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By Peter G. Groer

The commonly used exact methods (1-2) to determine the WL measure the total a activity or the total number of a counts during three preselected time periods. Due to the half-lives involved (TRaB = 26.8 min, TRaC = 19.7) I these methods take 3S minutes to complete the a activity Ra measurements. Methods using the total a counts, obtained at times less than about one RaB half-life after the end of sampling run into statistical 214 problems. These methods are almost blind to RaB (Pb214) as a consequence of its relatively long half period (see above) and the fact that RaB is a ß emitter. The way out of this dilema is to measure RaB directly through its ß activity. Since RaB's daughter Rae (Bi214) is also a ß emitter, the two f3 spectra have to be separated to obtain RaB alone. How this is accomplished 1s described in subsequent sections describing the theory of the IWLM and its calibration. 2.0 THEORY The IWLM samples air for two minutes and counts this airs ample for two minutes starting 3 sec after the end of the sampling period. The instrument has three channels. The lower a channel, the upper a channel, and one ß channel. The total RaA counts observed are accumulated in the lower a channel, the total RaC? counts are stored in the upper a channel. The total ß counts from RaB and RaC are recorded in the ß channel. These three quantities are functions of NA, NB, and NC, the unknown concentrations

Jan 1, 1975

By G. Tamaro

The World Financial Center is situated on a 60,000 square meter site at Battery Park City at the southern tip of Manhattan Island. The foundations for the buildings and the related infrastructure posed difficult design and construction problems since the site was filled land in the Hudson (North) River. Foundation construction was made difficult by both the geology and the existence of two railroad tunnels which passed under the site. The soils at the site were unsuitable to support construction of heavy structures, and as a result, all of the foundations had to be carried down to bedrock, or the glacial till over rock. Two buildings were supported on piling and special battered caissons which provided lateral support against wind loading. The other two buildings were supported directly on rock, requiring excavation to depths of 19 meters (63 feet) below grade.

Jan 1, 1989

By T. G. Sieber, T. D. Tiemann

The extraction of quartz from siliceous iron ores by dissolution in sodium hydroxide solution has been described in detail in AIME Transactions. l923 data reported covered the temperature range from 230-416°F, where a continuous increase in the amount of silica extracted with increase in temperature was found. It is the purpose of this paper to describe some unexpected results of more recent work exploring principally the range of 500600°F where higher rates and greater amounts of silica extraction were antici-p ted. In brief, the experimental procedure consists in digesting the ore under pressure in solutions of sodium hydroxide, filtering the suspension and weighing and analyzing the dried residue for iron content. The amount of extraction is calculated from the weight loss or from the iron analysis of the residue and that of the original ore.

Jan 1, 1969

By R. D. Hull

Paper written on project work carried out in partial fulfilment of B.Sc. (Eng.) (Mining) degree As a partial fulfilment for the degree of B.Sc. (Eng) (mining) at the University of the Witwatersrand, a dissertation was to be completed in the mining industry. This was done at Finsch mine, with the purpose of determining the best solution to the required secondary breaking problem. In order to complete the study of the secondary blasting method available for use in the new block 4, cave mining method at Finsch mine the following problem statement was identified and solved ?The methods currently in use, for the secondary breaking of oversize rocks at their source in the current production levels, are to be investigated, and their applicability to the new block 4mining project determined?. To effectively achieve this problem statement above; time was spent researching and investigating, in depth, the methods that are currently in use at both Finsch and Koffiefontein mines; so as to gain practical knowledge of these. The methods were identified and independently evaluated, taking into consideration factors such as costs of the equipment, time to break oversize rocks, advantages, disadvantages, safety and labour requirements, etc. This in turn then allowed for a direct comparison between the methods and the decision as to the best to apply to the new block 4 production level. The methods that were investigated included: ?Concussion blasting, where concussion bombs and lay-on charges are used to break hang-ups and boulders. ?Drill and blast methods, where holes are drilled in large rocks and charged manually with explosives. ?Emulsion secondary blasting, which is a new project in use at Koffiefontein mine from African Explosives Limited. ?The Ro-BustTM breaking system, a hydro-fracturing breaking system. Once all the methods had been evaluated and compared it was found that the Ro-BustTM Breaking system was the most applicable for the breaking of boulders, with, the Emulsion Blasting System being used for hang-ups. Further information and the more in-depth version of this report, is stored in the resource centre at De Beers?Finsch Mineand the School of Mining Engineering WITS University.`

Jan 1, 2002

By L. C. IlsLey

Many accidents rightly classifiable as electrically caused are not so classified for the reason that in numerous accidents the part that electricity played in causing the fatality is only suspected. For instance, a workman might receive a shock that would cause him to lose his balance and fall beneath a trip of cars; if no one saw the first part of the accident, the cause undoubtedly would be charged to "haulage." This paper covers a brief study of fatal and nonfatal electrical accidents. The first usually result from direct contact with the electrical circuit or electrical apparatus; the second more often are the result of arcing or flashing due to handling defective apparatus or making repairs on "live" equipment or circuits. It is hoped that helpful suggestions may be offered for minimizing accidents of these two classes.

Jan 1, 1938

By Sunil Koppalkar, Liming Huang

"Since late 1980s the research group led by late Professor Andre Robert Laplante at McGill University undertook fundamental studies and applied research of the Knelson Concentrator (KC) and developed a sustainable method to correctly estimate gravity recoverable gold (GRG). In the early time a concept of ‘free gold’ was used, it was defined as the gold that could be separated and recovered from gold ore by amalgamation. Due to health and safety hazards, its practical use had declined. Around 1994, a methodology using a 3-in Knelson Concentrator to measure gravity recoverable gold was established at McGill University. Through more than 10 years’ improvement and optimization, this technique had become a standard method to evaluate GRG for gold ores, gold plant streams and platinum group metals. Until 2006, about 200 GRG tests had been carried out at McGill University for the ores from all over the world. Recently, a modified version of GRG test (short test) with the advantages of reduced processing time and lower cost had been developed for the mundane needs of gold industry.INTRODUCTIONGold gravity recovery has evolved significantly over the past twenty-five years, mainly because of the advent of the Knelson Concentrator (Knelson 1988, 1990, 1992, Laplante 2000). Now, a series of Knelson Concentrators for different applications are manufactured and used in gold industry all over the world (Knelson Concentrators 2004).In 1980s the Knelson Concentrator gained acceptance from mining industry as an effective device for the recovery of gold from grinding circuit. Knelson Concentrator became the obvious choice because of its design features: a relatively long processing time without concentrate discharge (compared to some other centrifuges, such as Falcon Concentrator and Chinese Yunxi Centrifuge at that time), large throughput capacity, treating a wide size range of material, yielding a high grade concentrate with small mass that could easily be smelted. As more and more Knelson Concentrators were accepted in gold industry, mineral processing engineers faced with challenges: what are the separation mechanisms of the Knelson Concentrator? How much gold can be extracted for an ore if a Knelson Concentrator is installed? For answering these questions, a laboratory scale Knelson Concentrator was created."

Jan 1, 2007

By L. B. Hales

Expert control of grinding and flotation plants has been successfully used in the minerals industry since the 1970?s. The earliest of these systems were written in a hard-coded fashion in FORTRAN, BASIC or Pascal. Second generation systems were built using the first experimental expert system shells that were being developed in the artificial intelligence community. Later systems were deployed in expert system shells designed for real-time processing plants that also included the ability to model the process with neural network models and optimize setpoint selection through the use of genetic algorithms. Significant performance increases have been achieved using these systems, but in general, they suffer from the static nature of their rules and to a degree the process models also. Typical improvements quoted in the literature suggest throughput rate increases of 4 to 8 percent and recovery increases of 1 to 4 percentage points. In over 30 years of designing and installing expert systems we have never seen performance numbers less that these but have often seen numbers in excess of the high values. However, once the system has been installed and tuned up the performance usually does not improve much thereafter. Granted, the initial increases in throughput rate and recovery are significant but a question always lingers, that is, can the expert strategies be modified further to squeeze a little more improvement out of the system. The answer to this question is a resounding yes, however a complete understanding of what we do well as designers and operators of expert control systems is required as well as how we can improve upon our best practices is required to move us from the performance plateau we have been on for a number of years to a new higher level of performance.

Jan 1, 2009

By Randall J. Essex

The Construction Institute of the American Society of Civil Engineers recently published the second edition of a 1997 publication on geotechnical baseline reports. The new publication, called Geotechnical Baseline Reports for Construction, Suggested Guidelines, represents a 2-year effort that adds three new chapters to the original publication, as well as capturing practitioner commentary through two industry workshop sessions. The paper will overview the contents of the new publication, particularly the three new chapters.

Jan 1, 2008

OZ Minerals Limited owns and operates the Prominent Hill Copper-Gold Mine, located 140 km southeast of Coober Pedy in far north South Australia. The Prominent Hill mine comprises an open cut mine with an initial 10 year mine-life and an 8 Mtpa conventional grinding and flotation plant to produce high quality copper-gold-silver concentrates, which are exported by road to local customers and by rail to the port of Darwin for shipment on to Southeast Asian smelters. Mine and process operations at Prominent Hill are licensed to abstract a water supply of up to 26 ML/d, sourced from a borefield located 40 km and extending to 80 km east of the mine. The arid climate of the broader Prominent Hill region means that groundwater is important for sustaining community and pastoral industries in the region, and security of water rights for third party users is a critically important water management issue posing a significant challenge to the development of Prominent Hill. Depth to water table and the typically high salinity of groundwater in the region means there is little environmental dependence on groundwater within the immediate Project area (mine lease and wellfields). The Prominent Hill mine and associated infrastructure lies within the South Australian Far North Prescribed Wells Area (FNPWA), which was principally defined to ensure the ongoing security of the ecologically, socially and culturally significant GAB springs, of which the closest are found around 150 km northeast of Prominent Hill, and only 50 km northeast of the water supply borefield. Prescribing of the FNPWA meant that OZ Minerals was required to demonstrate to both State and Federal Government agencies that the mine's water supply is independent of that which supports GAB springs and other third party water users in the region. Recognising these potential obstacles, OZ Minerals successfully defined and developed a previously unknown industrial quality groundwater resource, separate from other important groundwater resources in the region that supply community, pastoral and environmental users, ensuring third party water user sustainability.

Jun 1, 2010

By C. D. Elifrits, N. B. Aughenbaugh

Introduction Federal and state laws enacted to regulate coal mining and the accompanying public concern about the adverse effects that mining might have on land use have focused much attention on the subsidence of the land surfaces over underground mines. Some questions asked are: • Will abandoned mines subside in the future even though they have exhibited no surface adjustment to date? • If so, when will subsidence take place? • Can a specific surface area be affected by subsidence more than once? • What surface form will the subsidence feature take? • Is there any way to predict when subsidence will occur and end? An attempt is made here to address these questions insofar as it is possible with available data and experience of evaluation of subcritical extraction conditions. Mining that results in subsidence features can be classified as supercritical, subcritical, and critical with respect to the minimum span lengths of the worked-out rooms (Fig. 1). A complete basin will not develop fully immediately over subcritical conditions because the span lengths of the entries are less than the critical dimension (Wardell, 1983). Passageways, entries, and room-and-pillar panels are all included in the subcritical category. Because of the short span lengths, subcritical mining conditions tend to be stable over the life of the mine unless adverse geologic conditions exist (Gray et al., 1974; Dunrud, 1976). Various roof control and support procedures are employed to maintain entry stability during mining. Little information exists concerning the time factor of subsidence over areas of subcritical extraction. Data that have been collected relate to longwall mines, whereby the cavity sizes are designed large enough to induce caving behind the working faces so that complete subsidence at the surface occurs within a short period of time. The UK's National Coal Board (1975) has reduced the enormous amount of data it has collected to empirical correlations and has published these correlations in its Subsidence Engineers Handbook. The handbook states that "None of the foregoing remarks applies to pillar and stall working," with respect to the section discussing the time factor of subsidence caused by longwall mining (National Coal Board, 1975, p. 40). To understand and evaluate how time relates to subsidence above room-and-pillar mines, one must first recognize how mine cavities deteriorate and fail. The propagation of failure to the surface must then be studied, and, finally, the failures that are manifest at the surface in the form of depressions accompanied by both compressional and tensional movements must be investigated. Failure of mine cavities Any cavity beneath the earth's surface represents a condition of nonequilibrium and tends to close with time. Failure of cavities in a subcritical mine can be classified as failure of the roof, failure of the floor, failure of the supports (pillars, cribs), and elastic rebound of the rock. One mode of failure may dominate, but generally combinations of the four will occur. Also, initial instability of geologic materials and structural features and in situ stress may be unknown factors that can contribute to cavity failure. Roof failure is the most obvious opening stability problem in most operating mines. The bridging capabilities of the roof rock are dependent on the rock's material strength, geologic discontinuities, and reaction to humidity changes in the air of the mine. This type of failure may vary in magnitude from gradual flaking to massive roof falls. Mine floor instability can be manifest in the form of a general heave over a broad area or of individual pillar punching. The weaker and thicker the immediate floor material, the more prone a mine is to experience floor problems. Water seeping into an area can soften the underclay, reduce its bearing capacity, and precipitate failure of support for the overburden.

Jan 8, 1986

Modelling and simulation are important aspects of flotation research, which may assist in the design of new circuits and the optimisation of existing ones. Flotation research in the AMIRA P9 project has developed a methodology for flotation plant modelling based on determination of cell (pulp) characteristics. froth characteristics, and ore floatability (using floatability components). The implementation of this methodology requires the determination of ore floatability, to which end a small flotation pilot plant known as the Floatability Characterisation Test Rig (FCTR) has been designed and then built and kindly made available to the AMIRA P9 project by Baker Process. The FCTR has a 2 tph capacity and consists of six 130 litre rougher/scavenger cells and six 50 litre cleaner/recleaner cells. The Mintek FloatStar pulp level control system is used to control the pulp level in all cells. A number of experimental procedures have been developed for using the FCTR to obtain the data required for the P9 flotation models. These procedures include how to determine the floatability parameters, Pi and mi, the bubble surface area flux, Sb, the mean residence of the pulp in the cell, t, water recovery. Rw, froth zone recovery, Rf, and the degree of entrainment, ENT. The flexibility of the FCTR allows it to be used in numerous flotation studies such as stream characterisation, reagent testing, grinding experiments, power studies, oxidation studies, and scale-up and simulation studies. This paper will describe the design and operation of the FCTR and the procedures that will be used to obtain data from the rig for modelling purposes.

Jan 1, 2000

On the 26th of June 2000 a hydraulic fill retaining barricade failed at the Bronzewing mine in Western Australia. The barricade failure resulted in the release of 19,000 m3 of saturated hydraulic fill into the mine and caused the deaths of three miners. Following this tragic accident, the practices and procedures of mines using hydraulic fills came under intense scrutiny by regulatory bodies and mining companies. At this time, the use of hydraulic fill at Normandy?s zinc/copper Scuddles mine was suspended and waste rock became the sole backfill material in use underground. By 2003, development of the adjacent Gossan Hill mine had progressed to a point where a self supporting fill material was required to enable full recovery of high grade ore. Cemented hydraulic fill (CHF) was identified as the optimal fill type and work began on designing appropriate management procedures and controls to ensure the safe implementation. This work included definition of the fill properties, plant design and construction, reticulation system design, design of stope barricades and drainage systems and fill placement control and monitoring practices. CHF placement began on 16th July 2004 and has continued to date. Significant operational experience has since been gained in areas including plant performance, fill product quality assurance, barricade construction, stope drainage and in-situ performance.

May 1, 2007

By L. C. IlsLey

The increasing use of Diesel engines for operating equipment on trunk-line railroads and for power-plant units has stimulated interest in the use of Diesel engines for other lines of work, among which is the possibility of substituting Diesel locomotives for trolley locomotives for mines. The possibility of developing Diesel locomotives for duty in American mines is not as remote as it might seem, particularly in view of the fact that locomotives of this type are already used in considerable numbers in European mines. A study of Diesel locomotives in Europe is contained in Report of Investigations 3320, Diesel Mine Locomotives - Development and Use in European Coal Mines, by George S. Rice and F. E. Harris.

Jan 1, 1938

By D. Harrington

The code of hoisting signals for use in mines hoisting from one level, as suggested in this publication, is submitted to induce consideration of this subject by representative groups of the coal-mining industry, such as the lithe Inspectors Institute of America, National Coal Association, American Mining Congress, and others, as well as to -furnish a code of signals for use in those mines operated in States that do not have regulatory hoisting codes in their mining laws, or regulations. The signal codes described in this publication apply only to mines hoisting from one level and to slope mines. Mines that hoist from more than one level are referred to Bureau of Mines Information Circular 7289 Suggested Hoisting-Signal Code For Metal Mine Shafts, which suggests signals for hoisting from various levels or stations.

Jan 1, 1944

By Pierre Rocque

The Red Lake Mine is located approximately 600 km northwest of Thunder Bay. This 545 tpd (600 tons/day) underground narrow vein gold operation is set to produce in excess of 14.8 tonnes (475,000 ounces) in 2001 at a cash operating cost below 75 U$/oz. The high-grade nature of this deposit (>55 g/t or >1.6 opt) coupled with its complex geological environment and relatively deep location dictated the choice of a very selective primary mining method, Mechanized Overhand Cut and Fill. In addition to geological challenges, mine design issues such as material handling, ground stability and requirements for yieldable ground support are also discussed in this paper.

Oct 1, 2001

By J. J. S. Sebastian

The process development described in this report was carried out at the Morgantown Station of the U. S. Bureau of Mines in cooperation with West Virginia University. An experimental laboratory-scale pilot unit to gasify coal dust in entrainment was constructed on the Campus of the University in Morgantown. The enormously accelerated demand for liquid and gaseous fuels and utilization of our immense coal resources require that a low-cost process be developed for the gasification of a wide variety of coals. Such a process would be a major factor in lowering the cost of synthetic liquid fuels. None of the proc3sses developed in Germany prior to and during World War II, such as the Winkler process, the H. Koppers dust gasification process, the Wintershall-Schmalfoldt process, etc., meet all the requirements for a low-cost process under American conditions. Nor has any other process designed and experimentally operated at atmospheric pressure during the post-war period in this country appeared to fulfill all of the necessary conditions for a low-cost process.

Jan 1, 1950

By G. G. Goble

Dynamic pile testing is now over 20 years old as a routinely applied tool for evaluating driven pile installation. The first test on a cast-in-place pile was performed more that 15 years ago. The research that produced the method began almost 30 years ago. But, questions still arise regarding the appropriate use of this technique so some review is useful. Today a number of methods including dynamic testing all depending in some way on the application of dynamics are in routine use. First, Wave Equation analysis can be used to predict pile driveability before going to the field. The same approach can be used during driving to estimate the bearing capacity based on the blow count observed in the field. Dynamic measurements, on the other hand, can only be used after pile driving has begun. They offer predictions of pile capacity as well as measurements of hammer, driving system, and pile driving performance characteristics. The first part of this paper will be devoted to discussing how the foundation engineer can use these tools. First, a brief review of what dynamic methods actually do. In Wave Equation analysis a numerical model of the hammer, driving system, pile, and the soil is created by the engineer. The hammer is dropped on the pile and using a discrete, dynamic analysis the motion of the individual pile elements is calculated as a function of time. Of course, input information must be supplied by the program user to describe the hammer, driving system, pile, and soil. In the current state of development, the primary problem in input data is with the hammer performance (efficiency) and the soil description. Research may be able to do a better job with the soil data, but hammer performance will always vary from hammer to hammer and is dependent on the affectiveness of the inspection process. Prior to beginning pile driving the Wave Equation analysis supplies the best available estimate of what will happen when driving begins. It gives an estimate of blow count during driving, driving stresses, both tension and compression in the pile, and for diesel hammers, stroke. The selection of the driving system can be checked with the results of Wave Equation analysis and modifications can be made if required. For example, if the blow count at the required capacity was deemed excessive by the contractor a larger hammer could be tried or if driving stresses were too high changes could be made in the cushion or the hammer selection could be modified. All of these modifications are possible with only the cost of a computer run. The primary questions regarding the accuracy and reliability of Wave Equation analysis at this time is with regard to the assumptions made to represent the soil characteristics and the difficulty in predicting hammer performance.

Jan 1, 1993

By C. H. Lee, K. Adham, D. Lemieux, J. P. Mai, A. M. S. Hussein, S. Francey

Copper concentrates contain an increasing amount of arsenic, as the older sources of cleaner ores are depleted. At the same time, the market-determined price penalties on arsenic rich concentrates are rising due to limited arsenic treatment capacity at smelters and increasingly stringent environmental emissions limits, necessitating arsenic removal from the copper concentrates. Heating the concentrate to about 700°C can remove significant amounts of arsenic (as elemental and/or sulfide); however, it is important to achieve that removal economically and with due consideration to post-roasting arsenic (toxic waste) treatment. A comparison is made among different roasting options (kilns, multi-hearths and fluid beds) to qualify their potential application to arsenic roasting of copper concentrates. Both direct and indirect methods of heating as well as inert, air and oxygen atmosphere options are considered. Technology comparisons are made with respect to the roaster’s operation, its off-gas treatment and arsenic stabilization. INTRODUCTION In the last twenty years, the arsenic content in globally produced copper concentrates have risen steadily due to the depletion of cleaner ores and the increase in complex concentrate production. Smelter contracts typically limit arsenic to less than 0.5wt%, with a penalty paid per unit of additional arsenic and other contaminants such as antimony. While penalties can vary, they can be on the order of $70/dry metric tonne of concentrate per 1% of arsenic. Strategies used by miners to avoid the price penalties have been to blend clean and complex concentrates, and to remove arsenic from complex concentrates to achieve smelter limits. Arsenic can be removed from copper concentrates by the heat-induced decomposition of the predominant enargite mineral (Cu3AsS4) at ~700°C. Roasting at such elevated temperature is a commercially proven option, but still suffers from process, cost and environmental challenges. After roasting, the released arsenic sulfide fumes can be separated from most of the entrained concentrate dust in cyclones. Then, the As2S3 laden off-gas can be oxidized to generate a still volatile oxide (As2O3), which can be further separated from the residual concentrate dust in a hot electrostatic separator. Next, the off-gas can be cooled with air or water, to either deposit the arsenic oxide in a dry or dissolved state. Dissolved arsenic acid can be oxidized to As(V) and reacted with iron to yield a stabilized ferrihydrite precipitate or scorodite that can be safely disposed. In the case of dry arsenic trioxide, it can be mixed with reactants (e.g. iron) and fluxes before thermal stabilization in a glass matrix, thus eliminating the need for costly oxidation.

Jan 1, 2019

By D. van der Veen

Mining companies and contractors are looking at Wirtgen Surface Miners to provide flexibility at their operations. Wirtgen Surface Miners have been used in the surface mining industry for over fifteen years. The principle behind the Wirtgen Miner is a rotating drum equipped with tungsten carbide tipped cutting tools that excavates and sizes the material. The drum helix augurs the mined material to the center of the drum where it is loaded onto the primary conveyor belt. From there the material is conveyed to the discharge belt and into a truck bed. The cutting drum is located in the center of the machine, near the center of gravity. This permits the machine to cut hard materials as the entire machine weight is converted into cutting forces. Conventional mining practices are process, equipment, and labor intensive. Furthermore, strict environmental requirements pertaining to noise levels, dust pollution, and blasting, near buildings or urban areas, limit the application of conventional methods. Mining/ Construction contractors are using Wirtgen Miners in various limestone excavation projects, such as highway expansion projects, and new roads in housing developments. Mining companies in the industrial minerals and coal industry are using Wirtgen Miners to load directly onto trucks, eliminating the rehandling process and ultimately, primary crushers.

Jan 1, 2002

By S. J. Lötter

Analysis of the major and minor components of raw zircon as well as plasma-dissociated zircon was undertaken using inductively coupled plasma optical emission spectroscopy (ICP-OES). Microwave-assisted acid extraction as well as flux fusion using lithium tetraborate were investigated as digestion methods. Microwave-assisted acid extraction samples were analysed with matrix-matched standards. The most successful microwave-assisted acid extractions yielded 44.3(1), 49.75(7), 78.3(3) and 90.0(7) per cent recovery for Zr, Hf, Al, and Fe respectively using sulphuric acid. In no instance was acid extraction capable of complete digestion of the sample matrix. A standard addition method was applied to the flux-fusion samples due to the high complexity of the sample matrix. Method validation for the flux fusion procedure was performed using the SARM 62 certified reference material (CRM) with acceptable recovery ranges being based on the 95 per cent confidence intervals of the CRM. Successful analyses were achieved for Zr, Hf, and Ti with apparent content of 66(6), 1.7(1) and 0.15(1) per cent respectively.

Jan 1, 2012