes per day and processing from varying ore types in one pit. A program called BOCCOST (blasting optimisation crushing conveying optimising SAG throughput) has been implemented to capture approximately 200 variables from blasting, mining and milling operations and assign them to a common point in space in the geological model in real time. Interpretive analysis of data from BOCCOST is used to model relationships between the 200 variables to determine which and how these factors affect SAG throughput. Once these relationships are determined, the blasting, ore blending and crushing process can be optimised to generate a product that maximises mill throughput. The relationships modelled from BOCCOST are also used to generate a SAG mill throughput estimator, which can be coded into the production block model. The block model can be reconciled with the geological block model for correlation by geological domain. Once this relationship is established, SAG mill throughput domains can then be established for predicting SAG mill throughput. This SAG mill throughput estimator is then used in conjunction with revenue calculations to determine an ore cut-off, which combines these two elements to maximise metal production.

Jan 1, 2002

By De Jong HJ

During the forthcoming reline of No.3 Blast Furnace at the Newcastle Steelworks of the Broken Hill Proprietary Co. Ltd., facilities for the screening and weighing o' coke will be installed. The equipment is needed to optimise the sizing and the quantity of coke immediately prior to it being charged to the furnace. Up till the time the furnace was blown out in November, 1982, coke was charged to the furnace by volume, ie by skip fulls only. This resulted in variation to the ore/coke ratio charged due to bulk density changes and erratic skip filling levels. This in turn affects the heat balance of the furnace and causes fluctuations in hot metal chemistry and temperature. A coke rate penalty has to be paid also. Coke layer thickness in the furnace burden cannot be controlled closely, resulting in loss of control over gas distribution in the furnace. A grizzly type screen was incorporated in the skip loading chute but this ineffective method left a great amount of fines with the coke being charged to the furnace. Furnace permeability was therefore reduced, particularly in the hearth.

Jan 1, 1984

By M Freeman

Significant improvements in the metallurgical performance at Pasminco Rosebery Mine have occurred over the last two years. Lead and silver recoveries have increased by more than ten per cent, lead concentrate grades are four per cent higher, zinc recoveries are up 1.5 per cent, and zinc concentrate grades have increased by two per cent. These impressive results have not occurred through the application of some new wonder reagent, but through the application of some fundamental metallurgical principals. The basic premise applied during this study was that to make an effective separation you must first achieve liberation. Therefore, the laboratory and plant studies examined the liberation characteristics within the lead circuit, and the impact of regrinding. The work demonstrated clearly that galena/sphalerite liberation was poor, and significantly impaired plant performance. Further, it was suggested that the application of lead regrinding of the lead scavenger concentrate and the lead first cleaner tailing would not only benefit lead metallurgy, but also improve sphalerite flotation. A similar approach was then applied to the zinc circuit. From these studies, solutions applying simple circuit changes utilising existing equipment were proposed and implemented. Further to the improvements in galena/sphalerite liberation, significant improvements in concentrate quality were achieved by reducing variation within the process. The implementation of changes in work practices negotiated in the Enterprise Agreement, employee contributions and specialist training also made a significant contribution to the unprecedented improvement in the lead and zinc flotation circuit performance. The results of these plant changes are discussed, along with the suggested scope for further improvement.

Jan 1, 2000

Sasol Roche Blasting Services (SRBS) has undertaken a process of trialing and evaluating the use of the SMI electronic initiating system with the specific purpose of being able to fully quantify the benefits of the system over a pyrotechnic system. After an initial trial of three shots in mid-2001, it was decided that to fully quantify the system, a complete strip would need to be fired using the system so that any losses due to ramps or end walls would be the same for both scenarios. The results have shown a significant improvement over the use of pyrotechnic initiators in several key areas including percentage cast. Through the use of survey results, the increase in cast and subsequent net improvement in blasting has been quantified. These trials have set out to compare each system in comparable situations to determine the real benefits, if any, of the electronic system over the pyrotechnic one. As the percentage cast is relatively easy to quantify using modern survey techniques, it was decided that this would be the principle method of comparison. However, while the assessment only included survey results, any improvement in fragmentation size and consistency would have flow on effects on reduced running and maintenance costs.

Jan 1, 2003

The key elements required to maintain final wall integrity and hence slope reliability are discussed. Failure modes and mechanisms in highly structured rock slopes are then reviewed. The impact of blast disturbance on rock masses in general is discussed and the relationships between the slope failure mode and blast disturbance is then explored. The question of how designers can incorporate such impacts into the slope design process is then addressed. This necessarily involves rock mass strength consideration and two case studies are used to demonstrate a recent dilemma in this regard. Some progress regarding this dilemma has also been reported for the second case study. The major conclusions are that: Slope reliability can be severely compromised if the slopes are damaged by blasting and this impact is not often incorporated into the slope design process. The location and extent of the blast damage will impact some slope failure geometries and failure mechanisms more than others. The concept of failure mechanism specific vulnerability needs to be further developed. The evidence indicates that this aspect is even more extreme for weak ground conditions. The quantification of the reduction in rock mass strength due to blast damage is not well understood and limitations exist with some recent guidelines. The use of the Hoek-Brown criterion for slopes in blocky rock masses requires considerable judgement. Further applied developments in this regard would be very beneficial to the industry. Some promising methods to incorporate blast damage estimates into the slope design process are emerging. It is good business to minimise final wall blast damage otherwise a whole range of issues relating to reduced slope reliability emerge.

Jan 1, 1999

Norway, a country large in area but small in population, has put large effort in protect- ion of its inhabitants in case of war. The Civil Defence has provided shelters for more than 50% of the population. Some of these shelters are put into rock. Since rock installations give large resis- tance against weapon effects and also by advan- tage can be used for several purposes in peace- time, an interesting development has taken place the last decades. In towns and cities you will find sport halls, swimming pools, bowling and shooting ranges etc in rock, which easely can be conver- ted to civil defence shelters. Some typical installations are highlighted in the following.

Jan 1, 1987

By Felice J. J

The assessment of the face velocity of blasts is important in the analysis and subsequent improvement of blast performance. POWERWAVE RADAR is a new tool which will make the collection of this data easier for blast researchers. The data collection technique ensures that a large amount of face velocity data is collected from a blast, and describes the velocity characteristics of the face at a new level of detail. This results in a greater understanding of the effect of drilling and blasting parameters on blast performance. Several case studies are presented which illustrate the collection technique, the type of data generated and how the data is used.

Jan 1, 1992

By A Califice, E Pirard, M Benzaazoua, R Mermillod-Blondin

Image analysis is more and more considered as a powerful tool for quantitative analysis of ores and concentrates. Apart from being very much dependent upon the quality of the imaging principle and the adequacy of the imaging sensor, quantitative image analysis is also the result of a long chain of material, image and pixel sampling strategies. The most reliable way to demonstrate the accuracy and the precision of modal analysis obtained from images is probably to use a blended material with known proportions of pure minerals and confront the results obtained from different analytical tools. This operation has been performed on a series of mineral blends mimicking the tailings of a flotation operation in a plant operating on massive sulfide mineralisation. The intention was to be able to better predict acid mine drainage potential from direct mineralogical observations. Selected sulfide minerals: pyrite (Py), pyrrhotite (Po), chalcopyrite (Cp) and sphalerite (Sp) were mixed as variable amounts within gangue minerals (quartz, calcite, dolomite and siderite). Typical blends contained six to ten per cent (Py); one to three per cent (Po); 0.5 to one per cent (Cp, Sp); 15 to 40 per cent carbonates and 40 to 75 per cent quartz by mass. The 1000 gram blends were carefully sampled and prepared for X-ray diffraction, chemical analysis by ICP-AES and optical microscopy image analysis (OMIA). Results obtained for the different analytical techniques are compared and discussed revealing the limits and strength of each method in the accurate quantification of sulfide and gangue minerals.

Jan 1, 2008

By Williams JK, Bolitho BC

Laverton Gold NL (Laverton) is the first junior Australian mining company to establish a viable mining operation in Indonesia. It successfully commissioned the Rawas plant in Sumatra this year with an average anticipated production of 85 000 ounces of gold equivalent (as gold and silver) per year, a feat of which Laverton is justifiably proud.Working in Indonesia and South-East Asia generally is very stressful for juniors and stretches human and financial resources to the limit - more so than in medium to large companies which can absorb the workload in-house more effectively.

Jan 1, 1997

By Lovett EP, Johnson CR, Dunlop GA

Seven streams of a low tonnage pilot plant operation on Cu/Pb/Zn ore from the Golden Grove Project were continuously assayed using an AMDEL In-Stream Analysis (ISA) system. The ISA instrumentation is briefly described as is the calibration procedure employed. The successful application of this instrumentation in the dynamic environment of a pilot plant operation is discussed. The operational sequence of the Golden Grove pilot plant is outlined along with the original project objectives and how they were achieved by the implementation of ISA. Results for the different complex flowsheets used are discussed, followed by the perceived benefits of installing such equipment in this operation.

Jan 1, 1986

By Remilton D, Raston GR

The low price of nickel which has prevailed since 1982 has dictated that unit production costs must be minimised. Early in the crisis, a decision was made within Western Mining Corporation to reduce unit costs by increased rates of production, not by a significant reduction in manpower. This paper details developments which have taken place at Kalgoorlie Nickel Smelter to enable the higher production rates to be achieved, or to increase energy efficiency. It is significant that most developments were achieved without the need for capital expenditure.

Jan 1, 1985

Carbonation of reinforced concrete is a potential durability issue for vehicular tunnels. This is particularly the case where elevated carbon dioxide concentrations exist and when the design life is 100 years or more. The process of carbonation can result in loss of passive protection to embedded steel reinforcement and initiation of corrosion. Therefore, tunnel design needs to consider the potential for carbonation on internal surfaces and how design life can be achieved in severe environments. This paper examines methods for predicting carbonation and how deterioration can be mitigated through appropriate concrete mix design and construction practices.

Jan 1, 2008

The St George orebodies are situated within the tectonically disrupted eastern limb of the Boogardie Syncline.Highly disturbed rafts of banded chert formations occur within a sequence of felsic volcanic tuffs. The chert forms the hostrock for the gold mineralization.The gold distribution within the irregular and narrow banded chert formations is erratic and patchy. The average gold content of the two orebodies is between 3 - 4 g/t Au.Economic mining of these relative small, irregular and low grade St. George orebodies can be carried out by using a highly selective mining method.The highly selective mining method uses an excavator as the principle mining tool. Blasting, breaking and loading of the rocks is done in a different way than by using a front-end loader as with the conventional mining method. Simple, and therefore cheaper, blasting breaks the rocks and lifts them up without major displacements.

Jan 1, 1984

The United StatesÆ reporting standard for the mining industry for securities purposes is contained in the Security and Exchange CommissionÆs Industry Guide 7. It defines proven and probable Reserves using its own definitions, and prohibits the disclosure of quantitative estimates, for all mineralisation other than those two Reserve categories (though disclosure of Measured and Indicated Resources as quantitative mineralised material estimates is now informally allowed). Similarly, it restricts disclosure of value estimates to Reserves only, which SEC policy generally requires to be on an historic cost accounting basis. The SEC does not maintain a formal Competent or Qualified Person policy. In March 1999, the US-based Society of Mining, Metallurgy and Exploration (SME) released an update of its 1991 guidelines for definitions to be used in reporting of Mineral Resources, Reserves and Exploration Information, closely abiding by the 1997 CMMI recommendations. However, without SEC recognition, reporting under the SME and CMMI definitions is effectively barred for US companies. The SEC intends to adopt the International Financial Reporting Standards (IFRS) of the International Accounting Standards Board (IASB). This will occur within just a few years, when the convergence project for development of the IFRS has reached a satisfactory point. The US is the largest financial supporter and participator in IASB. The Extractive Industries Standard of the IFRS will likely terminate Industry Guide 7. However, the effect of this international replacement will likely be equally restrictive. This could possibly neutralise the benefit of a CMMI-based global reporting standard. SME, the US society encompassing the widest range of mining industry professionals, does not have a Code of Ethics. It has no mechanism for requiring members to abide by a professional standard. SME is presently looking into possible solutions for this deficiency. US-based professional societies that do have a binding Code of Ethics, generally cater to a single profession, and are not just mining industry related. The American Institute of Professional Geologists (AIPG) and the American Institute of Minerals Appraisers (AIMA) are examples. The SME is considering creating a subsidiary body with an enforceable Code of Ethics. To support a CMMI-based global reporting standard, competent persons will need to work across international borders. A standardised mechanism for qualifying and registering competent persons will be needed. National rules and laws must allow competent persons to easily enter countries to perform their work. State issued licenses are increasingly required for much of the work performed in the US mining industry by engineers, geologists and minerals appraisers (valuers). Such licenses are not required by the SEC for Reserve reporting in the US, may not be required for valuation of mineral properties under certain circumstances, and except for real property valuer licenses, they generally do not have a binding code of conduct. However, state licensing of professionals forms a substantial and increasing barrier to interstate trade in professional services, and can be a prohibitive barrier to professionals from outside the US. Any rationalisation of this confusing patchwork of regulations confronting US minerals industry practitioners will only occur as part of larger, national change, hopefully aimed at compliance with international standards and protocols. The US does not have a valuation standard aimed specifically at the mining industry. The Uniform Standards of Professional Appraisal Practice, the national valuation standards, often must be applied to mineral property valuation, but contains no specific instructions for minerals. The author has campaigned against development of minerals valuation standards proposed by US minerals institutes. Instead he encourages the mining industry worldwide to place its support behind the initiative of the International Valuation Standards Committee (IVSC) to include an extractive industries section in its International Valuation Standards (IVS). This should provide a global set of valuation standards for the mining and petroleum industry within two years. This addition to IVS will provide essential valuation standards reference support for the extractive industries financial reporting standard of the International Accounting Standards Board. The IVS has achieved a high level of acceptance in the developed and lesser developed countries of the world. It provides a comprehensive framework of Generally Accepted Valuation Principles for the valuation profession internationally, for valuation of all property or asset types. IVSC is effectively a sister organisation to IASB. The IASBÆs International Financial Reporting Standards (IFRS), previously known as the International Accounting Standards (IAS), reference and quote IVS in some instructions for determination of fair value. IVSC is a non-governmental organisation (NGO) member of the United Nations and maintains liaison with many important international economic, accounting and financial agencies, such as the OECD, IMF and WTO.

Jan 1, 2002

By Skinner A. J, Thoman B. C

The general structure of microprocessors and their method of use is described, and de- tails given of their application in two parti- cular examples of instrumentation for mineral concentrators. One is in a pulp density gauge, and using this example, the way in which a microprocessor-based unit can be made to be self-calibrating is described. The other is in an on-stream analysis detector for uranium in solvent, where a microprocessor is used to re- place a mini-computer.

Jan 1, 1977

TUNGSTEN occupies an outstanding position amongst metals to-day, for by its use modern manufacturing methods have received a wonderful impetus. The important part played by tungsten in the recent war is not generally recognized. It was tungsten steel, in the shape of highspeed tools, that kept our soldiers supplied with munitions of war at more than one critical period. Tungsten added the necessary hardness and durability to various metals which were indispensable for carrying the war to a successful conclusion. In the words of...

Jan 1, 1921

Techniques and results achieved during the excavation of the Melbourne Underground Rail Loop (HURL) are summarised and discussed in the context of the various restraints present in a typical urban construction project. Mechanical methods (as distinct from those utilising blasting)accounted for the bulk of the excavation. Ground support was critical in this particular geological excavation setting, but is not discussed in detail except insofar as it constitutes a restraint to excavation progress.

Jan 1, 1978

By White PJ, Worrad C

The Hunter Valley Coal Preparation Plant and associated materials handling facilities commenced operation in mid 1982. The new plant and coal handling system were designed to integrate with existing mining and preparation plant operations, but also to be flexible to future mining and marketing developments. The system includes: raw coal stockpiles, a 900 tph dense medium/water washing cyclone preparation plant, clean coal stockpiles, a 7.8 km overland conveyor, large finished product stockpiles and a high capacity train loading plant.The plant's development is described with reference to the original planning objectives. Features aimed at providing operational flexibility and performance are emphasised, including the use of; automated stackers and reclaimers, modular plant, distributed PLC control, a single flight overland conveyor, a network of automatic samplers and blending options to assist quality control.Details are also provided of an innovative technique for control of reclaimer rail track forces, stacker and reclaimer anti-collision systems and the use of DC injection braking.

Jan 1, 1985

By G Partington

A regional scale prospectivity model was developed for Papua New Guinea (PNG) to identify areas of porphyry Cu-Au mineralisation. Weights of evidence modeling techniques were used to determine spatial correlations between porphyry Cu-Au mines and predictive maps created from available spatial data. These predictive maps were then combined into a final prospectivity map. Despite limited regional scale data the model has successfully identified areas of known porphyry mineralisation as prospective and has also identified areas where new mineralised systems may be discovered with further exploration. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008