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By C. A. Morais

The present work describes the development of an efficient and relatively simple process to obtain high grade CeO2 from a mixed rare earth chloride solution. The process involves cerium oxidation and precipitation by addition of a KMnO4-NaCO3 solution. The experiments were carried out at room temperature (25 1° C). The results indicated that the major parameters affecting cerium recovery are the molar ratio of KMnO4/Ce, the initial acidity of the chloride feed solution and final pH of Ce(OH)4 precipitation. In strong acid solutions (pH < 1), the oxidation of Cl to Clo took place in addition to the oxidation of Ce(III) to Ce(IV), so increasing the permanganate consumption. Conversely, low acidity (pH >3) led to coprecipitation of the other rare earth elements. Under the selected conditions, cerium was selectively precipitated as ceric hydroxide, together with some manganese dioxide. Further purification was carried out by the dissolution of Ce(OH)4 in HCl, followed by precipitation as cerium carbonate. The filtrate was neutralised with a Na2CO3 solution in order to recover the associated rare earth elements for further separation. The final product, assaying 99.7 % CeO2, was obtained with a recovery of nearly 100%.

Jan 1, 2003

By Dennis Molvik, Omar Fulton, Chris D. Breeds, Don Gonzales

This paper presents and describes the South Interceptor Parallel Phase III Contract C93012C, which involved construction of a nominal 2.7 m (9-ft) finished diameter sewer conveyance using both pipe jacking and conventional tunneling methods. Earth Pressure Balance (EPB) excavation was required to minimize the potential for settlement beneath a main rail line, overpass, sensitive wetland, areas of contaminated soils, and nearby structures. Ground conditions predicted in the Geotechnical Baseline Report included low plasticity, clayey silt (40 to 10%) and silty sand (60–90%) with pieces of wood such as logs, stumps, branches and other tree fragments. Soil cover ranged from 2.7 m (9-ft) to 5.4 m (18-ft) over the tunnel crown with a groundwater table between 1.5 m (5-ft) and 3.7 m (12-ft) deep.

Jan 1, 2003

By T P. Hynes

Submarine tailings disposal is conceptually an attractive option for managing reactive mine wastes in coastal regions by virtue of reduced sulfide oxidation under a water cover and no infrastructure to maintain after mine closure. However, the lack of detailed knowledge of metal leaching, dispersal of fine tailings and biological impacts in the marine environment has led to no operating permits currently in effect in Canada. Detailed chemical and ecotoxicological assessments at two historic copper mine sites (Little Bay and Tilt Cove) in the north coast of Newfoundland with tailings disposed in an estuarine to shallow (=100 m) marine environment have demonstrated reduced reactivity of sulfidic tailings when submerged under water. Only non-acute toxicity is detected in biota inhabiting the immediate vicinity (A review of another historic shallow marine tailings operation in the southern tip of Vancouver Island (Jordon River) with a high-energy setting also reveals problems with unconfined tailings dispersal and temporal biological impacts. Documented studies at two deeper (140 - 360 m) marine tailings disposal operations at the northern tip of Vancouver Island (Island Copper) and northwestern coast of British Columbia (Kitsault) again illustrate imperfect predictions of tailings re-suspension and dispersal. At these sites, bioaccumulation of tailings-derived metals appears to be minimal. There is evidence of rapid re-colonisation of the tailings surface by benthos but of different species than the original population. Integrating these observations with reported metal fluxes and biological diversity associated with submarine hydrothermal vents, the risks and benefits of deep-sea (>1 km) tailings disposal are discussed. To determine if submarine tailings disposal in deep, confined basins on the seafloor is environmentally friendly, detailed multi-disciplinary research incorporating physical, chemical, biological and toxicological components will be indispensable.

Jan 1, 2003

By Debbie Nakamura, Daniel Tempelis, John E. Shamma

The Metropolitan Water District of Southern California established a Board of Consultants to assist them in administering the design and construction of the Inland Feeder Program tunnels. The Board acts as an expert review body for the owner, looking at key issues that can potentially impact the success of the program. The use of the Board evolved over the life of the project, and its composition was modified to better address the needs of the owner, and the Program requirements. The experience, function, and value of such a board is analyzed and discussed in this paper.

Jan 1, 2003

By Hugh E. Cronin, Joseph J. Coluccio

The Columbia Slough Consolidation Conduit Project is a 12 ft. 0 in. inside diameter—15 ft. 4 in. excavated diameter tunnel, 8,300 lf. in length. The tunnel is divided in two parts a 4,460 lf. reach to the West and a 3,770 lf. reach to the East separated by a flow regulation structure in the middle. The project was built for the City of Portland, Oregon Bureau of Environmental Services (BES) by the Frank Coluccio Construction Company (FCCC) Seattle, Washington under a $22,600,000.00 contract starting in 1998 and completing the contract in 2000 at a total cost to the City of $25,448,000. An increase of 12.6% from the original contract. The tunnel was constructed in an alluvial sediment that ranges up to 1,500 feet thick. The sediment varies from ?ne silty sand and sandy silt (SM-ML) to coarse sand and gravel (GP-GM) with varying quantities of cobbles and boulders. Most of the tunnel was constructed above the water table although one reach of almost 1,000 lf. had water to above the tunnel crown. The contractor, FCCC, used a Lovat 15 ft. 3 in.900 hp shielded TBM with multiple doors (4) of variable opening to excavate and support the tunnel. Tunnel supports were 5 in. WF 16 lbs. per foot at 4 ft. spacing and4 in. Douglas Fir lagging. Tunnel excavation was worked in 10 hour shifts with additional equipment maintenance and repair on the off time. The original Geotechnical Design Summary Report (GDSR) established a baseline for contractual purposes of slightly over 5 boulders (between 12 in. and48 in.) per foot of tunnel. (Table 1) At the pre-bid conference, three test pits were excavated to approximately tunnel invert, one at each end of the project and one in the middle near the flow regulation structure. The test pits encountered a few boulders but did not seem to support the five boulders per foot (varied from one boulder per foot of tunnel to eight b/lf.). Subsequent to the pre-bid meeting and the test pits, BES issued any addenda which changed the baseline boulder quantity in the GDSR to 1.7 boulders per foot of tunnel (varied from0.2 to 3.5 boulders per foot) a reduction of 67% from the original baseline. It is interesting to note the two separate tunnel reaches and how they were evaluated in the GDSR. Originally the Eastern portion of the work was projected at5.08 boulders per foot of tunnel and the Western portion at 5.30 boulders per foot of tunnel for a variance of less than 5%. In the revised quantity the Eastern portion was projected at 2.01 boulders per foot of tunnel and the Western portion at 1.42 boulders

Jan 1, 2003

Six pioneers of the American mining industry will be inducted into the National Mining Hall of Fame on Saturday, Sept. 13, at the Museum Convention Center in Leadville, CO. The 16th annual Mining Hall of Fame induction banquet will begin with a reception and open house at 5:30p.m., followed by the dinner and program at 7 p.m. The six inductees include James M. Gerstley, the only living member, and George O. Argall, Jr.; John F. “Leadville Johnny” Campion; Charles R. Nailler; Edwin N. Pennebaker and Russell L. Wood.

Jan 1, 2003

By D. Rajkovic

Geothermal sources are exploited in two basic forms, i.e., the primary form of thermal energy and that converted into electrical energy by using an adequate thermodynamic cycle. There is a possibility of applying several processes for the conversion of thermal into mechanical or electrical energy, which depend on the thermodynamic characteristics of the geothermal water. Geothermal sources in Croatia do not contain steam of relatively high temperature, like in Italy, although both countries are nearly in the same position with respect to geothermal belt. Geothermal sources in Croatia are mostly so-called low-temperature geothermal sources with water temperatures lower than 100°C (Cubric and Jelic, 1993). A few of them have been exploited, although the percentage of utilization of their available power is still very small. The low-temperature potential is a major disadvantage when it comes to power generation, since state-of-the-art geothermal power plants require reheated steam or hot water to operate. There is a common belief that the optimum way of exploiting low-temperature geothermal sources is heat generation. Therefore, this analysis is especially aimed at potential users and showing the technical and economical possibilities of using low-temperature sources for conversion of thermal energy into mechanical work and electrical energy.

Jan 1, 2003

By Silvano Morelli, Giovanna Cassani, Renzo Bindi, Antonio Nicola

More than 70 km of main line and service tunnels have been excavated to date for crossing the Apennines between Bologna and Florence. A new design and construction approach, known as Analysis of the Controlled Deformation in Rock and Soils, (ADECO-RS), was adopted to tackle the extreme heterogeneity of the ground and the particular stress-strain conditions. The goal of this system is to obtain constant and predictable full section advance rates, even in very poor geology, with the highest possible level of safety and reliability. The execution of this gigantic project required the mobilization of 21 job-sites, with the concurrent operation of 30 excavation headings. The global production rates confirm the high quality of the design and the high level of industrialization reached during the construction stage, levels not previously obtained in similar conditions, using other approaches such as NATM.

Jan 1, 2003

By Patrick R. Taylor

The synthesis of high-purity ultra-fine barium strontium titanate powders (BST: BaO6Sro.4TiO3) has been performed in a non-transferred are D.C. thermal plasma reactor. Slurries of aqueous solutions of dissolved barium and strontium nitrates and solid titanium dioxide powders were used as precursors. Oxygen and argon were used as carrier gases, and pure argon and combinations of argon and nitrogen were used as plasma gases. The plasma torch power was varied, as well as the oxygen flow rate and the total molar concentration of the precursors. A graphite plate was designed to protect the torch electrode and lower the level of impurities in the product. A thermochemical analysis of the Ba(NO3)2-Sr(NO3)2-TiO2-H2O-O2 system was performed to predict the conditions for the formation of BST and the feasibility of the reaction, The powders collected from the different sections of the reactor were characterized using Transmission and Scanning Electron Microscopy, X-Ray Diffraction, and ICP chemical analysis. The powders produced showed high conversion to BST, ultra-fine particle size (< 30 rim) and high purity, which makes this a potential process to produce ceramic materials for electronic devices.

Jan 1, 2003

The 2003 SME Annual Meeting and Exhibit will take place Feb. 24-26 in Cincinnati, OH. The meeting will feature a host of special symposia and programming geared toward the industrial minerals and aggregate industry sectors. This programming focus is particularly relevant for this annual meeting, as it will be hosted in the center of America’s transportation hub and industrial mineral center. Cincinnati, located on the Ohio River, is key to the movement of America’s supplies and construction material needs.

Jan 1, 2003

By A Williamson

The New South Wales Department of Mineral Resources objective is to use data and information to undertake a detailed analysis of incidents and accidents to identify risks so that the predictable can be foreseen and avoided. The Department of Mineral Resources has established a computerised database called COMET (COmmon Mines EnvironmenT) to capture information on accidents incidents, inspections, audits and accreditation in improving safety and environment performance. This data together with data from Coal Mines Insurance and WorkCover NSW is being used to provide trend and comparison information. The NSW Injury Risk Management Research Centre at the University of NSW has been engaged by the Department to collate and prepare a detailed analysis of the data. Through this process, five areas have been identified for further research. These being: electrical energy, mechanical equipment, work environment, hours of work, and contractors involvement accident and incidents. The paper covers: the establishment of a mix of performance measures for the industry to indicate whether the safety performance is improving; the provision of data to provide useful comparisons and benchmarks against which companies can compare performance; the development of positive performance measures; the findings and outcomes of the detailed analysis of electrical energy; shocks; the provision of information to industry; an outline how the data is being used to determine departmental; operational priorities; and future plans to undertake research into the other areas identified.

Jan 1, 2003

By P R. G Milne

A risk-based approach to optimising pit wall slope angles was trialled in the design of a 60m deep open pit in extremely weathered and distinctly weathered materials in the Kalgoorlie area. The pit used for this approach was Stage 1 of a three-stage open pit project. The Stage 3 pit will require long term stability, as it will contain the portal for a long life underground project. Information from failures induced by steeper wall angles used in the Stage 1 pit would be valuable in predicting and preventing long-term stability issues in Stage 3. In this approach, the pit wall slopes are based not on the normal factors of safety, but on the assessment of the probability of failure and the direct and indirect costs of dealing with the failure when it occurs. In this example, the benefits and risks of adopting steeper wall angles were compared in a series of graphs. These charted the increasing probability of failure and simultaneous decreasing factors of safety with increasing pit wall slope, and the range in the possible volumes of circular failures for increasing wall angles. These were brought together in a graph showing the potential excavation savings (in BCM) and the probable cost of a failure (probability of failure times the probable volume of the failure). The resulting pit design was based on the project Mining EngineerÆs semi-quantitative assessment of where and when a higher risk of failure was acceptable and where it was not acceptable as it may have unduly affected the integrity of haul roads or production. The design incorporated wider than normal berm widths to accommodate anticipated failures and to enable modification of the wall configuration if required. Several re-designs were required during the life of the project in response to aggressively induced failures. It is considered that this risk-based approach provides a practical route to optimal pit design and operation but it requires an experienced, dedicated and efficient mining team for it to be implemented with benefit.

Jan 1, 2003

By K Matsui, R N. Gupta, H Shimada

Roof falls and failures of powered supports were major threats at longwall face. Abnormal geological conditions were caused roof falls and shield damage. Therefore continuous monitoring and analysis of strata behaviour was imperative on real time for forecasting adverse behaviour. Novel PXI instrumentation system was successfully developed for continuous monitoring and analysis of supports pressure, leg closure and gate roads convergence. However, this paper briefly examines the novel gate roads convergence monitoring system with field applications.

Jan 1, 2003

This paper reviews rehabilitation, closure, and post-closure management of the Tui, Golden Cross, and Martha Mines, all of which are located in the Waikato Region of New Zealand. There was no requirement for rehabilitation of the Tui mine, which was abandoned in 1973. There was a requirement to rehabilitate the Golden Cross mine. Mining at that site ceased in 1997, and rehabilitation is now well advanced. When first approved, there were some requirements for rehabilitation of the Martha Mine, but when reconsented in 1998, those were extended, and in addition a requirement for post-closure management was included. As a result, a Trust, funded by the mining company, has been established to take long-term responsibility for the site following completion of closure. The different rehabilitation/closure requirements at each of these sites illustrates that we have learnt something from the experiences of the past.

Jan 1, 2003

By J. P. Piguet, Y. Wileveau

ABSTRACT : An experimental programme for damage assessment was performed in the vicinity of the main shaft of Andra’s Underground Research Laboratory, currently under construction in the East of France, when the shaft is crossing the Kimmeridgian marls between 80 and 100 m depth. The mechanical behaviour was analysed by mean of convergence and displacement measurements. The disturbance into the wall was assessed using numerous methods such as measurement of sonic velocities, permeability measurement and VSP measurement in radial boreholes. The intensity of the damaged zone is low, and its extension does not exceed 0.5 time the radius of the shaft. It does not seem to depend on blasting patterns. ZUSAMMENFASSUNG : Ein Forschungs- und Versuchsprogramm wurde aufgestellt, um die beschädigte Zone im Bereich der Kimmeridgemergel zwischen 80 und 100 Meter Tiefe beim Zugangsschacht des im Bau befindlichen Andralabors im Osten Frankreichs zu berechnen. Das mechanische Verhalten der Formationen wird auf der Grundlage von Konvergenz- und Verschiebungsmessungen ermittelt. Verschiedene Messmethoden, wie z.B. mikroseismische Geschwindigkeite Messungen, Permeabilitäs- und Beschleunigungsbestimmungen in strahlenförmigen Bohranordnungen, erlaubten die Ermittlung des Beschädigungscharakters der Schachtwand. Die Intensität der beschädigten Zone ist niedrig, ihre Ausdehnung übersteigt nicht die Hälfte des Radius des Zugangsstollens und scheint unabhängig vom Schema der Sprengstoffanordnungen zu sein. RESUME : Un programme expérimental visant à évaluer la zone endommagée autour du puits d’accès du Laboratoire de Recherche Souterrain de l’Andra actuellement en construction dans l’Est de la France a été mis en œuvre lors de la traversée des marnes du Kimméridgien entre 80 et 100 m de profondeur. Le comportement mécanique des formations est évalué à partir de mesures de convergence et de déplacements. La mise en œuvre de nombreuses méthodes, telles que des mesures microsismiques, des mesures de perméabilité et d’accélérométrie en forages radiaux, a permis de caractériser l’endommagement en paroi du puits. L’intensité de la zone endommagée est faible et son extension ne dépasse pas 0,5 fois le rayon du puits. L’endommagement semble indépendant des schémas de tirs testés.

Jan 1, 2003

By I Gipps

The mining industry has come through a period of major change in community expectations regarding safety and environmental impact and these changes can be expected to continue in the future. These changes are ultimately reflected in Government regulations and industry safety standards and form the basis of the ælicense to operateÆ. Equally, advances in technology have made possible new equipment and processes either available now, or close to completion, that will allow mines to meet these more stringent expectations if properly introduced. Changes in technology provide opportunities for mine management to introduce new systems that will remove people from hazardous areas and lead to improvements in the ætriple bottom lineÆ. In a longer time frame of five to ten years, novel and advanced technologies that are currently being developed will deliver new mining methods and conversion of presently uneconomic resources to ore. This is consistent with the time frame required to develop a new mine from discovery. Strategic decisions can be taken now by mine designers to enable the introduction of these major technology changes. Examples of both practical and strategic opportunities are drawn from the integration of rock cutting/blasting, automation, electronic communications and new mining methods. This paper discusses emerging industry trends, changes to legislative framework and some practical choices for existing and imminent technology.

Jan 1, 2003

As the awareness and concerns on subsidence issues increase, there are clear, challenging and credible community expectations for responsible mining, public safety, optimal resource recovery and effective land use and environmental management, coinciding with a changing and strengthening regulatory environment being implemented by the NSW Government. This paper discusses a number of areas where cultural changes in the mining industry will assist with improved subsidence management to meet the enhanced standard.

Jan 1, 2003

By Ian Orford, Peter Radziszewski, Lud Strah

"An autogenous grinding circuit was commissioned at the Brunswick concentrator in October 1998. The AG mill was subsequently converted to SAG operation in May 1999 for a number of reasons. The mill had 48 rows of the NORCAST top-hat integral lifter/liners configured in Hi-Lo mode. A charge motion simulation study, the results of which are the subject of this presentation, was initiated to develop a better understanding of SAG mill behaviour. Using a design of experiments approach, a lifter face angle was determined that would increase mill power draw. Once determined, lifter profiles were modified and installed in July 2001, and a second set installed in February 2002. Resulting changes in mill power consumption are presented.INTRODUCTIONThe Noranda Inc. Brunswick Mine, located near Bathurst, New Brunswick, is a large lead/zinc mine and began milling ore in 1964. The ore is massive sulphide with approximately 20% valuable minerals, 60% pyrite and 20% silicates. In October 1998, an autogenous grinding circuit was commissioned at the Brunswick concentrator (Cooper, Orford, Larsen, 2001).At the time, the autogenous grinding circuit replaced existing surface crushing plants, fine ore storage, rod mills and primary ball mills. The 8.54 m diameter x 4.27 m long (EGL) ANI mill was subsequently converted to SAG operation in May 1999.The mill had 48 rows of the NORCAST top-hat integral lifter/liners and was operated initially with all shell lifters at the same height. Following problems with packing and abnormal wear pattern, the profile was changed to a high-low configuration.Further, it was found that over the life of the lifters, mill power draw and throughput varied considerably. Although a change in mill power draw was expected following lifter replacement (predicted during mill design to be in the order of 300-400 kW), the replacement of the worn lifters with new high lifters resulted in mill power draw decreased by some 1000 kW."

Jan 1, 2003

The spatial distribution of copper grades at the Mansa Mina project is highly variable due to the presence of high grade copper/silver/arsenic breccia bodies. Copper grades within the breccia bodies tend to average about 4.5% copper while grades in the surrounding stockwork average about 1.0%. The breccia is known to occur in the vicinity of significant controlling structures, however, the outline and therefore the thickness of the bodies are far from regular. Due to the high grade of these bodies a significant proportion of the value of the project is derived from the breccia tonnages. The irregularity in the outlines/thickness translates into an uncertainty in the breccia tonnage and therefore in the value of the project. Acknowledging the economic importance of the breccia bodies and the risk associated with the breccia tonnage uncertainty, significant additional drilling has been proposed to both understand the spatial distribution of the breccias and reduce project risk. The costs associated with this additional drilling are not inconsequential; thus, a reasonable question is ‘what value is derived from this additional drilling’? To obtain an answer to this important question, a simulation approach is applied. First the deposit is simulated using the existing drilling and the uncertainty in the resource is defined. Next the proposed drilling program is simulated and the simulated data are added to the existing data. Using this expanded data set a second simulation of the deposit is created and once again the uncertainty in the resource is defined. Using this approach, the reduction in the uncertainty in the resource can be determined. To convert this reduction in uncertainty (or reduction in risk) in the stated resource into a dollar value, a method of defining the increase in the project rate of return necessary to account for risk is presented. Using the two different rates of return, the difference in project NPV and hence the value of additional drilling is determined.

Jan 1, 2003

By T. F. J. Hälbich

Namakwa Sands aims to conserve environmental resources and prevent or minimize environmental impacts from its operations. The challenge faced by Namakwa Sands is the rehabilitation of the arid winter rainfall Strandveld and lowland Succulent Karoo vegetation zones affected by its mining activities. Extensive experimentation with different rehabilitation methods resulted in the development of an effective rehabilitation programme. The use of topsoil as a seed bank and shade-cloth as windbreaks have significantly aided the rehabilitation process. The aim of the programme is to stabilize the soil environment so as to allow the germination and development of the local plant species. The ability to control wind erosion is critical to the success of the rehabilitation effort. A programme of biodiversity audits has been started to measure the recovery of plant species in the rehabilitated area. The principle of continuous improvement, coupled to site-specific rehabilitation studies, is applied to enhance the rehabilitation programme.

Jan 1, 2003