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By Donald P. Richards, William M. Greenslade, Daniel E. Albers

INTRODUCTION The application of oil field technology to large diameter hole drilling is beginning to offer a cost effective alternative to conventional shaft sinking methods. The drilling of ventilation and small production shafts are, of course, not new. The major constraint to the drilling of large diameter production shafts has been the inability to drill holes large enough and straight enough to install and operate relatively high volume hoisting equipment. This paper discusses recent advancements in drilling technology as applied specifically to large diameter holes for use in the mining industry. The paper emphasizes the geotechnical and hydrologic considerations in assessing site conditions and their application to drilled shaft technology. The authors worked together on a recent feasibility study for a 6 m (20 ft.) diameter 975 m (3,200 ft.) drilled shaft in New Mexico. Their individual experience in drilling and geotechnical investigations related to shaft sinking is world wide. DRILLING TECHNOLOGY Large diameter hole drilling has been a natural evolvement of oil well rotary drilling techniques. Most problems that were encountered in the rotary drilling of large diameter holes have been

Jan 1, 1981

By Ronald D. Hill

The occurrence of acid mine Drainage (AMD) with coal mining has been well documented. (1) Less documentation is available of its association with other types of mining, e.g., copper, gold, zinc, and sulfur. Yet there are many locations in the western states where acid mine drainage is as great a pollution problem as in Appalachia and in some cases, because of the high copper, zinc, and arsenic concentrations, they present an even more difficult problem. Until a few years ago, it was generally believed that the neutralization of acid mine drainage was uneconomical thus, AMD was allowed to discharge freely into our streams. However, the demand for good water finally dictated that the mining industry be included under pollution laws. In 1964 the Commonwealth of Pennsylvania passed a law requiring that all active mine discharges meet a discharge standard of pH 6-9, iron less than 7 mg/1, and the water must have a net alkalinity. Several other states now require active mines to treat AMD. In all but a few cases, lime neutralization, often in conjunction with aeration, has been the treatment method used. The high cost of lime as compared to limestone and the poor quality sludge, (slow settling, large volumes, and low solids content) has stimulated work in the utilization of limestone. This paper reports on the current state-of-the-art of limestone treatment of AMD.

Jan 1, 1970

By K. S. Narayanan, Marcia L. Bartges, K. S. Venkataraman

The starting powders' physicochemical properties and consistency are essential for technical ceramic products to meet their performance specifications. The need for finer and more consistent powders has opened new technologies for synthesizing powders from atoms and molecules. However, submicron and near-micron powders obtained from conventional comminution and classification techniques are still competitive. This paper shows several examples from electronic ceramic applications of how we can use powder characteristics for micromanaging by design the ceramic properties such as the green and fired densities, slurry rheology, shrinkage during sintering, and the microstructure of the sintered bodies. The cross-disciplinary nature of the technology requires that the researcher not only should have a firm grip on the fundamentals of one or more disciplines, but also should be generally aware of the intricacies of other disciplines as well.

Jan 1, 1992

By B. Devulapalli

A mathematical model of the industrial hydrocyclone based on fluid dynamics is a better alternative to the currently existing empirical models. The swirling-flow velocities are determined by solving the Navier-Stokes equations with an appropriate turbulence model. The solution of the momentum-balance equations yields the flow field inside the hydrocyclone which determines the particle trajectories, and subsequently the classification curve. The essence of the model is that the physical dimensions of the hydrocyclone and the slurry characteristics can be incorporated, and the influence of these parameters reflects on the flow predictions. The predicted tangential and axial velocities in a 250-mm hydrocyclone are in good agreement with the laser-Doppler velocimetry measurements. Finally, the predicted classification curves show good agreement with experimental data measured on a KREBS Dl0B hydrocyclone.

Jan 1, 1993

By D. J. Hutchinson, S. Nickson

Cable bolts are used as a means of rock support around underground excavations in many mines across Canada and around the world. A substantial body of research on cable bolting was conducted at a number of Canadian universities and mines from the mid-1980s through the 1990s. Since then, research into selected areas of cable bolting practice has continued in Canada. The research has focussed on cable bolt instrumentation and on the inclusion of cable bolts in empirical stope design techniques. A review of cable bolting practice is now warranted at many mines. It has been five years since the completion of the previous substantial body of Canadian academic research and the associated advancement in understanding of cable bolt design, implementation and verification practice. Attempts were made at that time to transfer the new design procedures and performance assessment technologies to mine-site personnel. In some cases, this was effective, and ground control personnel continue to improve on their cable bolting practice at each specific mine site. However, at other sites, experienced people have moved on, and the new, less experienced personnel do not have access to the training or technical resources required to improve their understanding of the subject. In other cases, the technology was not transferred effectively to practitioners, with the result that substantial improvements can be made to the cable bolting practice at those mines. Guidelines for auditing cable bolting practice are provided in this paper. The guidelines include a discussion of the objectives of the audit, suggestions for audit procedure and a summary of the possible outcomes of a cable bolt audit. The objectives of an audit might include assessing the reasons for unexpected cable bolt failures, evaluating the quality of the installation procedures, quantifying the efficiency of the cable bolt system and assessing training requirements and procedures. A cable bolt audit should include consideration of all aspects of the cable bolting cycle, including the design, implementation and verification phases of the operation. At the end of the audit, a ranking should be assigned to the components of the cycle. The ranking system can then be used to identify items that require immediate attention, others that could be improved and others that are adequate. Following completion of a cable bolt audit, increased confidence in the support system and its application is generally, found, along with the potential for cost savings in many cases.

Jan 1, 2002

By E. Bonates

Truck/shovel systems are a major form of materials handling in open-pit mines in spite of the high associated capital and operating costs. Mine management is usually faced with a decision to purchase new equipment in order to support the steadily increasing on production. These decisions involve a high degree of uncertainty with respect to future demands and technical developments. This paper describes a computer simulation model for evaluating the optimum equipment fleet in an open-pit mining operation. The system is based on a stochastic simulation program which accounts for the various mining and economic parameters. It calculates the type of equipment and the optimal number of trucks needed to meet the production targets. Two types of selection criteria: maximum rate of production or minimum cost can be applied.

Jan 1, 1989

By M. J. Virnig, Christopher A. Fleming

THE CIP PROCESS "IN THE RIGHT PLACE AT THE RIGHT TIME? After its tentative introduction to the precious metals mining industry in the earlier part of this century, the carbon in pulp (CIP) process has now come of age, and is the process of choice on all new gold mills. Well over 50 percent of all gold that is mined each year is recovered by adsorption on activated carbon, and the percentage will increase in the years ahead, when old mills using Merrill Crowe technology come to the end of their lives, and as the proportion of world gold production from low-grade resources increases. The pioneering process development work in this field, which was mainly concerned with carbon elution, was carried out by Zadra and his colleagues at the United States Bureau of Mines in the early 1950's (Zadra et al., 1950, 1952), and led to the commissioning of the first large-scale, industrial CIP plant, at the Homestake Mine in South Dakota, in 1973 (Hall et al., 1974). From there, the process spread rapidly, firstly in South Africa in the late 1970's. and then throughout the rest of the gold producing world in the 1980's. There were several factors that led to the meteoric (by gold industry standards) acceptance and successful implementation of this new technology into gold processing operations worldwide. Firstly, and perhaps most fortuitously, the development of the technology closely paralleled the 1968 release of the gold price from the rigid constraints of the $35/oz. gold standard. With the value of the metal allowed, for the first time in modern history, to fluctuate in response to free market supply and demand forces, the gold industry witnessed an unprecedented boom as the price of their commodity increased ten-fold in a remarkably short period of time. This had several important spin-offs as far as new process developments were concerned: The profits realized by established gold-mining companies increased enormously and, consequently, there was more to spend on research and development and exploration for new deposits.

Jan 1, 1993

By Corale L. Brierley

Bacteria have long been used for the extraction of copper during dump leaching of sulfide minerals and in the recovery of uranium from mined-out areas. However, bacteria can also be used in extraction of trace metals from copper ores and waste materials. Molybdenum, tungsten, nickel, cobalt, gold, silver, and other strategic metals can potentially be released from ores and wastes by biological processes. The chemistry and biology of these reactions, the potential for using the processes, and the state-of-the-art of the technology will be discussed.

Jan 1, 1983

By Robert W. Buechley, Charles R. Key, Jonathan M. Samet, Marion V. Morgan, Arnolfo A. Valdivia

INTRODUCTION The Uranium Epidemiology Study at the University of New Mexico was initiated in 1977 with the objective of assessing health effects of uranium mining in the Grants, New Mexico, area. The planned approach was a cohort study of mortality that would capitalize on the availability of health records at the Grants Clinic. During the first year, emphasis was placed on determining the feasibility of the proposed study: Were adequate records available? What was the quality of available information? Could a cohort be established? The first year's work confirmed the study's feasibility (Buechley, 1979). Subsequent efforts have focused on the health and exposure data base and comprehensive follow-up. A retrospective cohort study of early miners is in progress; a prospective cohort study of miners who began working under the current Federal standard is planned. This report will summarize the current status of the Uranium Epidemiology Study. A chronology of the study's activities follows (Table 1). TABLE 1. Uranium Epidemiology Study Timetable 12/77 Official start of study. 12/77-8/78 Abstracted Grants Clinic records of 21,780 persons examined for mining companies from 7/57 through 12/76. Checked company personnel records to establish who had worked underground 1 year or more through 12/76. 7/78- Obtained physical exam and mining history information on qualified miners from Grants Clinic and companies. 9/78- Obtained working level month information from companies and other sources. 12/78- Checked qualified miners list with New Mexico death tapes and New Mexico Tumor Registry files. 9/80- Submitted qualified miners list to Social Security Administration for search of its records. 12/80- Obtained copies or abstracts of early State Health Department and Mine Inspector's reports. 3/81-4/81 Conducted Pilot Respiratory Disease Survey. 3/81- Verified underground status of qualified miners via company personnel records. 3/81- Verified smoking and mining histories of qualified miners via Grants Clinic records. 3/81- Began establishing cohort with first underground experience after 1970. 4/81- Checked qualified miners list with Post Office, Voter Registration Office, Motor Vehicle Division, telephone directories, city directories, and other sources. BACKGROUND Uranium Mining in New Mexico The Grants, New Mexico, uranium belt measures some 110 by 25 miles in Cibola, McKinley, and Sandoval counties (Kelley, 1963). The three chief mining districts are, from east to west, Laguna, Grants, and Gallup. Average annual production was about 5,500 tons, or 45% of United States uranium, from 1966 through 1978. Despite a drop in this figure in 1979, to 40%, New Mexico still leads the nation in uranium reserves and production (Hatchell, 1981). In 1918 carnotite, a yellow uranium vanadate, was identified in the Shiprock area (Chenoweth and Learned, 1980; N.M. Energy and Minerals Department, 1981). It received little attention at the time because of its apparently limited volume. In 1950 an important uranium outcropping was discovered by chance in limestone at Haystack Butte, northwest of Grants. In 1951 deposits were discovered in sandstone at Poison Canyon, north of Grants, and at Jackpile, northeast of Laguna. In 1955 finding of radioactive cuttings at an abandoned oil test site near Ambrosia Lake led to drilling and discovery of the first underground deposits (Melancon, 1963). Ore bodies were also found near Church Rock in the 1950's (Rautman, 1977). A uranium rush followed. At various times during 1952-1962, 60 mines and 5 mills were in operation (Gay, 1963). In the early 1960's the price of uranium fell, and many miners left the area. Subsequent market fluctuations have produced shutdowns and consolidations, development and expansion. Many early uranium miners came to New Mexico with

Jan 1, 1981

By Wolfgang Pietsch

Roller presses were first invented in the middle of the 19th century, for the economical size enlargement of coal fines as fuels. Coal briquettes became quickly accepted for industrial and domestic use giving rise to a large and sucessful industry, particularly in Europe, Japan, and North America. When, towards the middle of the 20th century, coal was more and more replaced by other energy sources, such as electricity, gas, and oil, roller press manufacturers searched for alternate applications of this equipment. In addition to contemporary coal briquetting, in fields such as smokeless fuel and form-coke, it was found that redesigned and modernized roller presses, which are now capable of exerting high forces, are versatile machines for many tasks in mineral processing. Today they are used for: - the "classic" pressure agglomeration and - the "new" high pressure comminution. In pressure agglomeration, the characteristics of fine minerals are improved by forming briquettes or granulated products from compacts. During size enlargement with roller presses briquettes are directly obtained while granular materials are produced by crushing and sizing of compacted sheets. The processes are carried-out essentially dry and often do not require binders other than those inherently contained in the feed and "activated" by the high forces and/or elevated feed temperatures (e.g. hot briquetting). Therefore, no foreign materials (impurities) are added. Another advantage of the technology is, that wide particle size distributions are acceptable or desirable as feed materials, including millimeter or even centimeter sized particles. Plastic particles deform and brittle materials are crushed during pressure agglomeration. A relatively new application of roller presses in mineral processing is the utilization of the crushing effect when brittle materials pass the nip area between the rollers. It was found that this crushing mechanism is very efficient thus saving energy, particularly in grinding circuits handling large capacities. The paper introduces the fundamentals of the process and describes the design as well as applications of modern roller presses in mineral processing.

Jan 1, 1995

By Harry R. Asche, Manfred K. Lechner

The Cross City Tunnel comprises 2km of a new underground traffic route in Sydney, Australia. The route is very complex, involving some six separate tunnels and three underground Y-junctions. For almost 200m the six tunnels run parallel at different level sunder William Street, Sydney. Almost all of the route runs adjacent to the City Business District of Sydney and adjacent to or below many major buildings and services. The planning and design of this project is described. The geometric arrangement is achieved with a strong dependence on 3D road design packages. Road alignment constraints include land acquisition and proximity to existing tunnels and basements as well as maintaining separation from the other tunnels in the scheme. Geotechnical and hydrogeological studies are described. Findings discussed include the high horizontal stress field in the Sydney area and investigation of incised palaeochannels on the route. Methods of design for the tunnels and Y-junctions are described, as well as methods of settlement prediction for the buildings and services. The latter includes the settlement assessment for more than 200 buildings, many in excess of 20 storeys, as well as services including all of the city railway lines in Sydney.

Jan 1, 2003

By Joseph Renk, David Akers, Glenn Shirey

Each year, US coal cleaning plants landfill or impound millions of tons of high-quality, fine-sized coal. This coal is not only difficult and expensive to capture during cleaning, but, if captured, can pose serious materials handling problems. The GranuFlow. Technology was developed and patented by the U.S. Department of Energy (DOE) to address these problems. GranuFlow involves the addition of a coal binding agent such as an asphalt or heavy oil emulsion to coal to reduce moisture, dusting, and freezing and to improve the flow properties of the coal in bins and chutes (1, 2, and 3). When the emulsion is added before mechanical dewatering, the binding agent causes the formation of fine-sized coal agglomerates that dewater better than untreated coal. In addition, the binding agent increases the capture of ultra-fine coal in screen-bowl centrifuges. Previous work by DOE has also demonstrated that such treatment results in a significant reduction in dustiness and a reduced potential to freeze. To address concerns about the handling and combustion characteristics of GranuFlow treated coal, DOE performed a pilot-scale pulverization and combustion test (4). No problems were encountered during pulverization or combustion, and use of this fuel in a p.c. boiler was found to be feasible from a technical perspective. CQ Inc. has an exclusive license from DOE to market this technology and is currently performing a series of commercial demonstrations to determine if GranuFlow is both technically and economically viable.

Jan 1, 2005

By David J. Dunn

Materials related problems at mines can be big ones - like a newly completed 1 -m (3.5ft) water pipeline burst during initial filling, grinding ball consumption at double the typical norms on startup of a new semiautogenous grinding (SAG) mill circuit or 30 open-pit haul trucks in the shop for new bed liners after less than a year’s service. Materials engineering provides solutions to these kinds of equipment problems by selecting good materials and designs, by trouble-shooting service failures and by maintaining high quality in vendor-furnished materials and components. Materials with good properties, correctly made and fabricated, correctly installed in mining and processing equipment, produce ore and final products reliably and efficiently. Materials engineering, applied during design phases, specification writing, and receipt and installation of materials, ensures that equipment will have the best possible shot at performing up to expectations. Good calls on materials properties - specifying state-of-art materials produced by competent manufacturers - help mine managers to reduce downtime and mining and processing costs. Materials that are improperly made or specified can make a mining operation less efficient or, possibly, uneconomical.

Jan 1, 1992

By D. C. Torre

Since the early 1960s, there have been efforts to develop and produce reliable continuous haulage systems capable of taking the full output of a continuous miner and transporting it, in one continuous flow, from the face to the tipple. The majority of the successful continuous haulage systems were placed in operation in the early 1970s. These were all of the bridge conveyor type. They usually consisted of bridges and mobile bridge carriers (MBC) attached at the inby end to the continuous miner and at the outby end to the panel conveyor itself. These successful bridge conveyor continuous haulage systems are either of the belted or chain type. The most successful belt type continuous haulage systems are those manufactured and marketed by the Long-Airdox Co. Until early 1977, Jeffrey Mining Machinery Division manufactured and marketed the most successful chain conveyor type haulage sys¬tems. In 1977, Long-Airdox reentered the market with a chain-type system to complement its belted system. The original bridge-type continuous haulage system was introduced to the coal mining industry in the early 1960s by the old Long Co., a predecessor to the current Long-Airdox Co. These original units were of the chain conveyor type. In the early 1970s, there were also developments in continuous haulage, employing different material handling media. These in¬cluded the Serpentix, a flexible type belt, introduced by the Joy Manufacturing Co. There was also a serious attempt to introduce hydraulic-type continuous haulage by Consolidation Coal Co. and Conoco Research. Despite some startling successes, particularly with the bridge-type haulage systems, the general and widespread application of continuous haulage has eluded the mining industry. Some of the problems are related to underground conditions; others to people, both management and labor. One of the greatest obstacles to universal success continues to be the difficulty of accepting the philosophy as well as the machinery of continuous haulage. Nevertheless, efforts continue to spread the success of commercial and viable systems in the industry. There is also effort to improve on these systems, and on methods for their successful use. In addition, efforts continue, with private and public support, to develop new types of continuous haulage equipment and systems. Bridge Type System Developments Because they have already been successful in some US and overseas mines, new developments in bridge-type systems will first be touched on. The Long-Airdox Co. has continued to improve both its belted and chain continuous haulage system. In the belted system, the company recently introduced a new design that will be mainly applicable in higher coals and in noncoal mining applications, as shown in the accompanying figure. This new system is equipped with 305-mm-diam (12-in.-diam) pulleys in the bridges and mobile bridge carriers, in place of the 150-mm-diam (6 in.-diam) pulleys in the standard system. The modification is designed primarily to improve belt life and keep belt problems to a minimum. An operator, the Clinchfield Coal Co., a Division of Pittston Coal, developed the detaching of the bridge-type continuous haulage system from the miner by placing a mobile bridge carrier at the head of the string. However, Long-Airdox and Jeffrey have now made this an option to their at¬tached-type system. In the US, there are many chain type haulage systems detached from the miner with an extra MBC at the head. There are two such belted systems

Jan 7, 1982

By F. C. Bond

Nature of Empirical Calculations The size reduction of large tonnages of ore and rock is an operation of great magnitude. It is a necessary and important part of industry. Its development has been motivated by practical need and has followed the path of an industrial art without much help from theoretical science. Knowledge has been accumulated from experience. Trial and error established the methods; then collected data were tabulated and served as the basis for empirical equations that have been continually modi¬fied and amplified as new data became available. These equations now constitute the bulk of our present knowledge of comminution. There is no accepted scientific theory that is basic to comminution. In electrical, mechanical, and civil engineering, as well as in many other industrial activities, such theories exist and are extremely help¬ful, but rock is essentially heterogeneous, and the zones of weakness that control its breakage are thoroughly diversified. No theory has yet been discovered which can account for the variability of rock, although many attempts have been made. Empirical equations tell nothing of the why of a phenomenon, but if they are properly derived they can tell much about the how. They always represent only an approximation of behavior but never a law. In a proper empirical equation a symbol is assigned for each of the variable quantities that obviously affect the relationship. In a grinding mill these include mill diameter, mill speed, and feed rate among them. In setting up and revising an empirical equation the cardinal princi¬ple in establishing and modifying it is this: any change must be strictly ascribed to the variable which caused it. A useful empirical equation is rendered useless when a change in any convenient coefficient or exponent is made to make it fit a particular set of data, without certainty that the altered coefficient or exponent is the responsible variable in the new data. Such indiscriminate revisions have brought the use of empirical equations into some disrepute. When existing equations are changed to accommodate new data it is a good rule to make a change which gives results intermediate between the new and the old. A halfway point is usually a good choice.

Jan 1, 1985

By Ottmar Burghardt

Sintering of iron ore has undergone a dramatic development world-wide. Today, the annual world production amounts to approximately 600 million tons. At present, the sintering process in competition with pelletizing, seems to offer certain advantages inasmuch as it allows the use of solid fuels. Also, its charging behaviour in the blast furnace is, in general, considered as being better than that of pellets. This is true, in particular, for the charging behaviour and the gas permeability in relation to the grain size. Moreover, instead of charging limestone into the blast furnace, for instance, the basic components which are necessary for the burden materials can generally be supplied in a simpler and more cost-effective way by using basic sinter instead of basic pellets. While in sintering, with basicity rising to the range of 1.6 to 1.8 CaO : SiO2, the capacity increases and the sinter quality shows improvements in most of its characteristics, the pro¬duction of basic pellets generally requires a higher fuel rate, when compared to acid pellets, while production capacity decreases and some of the quality characteristics deteriorate.

Jan 1, 1982

By Ernesto Maldonado, Jesus Romero Benitez, Zach Agioutantis

Numerous researchers worldwide have investigated the prediction of ground movements due to underground coal mining utilizing different analytical, empirical, and numerical models. These studies have primarily focused on the development of prediction methodologies for either flat or gently dipping seams under variable topography, and only a few studies are available that have investigated the prediction of ground movements over inclined seams. Although most inclined coal seams are in China, India, and other countries worldwide, a few inclined coal seams (with a dip of 10 degrees or greater) are also present in the US. Currently, the prediction of ground movements for inclined coal seams using empirical methods utilizes the same methodology for horizontal seams. It consists of dividing the inclined seam into horizontal segments, calculating deformations due to each segment, and superimposing the calculation results. This paper presents a new tool that provides a methodology for modeling subsidence under inclined seam conditions. Examples based on subsidence measurements available in the literature are presented. The goal is to implement this methodology into the Surface Deformation Prediction System (SDPS).

Jun 25, 2024

By Dirk van Zyl

It can systematically assess if the control and management systems designed for protection of sensitive ecosystems are adequate. The results of the assessment can help to identify key elements in the project that pose higher risks due to uncertainties in design. These assessments can then be used to make recommendations to further manage and reduce risks as the project is developed. QUALITATIVE RISK ASSESSMENT The general principles of a risk assessment are well summarized by Kaplan and Garrick (1981): "In analyzing risk we are attempting to envision how the future will turn out if we undertake a certain course of action (or inaction)." Fundamentally, therefore a risk analysis consists of an answer to the following three questions: What can happen? (i.e. what can go wrong?) How likely is it that that will happen? If it does happen what are the consequences?" Risk assessments can be performed using various levels of sophistication depending on the amount and accuracy of data available. A qualitative risk assessment uses descriptors throughout to express the level of risk. The definitions of the descriptors are presented in terms of the magnitude or concentration of contaminants. The results of a qualitative risk assessment can be used to: a)Document the evaluation and decisionmaking process. Although differences of opinion may exist about the definitions of the descriptors, the process is well-documented; b)Express the relative risk associated with specific activities or design elements; and, c)Select those failure modes or release mechanisms that may result in significant risks. These mechanisms can then be further developed in quantitative risk assessments. A qualitative risk assessment can be performed in a systematic approach using four steps (Van Zyl, 1987): A qualitative environmental risk assessment can be used to describe the risks associated with the development of a new mine and to make an evaluation of the adequacy of its design for environmental protection. The relative magnitude of risk associated with selected failure modes and exposure/consequence scenario assessments is the final result of a qualitative risk assessment. These failure modes are based on site specific areas and components, and mining and construction phases. The four steps of a risk assessment (hazard assessment, exposure assessment, consequence assessment, and risk characterization) are used in the development of a qualitative risk assessment. Relative magnitudes (using a five point scale of negligible to high) for each step, can be quantified in a qualitative risk assessment. Development of the descriptors for the relative magnitudes in each step is a very important part of a qualitative risk assessment. The success of a qualitative risk assessment depends on the adequacy of the information base and the subjective judgements made in each step. The quality of the risk assessment is, therefore, dependent on the experience of the assessors. A mining project in a sensitive coastal environment is presented as an example to demonstrate the application of a qualitative risk assessment. INTRODUCTION Environmental impacts from mining operations have been a significant factor in the last century. This was especially the case prior to the development of a better understanding of environmental processes and the potential impacts of acid rock drainage (ARD), and associated heavy metals, or the uncontrolled disposal of tailings and waste rock (Smith, 1987). Much care has been exercised over the last two decades in designing and operating mines to limit the environmental impacts as far as possible. All new mines are specifically designed with mitigative methods to manage such potential environmental impacts. Attention is directed to ARD impacts, safe disposal of mine waste rock and tailings, transportation and storage of chemicals and fuels, and final reclamation. A qualitative risk assessment can be used to address all project systems and activities that may potentially pose a risk to the environment.

Jan 1, 1992

By Rock M. Poulin, Bruce G. Moulton, Daniel E. Nowak, David T. Cass

The Yacambu Irrigation Tunnel Project of 34 km, 5 meter diameter circular and horseshoe section, has been under construction since the early 1970's. Notable among the excavation challenges is high ground cover of 3,000m creating large lithostatic pressures in the tunnel alignment with subsequent plastic flow of the ground in the tunnel walls. The tunnel may converge from small amounts to 1 or more meters of diameter over long sections. Several excavation techniques have been attempted but all without desired results. The paper proposes a new machine concept that uses the history of ground experience as its basis for design.

Jan 1, 1995

By Wallace W. Wilson

It scarcely 1s possible to read a new issue of any of the principal mining trade journals without noting some mention of a major new overseas mining venture with which one or more domestic companies are involved. These projects seem to follow a fairly consistant pattern; most are large open pit mines, with relatively low grade ore bodies but huge reserves; the total price tag will be in nine significant figures and around half or more of the total cost will be for infrastructure. West1 noted that nearly $7 billion is being invested annually for new mining projects and the expansion of existing mining ventures, in the free world. He anticipates that by the year 1975 such investments would reach the $10-11 billion annual figure, and that in the five year period 1972-76 total capital requirements can be expected to aggregate around $45 billion. The proportion of this total investment which will be financed in some manner is difficult to estimate because of the variety of available financing arrangements. West estimated that around 75% of the total capital would come from internally generated funds, with the balance from external sources. Conceivably a substantially higher percentage could be attributable to external financing, especially it the trend of recent mineral development in Canada and Australia is any criterion, and of course, including local sales of equity as a part of the package.

Jan 1, 1973