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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

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 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

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 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 Siân E. Boyd

Studies of benthic recolonization in the aftermath of marine aggregate dredging in the U.K. and elsewhere are limited and are largely confined to experimental circumstances. Investigations of the physical and biological status of licensed extraction sites in the U.K. at various times following cessation of commercial dredging are very limited, and so judgments as to the likely progress towards environmental restoration and the time-scales involved continue to be based on predictions rather than real data. This field-based research programme was commissioned to enhance the understanding of processes leading to physical and biological recovery of the seabed following dredging, thereby aiding the identification of practices to minimize environmental harm at licensed sites, and to promote rehabilitation on cessation. The outcome of survey work will have the notable benefit of allowing questions about the present status of locations hitherto subject to commercial exploitation to be answered directly, rather than by inference.

Jan 1, 2002

By Marie-Pierre Bourdouxhe-Barnich

Since 1997, in partnership with the Laboratoire Central des Ponts et Chaussées in Strasbourg, ProfilARBED has been carrying out a vast study to qualify the improvements jetting can make to vibratory driving of steel sheet piles, and to understand its effect on the surrounding ground and on the sheet piles themselves. The process basically involves discharging a fluid (mostly water, sometimes in association with air) at controlled pressure and/or flow rate near the toe of the sheet pile being driven. The steel jetting pipes are attached to the sheet pile and are connected to the pumps by hoses. The jet of fluid loosens the soil, thus reducing the resistance at the toe of the sheet pile. Depending on ground conditions, the fluid that flows along the pile can reduce skin friction. Four soil types were involved in our experiments. Each site was instrumented: the driving parameters and the geotechnical characteristics of the soil before and after vibratory driving and jetting-assisted driving were recorded. Each test provided its own particular information which contributes to overall thinking on the matter and is of help to project managers who are often confronted with rapid driving to the final depth.

Jan 1, 2002

By Vladimir M. Korolev

The field studies conducted at the experimental-production sites allowed to develop the technology of arranging drilling piles in loess subsiding grounds over 25 m deep and over 250 mm in diameter, to select optimal compositions of flush fluids, to assess the carrying capacity and field of use of the piles under test and to produce a special equipment. The dependence of the ultimate axial pressing-in load on pile driving into the non-subsiding section, its diameter and method of fulfillment, as well as the ground moisture dependence of the specific ground resistance along the piles' side surface within the limits of the subsiding section were determined. The study results allowed to reduce the length of the work piles and the number of bars in the reinforcement frames. The obtained experimental data enable to give a preliminary assessment of the piles' carrying capacity under complicated engineering-geological conditions of subsiding grounds.

Jan 1, 2002

By Lennart Mukka

The Kiruna Mine in Sweden currently has three ventilation systems. The first two (a new and old system) serve the production areas. The third system is used for the facilities on the former main haulage level 775. That area includes offices and workshops for load haul dumpers (LHD) and drill rigs. The third ventilation system also covers the crushing and haulage on level 1045. At the present time, the total airflow for the mine is 1,600 m3/sec(3.4 million cfm). The current system serves the levels above the 775 level. The new one is for the levels between 775 and 1,085 m (2,540 and 3,560 ft), which are needed for the new ore body. When all of the production is below level 775, the old ventilation system will be closed down.

Jan 1, 2002

By C. Menidiatis

The first cement plant of TITAN Cement Co was founded in Elefsis in 1902. It was the first cement industrial facility to operate in the Balkans and in the Eastern Mediterranean region. Currently have four cement plants in Greece producing 5.4 million tons per annum, and 25 ready-mixed concrete sites producing 1.4 million m3 annually. It has a total of 20 quarries, 14 of which are producing materials used in the making of cement while the remaining six produce aggregates used in the production of ready-mixed concrete. All plants in Greece are accredited for ISO 14001. The restoration of quarries began in 1976 at the company?s limestone quarry of the Patras plant, and was soon extended to all quarries. At that time, a department responsible for all environmental issues was established. To date, over 700.000 shrubs and trees have been planted and maintained at quarries, plants and ready-mixed concrete facilities, while over 100,000 trees have been donated to municipalities, communities, customers and to the Greek state.

Jan 1, 2002

By Trevor I. Addenbrooke

Stress reducing piles were used for the first time at the Queen Elizabeth II Conference Centre near the Palace of Westminster in London, UK. The inclusion of these piles directly beneath heavily loaded columns was to reduce the high anticipated bending stress in the foundation raft, and to eliminate local yield of the London Clay beneath the column locations. Load cells were placed in one of the stress reducing piles during construction. The data showed that the pile carried about 30% of the column load. This can be contrasted with conventional piled raft design where the pile carries upwards of 80% of the column load. The build up of load on the pile and pile displacement have been accurately reproduced using coupled finite element analysis. These numerical results demonstrate the value of geometrically simple axially symmetric analyses for modelling a pile-enhanced raft. On site, excavation preceded construction of the raft and subsequent pile loading. Failure to model this construction sequence caused the shear strength to mobilize at the base of the pile first, during loading, whereas following the construction sequence caused the shear strength to mobilize at the top of the pile first.

Jan 1, 2002

By K. Spence

"The notion of “value” has always been a subjective and contentious issue. Indeed, value is in the eye of the beholder. There are as varied methods and practices for valuing property, as there are industries in which they are applied. For example, there is replacement value, insurance value, salvage value, appraised value, book value, and fair market value, to name a few, although in the mining industry, valuations usually refer to fair market value.In the Canadian mining industry, at present, there are no comprehensive regulations or guidelines that specify which approaches or methods are appropriate for use in the valuation of mineral projects. In January 1999, The Mining Standards Task Force of the Toronto Stock Exchange and the Ontario Securities Commission recommended that the Canadian Institute of Mining, Metallurgy and Petroleum (CIM) establish a committee to review and advise on approaches and methodologies for the valuation of mineral properties. Among the approaches to be considered are included the following: the discounted cash flow approach, the cost approach, the option pricing approach and the market comparables approach. In addition, methodologies differ depending on whether the project is at the exploration stage or the producing stage.The CIM Special Committee on the Valuation of Mineral Properties (CIMVal) expects that its final report will form the basis for a Canadian code or standard for the valuation of mineral properties."

Jan 1, 2002

By T. Mudder, R. Cellan, R. Waterland, J. Whitlock, B. N. Nelson

The effectiveness of anaerobic in-situ biological treatment for the immobilization of selenium, molybdenum, and uranium in an alluvial aquifer was examined using long-term column tests. A series of organic substrate and nutrient combinations were tested to determine removal effectiveness, optimum supplement concentrations and ratios. Final column testing was conducted to determine the chemical stability of the treatment by-products/treatment compounds by dosing the columns continuously with elevated redox untreated alluvial groundwater.

Jan 1, 2002

By R Gilbertson, N Freeman

Metallurgical accounting is key to the control and production planning process of any mining operation. This is even more crucial for complex operations involving mining, concentration, smelting, refining and marketing. The tracking of multiple metal product and contaminant components through the operation can improve process predictability and inventory management. Appropriate use can be made of æhigh quality dataÆ for strategic reserve utilisation, mining operations, milling operations, etc. This information enables the optimisation of all aspects of the mining and processing operations. This case study discusses a metal balance implementation for WMCÆs Olympic Dam operations; a large integrated mining, concentration and refining operation, which used an existing off the shelf statistical data reconciliation package developed for the oil industry. It was extended to track and balance the metal co-products across the entire integrated mining, mineral processing and refining plant. The key benefits discussed are tight integration with existing data collection systems, formalisation of previously informal processes, and leveraging the development and support available for a widely used package. The project provided a solution for the site metallurgical balance spanning the mine and processing plant. The solution facilitates a bridge between the planning and production worlds, using a common data model across the site.

Jan 1, 2002

By A. Boominathan

The behaviour of single piles under lateral dynamic loading is very critical and the study is still a current field of research since 1950's. Though many methods have been developed analytically to estimate the dynamic lateral stiffness, very limited dynamic testing on full scale piles were carried out to study the response of piles under lateral dynamic loading. Hence, field lateral dynamic vibration tests are conducted on driven precast concrete square pile of 400mm size and driven cast in-situ concrete piles of 400mm and 500 mm diameter at a petrochemical complexes site at Haldia (India). The results of steady state and free vibrations tests are discussed herein and compared with the response of the piles estimated from PILAY.

Jan 1, 2002

By D A. Kepert, I J. Tehnas, M A. Pudovsk

BHP Billiton (BHPB) was the first company to start iron ore mining in the Pilbara at Mt Goldsworthy in 1966 through Goldsworthy Mining Limited (GML - then Consolidated Goldfields Australia, Cyprus Mines and Utah). Operations later started at Newman on Mt Whaleback in 1969 with the Mt Newman Mining Joint Venture (MNM û then comprising American Metals Climax û AMAX, Colonial Sugar Refineries û CSR and BHP). In 1986 it acquired majority ownership of MNM, and at the same time the previously 100 per cent BHPB owned but undeveloped Yandi property came on board. Purchase of Jimblebar (formerly McCameyÆs Monster) occurred in 1990 and full ownership of Goldsworthy followed in 1991. With the exception of Jimblebar (100 per cent owned), all mines are now 85 per cent BHPB and the balance with Itochu and Mitsui. This evolution of the company resulted in an eclectic mix of mines/ores, each with their varied exploration and evaluation histories. Discussion of some aspects of these histories, and reflections on changes in exploration-related activities with particular reference to discussion of advances in geological understanding since the 1960s forms the basis of this paper. BHPB presently has open cut mines at four main centres û Newman, Jimblebar, Marillana Creek (Yandi) and Yarrie û and is currently developing the former GML Area C near Yandi. With the exception of NewmanÆs Mt Whaleback mine and immediate satellites, all are contract operated. Ore is carried on BHPB railroads (696 km total) for export through the companyÆs Nelson Point or Finucane Island shipping facilities at Port Hedland. Some is directed to the BHPB Boodarie Iron hot briquetted iron plant near Finucane Island. Over 73 Mt of ore was produced by BHPB in calendar 2001, and the company has now mined over 1500 Mt in Western Australia since their operations at Yampi Sound first started in 1956.

Jan 1, 2002

By E. Dendy Sloan

An overview of hydrate properties is given, with emphasis on unusual deviations from ice, the most common solid water form. Reliable sample preparation and reproduction of in situ hydrates provide the foundation for all hydrate science and engineering. Relations are given to connect the three domains in the title: (1) micro-scopic properties measured with Raman, NMR, and diffraction spectroscopy, (2) meso-scopic properties measured with single crystals, and (3) macro-scopic properties measured with pressures, temperatures, volumes, etc. A principal illustration relates micro-scopic and macro-scopic domains. Experiments provides the basis for improving statistical thermodynamics model for these compounds. To date, this model is one of the most commonly used industrial statistical thermodynamics applications, based upon the classical model of van der Waals and Platteeuw (1959). Microscopic measurements and simulations indicate model assumption improvements, resulting in the next generation of the statistical thermodynamics for improved macroscopic property prediction.

Jan 1, 2002

By M. England

Test equipment has been developed to record automatically both the displacement of the pile head and the load applied during a conventional maintained load pile test. Some systems also have, in addition, been fitted with the facility for maintaining the applied load, as set by the operator, at very constant levels. The advantages are both commercial and technical, but a well trained operator has to be in attendance to control the test. Since typical test specifications in the UK require more than 19 hours to complete, it became inevitable that at least one equipment operator remained on site to expedite the test for its duration. Although electronic measurement and data logging of load tests may be more safe than previous direct observation of dial gauges. A single person remaining on a construction site alone is not to be recommended, even if they are just supervising the test. Further development of the testing system produced equipment which will perform the entire test specification as required without operator intervention. To achieve this, full automation is employed. The patented method particularly addresses the safety requirements and by using additional sensors, detects any uncharacteristic behaviour of the pile under test or of the reaction system and the equipment takes appropriate action in a controlled and safe manner. The quality of test data returned from these automated systems is a key element when analysing pile behaviour with models such as CEMSOLVE? and TIMESETTM. These analysis methods often indicate ground disturbance resulting from installation technique and have allowed pile design to be optimised using actual field data rather than theoretical considerations alone. An additional feature is remote access, this allows the data recorded to be transferred and the progress of the test to be viewed from practically any location. This permits experts to view the data 'live' and allows rapid diagnosis of any problems with the expected pile behaviour.

Jan 1, 2002