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By C. Timothy Shaw

Traditionally, only the large mining companies have maintained specialist departments in such areas as Rock Mechanics, Ventilation and Safety. To the small companies this has been a luxury that they could ill afford. Any work required by such companies in these areas, more complex than could be handled by the existing staff, was done by consultants. This situation is changing though and there is a need arising for many specialist departments. These changes are partly being brought about by the effects of inflation as the ever increasing costs are causing more and more operators to increase the size of their operations in search of economies of scale. In addition though the plethora of new laws and regulations are creating a need for many more specialists in all areas of mining in order to ensure compliance. The abovementioned factors, added to the existing Pattern of mines endeavoring to improve the working environment for their labor force, both for reasons of practical labor relations and also due to further legislative pressures, have thus created a climate where, in the near future, departments such as Rock Mechanics, Safety, Ventilation, Environmental Engineering and Subsidence Control will be commonplace in mining companies. It will no longer be practical to function without such services. Many mining companies already maintain such departments and this has particularly been true of the big mining groups of South Africa. From the experience gained by many of these large companies with specialist departments, it is clear that the maintenance of a cadre of experienced, competent professionals in such a department has not always been easy. It would seem from the experience gained that one can generalise and state that graduate mining engineers tend not to view specilisation as an optimum direction for their career development. It is of course true that many professionals, especially those with higher than a bachelors degree, do view these areas as valid career options, but even here experience shows that wastage is high. The time therefore seems to be ripe to take a look at this area in some detail to see whether reasons for the problems can be isolated. Working from that some suggestions can be made as to directions in which improvements might be made. If the challenge of the demands of the new regulations are to be met then such improvements must be made.

Jan 1, 1980

By Kaye P. Strong, Desmond M. Levins, Anthony G. Fane

1. INTRODUCTION The safe disposal of tailings is the most important environmental question facing the uranium mining industry today. This is because tailings present a major long term radiological hazard as they contain about 71% of the radioactivity originally in the ore. The magnitude of the problem can be appreciated by considering the quantity of tailings involved. For example, projections of milling programs in Australia indicate that there will be 100 million tonnes of tailings produced by the year 2000 (Levins 1980). The United States currently has in excess of 100 million tonnes and by the year 2000 will have between 900 and 1700 million tonnes (Landa 1980). Present options for tailings rehabilitation include leaving them above ground, returning them to the mine or placing them in specially excavated pits. In any event, the tailings will be covered with earth and revegetation attempted. This will remove the problems of airborne radioactive dust and water erosion of the tailings, at least in the short term, but diffusion of radon-222* from the tailings may still occur. The Atomic Energy Control Board of Canada (1981) has proposed a maximum allowable radon flux from rehabilitated tailings of 0.074-0.37 Bq m -2s-1(2-10 pCi M-2 s-1); the exact level is to be determined "after discussion with other regulatory agencies and the industry". The United States Nuclear Regulatory Commission (USNRC 1980) has been more restrictive in recommending a maximum flux of 0.074 Bq m -2s-1 (2 pCi m-2s-1). As a guideline they also suggested a minimum depth of covering material of 3 m to achieve this surface flux for tailings typically found in the western milling regions of the United States. The design of rehabilitation schemes is aided by a knowledge of radon transport through tailings piles. In this paper we present the results of a theoretical analysis and experimental study of radon diffusion through selected Australian tailings and cover material. The minimum cover criteria of 3 m is reexamined in the light of these findings. [ ]

Jan 1, 1981

By Richard D. Harvey

Petrographic properties of carbonate rocks are useful guides to the utilization of these rocks in SO2-scrubbing systems. High porosity and fineness of grain are thought to be the principal properties that contribute to high dissolution rates of the rocks in the scrubbing liquor. Lake marls and chalks are the major types of carbonate rocks that have these properties. Lake marls are composed mainly of equant grains of calcite (mean grain size generally less than 4 microns) weakly agglomerated in- to larger, porous particles. The marls commonly consist of 80 to 90 percent CaCo3 as calcite and aragonite. Impurities are, for the most part, quartz silt and organic matter. The average pore volume for samples of lake marls (1- to 1.2-mm particles) is about 0.50 cc/g, which corresponds to a porosity of about 57 percent. The mean size of pores in these marls is generally between 1 and 2 microns in diameter. Surface areas of lake marls range from 0.8 to 6.8 m2/g. Chalks have grain sizes and shapes similar to those of lake marls, but they generally have smaller amounts of quartz and organic matter and minor amounts of clay minerals. Pore volumes differ from one chalk formation to another; the 1- to 1. 2-mm particles average about 0.20 cc/g, which corresponds to a porosity of about 35 percent. The mean diameter of pores in chalks tested ranges from 0. 15 to 0.76 micron. Surface areas of chalks range from 3. 2 to 20. 1 m2/g. In the United States lake marls are restricted largely to Pleistocene- age sediments that occur in the states around the Great Lakes. Chalk and chalky limestones are restricted mainly to the Upper Cretaceous and Tertiary strata in the Kansas-Nebraska-Colorado area and in the south- eastern states, from Texas to Florida. Results of laboratory tests of the relative dissolution rates of samples at pH 6 and 44°C indicate that, in addition to many lake marls and chalks, oolitic aragonite, pelecypod shells, and carbonate waste sludges from certain industrial plants also have high dissolution rates.

Jan 1, 1974

By R. Cook

Knowledge based applications are becoming important to Associated Manganese for efficiently dispatching ore of appropriate grades to customers on time. The G2 expert system shell has been used to develop blending and scheduling applications using a combination of object-oriented rule based, procedural, and heuristic approaches. The blending application, for example uses a heuristic approach for creating blends from thousands of small stacks of manganese ore of various grades and sizes, to meet customer specifications while fully exploiting the available inventory. Data capture and data warehousing have become important issues, and the Internet shows strong potential for distribution of pre-processed information.

Jan 1, 1997

By S. D. Thompson, L. Adler

J.R. Sturgul Thompson and Adler (1988) present a new simulator for use in designing conveyor belt systems for underground mines. Their model uses a large Fortran program to do a Monte Carlo simulation. Their approach is similar to that done by other researchers, such as Stanford (1965) and Newhart (1977). All Fortran based simulation models use an imaginary clock that is advanced a time increment. At each advance of time increment the program has to determine what is to take place in the system. Since many things can take place at different places in the system, this approach requires that a large amount of logic is needed at each step of the program. This, then, necessitates a great amount of jumping between different portions of the program. In fact, the Fortran program, CMBCS, takes up to 15 to 20 minutes to run on the mainframe and several hours for the PC. Such execution times are typical of Fortran based simulation studies. There have been other examples of Fortran based simulation studies in mining. Cross and Williamson (1969) presented a model of a working open-pit copper mine. Fosinato (1982) presented a model of the bucketwheel excavators for the large open-pit mines in Southern Victoria in Australia. These excavators discharge into a complex conveyor system, which can be thought of as being similar, but more complicated than the one modeled by CMBCS. All previous simulation studies using Fortran as the source code have several things in common: they all are very lengthy, often being of the order of 10,000 lines of code and take a great deal of CPU time to execute. The program of Fosinato takes more than 4.5 hours to run on a large mainframe. Also not mentioned by Thompson and Adler is the actual time it took to write the Fortran code. This, too, can be considerable, as Fosinato's program took several man years to write and de-bug. In order to change it, as the parameters change or as the mine increases, further large amount of time is needed. An alternate to such Fortran based programs is provided by using a special computer language known as General Purpose Simulation System (GPSS). This language is designed to solve a wide variety of discrete event simulation problems and appears to be particularly suited for mining situations as shown by Sturgul and Yi (1987). Although GPSS was introduced as far back as 1961, it has not been used in mining to any great extent. However, the original form was quite crude and inefficient compared to modern versions. Perhaps with the increasing popularity and availability of these recent versions, this will change. Two such versions are GPSS/H for the mainframe and GPSS/PC for the personal computer. GPSS/H allows for interactive usage, such as allowing input data to be entered via a menu. GPSS/PC has excellent graphical capabilities and one can actually view the simulation in progress. In addition, one can halt the simulation and change values of various parameters. If a particular portion of the simulation is in progress via a concept known as "microwindows." These new versions have greatly increased the potential for using the language for mining situations. Mining applications of GPSS have been given by Sturgul and Yi (1987), Sturgul and Harrison (1987), Sturgul (1987), and Sturgul and Singhal (1988). Schriber (1987) presents a summary of the recent advances in GPSS.

Jan 12, 1988

By J. Kulczycka

Poland in time of transition had been dealing with the remnants of the previous regime ? particularly in the field of environmental protection. The burden left was tremendous and there was a need for fast and effective tools for improving the environment. The idea of environmental protection had been supported by the introduction of a new environmental policy that underlined the importance of sustainable development in industry in the beginning of 1990s. This policy introduced high environmental fees and fines ? a concept not very popular in Europe in that time ? and good only for a country in transition to boost the protection of the environment. While this policy had its role to play, its role is now completed. It is time to move forward, especially when these environmental charges affect the international competitiveness of industries so much, and at the same time have virtually no influence on environmental protection investments any more.

Jan 1, 2005

By Tom Skodack

Mine and tunnel contractors face a complex environment-one in which economic risks are high, operating costs grow ever higher, ore grades are lower or recovery more difficult, and civil construction projects are intensely competitive on a world-wide scale. Within the context of this environment, the risks and rewards of proper machine selection for rock excavation have become proportionately large. Speed, depth and scope of analysis, and extensive supporting information are indispensable in the selection process. Equipment designs and their applications are also myriad and diverse. Several equipment alternatives and excavation techniques may have to be evaluated at once to choose the most cost-efficient approach. The following examples are typical of the current demand for more detailed equipment analysis: • An aggregate supplier starts a new quarry. He knows his targeted tonnage, blasting restrictions, and previous operating costs from other quarries. But he must improve on his old costs. What drill pattern, hole size, and bench height will give lowest cost per ton? How many crawler drills and what type will produce this tonnage most efficiently? • A mine is using a fleet of twin pneumatic ring drills for long hole drilling to initiate their cave. The mine is facing both air shortages and increasing operating costs with decreased efficiency in the ring drill fleet. If they invest in new hydraulic long hole drills, what impact will each drill unit have on production? Each twin drill unit? What configuration gives best operator efficiency and subsequent reduction in manpower? Which configuration gives the best return on investment? • A tunnel contractor is bidding a long straight water tunnel by conventional drill and blast methods. What is the optimum number of drill booms for the tunnel cross section and excavation schedule? How many rounds per day can he achieve? What are his total project drill, blast, and muck costs? In the past, such questions could be answered, but only approximately at best. One good prediction could involve many hours of laborious calculations that had to be repeated each time a new parameter was introduced or an existing parameter changed. In 1980, increasingly complex analysis, coupled with increasing need and quick response times demanded by industry, led Atlas Copco's project department to turn to the computer. New computer programs based on theoretical considerations and three decades of worksite performance data were developed for evaluating mine and tunnel contractors' equipment needs, productivity, and partial or total operating cost calculations for most conventional drill and blast excavation techniques-including shot rock loading and transportation. This Computerized Analysis of Rock Excavation-or CARE-program has since been available to the mining and construction industry. From each program specific results can be pre- dicted, including: • Productivity Calculations-Rock drill penetration rate for a given drill, hole size, and rock type, optimized for the best drill steel life; net machine productivity (drill-out time or drill meters-footage-per shift); total drill round time, including charging, blasting, loading, and haulage; suggested drill pattern, computer printed, including hole size for a given rock drill, rock type, and associated blasting restrictions for either drift rounds or benching applications; long-hole drill meters (ft) per drill shift; breasting down (upper drilling) drill meters (ft) per drill shift; and comparison between continuous loading machine capacity and LHD capacity. • Operating Cost Calculations-Operating costs expressed as cost per drill meter (ft), cost per cubic meter (cubic yard) of excavated rock, and cost per meter (ft) of tunnel advance. These costs may be calculated using as many cost centers as the mine, quarry, or tunneling contractor wishes. Specific operating costs may cover drill rig operating costs only, less capitalization; drill rig operating costs, including amortized equipment investment; drilling and blasting costs; drill, blast, load, and haulage operating costs; long-hole drilling operating costs per drill meter (ft) or per blasted cubic meter (cubic yard) of rock; and loading and transport operating costs. In all the above cases, any number of cost and capacity calculations may be run by simply changing important cost center variables to judge their net effect. Accuracy as a Function of Input Data and the Statistical Data Base Accuracy of a projection clearly depends heavily on the data base from which the projection is drawn.

Jan 11, 1982

By Donovan F. Symonds

INTRODUCTION The selection of the optimum coal preparation plant flowsheet is a vital part of the development of a new plant or the expansion of an existing facility. Selection of an inappropriate flowsheet or individual equipment items can result in costly production losses, or needless expenditures or redundant or oversized equipment. The accuracy of the flowsheet selection process is, like most decisions, heavily dependent upon the amount, reliability, and quality of the database. A flowsheet which is based on simple borehole information from an area that has experienced little or no previous mining activity must necessarily include significant allowances for uncertainties. However, a plant which is to be built at an existing mine with good information on run-of-mine (ROM) coal quality, as well as bulk washability data and accurate projections of future quality, can be optimized. The following chapter will describe the processes which should be followed to select the most appropriate flowsheet for each unique operation. They include: 1. Examining and adjusting the washability database to reflect the ROM feed. 2. An evaluation of clean coal specifications. 3. Selection of the level of washing required. This includes no washing, if the coal is already at the desired specification, all the way through to complex total washing circuits for metallurgical grade coals. 4. Selection of the appropriate circuit such as dense medium bath vs. Baum jig. The most appropriate circuit is generally determined on the basis of economics. An approach for performing the evaluation will be desired. 5. The steps that need to be followed to develop a balanced plant flowsheet. ADJUSTING WASHABILITY DATA It is not unusual to have as many as 10 to 20 sets of washability information available for a particular mining property. These may be a combination of core and bulk samples or all bulk samples. In the latter case, they may also be face and/or ROM samples. It is necessary to reduce all of this information to a single set of washability data that is representative of the mean feed to the proposed preparation plant. This set is used to compare the clean coal yield and quality characteristics of the various flowsheet options. The term "representative" has some serious negative connotations. It is recognized that ROM coal quality will vary throughout a mine. However, over a period of 250 to 350 days per year, certain trends can be established. If possible, this "representative" sample should be close to the coal quality of the mean daily sample in terms of raw ash and sulfur contents, clean coal yield, and clean coal ash and sulfur content. If possible, this sample should be within the

Jan 1, 1991

By C. C. Nolan

As the size of the mills get larger and the liners get heavier, a better means had to be found to handle liner replacement. McLellan Industries is famous for their innovative ideas and was called upon by an engineering company to develop a mill liner crane. The first crane was developed for Similkameen about 1969 to serve a 32' 0 x 14' Long SAG Mill. The next was Island Copper in Port Hardy, B.c., the same size as Similkameen in 1970. At that time, we took existing hydraulic cranes and modified them to meet the mill configuration. In 1973, we developed a completely new approach for the Southern Peru copper mine at Tacna, Peru for a Ball Mill, size 16'-6" 0 X 19' Long. Each installation required a design study to meet the change in mill size, trunnion size, elevation of floor to feed trunnion, area at the feed or discharge end of the mill. We have supplied self-propelled units as well as lift in. When there is no room at the feed end and if the mill has a trunnion overflow discharge, we have the mill supplier provide a structural frame to span the sump and move the mill liner handier into position with the use of the overhead crane or a mobile crane.

Jan 1, 1999

By H. R. Manouchehri

The responses of calcite, feldspar, and quartz minerals In a laboratory free fall electrostatic separator, before and after tribocharging with stainless steel, PVC, and copper plates, have been investigated. The effect of H3BO3 and BaCl2 chemicals pre-treatment on the electrical properties of the minerals is examined. The changes in the electrical properties are discussed with the determined charge, dielectric constant, and electrical conductivity of the mineral samples. Electrical properties of the minerals and their responses to the electrical field during separation, after tribocharging and chemical pre-treatment, are explored for the need to characterize the electrical behaviour of the minerals.

Jan 1, 1998

By Shijie Wang

The metals of value in tetrahedrite are copper, antimony and silver. A new hydrometallurgical process is proposed to recover these metals from tetrahedrite. The process consists of leaching concentrate with ferric fluoborate, solvent extraction, electrowinning and residue treatment. Products from this process are high-purity SX-EW copper and antimony and a high-grade silver residue that will be further treated in a hydrometallurgical process for early release of silver. The process has advantages, such as achieving rapid leaching rates at modest temperatures with high metal recovery. Most pyrite is not attacked. Thus, it remains in the leach residue along with elemental sulfur.

Jan 1, 2003

By P. D. Lafleur

A concerted effort to determine the quantities and effects of trace elements in the environment requires the application of a number of different analytical techniques in the same or in different laboratories. The interpretation of analytical data is often difficult because of differing results between analysts or even by the same analyst at different times. Standard Reference Materials (SRM), which are certified for their trace element content and are in a matrix similar to the one of interest, can greatly increase the accuracy of analysis and the reproducibility between laboratories. The United States National Bureau of Standards (NBS) has developed a number of SRMs applicable to the determination of trace elements in environmental materials. Two of these, SRM-1571, Orchard Leaves, and SRM-1577. Bovine Liver, are excellent for biological tissue analyses. Several new standards are of value for fossil-fuel analyses. These are: SRM-1632. Trace Elements in Coal; SM-1633, Trace Elements in Fly Ash; SM-1634, Trace Elements in Residual Fuel Oil: and SRM-1635, Trace Elements in Gasoline. In cooperation with the US Environmental Protection Agency, the NBS has recently concluded an interlaboratory comparison involving analyses by more than 60 laboratories on these fossil-fuel materials. The resulu of this intercomparison and the broad range experience with the biological materials will be presented showing both intratechnique and intertechnique variations, and the sensitivities and comparisons with the values certified by NBS.

Jan 1, 1975

By St. E. Deák

There is a large preoccupation concerning the development of expert tools (ET) in the mining industry, in order to minimize the impact from waste dumps and processing residues on the environment. In this paper, the authors present a new approach for the development of an expert tool for each area under study, in order to minimize production and disposal of mining wastes on the environment, by taking into account the DKRControl method as well as the Ecomining principles, regarding among others hazard identification, impacts and monitoring. Due to the complexity of this topic a reliable ET requires input from a number of interested stakeholders. The design and management of a mining waste disposal site over its entire life cycle is also considered very important.

Jan 1, 2008

By James W. Babcock

Introduction Geologic ore deposit models are key to any exploration program. In the search for ore deposits, the geologist first tries to understand the genesis of known ore bodies. During reconnaissance and evaluation of a prospect, a valid exploration model of a known ore body can help the explorationist focus on critical geologic attributes of the target area. Exploration models can conserve exploration funds that might otherwise be spent collecting data not critical to delineating an ore body. This article examines the benefits of using models, factors to be considered in developing models, and examples of the way recent models have evolved. New exploration concepts and techniques are developed in response to increased competition in the mining industry. New techniques can give an exploration group a slight edge that may translate into a discovery. Mine geology staffs may find previously unlooked for extensions to the ore body by applying new genetic concepts. When all appropriate techniques are applied to exploration and mining efforts, greater efficiency and increased profits may result. Before the 1950s, scientists speculated on the genesis of ore deposits and other natural phenomena. But they presented their results as if universal and final, even though they applied to only a few deposits. Because it did not provide sufficient criteria to distinguish the genetic processes, the classic conflict between hydrothermalists, epitomized by Lindgren, and nonhydrothermalists did not help the minerals explorationist much. Important information about individual ore deposits, such as age of the host rocks and mineralization, composition of the mineralizing fluids, and separation of mineralizing and nonmineralizing events in the paragenetic sequence, could not be gathered with past equipment and methods. But these early concepts of ore genesis contained excellent empirical observations, perhaps the most useful parts of these hypotheses. Through the years, prospectors have found most of the ore deposits in the world using direct observations and their collective empirical wisdom - an empirical model. The geologist's contribution becomes increasingly important after the more obvious surficial ore deposits have been discovered. In Europe and North America that time has arrived. With the introduction of sophisticated equipment and matching techniques in the 1950s in geochronology, geochemistry, geophysics, remote sensing, and computers, many previously equivocal genetic questions can be resolved. This proliferation of highly technical data has allowed the construction of many well-founded genetic models.

Jan 12, 1984

By A. K. Bakshi, Komar S. Kawatra

A plant trial of a new on-line pressure vessel rheometer for slurries, developed at Michigan Technological University, was carried out at a nearby copper concentrator. The rheometer measured the flow curves (shear stress vs. shear rate) of chalcocite slurries. Viscosity of non-Newtonian slurries changes with shear rate and so, for such slurries viscosity measurement at a single shear rate (often seen in the literature for grinding and classification studies) cannot be correlated to process performance. For these slurries, viscosity at various shear rates can be measured from flow curves generated by the pressure vessel rheometer. Other rheological properties, such as flow type and yield stress can be determined by this rheometer to better characterize the slurries. The slurry at the copper concentrator consisted of ground chalcocite ore. The solids content in the slurry varied between 30-60 % by weight. Top size of the particles was 125 micron, and 80% passing size was 34 micron. Measurements by the pressure vessel rheometer showed that most of the slurries had pseudoplastic flow at shear rates below -3000 sec-l, where the viscosity of the slurry decreased with increase in shear rate. Above -3000 sec-l, like a Newtonian fluid, the viscosity of the slurry remained steady. Flow curves and viscosity from the pressure vessel rheometer were verified with a Brookfield viscometer and a vibrating sphere viscometer, and the results were found to be accurate.

Jan 1, 1997

By Jiachen Wang, Nan Wang, Yang Li

The energy structure and consumption ratio in China determine the practical demand for the collaborative mining of coal and co-associated resources. The multi-layer mining of coal, uranium, coalbed methane, and oil and gas co-associated resources, represented by the Ordos Basin, Junggar Basin, and Tarim Basin, faces numerous challenges. Additionally, coal has been found to coexist with various mineral resources in 33 coal-bearing basins worldwide. The scientific issues related to the multi-layer development of coal related co-associated resources urgently need to be addressed. This paper discusses the unique challenges and potential solutions in the multi-layer development of coal-related co-associated resources. The challenges include large extraction space, high mining intensity, intense overburden movement, rapid surface subsidence, and severe overburden damage due to repeated mining disturbances. Proposed solutions include the establishment of a correlation mechanism between multi-layer mining and the carrying capacity of the overburden environment, analysis of the impact characteristics of multiple field couplings, and exploration of their superposition evolution laws. The paper also proposes the development of a comprehensive evaluation and prediction system for overburden environmental capacity loss, a global sensitivity analysis model for overburden environmental capacity, and an intelligent identification and early warning system based on multi-source information fusion. These solutions aim to achieve scientific and precise mining with minimal overburden environmental capacity loss. And the multi-layer development of coal-related co-associated resources is a complex task that requires a multidisciplinary approach and innovative solutions, and further research is needed to validate these strategies and explore new methods and technologies for efficient and sustainable extraction.

Jun 25, 2024

By John C. Braithwaite

Gold production commenced in New Zealand during the gold rush of 1861, and recovery to date is over 900 tonnes, almost 60% of which was alluvial. New Zealand pioneered development of bucket line dredges during the 1880's. The advent of the modern hydraulic excavator and increased gold price led to a resurgence in alluvial production with about one hundred plants in operation in 1988. The processing plants are mainly floating, with throughputs of 50-100m3/hr fed by backhoes of 20-40 tonne operating weight. Some larger plants with more sophisticated recovery systems have commenced over the last few years, with the largest using a 180 tonne backhoe.

Jan 1, 1989

By A. Benchekroun

The phosphate mining industry is confronted everywhere in the world with financial difficulties and low prices which prohibit further investments and development of new mines even in regions with a comparative cost advantage (North America/ North Africa/ and Middle East). But old mines are being progressively exhausted/ and if no replacement mines come on stream in the near future/ we may soon find ourselves (around the year 2000) with a global annual production capacity of 160 million tonnes of marketable phosphate rock instead of the capacity of 200 million tonnes existing today. Unless prices improve/ phosphate rock/ a non-renewable resource and a vital commodity to world agriculture/ may turn to be in short supply to world fertilizer industry. Whatever the extent of recovery of fertilizer demand/ the expected decline of the production capacity during the 1990 I s is bound to cause the disappearance by the year 2000 of the important surplus characterizing today the supply/demand balance.

Jan 1, 1995

By Paul J. Smith, Eudomar A. Silva, Quang D. Tran, J. Milton Brooks

The Dallas Mill Creek Drainage Relief Tunnel is an 8.04 km (5 mile) tunnel that will provide 100-year flood protection for impacted neighborhoods in the east Dallas area. “Big Tex” is a main beam gripper TBM capable of changing diameters in mid-tunnel to excavate 2.83 km (9,290 ft) of 11.45 m (37.58 ft) diameter tunnel and 5.21 km (17,095 LF) of 9.93 m (32.58 ft) diameter tunnel. Construction began in April 2018 and is anticipated to be completed in 2024. This paper will discuss the challenges and lessons learned during assembly and re-assembly, start-up and mining with “Big Tex.”

Jun 13, 2021

By R. Y. Wan, J. D. Miller, P. L. Sibrell

Three different refractory carbonaceous gold ores from the Carlin operation in northeastern Nevada were investigated to characterize the effect of passivation treatments on the nature of the carbonaceous material. The carbonaceous material was chemically isolated from the ores and passivated residues, and examined by FTIR spectroscopy, elemental analysis, and gold adsorption capacity. The main component of the carbonaceous material in these ores was found to be a naturally occurring activated carbon-type compound. Hydro-carbons were detected on rare occasions, but no evidence was seen for humic acids. Ore samples were passivated by autoclaving, or by treatment with sodium hypochlorite or gaseous chlorine. In some of the passivation tests, a new peak was observed in the IR spectra of the isolated carbonaceous material, that was due to carbonyl functionalities. However, all of the passivation treatments tested decreased preg robbing significantly. This suggested that the appearance of the carbonyl peak was due to the severity of the conditions during passivation, rather than the method used.

Jan 1, 1990