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By V. A. Leach, Lokan. K. H., S. B. Solomon, R. S. O’Brien, L. J. Martin, K. N. Wise

INTRODUCTION The development during 1979 of a relatively small, but high grade (10,000 tonnes uranium at an average grade of 2 per cent), uranium ore body at Nabarlek in the Northern Territory, Australia offered an excellent opportunity to obtain detailed radiation data for an open cut mine operating during the dry season. The ore body (Queensland Mines Limited-1979), which was completely extracted in a period of four and a half months, consisted of a vein type deposit dipping at 30 to 45 degrees and contained a central core of pitchblende in massive and irregular pods, surrounded by lower grade fine grained disseminated pitchblende. Mineralisation extended from the surface to a depth of 72 metres over a length of 230 metres with an average but variable thickness of 1D metres. Ore near the surface had been heavily weathered and complex secondary minerals were formed which had dispersed from the main vein. Mining was carried out with large earth moving equipment. Overburden and weathered surface ore were removed initially with scrapers. At greater depths bulldozers were used to rip and assemble ore and rock at each level, and these were removed by large trucks to the ore and waste rock stockpiles. Where necessary, blasting took place during shift changes each evening. Mining was essentially continuous with two ten hour alternating shifts working for thirteen days out of fourteen. At the completion of mining a relatively small excavation (335m x 185m x 70m) remained, and this will serve as a tailings repository during the milling phase. FIELD MEASUREMENTS The inhalation of radon daughters, arising from the radioactive decay of radon gas is well established (Archer et. al. 1973) as a potential hazard in the uranium mining industry. Control over radon and its daughters to ensure that recommended exposure limits are not exceeded is achieved by providing adequate ventilation, and under normal circumstances natural ventilation from an open pit should be sufficient. However, during the dry season it is not uncommon for stable atmospheric conditions, with little horizontal air movement, to develop - particularly at night - and significant radon daughter concentrations may accumulate. Throughout the entire mining period measurements were therefore made of radon and radon daughter levels at representative locations within the pit and on the ore stockpile as it developed. Initially these measurements were carried out manually, using the Rolle method for radon daughters, (Rolle 1972) and .scintillation cells (Lucas 1964) or a two filter tube for the determination of radon (Thomas 1970). For the latter half of the period however, a continuous recording instrument, developed within the Laboratory was used to provide a detailed record of radon daughter levels within the pit. At the same time, continuous readings of wind speed and direction, and vertical temperature gradient between 10 and 3D metres were recorded on a 30 metre meteorological tower, situated 800 metres from the pit. Radon Emanation Rates It is evident that radon and radon daughter concentrations depend on the grade, or more particularly, on the surface radon emanation rate of the ore which is exposed. Accordingly, as the mine progressed, detailed measurements were made of both of these quantities. The surface emanation rate of radon was determined for each ore bench as it was exposed by placing an extended array of canisters, filled with freshly degassed activated charcoal, face down on the ore for a known time. These canisters, which had previously been calibrated in the Laboratory, adsorb radon with high efficiency, and the total radon adsorbed is measured after retrieval by detecting the gamma rays from the trapped radon daughters (Countess 1977). At the same time, as each canister was placed in position, a measurement of the local ore grade was made for each location. This was achieved with a calibrated sodium iodide scintillation detector, adjusted to detect the 609 keV gamma ray from the isotope 2148i, a decay product of radium. Finally, measurements were made of the radiation field 1 metre above the surface, with a gamma ray survey meter, which was calibrated in the Laboratory. The relationship between the scintillator count rate and ore grade was determined by comparing the scintillator output with the gamma monitor, and relating the latter measurements to ore grade (Thomson and Wilson 1980). It was observed that while emanation rates and ore grades varied widely, the ratio of emanation rate to ore grade was in general fairly stable. A plot of this ratio is presented as a function of depth below the original surface in Figure 1. For most observations the ratio is constant at a value of 80 Bq m-2 s -1 per unit ore grade, where ore grade is expressed as percentage of U308. At the surface however, where the ore was weathered, the ratio was about a factor of three higher, and at two particular depths, where high grade pitchblende was being removed, it was very much lower. This was not unexpected as earlier Laboratory studies of drill core samples from Nabarlek had indicated that the emanation coefficient (the fraction of radon produced within the ore which escapes from the mineral particles) decreases with increasing ore grade.

Jan 1, 1981

By Steven W. Hunt, Steven B. Fradkin, Roger J. Maurer

During the 1980s and 1990s, twenty deep shafts were constructed in Milwaukee to depths from 85 to 91 m (280 to 300 feet) through soil and weak rock thicknesses ranging from 37 to 69 m (122 to 227 ft). Adjacent compressible soils, settlement sensitive structures and high groundwater levels required that shafts be constructed without dewatering. Contractors attempted several methods of ground support and groundwater cutoff. Significant problems developed during construction of 11 of the 20shafts. One shaft collapsed; groundwater blow-ins occurred at five of the shafts; and seepage caused unfrozen windows at three of the freezewalls. Ultimately, combinations of grouting and ground freezing were utilized to complete all of the shafts into bedrock. This paper discusses the main design and construction challenges experienced and the lessons learned.

Jan 1, 2003

By W. J. McDonough

Rapid growth and acceptance of engineered materials have changed the way we live. We have come to expect improved performance at less cost. At the same time, our awareness of societal and environmental issues created by these materials during and after their lifetime has been heightened. As a result, material lifecycle analysis is receiving considerable attention. Material lifecycle analysis evaluates the cost/effective tradeoffs at each stage of a material's life: feedstock, fabrication, performance, recycle, and disposal. The U.S. Bureau of Mines investigates a material's lifecycle using technical cost models augmented with decision and impact analyses. Results of these studies are useful in gaining a better understanding of current material selections and illustrating the multifaceted issues associated with engineered materials in today's society.

Jan 1, 1992

By John F. Slonaker

This report is a review of current research being conducted in the United States which is intended to increase the utilization of coal ash. In order that this report be as timely as possible, the majority of information was obtained by direct comunication with the people listed in the references. Due to the magnitude of the flyash research program, some projects may be inadvertently omitted. Field research on flyash for use as an agricultural fertilizer is being monitored at Virginia Polytechnic Institute and State University.1 This research is directed at determining the plant nutrients that are available in flyash as well as the quantities of flyash that can be applied to agricultural soil without adversely affecting plant growth, Coal mine spoil and refuse bank reclamation with power plant flyash is being demonstrated by United States Bureau of Mines, Morgantown, West Virginia.2 Numerous highly visible coal refuse piles and strip mine spoil banks contribute to air, water, and land environmental problems. Revegetation of several experimental sites with flyash from bituminous coal-fired power plants was undertaken in West Virginia and Pennsylvania. Conventional farm equipment was used at some of the sites while large earthmovers were required at others. The flyash served as a neutralizing agent, dilutent, and soil amendment to provide some nutrients which enhanced vegetation of the barren areas, Estimated cost of reclamation by this method is $300.00 per acre of previously leveled area. This figure can vary considerably depending upon the topography of the site, haul distance, quality of the soil and quality of flyash.

Jan 1, 1974

By W. A. Weimer

Coal and coal mining is no longer the mighty king of industry and in our daily lives and homes that it once had the privilege of commanding. Many of you will remember that one of the chores of your youth was to bring in the scuttles of coal, morning and night, to feed the heater or stoke the furnace in the morning and bank it at bedtime. Growth of gas and oil have displaced coal in home furnaces and commercial buildings, and have taken over some segments of industrial markets. The coal burning locomotives have virtually disappeared in favor of the more efficient diesel engine. However, coal as a prime mover still holds its strategic position as is evidenced by act that the electric power industry almost entirely depends upon coal for its generation.

Jan 1, 1961

By Wilbur H. Smith

Geologic mapping techniques at the Bingham Mine have evolved as rapidly expanding applications of geological data have caused new methods to be utilized. The most significant changes in method have been in the preparation of the base map and in computer application of collected data. Formerly maps were prepared by surveying with transit or plane table. Currently a photogrammetric map, on the scale of 1-inch equals 200-feet, is prepared semi-annually and continuously updated to keep pace with the removal of more than 350,000 tons of material daily. Larger scale bases for specific problems, such as areas having unstable slopes, are prepared by use of aerial and terrestial photography and photo mosaics. Note sheets designed for computer application enable fast processing of the data. Application of geology at the Bingham Mine has been increasing rapidly in recent years. The effect of structure, rock type, and alteration on slope stability, the relationship of sulfide mineral distribution to concentrating results, the effect of rock and mineral types on waste dump leaching, and requirements of a reliable internal source of silica flux for smelting are a few of the problems which require the collection and application of geologic data.

Jan 1, 1968

By I. E. Odom

An electron optical and microprobe study was made to determine the physical and chemical nature of the silica minerals that occur as natural impurities in bentonite and montmorillonitic fuller&apos;s earth clay products (both granular and powder) and that occur in <10-µm dusts from plants that process these products. The purpose of the study was to determine if discrete "free" silica minerals, such as quartz, could be observed using SEM and EDS methods. No “free" silica minerals could be observed in the SEM images of the granular and powdered products, either among or on the surfaces of the particles. Also, no “free" silica could be identified by either SEM or EDS analyses of the dusts, even though quantitative X-ray diffraction analysis indicated that trace amounts of quartz occurred in all samples. It was determined that these quartz and other silica minerals were encapsulated or coated by montmorillonite. Vigorous washing, however, removed some of the clay coatings, so that small amounts of silica minerals could be seen by SEM and EDS analysis. It was found that all primary crystalline quartz grains in the bentonites have diagenetic overgrowths consisting of a mixture of montmorillonite, opaline silica and possibly microcrystalline quartz. Detrital quartz grains in the fuller&apos;s earth have thin diagenetic overgrowths of opaline silica, also containing montmorillonite. The clay encapsulation of the silica minerals in the products studied, as well as in the potentially respirable (<10-µm) dust produced during manufacturing of bentonite and montmorillonitic fuller&apos;s earth clay products, is considered to be an important factor influencing the potential health effects (e.g.. silicosis) of the contained silica. Even if clay dust containing silica should be inhaled, the montmorillonite encapsulating the quartz and other silica minerals would prevent direct contact of the silica with lung tissue. The clay encapsulation of quartz, as well as the highly hydroscopic nature of montmorillonite, may explain why not a single confirmed case of silicosis has ever been reported among plant workers in more than 65 years of production.

Jan 1, 1998

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 E. Berrezueta

Automatic digital phase imaging should yield unbiased and representative characterization of gold ores. However, this is not a simple task due to low gold grades, fine grain size, possible complex mineralogy, nugget effect, etc. A critical test was done by two methods, using the same sections of a gold-rich ore: with an optical (OM) and with an electron microscope (EM). In general, the two methods are consistent and useful for ore processing. There are some minor differences e.g. the detection of very fine gold grains is enhanced by EM.

Jan 1, 2001

By P. A. Meyer

The Tenmile Range is a north trending zone of high relief within the central Colorado porphyry-mineral belt, located between Leadville and Breckenridge. (Figure 1, the Index Map of the area surveyed.) The Climax mineralized zone is located at the southern end of the range on the northwest side of the Continental Divide. This portion of the total area surveyed will be discussed in detail today. A fixed wing aeromagnetic survey was flown over this range and mineralized zone in the fall of 1957. The survey was run as an experiment to see if a useful geophysical tool could be applied in the exploration for similar type deposits. The purpose of this paper is to describe the results of this survey and the approaches used to aid in the interpretation of the total intensity data.

Jan 1, 1968

By C. W. Matthews

Introduction Screening is an art, one of the oldest in the process field today, and one of the most widely used in our present age. Screening is being applied to an ever-increasing number of assignments, in an ever-expanding circle of industries. Screening is defined precisely as a mechanical process which accomplishes a separation of particles on the basis of size and their acceptance or rejection by a screening surface. Particles are presented to apertures in a screening surface and rejected if larger than the opening, or accepted and passed through if smaller. Screens are machines with screening surfaces used to classify materials by size. The screening surface is the medium containing the apertures for the passage of the undersize material. Screens are put to many uses - size separation, dewatering, desliming, media recovery, scalping, trash removal, washing, dedusting, conveying, concentration, and many combinations of these functions. It is interesting to note that screens are used for handling commodities

Jan 1, 1985

By James Douglas

For the past several years, inflation has placed increasing pressure on our economic system. The total effect of inflation is complex when combined with other factors which affect the economics of equipment. A mathematical model is described herein which can be programmed on a computer to determine the effect of inflation on economic life and profits after taxes. The computer output results in graphic plots which clearly show the relation of various percentages of inflation to life and profits. Inflation has become a common topic of conversation in the recent past. What is it and how can it be measured? What effect does increased inflation have on equipment policy? Research now in progress at the Construction Institute at Stanford University is beginning to unravel some of the mystery of inflation. As a start, let us answer the first question by defining the word inflation. The dictionary says that inflation is "an increase in the volume of money and credit relative to available goods resulting in a substantial and continuing rise in the general price level. It appears, in fact, that we are in an inflationary spiral which is "a continuous rise in prices that is sustained by the tendency of wage increases and cost increases to act on each other." 3 Inflation behaves just like compound interest. It takes more dollars of future years to buy an equal amount of a given commodity, be it a material or a service. Let us assume an annual inflation rate of 5 percent. Assume that 1Associate Professor of Civil Engineering, Stanford University, Stanford, California. 2Webster&apos;s Seventh New Collegiate Dictionary, Springfield, Mass., G. and C. Merriam Co., 1969. 3Ibid.

Jan 1, 1972

By K. Kavouridis

On 30 April 2004, a large scale slope failure incident occurred at the external waste dump facility of the South Field Mine, in the Western Macedonia Lignite Center, Greece. This landslide involved the mobilization of waste overburden material (that was continuously deposited for the last 20 years) in the order of 40 Mm3, while the material that moved outside the boundaries of the waste dump was in the order of 3 Mm3. The factors that led to failure as well as the procedures and measures taken in order to stabilize the failure and resume normal operations at the South Field Mine are presented and discussed. Emphasis is given to the impact on mine operations and the cost related to resuming of normal production operation as well as to implementing important modifications and improvements of the materials handling system.

Jan 1, 2006

By S. Bastola

Over 80% of roof falls in Illinois coal mines occur at intersections. Regular intersection geometries with sharp corners have been typically analyzed in literature. This study has analyzed stress distribution around typical field 4-way intersection geometry and compared it with similar data for regular four-way intersection geometry. These analyses were performed using 3-D numerical analyses for a typical lithology associated with No 6 coal seam in southern Illinois. Linear elastic and non-linear analyses, using Hoek-Brown failure criteria for different lithological units, were performed. The 3-D models incorporated bedding planes and pre-mining horizontal stresses. Effect of diagonal widths of the intersection and pre-mining horizontal stresses were examined due to their influence on stability. In addition to stress distribution, contours of safety factors, and displacement analyses were performed to assess stability of intersections.

Feb 27, 2013

By N. Harrigle, Tsutsumi

Very fine wet sizing of minerals such as kaolin, precipitated calcium carbonate, lime milk, and clay slip is a difficult process to achieve using standard vibrating screens. With particle sizes ranging in the sub-microns combined with the agglomerating tendencies of certain materials, screen blinding becomes a serious issue. Sizetec, Inc. has developed an innovative screening equipment to help solve this problem. The High Performer Screen uses powerful linear vibrations to help break apart agglomerated particles and prevent screen blinding. Optionally fitted with the Air Explosion Screen Cleaning System, compressed air can be periodically injected into the screen underflow chamber to clean the screen surface without the use of water sprays. This paper highlights some of the key features of the Sizetec High Performer Screen and describes typical performance that can be expected based on results from various trials conducted in the kaolin industries.

Jan 1, 2002

By J. E. Gebhardt, D. A. Rice, P. E. Richardson

An improved understanding of the significant role of electrochemical reactions in sulfide flotation has evolved in the past 20 years, This understanding has been accompanied by a corresponding increase in attempts to control the electrochemical potential of flotation pulps for monitoring and controlling sulfide flotation circuits to improve metallurgical performance. This paper discusses the basic electrochemistry of sulfide flotation and the use of electrochemical potential as a control parameter.

Jan 1, 1993

By G. Brien, O&apos

Selective in-plant breakage was investigated at a Central Queensland, Australia mine. Component seams and size fractions from in-plant samples were characterized petrographically and probability analysis of vitrinite reflectance data used to track the distribution of seam proportions through the plant. Results show that the 2 seams reported differentially to coarse and fine circuits, mainly as a function of coal type rather than rank. Seams were also preferentially concentrated in different size fractions of the coarse circuit. Breakage in the coarse coal centrifuge generated approximately 4% of -0.5 mm fines, but was not seam specific.

Jan 1, 1996

By Fathi Habashi

WHILE HYDROGEN SULFIDE precipitates metal sulfides from aqueous solutions, other gases such as sulfur dioxide, carbon monoxide, and hydrogen, under certain conditions, precipitate the metals directly. This can be achieved at high temperature and pressure. Such processes are of great technical importance, since metals of high purity are precipitated economically in a powder form. As a result of the availability of such powders on a large scale. processes for compacting metal sheet and other mill forms directly from the

Jan 1, 1970

By Mathew B. Revell, Martyn L. Bloss

The paste fill system at BHP Cannington&apos;s underground silver-lead-zinc mine is described. The paste fill system has been operational since December 1997 and is the first of its type in Australia. Technical and operational learnings since stope filling commenced are presented. Topics described include plant performance, reticulation system design and construction, pipe wear and failure, rheology, in situ performance and laboratory testing.

Jan 1, 2001

By Richard Jr. Ray, David Johnston, Phil Blankenship

Injection of inert gases to combat mine fires has been practiced in various parts of the world for a long time. Of late, nitrogen has become the preferred inert gas for control of mine fires and safe salvage of longwall equipment as compared to carbon dioxide or fuel gases produced from burning of fuel. In India, carbon dioxide has been used for fire fighting in a number of mines during the 1960s and 1970s. More recently inert gas produced from burning of fuel oil in surface plants has been used in controlling the atmosphere in fire areas in two mines. In yet other cases, liquid nitrogen has either been poured directly into fire areas in liquid form or injected in gaseous form to keep the fire in check. Nitrogen produced in liquid form in an oxygen plant is more costly than nitrogen produced from PSA (pressure swing adsorption) based plants. A PSA-based plant has been installed in one of the Indian mines in 1986 and more are in the offing. This paper reviews the application of various inert gases in Indian mines and discusses the likely trend of inert gas application in Indian mines in the future.

Jan 1, 1989