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By M. Kawulak

The necessity to protect the environment can limit mining activities and make some areas less attractive for the prospecting and exploration of mineral deposits. In Poland, the main environmental factors that restrain Irumng are: 1. Regional A Protection of the landscape B. Protection of ground water from contamination and depletion 2. Local A Conservation of fertile soils B. Conservation of forest resources C. Preservation of natural, cultural, and historical monuments The regional factors listed above that can limit mining are presented on a map of Poland. These data, combined with maps of known and potential mineral deposits, make it possible to delineate general levels of limitation for various mining-related activities varying from "no existing environmental limitations" to "no allowed industrial activity" As an example, a compilation of such data is presented for lignite exploration and mining in Poland. Lignite deposits occur within Upper Paleocene to Upper Miocene clastic strata at depths ranging from a few to 300 m. The thickness of the lignite is generally a few meters, but can locally reach over 100 m within grabens. As a result, the overburden-to-lignite thickness ratio varies from less than 1 to over 20. Within the same Tertiary strata, and within overlying Quaternary strata, several aquifers exist that produce good quality water that may be contaminated or depleted during lignite mining. The protection of these ground waters is the main factor limiting lignite mining and should be addressed in mining and environmental policy and planning.

Jan 1, 1996

By Robert M. Valentine, Randall L. Lentell

Interpretive geotechnical investigations were performed for the construction of approximately 15,250 m (50,000 ft) of wastewater interceptor tunnels in Austin, Texas. Subsurface materials consist of claystone (or clay shale), siltstone, altered volcanic tuffs, chalk and limestone. Special conditions include multiple crossings of Onion Creek with cover ranging from about 1/2 to 3 m (2 to 10 ft.), and the potential for mixed-face conditions consisting of water-bearing gravels overlying clay shale or siltstone. The methods and results of the geotechnical investigations are discussed and the inferred construction conditions are compared to those encountered during tunneling. A suggested format is presented for interpretive geotechnical reports for underground construction projects.

Jan 1, 1985

By L Baumgardner, A. V. Castelli

Barite In 1987, United States mine production of barite increased 15.870, consumption (sold or used by grinding plants) increased by 6.97, and imports are estimated to have fallen by 19.57. World mine production decreased by 137, according to the US Bureau of Mines. The value of US produced barite, fob mine, decreased 1.4%, according to the Bureau. The declared value for cif US port of all imported unground barite during the first 10 months of 1987 decreased from $39.02/t ($35.40 per st) to $37.16/t ($33.71 per st), the Bureau stated. Nevada continued to be the leading US producer of' barite with 637r of the total. It is followed by Georgia, Missouri, California, Tennessee, and Montana. The Bureau of Mines estimates 657 of the US mine production was used as a weighting agent in drilling fluids. The remaining 35°/r was used in barium chemicals, glass or as a filler. Most of the production from Missouri, Georgia, and Tennessee was used in the non-oilfield sector. This sector continued to increase. Of the total consumption (used by grinding plants and chemical manufacturers), it is estimated that 8070 was used in drilling fluids and 2017( in the non-oilfield sector - barium chemicals and fillers in paper, plastics, and glass. The tonnage consumed in the drilling fluids market increased slightly. But the average number of rotary rigs operating decreased from 964 in 1986 to 936 in 1987. This is the lowest number of operating rigs reported since 1949. The increase in consumption in this sector is due to an increase of rigs operating in the US Gulf and other higher consumption areas over 1986. Crude barite imports were estimated to be down by 19.5% in 1987. Still, they accounted for 637 of the barite consumed in the US. During the first 10 months, China continued to be the leading exporter to the US with 86.970, followed by Mexico with 10.997, and Morocco 2.107(. About 5Y of the imported ore was used in the nonoilfield sector. Ground barite imports dropped from 19.8 kt to 8.8 kt (21,800 st to 9800 st) in 1987. Of this amount, 1.4 kt (1598 st) was used in drilling muds and the remainder of the non-oilfield use. During 1987, a few more grinding plants that supplied the drilling fluid market were closed. Along the US Gulf Coast, there are 13 operating plants versus a high of 31 in 1981. Cameron Offshore reopened its grinding plant at Cameron, LA. New Riverside Ochre Co. of Cartersville, GA, purchased a jigging-washing plant in Missouri and plans to place it in operation this year on a new deposit near Cartersville, GA. Milpark purchased Hughes Drilling Fluid in 1987 and operates under Milpark. US mine production will probably stay about the same as 1987. Price increases in the 10 % range for imported ore are expected due to water freight and the weak dollar. Baker Hughes estimates the average number of operating rotary rigs at 1070. A slight increase is expected in the non-drilling fluid market (chemicals, glass, and filler). Bauxite and alumina L. Baumgardner, US Bureau of Mines Domestic bauxite production in 1987, expressed as dried equivalent, was 581 kt (640,400 st), a 14% increase over 1986. US mine production amounted to less than 170 of total world production. Virtually none of the domestic bauxite was consumed in the production of primary alumina metal. About 30% of the bauxite produced by US mines was calcined to produce 117 kt (128,970 st) for use in abrasives, catalysts, chemicals, proppants, and refractories. Most of the uncalcined bauxite was refined to specialty aluminum oxide (alumina) forms. Metallurgical grade bauxite was imported from 10 countries in 1987. Principal suppliers of the 9.8 Mt (10.8 million st) were Guinea (4270), Jamaica (3501,), Australia (127), and Brazil (57). The average value, delivered U.S. ports, cif, as reported to US Customs Service, was $29.50/t ($26.76 per st). Calcined refractory grade baux-

Jan 6, 1988

By Joe Roby

Rolling disc cutters are the business end of hard-rock and mixed-face tunnel boring machines (TBMs). Since their first successful employment on a TBM more than 50 years ago, disc cutter technology has constantly evolved, allowing modern TBMs to excavate very hard and abrasive rock efficiently. Disc cutters have also been employed successfully on earth pressure balance (EPB) and slurry machines, cutting rock under water and ground pressure. The range of materials excavated by machines today is broader, excavation rates are higher and cutter costs are lower than ever before, proving the value of investment in cutter development. Disc cutters are used on a range of tunneling equipment, from pipe jacked slurry micro-TBMs less than 1 m (3.3 ft) in diameter to 15 m (49 ft) in diameter, hard-rock boring TBMs. The geological conditions under which they are employed range from sands and gravels, with several bar of water pressure, to extremely hard, massive rock with UCS up to 420 MPa. Regardless of the type of machine or geology, one thing remains constant: changing worn out cutters is costly. When cutters must be changed in the middle of a tunnel, the contractor incurs the cost of downtime as well as the cost of refurbishing or replacing the cutters. In the case of catastrophic cutter failures, the project can be stopped completely for long periods, and the costs mount up rapidly while tunnel production is at a stand still. Catastrophic cutter failures include the occasion when hard-rock disc cutters are failed in groups (called a ?wipeout? phenomenon) and the operator fails to stop the machine, which results in severe damage to the cutterhead. The cause of this can be either an undetected failed cutter propagating damage to surrounding cutters or operator error in steering. Regardless of the cause, the resulting damage can take days or even weeks to repair. When cutters fail prematurely on EPB or slurry machines in certain geological conditions, it is impossible to evacuate the chamber and, therefore, impossible to get [ ] into the chamber to change the cutters. The solution is frequently an unplanned intervention shaft that must be sunk at great cost. The importance of being able to predict cutter life accurately, and in all geological conditions, cannot be overemphasized. For these reasons, cutters have been developed for specific machine types and sizes, as well as for specific geological operating conditions. Different size cutters are required for different size machines. For example, while 483- and 508-mm (19- and 20-in.) cutters are used on large diameter TBMs, it is impossible to employ cutters so large on a small micro-TBM. Also, the cutter must be designed for the specific geological conditions under which it will be operating. The disc cutter rings required to bore extremely hard rock are the most expensive of cutter rings. However, they provide little advantage in weaker rock formations where less expensive rings will do the job as well. It is important to choose the correct cutter for the machine and the geological conditions in order to get the best balance of cost and risk.

Jan 1, 2009

"During his presentation at the 2016 George A. Fox Conference about the history of public-private-partnerships (PPP) in the tunneling and underground construction industries in New York, Vincent Tirolo, Jr., told a story about how, as a young engineer in the late 1960s, he and others pooled money to purchase a calculator for $75 that had the ability to perform sine and cosine functions. That was a big deal in those days and would make their job much easier. Oh how far things have come. Tunnel and underground construction engineers can now virtually map out and plan entire projects before the first shovel ever breaks ground. And the machines that are used to build the tunnels have advanced in ways that could not have been imagined 50 years ago.The calculator is just one example of innovation in the industry and on Jan. 26, more than 400 industry professionals attended the George A. Fox Conference at the Graduate Center of New York (CUNY) to learn more about the next innovations, new tunneling technologies and what the future might hold for the industry. The conference included sessions on contracting models, rescue and fire life safety and new technological developments as well as an international project spotlight presentation from Nasri Munfah about the Eurasia Tunnel, connecting the European and Asian sides of Istanbul, Turkey.The project, also known as the Istanbul Strait Road Tube Crossing project, was named the 2015 Major Tunneling Project of the Year by the International Tunneling and Underground Space Association.The tunnel boring work for the 3,344-m (11,000 ft) long tunnel under the Istanbul Bosphorus Strait was completed in August, heralding a new era in tunneling.Tunnel boring work was launched in April 2014 with a ceremony with then Prime Minister Recep Tayyip Erdogan in attendance. The work was completed on Aug. 22, 2015 with Prime Minister Ahmet Davutoglu participating in the ceremony."

Apr 1, 2016

By Greg Barfoot, Kurt Keskimaki

The Henderson Mine is located approximately 50 miles west of Denver, Colorado. A project is underway to replace the existing rail system which transports molybdenum ore 15 miles from the mine to the mill using three flight conveyor system. The first conveyor is a 1 mile, high lift conveyor which transports the ore from an underground crushing station to the end of the existing rail tunnel. The second conveyor is 10 miles in length and utilizes the existing rail tunnel to transport the ore from the mine, which is on the east side of the Continental Divide, to the mill located on the west side. The third conveyor takes ore from the tunnel portal to the mill through a series of 7 horizontal curves and inclines up to 15 degrees. The project applies advanced conveyor design to tackle the installation of the system in an operating mine and achieve the highest possible level of reliability. This paper outlines the design process for this system, discusses the options which were evaluated and how the current design evolved.

Jan 1, 1998

By Gordon T. Clark, James R. Struthers, Celal Kirandag

INTRODUCTION Project Background The Washington State Department of Transportation (WSDOT) hired the Seattle office of Parsons Brinckerhoff to lead a team of consultants to produce an Environ-mental Impact Study and perform conceptual and preliminary engineering. The pur-pose of the Alaskan Way Viaduct and Seawall Replacement project is to replace the existing earthquake damaged and aging viaduct and sea wall, adjacent the downtown waterfront of Elliott Bay, with structures that have improved earthquake resistance and that maintain or improve mobility and accessibility for people and goods along the existing corridor. With an estimated replacement cost over $4 Billion and construction duration exceeding 8 years, it is one of the largest transportation design projects on the West Coast of the United States today. Seattle, Washington is a city of over 2 mil-lion people in the Northwest corner of the United States. Ever since the Klondike Gold Rush in 1897, Seattle has been considered a departure point to Alaska. Because of this, the street along the waterfront was named the Alaskan Way in 1930. Alaskan Way Viaduct and Seawall The Alaskan Way Viaduct (AWV) carries State Route 99 along the shoreline of Elliott Bay through downtown Seattle and is a vital part of Seattle’s highway system. The viaduct carries approximately 110,000 vehicles per day or 25% of all north-south traffic through Seattle (Figure 1). It is 3.4 km (2.1 mile) long with 3 lanes in each direction and was constructed of cast-in-place reinforced concrete between 1952 and 1956. The wear and tear of daily traffic, salty marine air, and several earthquakes have taken their toll on the facility. Studies in the mid-1990s provided early evidence that the viaduct was nearing the end of its useful life. The viaduct’s increasing age and vulnerability was apparent by crumbling and cracking concrete, exposed rebar, weakening column connections and deteriorating railings. In early 2001, a team of structural design and seismic experts began work to determine whether it was feasible and cost-effective to strengthen the viaduct by retro-fitting it. In the midst of this investigation, a 6.8 magnitude earthquake shook the Puget Sound region (the Nisqually Earthquake, located 56 km (35 miles) from Seattle and deep below the surface) caused moderate damage to the reinforced concrete structure. WSDOT closed the viaduct for inspection and repairs intermittently for several days over a period of several months.

Jan 1, 2007

By J. L. Gent

Compressed air distribution networks are essential for powering equipment in many mines even though some mines are replacing them with electrical power for hydraulic drills. Compressed air can be costly especially if the system is poorly designed and maintained. This paper outlines a technique for proper compressed air system design that will help mine managers reduce compressed air power costs; an important topic in today's highly competitive international minerals market. Compressed air system design is complex. It requires specifying: 1) air quantity and pressure in all branches of a large network, 2) proper location and types of valves and fittings, 3) the network solution that determines compressor requirements, 4) optimal hose and pipe, diameters, 5) receiver and compressor accessories, and 6) required capital and operating costs.

Jan 1, 1989

By H. Sevim, M. K. Mohanty, Y. P. Chugh

The economics of “Conventional” and “Advanced Fine Coal Cleaning” (AFCC) circuits for refuse pond reclamation as well as active mine/preparation plant applications have been evaluated. The benefits of innovative tailings management schemes on the profitability of mining enterprises have also been evaluated as a part of this study. Analyses have been conducted for scenarios involving generation of two different product qualities of 5.81%, a quality that was obtained during AFCC circuit operation at SIU, and a more typical 8% product ash. The inability of the conventional circuits to achieve profitability while producing the lower ash content product is revealed from this approach. The spiral-only circuit is unable to produce a 5.81% ash product. A different version of the same circuit involving spirals and column flotation produced the desired product quality but could not maintain profitability. The AFCC circuits on the other hand, achieve net present values greater than $6 million, with return on investment in excess of 50%, in the water-only as well as dense medium mode, with and without tailings management. Addition of tailings management system to any of the circuits is found to enhance the project economics. The comparison of water-only and dense-medium applications of the AFCC circuits indicate a better suitability of the dense-medium circuit for producing premium quality products. Application of AFCC circuits in active mines offer better economics compared to applications in refuse pond recovery operations. The superior project economics are a result of reduced overhead cost and use of existing material handling facilities. Sensitivity analysis reveals the significance of capacity utilization on project economics.

Jan 1, 2002

By Sergio Estebanez, Martha Gross, Ruben Rubal, Yvonnick Rescamps, Alexandre Cochennec

The Hampton Roads Bridge-Tunnel (HRBT) Expansion project in coastal Virginia, USA will add two 1.5-mile (2.4 km) TBM bored tunnels alongside two existing immersed-tube tunnels between artificial islands. The site’s unusual constraints and the requirements of a large-diameter variable-density TBM shaped the design-builder’s decisions for handling TBM inputs and outputs, siting the TBM plant and supporting equipment, and sequencing tunnel-construction operations. This paper addresses the logistics necessary to enable key functions of the 46-ft (14-m) TBM and its ancillary equipment, including transport of most materials by barge, U-turn of the TBM on an artificial island, and delivery of materials for the second tunnel through the first one while interior structures are under construction.

Jun 13, 2021

By Tim Q. Haldane

The ability to efficiently process lowgrade ores has allowed the Gold Fields Mesquite Mine in Imperial County, CA to expand from a 2.1 Mt/a (2.3 million stpy) rate in 1986 to its present 7.3 Mt/ a (8 million stpy) processing rate. Increased tonnage demands led to the 1989 construction and startup of a dump leach pad to supplement the existing heap leach operation. This resulted in an excellent opportunity to compare the two processes at the same operation. Additional operating costs associated with the crushed ore heaps are justified through enhanced recoveries, even at very low ore grades. Gold Fields' Mesquite Mine is a gold heap leach facility located about 55 km (35 miles) east of Brawley in southeastern California. Five open-pit mines will be developed over the projected life of the property, covering a total area extending to a maximum of 5.5 km (3.4 miles) to the east and west, and 2.4 kin (1.5 miles) to the north and south. Mesquite will process 7.3 Mt (8 million st) of ore and produce more than 6.2 t (200 000 oz) of gold in 1990.

Jan 1, 1990

By Alejandro Prieto

Traditionally, Mexico has been a mining country. This industry has played a very important role in our country's development, creating jobs, integrating geographical regions - generally very remote from urban communities - and, an essential factor in our present day economy, generating an influx of foreign currency. The Fluorspar mining industry's development started in the 1920?s, but it was not until World War II that its exploitation became consistent and started growing. During the last few years, Mexico has become the world's leading producer, with an annual output of more than one million tons, which directly generates over 3,000 jobs. The actual proven reserves can guarantee fifty years of production at this same annual rate, and it is due to this fact that the producers have not increased their reserves. However, there is concrete information of the existence of several deposits, extending from the northern border to the gulf of Mexico, forming the "Fluorspar Belt? in Mexico.

Jan 1, 1986

By E. Fernandez

HIGH SPEED RAILWAY NETWORK Spain is a very adequate country to develop the high speed railway network thank to its geographical feature which has a 600km long radius, from Madrid- the capital that covers mostly the whole country. Therefore, the railway is a major competitor of the airline. In Spain, the new access to the north and northwest is nowadays the most important railway project which will allow a significant saving of time in the near future to the central plateau and the northern territories. Time savings as well as strict environmental considerations have been the main objective of various studies during the last decade leading to Guadarrama and Pajares tunnels as ones of the optimum solutions. Cordoba-Malaga high speed railway, the extension of the present Madrid—Sevilleline, through the Abdalajis range and the rail project to cross oriental Pyrenees between Spain and France are another two samples of large tunnels currently underway. In these four projects, the ground already encountered and to be soon encountered is highly variable, from very hard granite and gneiss in Guadarrama and Pertus to very poor argillite in Abdalajis, shale in Pajares and schist in Pertus. A number of faults are also expected. Hence, double shield hard rock TBM has been chosen. Figure 1 shows a general scheme in four projects. These four projects represent a total of 2 × 68 km of which 87 km are under DRAGADOS contracts. PROJECTS UNDERTAKEN BY DRAGADOS Guadarrama Tunnels This project is the longest twin tunnel with 28.377km, in Spain and considered one of the longest in Europe. The operating speed will be 300 km/h. This tunnel will link Madrid and the north territories through Guadarrama range. (Figure 2). The south portal is placed at el. 997.8m above the sea level. The tunnel starts with an inclination of 3‰, increasing until 15‰. After 6,620m length, the tunnel passes under the Morcuera ridge with an overburden of 960m. After 13,400m length, the elevation is 1,024m which is the highest point, and then the tunnel declines with a slope of 9.5‰, 2‰ and 19‰ until the north portal in Segovia province. At the border of Madrid and Segovia that is Penalara peak, the maximum

Jan 1, 2005

By P. Arell, D. Folkes

This paper presents the basics of EPA’s Hazard Ranking System (HRS), which is used to evaluate sites for possible inclusion on the Superfund National Priorities List (NPL). The paper describes the surface water, ground water, air, and soil exposure pathways and how they are applied to mining sites. Key factors contributing to the site score include the likelihood of a release, waste characteristics, and the targets for each pathway. Waste volumes, definitions of landfills versus surface impoundments, and background concentrations are of particular importance to mining and smelting sites. Because of the presence of metals, large waste volumes, and observable releases, mining and smelting sites often receive high enough scores to be proposed for the NPL based on a single path-way. Neverthess, owners and operators can take steps to reduce the risk of being scored, and to reduce the potential for high scores.

Jan 1, 2004

By W. Baguley, L. P. H. Greenhalgh, R. P. Riley

The traditional impeller system for aeration and suspension of slurries, e.g. in bacterial oxidation plants, is the vertical flat blade turbine (VFBT) . This type of impeller is energy-intensive, which results in a heavy-duty design of shaft, gearbox and drive. The Mixtec BX04 agitator development programme is designed to evaluate the use of the new generation of hydrofoil impellers which consume less power and thus have potential for capital and operating cost savings as well as being possibly less damaging to the bacteria. The early tests on pyrite oxidation in a 300 litre laboratory pilot tank using the Thiobacillus ferro oxidans bacteria, showed that hydrofoil impellers had superior characteristics to the VFBT impeller and to air-agitated pachucas, with lower energy input. The geometry of the air sparge ring was found to be very important in optimizing the system. These early successes resulted in a prototype impeller and sparge ring beinq tested in a 9m3 tank where oxygen uptake in water, impeller cavitation at different impeller speeds and air flows were evaluated. Resulting from this work was the supply of an agitator unit to an operating bacterial oxidation plant where it has been successfully evaluated. This paper describes the development work so far carried out

Jan 1, 1992

By Aydin Shaterpour Mamaghani, Cemal Balci, Nuh Bilgin, Mucahit Namli, Hanifi Copur

"It is expected that more than 10 Billion USD will be spent in Istanbul in coming years on tunnel boring especially with EPB-TBMs. However, the geology of Istanbul is very complex. Geologic formations changing from Paleozoic to Cenozoic ages cause tremendous problems due to frequently changed rock formations and andesite and diabase dykes. This paper summarizes a universal model to predict the performance of EPB-TBMs which is created upon the data base collected from several projects. The model first is based on predicting field specific energy and power consumed of TBMs using geo-mechanical properties of the excavated material and TBM diameter. Later net production rate is calculated using field specific energy and power consumed by TBM. A methodology to predict machine utilization factor permits to calculate daily advance rates. The validity of the model is tested using the data obtained from two recent metro tunnel projects. 1. INTRODUCTION It is expected that in a near future a total length of 400 km will be excavated in Istanbul in a complex geology. Selecting proper tunneling equipment, organizing an effective operational management with the right tunneling crew will be a major concern for an efficient scheduling of the future projects necessitating to create a model to estimate daily advance rates. Several TBM performance prediction models with few on the prediction of machine utilization time were realized in the past. However, there is quite limited number of research studies on predicting the performance of EPB TBMs. Specially predicting daily advance rates in complex geology, in mixed face, in fractured rocks, in transition zones etc. are in big concern (Namli et al. 2013, 2014). The first experiences in Istanbul with a gripper type TBM was a nightmare, roof collapses caused big delays in tunnel excavation (Bilgin 1993). A typical example to EPB-TBM was Kadikoy-Kozyatagi tunnel, changing TBM from opened mode to closed mode with few modifications on the cutterhead resulted a tremendous increase in the daily advance rates (Bilgin et al. 2009). The data collected from several tunnelling projects served a basis to create a model to predict daily advance rates of EPB TBMs. Within the frame of a research program the validity of the model was tested in Uskudar-Umraniye–Cekmekoy-Sancaktepe metro project and very recently in Mecidiyekoy-Mahmutbey project."

Jan 1, 2016

By John Marsden, Mike Botz

A variety of modeling techniques can be utilized to forecast metal production at heap leaching operations. These approaches reflect a wide range of complexity, flexibility, time to implement, cost, and accuracy. For many operators, a spreadsheet-based modeling technique is attractive since the calculations are directly accessible, models can often be developed by site staff, and the results are generally easy to extract and interpret. The authors have developed a spreadsheet-based modeling technique that provides a high degree of flexibility, while still considering detailed operating information for ore properties, leach kinetics, scaleup factors, lift height, and in-heap metal inventories. The technique involves establishing kinetic leach curves for each ore type to characterize metal extractions, followed by application of separate metal recovery curves to define the rate at which leached metals exit the heap in pregnant solution, taking into account delays due to the in-heap solution inventory. At any point in time, the difference between total metal extracted and total metal recovered is equal to the in-heap inventory of the leached metal. This modeling technique is particularly useful for larger multi-lift heaps where delays in metal recovery are appreciable due to in-heap solution holdup. The technique is also applicable to sites with multiple heaps, leach cycles, and/or metal recovery plants (e.g., carbon columns for gold; solvent extraction for copper). This paper describes the modeling technique, including input data required and methods for defining kinetic leach curves and metal recovery curves. The technique is compared against an alternative spreadsheet technique using a simplified in-heap solution inventory calculation to forecast metal production, which has proven to be effective at a number of sites.

Sep 3, 2019

By D. L. Petersen, C. R. Nelson, B. K. Nelson, B. D. Wagener

The Lafayette Bluff tunnel, currently under construction for the Minnesota Department of Transportation (MnDOT), will be among the widest highway tunnels in the United States. The 199-meter tunnel is being constructed in a closely jointed, variably weathered diabase rock mass. Cover above the tunnel crown ranges from 4 meters to 27 meters, and is less than the tunnel excavated width of 18.3 meters for about 60 percent of its length. These factors dictated special support and lining design, limitations on excavation sizes and required sequences for support installation. Tunnel excavation is by controlled blasting, with multiple top headings and bench. Rock support and lining consists of external portal beams, rockbolts and reinforced shotcrete. A final concrete lining provides structural support for the rock mass and the membrane waterproofing system.

Jan 1, 1991

By Steven Atkin, Rens Verburg, Bryony Hansen, David McWharter

The use of paste tailings as underground backfill and for surface disposal is rapidly expanding, and with it comes the requirement to understand and predict its long-term environmental stability. This paper presents the results from a kinetic testing study performed on cemented tailings paste mixtures under both subaqueous and subaerial conditions. In addition, the effects of grainsize reduction are investigated. It will be demonstrated that the long-term weathering behavior of tailings paste is controlled by its physical and chemical characteristics, as well as its placement conditions. The testing indicates that subaqueous disposal of paste inhibits acid generation, whereas the exposed samples produced acidic leachate despite the presence of cement added to meet geotechnical requirements.

Jan 1, 2000

By J. H. Lalor

The Olympic Dam deposit was discovered in July 1975 with the intersection of 38 m (125 ft) of 1.05% copper in diamond drill hole RD 1. A further eight holes were drilled with only marginal encouragement to November 1976 when RD 10 cored 170 m (558 ft) at 2.12% copper and an economic discovery was confirmed. The discovery of Olympic Dam is an excellent example of the application of broad-scale scientifically based conceptual studies to area selection combined with the backing of an exploration management willing to support its exploration scientists in testing their ideas with stratigraphic drilling. It also illustrates the persistence required in mineral exploration. The project began in 1969-1972 with the development of a conceptual model for the formation of sediment-hosted copper deposits. This model suggested that the alteration of continental-type basaltic rocks could release copper into solution from which it could be concentrated in favorable stratigraphic positions. In mid-1972, this concept was applied to a review of the Proterozoic and Lower Paleozoic rocks in South Australia aimed at defining targets for stratigraphic copper deposits.

Jan 1, 1991