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By Marcello Crispi, Valdir Silva, Juarez Moraes

Companhia Vale do Rio Dote - CVRD is the largest mining company in Brazil and the largest iron ore producer in the world. Serra Geral Mine (SGM) is located at Iron Quadrangle of the State of Minas Gerais, approximately 80 kilometers from Belo Horizonte. Hematite and Itabirite are the two main minerals. A blasting with a spherical charge has been introduced at Serra Geral Mine, an iron ore producer in Brazil, belongs to the CVRD (51%) Kawasaki Steel Corporation (24.5%) others (24.5%), in order to improve fragmentation, as well, load, transportation and crushing productivity. This paper will present the results of a successful blast design with a spherical charge carried out by Serra Geral Mine, the Department of Mining Engineering at Escola de Minas - Federal University of Ouro Preto-UFOP associated to a Blasting Engineering Consultant. The results obtained in the field tests and how it was possible to increase the blast pattern in 53%, which allowed one reduction around 31% in the cost of blasting operation in the Serra Geral Mine, will be discussed in details.

Jan 1, 2002

By K. Kohli

A case study involving a historic structure undermined by longwall mining is presented in this paper. The location of this study is in South Western-Pennsylvania; USA. The structure is 150-years old and subsided 4.5 feet. This paper discusses the mitigation measures taken to reduce the subsidence damage and its effectiveness.

Jan 1, 2002

By S Sandover, D Glenister

Alcoa World Alumina Australia is committed to sustainability principles as a basis of business success into the future. In March 2001, Alcoa Inc chairman Alain Belda announced a set of far-reaching environmental goals for the corporation, with the challenge that they should be achieved in ways that enhance economic and social performance, while substantially reducing environmental impact. Application of Cleaner Production methods is seen as the key to achieving these joint objectives. In Australia Alcoa has launched a co-ordinated effort to accelerate our application of Cleaner Production principles to delivering cost-effective in-process solutions to environmental issues. Our Western Australian Operations are a signatory to the WA Cleaner Production Statement, through which we provide a Cleaner Production Plan to the State Government on a voluntary basis. This paper describes in general terms AlcoaÆs goals, achievements and directions in applying Cleaner Production to enhance business performance in the economic, environmental and social dimensions. Quantification of the benefits and tracking of progress in quantitative terms is a key challenge for the future

Jan 1, 2002

By P. Desclaux, A. Gosselin

"In 1999, PFC measurements were carried out at Alcan smelters as part of a large measurement campaign led by the Canadian Aluminium Association. Side worked prebake (SWPB) and horizontal stud Söderberg (HSS) plants in Arvida were the selected sites. CF4 and C2F6 emissions were measured continuously in the exhaust duct and at the roof vents for a week. In parallel, voltages from four designated cells were recorded at a high scan rate. Results were analyzed and correlations between voltage, anode effect duration and PFC emissions were tested. Some fundamental anode effect mechanisms were proposed and validated with the observations. IntroductionFollowing the international agreement reached within the scope of the Kyoto protocol, voluntary partnerships have been established in many countries especially for the aluminum industry. It is well known that the PFCs that are periodically emitted during aluminum production are the major source of fluorocarbon emissions. The latter are part of the greenhouse gases. In the fall of 1999, Alcan announced that it will adopt, promote and regularly renew a long-term greenhouse gas management commitment at all of its facilities within the framework of the so-called TARGET program that was implemented during 2001. The program is intended to produce on-going reductions, which will be reported publicly on an annual basis.Improvements in the understanding of the mechanisms leading to PFC emissions will contribute to targeting the most appropriate reduction actions. PFC measurement campaigns have been driven toward this end. The first measurement campaign was conducted in 1993 in order to get a picture of the emissions and a base line. The last measurement campaign was conducted in 1999 and its main objective was to compare current emissions with those measured in 1993 and to confirm the accuracy of the predictive equations for the calculation of PFC emissions. This campaign has been conducted by the Canadian Aluminium Association and measurements were made in plants using different technologies. Results of this campaign have already been reported by Bouchard et al. (2001)."

Jan 1, 2002

Resources and reserves are critical inputs into the determination of an operating mineÆs financial results and balance sheets, but how well understood is this fact. Do the investors, directors, accountants and geologists/engineers responsible for preparing or relying on relevant aspects of the end results properly understand the inputs and outputs and the associated risks that may be established. The first step is to understand how financial reports are impacted. The most obvious, and best known, impact is in the calculation of depreciation and amortisation charges against long term assets. In addition, however, there is a requirement to regularly determine whether asset book values are impaired û this is nearly always performed globally by the preparation of a discounted cashflow model for a mine which is usually based on a mine life as determined from the resource and reserve statement û the particular driver here is normally the short and long term production plans. A key aspect of the short term production plan is that it would normally not assume that the reserve and resource statement implies consistent grade, stripping ratios, etc. However, outside of the early years of a plan, more generic assumptions of these variables are often made in conjunction with the reserve and resource statement. Depending on the timeframe of the detailed production plans, this can have a large impact on a projectÆs net present value. Other financial balances that may also be impacted include restoration and rehabilitation provisions, retrenchment provisions and deferred or equalisation stripping accounts. The age old question of whether all reserves should be used or whether some or all of the resources should be included for financial reporting purposes has never been adequately resolved. It is our view that there should be no prescriptive answer to this question but judgement of all professionals involved in the process needs to be included. Furthermore, the company needs to be able to support their conclusions with well thought out and appropriate answers. This may not be in line with the approach that certain accounting standard setters may be proposing or taking, and this paper will outline the current status of global requirement and the likely future directions. Whether reserves or resources are utilised, does not change the key requirement that those preparing or using reserve and resource statements need to understand key aspects. For example: geologists/engineers do they know how reserves or resources will be used? have they imparted information on variability of key drivers such as grade or depth or dilution? do they know that major financial/business altering decisions may be made based on the analysis? accountants do they understand where the numbers have been derived from and the assumptions that may have been made in their determination? do they understand the degree of accuracy (or inaccuracy) that may exist particularly with resources)? do they understand the history of resource reconciliations and what it may mean for the future? directors do they understand the processes undertaken by the company to prepare the financial report and the interaction between the geologists/engineers and accountants? do they understand the potential sensitivity of results to the input variables? Financial reporting is extremely reliant on the use of the reserves and resources, however, the geologists/engineers, accountants and directors do not always understand the interactions between themselves which may lead to misleading public reporting. More education and communication between various parties is needed.

Jan 1, 2002

In February 2001, Kalgoorlie Consolidated Gold Mines (KCGM) commissioned its first full-scale ultra fine grinding (UFG) plant to supplement existing roaster concentrate treatment capacity. This process involves the fine grinding of refractory pyritic concentrate to 10µm, followed by direct cyanide leaching for the recovery of gold. By this means gold is economically extracted from the concentrate without the need to first oxidise the host pyrite. This paper details the history of the project from initial laboratory testwork comparing possible treatment options, to current performance of the 12 tph plant. This includes the cost comparison of the major treatment options, the laboratory and pilot scale UFG performance, the UFG mill selection, cyanide leaching of UFG product, commissioning and plant performance to date.

Jan 1, 2002

By Gustavo E. Armijo

This job was done in Morristown, NJ, with mono fluid system jet grouting for the construction of a new bank building. After the demolition of the existing two story structures, an excavation in loose sandy fill materials was necessary in order to reach the new structure basement level. Due to this jet grouting was selected as a medium to provide both excavation support and permanent underpinning, minimizing the adjacent building settlements. These two adjacent buildings were partially underpinned with a "gravity wall" made with 2 and 3 rows of secant vertical and inclined jet grout columns. Besides the classical jet grouting control methods, during the jet grouting execution, all the drilling and grouting parameters were recorded by a proprietary system called "Slogger". Additionally, after the jet grouting execution, an innovative result control technique was used by means of the application of the same parameter recording system. Some of the production columns were re-drilled and a comparison was made between the obtained drilling parameters and those obtained for the same age test columns. Under the referred existing conditions and in comparison with the conventional underpinning techniques, this project demonstrated that jet grouting, with proper execution and result control, can be faster than them and can maintain the building structural stability and act, at the same time, as a retention system minimizing the existing building settlements.

Jan 1, 2002

By A. L. Boerner

Off-highway tire costs represent a significant portion of the total mining costs in openpit, truck-shovel operations. To extend the lives of tires, the site-specific factors influencing tire life should be investigated Valuable data can be obtained by combining historical operational data captured by a mine dispatch system with detailed tire and maintenance histories. Assuming that failure counts satisfy a Poisson distribution, F-tests can be applied to determine significant deviations from desired or target counts. The methodology developed in this paper can be used to identify the haul routes and loading and dumping zones that have significantly higher incidences of tire failure. Corrective action can then be targeted at these zones by modifying the shovel or truck operator practices; changing the haul route maintenance and clean up practices; or altering the bench, ramp or waste dump design parameters. An example is given of the correlation of tire separation and tire impact failures with haul routes for a fleet of nine Caterpillar 793C trucks in operation at the Chuquicamata Mine in northern Chile. A high incidence of impact failures was observed for the ex pit ore crusher and for tires installed in the left outer rear position on the trucks. The latter was postulated to be due to a preference for drivers to execute right-hand turns prior to dumping. Recommendations were made to revise crusher and dump cleanup practices and investigate the feasibility of super-elevating the surface of dumping zones to reduce ground pressure on the left rear tires.

Jan 1, 2002

By B. K. Parekh, Z. Chen

INTRODUCTION The need for cleaning and recovery of fine (minus 28 mesh or 0.5 mm) coal fraction has increased in recent years. This results from realizing a substantial recovery of ultraclean coal from the waste stream improving overall Btu (heat) recovery, providing extra revenue for the coal industry. Also the potential of using the clean coal so obtained for making coal-water mixture which could replace oil. An additional benefit of recovery clean coal from the waste stream is reducing environmental concern of burning uncleaned coal and in waste disposal. Deashing of coal by physical beneficiation processes is limited by the degree to which ash components are liberated from coal. Conventional processes have been inefficient in terms of Btu recovery, for ultrafine coal. Chemical cleaning methods, which involves leaching of ash material from coal, have provided ultraclean coal at high Btu recoveries, are more costly than the physical cleaning methods. An advanced physical separation technique that appears to address the need discussed above is selective flocculation. This technique which has been successfully utilized in iron ore beneficiation offers the potential of processing fine and ultrafine coal to produce a clean fuel. OBJECTIVES The main objective of the present study is to investigate applicability of selective flocculation technique for recovery of clean coal product from the waste coal slurry supplied by the Peabody Coal co., from their three different coal preparation plants. It is also the objective of the program to conduct preliminary economic study of the selective flocculation process.

Jan 1, 2002

By K. Komnitsas

Activities in the mixed sulphides industry, such as mining and beneficiation, cause adverse impacts to the environment due to excavation, treatment and disposal of low-grade ores and tailings containing residual sulphide minerals. The greatest impact is caused by the oxidation of sulphide phases contained in the tailings and waste rock and the subsequent production of leachates characterized by low pH and high concentration of heavy and toxic elements and sulphates, called acid mine drainage, that contaminates soils, surface- and groundwater. Therefore, rehabilitation of these sites is required in order to render these pollution sources inactive and minimize environmental impacts. The calculation of risk, based on acid mine drainage probability and magnitude of consequences at the disposal sites offers engineers, environmental scientists and authorities a valuable tool for the selection and application of the best remediation technology. Several parameters, such as the chemical and mineralogical properties of the wastes, the most probable pathways the contaminants follow, the potential receptors and the exposure scenarios have to be taken into account. Therefore, risk is the most critical parameter in decision-making regarding management of mining wastes and rehabilitation of disposal sites.

Jan 1, 2002

The Musselwhite mine, located in northwestern Ontario, Canada, has been an underground narrow-vein gold producer since the spring of 1997. As an exploration project at the feasibility stage, much effort was undertaken to generate a geostatistical resource model that would integrate the orebodyÆs geological features, as well as the controls on mineralisation. Today as an operating mine producing over 200 000 ounces of gold per year, reconciliation studies of the tonnes and grades treated at the mill, with the feasibility model, for longer time periods, and with the grade control models, for shorter time periods, show results that are in good agreement. It was clearly demonstrated with the reconciliation to production, that the key to good reconciliation remains in the proper selection and application of the geological resource estimation method. The application of a grade interpolation technique capable of capturing threedimensionally pertinent geological features, as well as accounting for spatial grade continuity, proved to be successful in the predictability of tonnage and grade at the Musselwhite mine. Along with good mine practices, this approach, which was carried through to the operation, has produced excellent reconciliation results. The ongoing reconciliation studies at Musselwhite allow for a constant revision of the grade estimation strategy. In return, this optimisation process adds value by raising the accuracy level of production expectations. As this is an evolving practice at the mine site, further implementation developments are recommended to integrate these reconciliation procedures on a more regular basis.

Jan 1, 2002

By W. A. Wilkinson

In creating a surface mine design, a complicated series of events may be required to meet both mining and environmental objectives. Envisioning the mine at every step of the operation can greatly assist the engineer to identify design and operational problems that might otherwise go undetected until the field operations reach the problem. Providing operations a visual progression of the mine ensures that critical designs generated by the engineer are understood and effectively communicated to operations. Providing the plan as electronic data to the surveyors and/or on-board GPS systems can ensure successful implementation of the design. This paper discusses using computer technology to generate a virtual mine plan and strategies to consider when communicating a virtual mine plan through electronic and paper formats.

Jan 1, 2002

By S. Fawell, H. R. Manouchehri

The main electrophysical properties, i.e., dielectric constant and electrical conductivity, of pure calcite, quartz and wollastonite mineral samples were measured and their triboelectric charge attributes were investigated by contacting minerals particles with different tribochargers made from different materials. In addition the energetic work function values for mineral samples were estimated due to their acquisition charge. Besides, the behaviour of triboelectrically charged of different particle size fractions of mineral samples were inferred. Finally an attempt were made to translate the findings from single mineral systems to a real carbonate ore. The results exposed good prospects to beneficate the examined minerals by triboelectric separation.

Jan 1, 2002

Rotary kiln incinerators are widely used in the incineration of various types of hazardous wastes. However, the complex transport processes within the incinerator are not well understood. Due to large variations in waste types and difficulties in feed characterization, the incineration process meets great challenges in a smooth operation, and expects uncertainties in the process chemistry and emission control. In order to get better understanding of the incineration process, process simulation was made on the kiln behavior by using Computational Fluid-dynamics (CFD) to characterize gas flow, temperature distribution and waste combustion in the incinerator. Temperature measurement was conducted in an operating incinerator to validate the CFD model. This paper addresses the environmental issues related to the hazardous incineration process, and reports the recent simulation results on gas flow and mixing, combustion heat transfer, and potentials to reduce emissions.

Jan 1, 2002

By G Haywood

This paper presents the evolution of the planning, scheduling and mining practices at the Yilgarn Star underground. The paper will concentrate on the principals of æjust in timeÆ and the impact of such practices on mine planning and scheduling and subsequent development and production. The principals of æjust in timeÆ were developed to minimise the impact of creep and time dependent failure of the ground in the ore and hangingwall zones. These zones are characterised by altered schistose material with inherent weak rock strengths compounded, at depth, by the maximum principal stress of the virgin stress field approaching the UCS of the rock mass. Yilgarn Star underground has and continues to develop the æjust in timeÆ methodology to ensure the continued viability of the mine. The mine continues to use longhole open stoping mining methods to ensure high levels of productivity with minimal dilution and at an acceptable cost of production.

Jan 1, 2002

By A. D. Nicholson

This paper presents an approach to quantitatively calculate the neutralization of acid by silicate minerals, based on the chemical kinetics of acid reacting with silicates. This approach incorporates incongruent dissolution mechanisms and the effects of silicate iron content on net acid consumption, and offers guidelines for considering the extent to which specific silicate minerals will react. This approach differs from previous methods of estimating silicate buffering: it is based more on the fundamental chemistry of acid generation, and less on potentially misleading empirical measurements of acid neutralization.

Jan 1, 2002

By M. C. Pietrobon

"A common problem in assessing the applicability of laboratory flotation data is determining how closely conditions during laboratory testing of the ore matches those that occur in a plant. Typical laboratory based investigations do not consider factors such as water quality, pulp temperature and the pulp chemical environment during both grinding and conditioning on laboratory flotation performance. Disregarding these important factors may seriously compromise the validity of conclusions based solely on laboratory experimental results. Furthermore, considering these factors during the flowsheet design stage in the development of new ore resources may reduce financial risk associated with building a new plant. A methodology is described here which embraces these factors in an attempt to bridge the gap between laboratory and plant. The methodology should be considered a vital first step in all laboratory based experimental programs and has implications for fundamental studies on the flotation behaviour of single minerals. This methodology increases the confidence with which findings of laboratory based studies can be transferred to the plant and highlights the effect of variables which may be accessible to manipulation in the plant.Pulp chemical parameters, such as pulp dissolved oxygen demand, pH, Eh, mineral oxidation and solution composition were manipulated in the laboratory by adjusting the duration of gas purging after grinding, the process water input and pulp temperature. A key finding was that matching of the laboratory pulp chemistry to the plant pulp chemistry was dependent upon oxidation after grinding. In turn, mineral oxidation was dependent upon the pH in grinding, water composition and the duration of oxygen purging after grinding. The methodology closely matched the dissolved oxygen demand and surface chemistry of laboratory and plant pulps."

Jan 1, 2002

By J. Um, B. Morin, P. H. S. W. Kulatilake

Development of a three-dimensional mine visualization model for a section of the mine is addressed first. Discontinuity orientation and location information was taken from this visualization model for use in slope stability analyses. Estimated shear strength properties of discontinuities and mechanical properties of intact rock from the rock mass samples obtained from the mine are discussed next. The paper is then focused on the calculated maximum safe slope angles based on the performed kinematic and block theory analyses using the mapped discontinuities at the mine. Finally, the effects of water that exist in the rock mass, tension cracks, slope face inclination, overall wedge height and double benching on factor of safety of wedge stability are illustrated through limit equilibrium slope stability analyses.

Jan 1, 2002

By R. Drummond

The fourth Teetered Bed Separator (TBS) has just been installed in Australia, and trials have been run in many sites. There is a growing recognition of the potential advantages of using TBS technology to treat coal in the ?3+0.25 mm size range, at cut points below 1.60. From these activities, there has been a substantial growth in knowledge with respect to application engineering and operational functions. The paper briefly describes the installations, including flowsheets, and so provides a background to the potential deployment of TBS technology. There are a large number of potential applications for TBS technology, including treatment of fine ROM coal in new plants, or in upgrade situations for re-processing of spiral product, or scavenging coal from coarse tailings. As well, cost effective capacity upgrades are possible by using TBS units for treating the sands size fraction. Issues arising from Australian TBS installations and application engineering are also discussed.

Jan 1, 2002

By C Skublak

The Government of Canada recently passed a new regulation to control the liquid discharges from metal mines in Canada. The Metal Mining Effluent Regulation of the Federal Fisheries Act will come into force within the next six months. As a result the Ontario Regional Office of Environment Canada has developed a compliance promotion program to accompany the new regulation. How the mines implement the regulation will be key to its success. This paper will briefly outline the components of this regulation, including the reporting structure, the discharge parameters and limits, as well as the requirement for the mines to conduct long-term environmental effects monitoring on their effluent discharge. The presentation will give a brief account of the compliance promotion program, and then focus on the spill trends from Ontario mining operations. The province of Ontario has the largest concentration of metal mining operations in the country with approximately 40 active mines.

Jan 1, 2002