Search Documents

By Robert E. McIvor

The Functional Performance Equation for Ball Milling” was first presented in 1988. It now has been used successfully in more than a dozen mineral processing plants. This powerful, yet simple tool provides a new level of understanding of closed circuit grinding. It shows how grinding circuit efficiency is in reality comprised of two distinct efficiencies. It demonstrates how circuit production rate is related, collectively, to these two efficiencies, mill energy input, and the grindability of the ore. It links circuit performance to design and operating variables that can be manipulated, and creates an effective strategy for making plant improvements. This paper covers the derivation and industrial validation of this equation. As part of an engineering and management system that also incorporates suitable metrics and process control, other operators can now use this tool to make improvements and to manage the performance of their grinding operations with clarity and confidence.

Jan 1, 2005

By Abhijit Saha

"Two analytical closed-form elastic-rigid-plastic solution methods to predict the rigid foundation behaviour on stone-column reinforced soil are compared, both of which takes into account the stone material yield within the host soil according to stress-dilatancy theory. These are the mechanistic methods developed by the author (2004, 2005) [that presently incorporates the dilatancy angle as per Schanz and Vermeer (1996)] and that developed by Pulko and Majes (2006), that takes into account the column yield as per Rowe dilatancy theory. Since optimal design of stone column necessitates optimum stress concentration on column, which is generally composed of dense gravel with/or without sand, the vertical stress on granular column is often close to its peak strength and the material dilates. To arrive at closed-form analytic solution to this complex soil-stone column interaction problem, some common assumptions like axi-symmetric soilstone column ‘unit-cell’, elastic host soil and rigid-plastic Mohr-Coulomb stone column material are combined with equilibrium and kinematic conditions. The results reflect the beneficial effect of dilatancy within the optimal range or techno-economic domain of area-ratio. The settlement predictions are compared with other analytical methods available in literature as well as with measured settlement reduction of stonecolumn reinforced ground at different subsoil conditions around the globe reported in literature.INTRODUCTIONStone columns or granular piles are frequently used in stabilization of soft clays, silts and loose silty-sands with large amount of fines. The majority of analytical methods assume infinitely wide loaded area with end-bearing columns having constant diameter and spacing that approximate to axi-symmetric conditions, and the approach is known as ‘unit-cell concept’. Several analytical solutions are available, and many of them (Aboshi et al; 1979, Balaam & Booker; 1981) are based on elastic approach considering the stonecolumn and surrounding soil as elastic materials. However, elastic methods give the ratio between the vertical stress in the column to soil (stress concentration factor) approximately equal to the ratio of constrained modulus of both materials. This ratio was found to be considerably higher than measured in the field and it is believed that elastic methods may overestimate the effects of stone columns on settlement reduction (Barksdale & Bachus, 1983). The elastic and elasto-plastic solutions presented by Balaam and Booker (1981, 1985) indicate that the problem can be idealized by assuming that the stone column is in a triaxial state and possibly yielding, such that there is no shear stress at the stone-soil interface and no yielding in the soil. Similar assumptions of stone column to be in a state of limiting equilibrium and under a triaxial stress state are considered in other methods also (Priebe; 1976, Van Impe & De Beer; 1983, Van Impe & Madhav; 1992, Saha & De; 1994, Saha; 2004, 2005, Pulko & Majes; 2006). In majority of the methods it is assumed that under load the stone-column yields at constant volume. However, the last three cases cited consider another parameter; the dilation of stone column. In Van Impe and Madhav’s (1992) and author’s (2004, 2005) method, the dilation is taken into account through the final value of the volumetric strain of column, whereas Pulko & Majes (2006) considered the stone column as Mohr-Coulomb rigid-plastic; dilating at yield in line with Rowe (1962) dilatancy theory."

Jan 1, 2015

By R. W. Stahl

An emergency is defined as an unforeseen combination of circumstances that calls for immediate action. When applied to a coal mine, an emergency may call for prompt removal of the men to the surface through travelways other than the haulageway or intake airways, which are generally contaminated with irrespirable air as a result of an explosion or fire. Therefore, maintenance of adequate and travelable escapeways from all working areas of a mine is vitally important insurance against disaster. Several mine disasters could have been avoided if well-defined escape routes had been provided and made known to all mine employees. Such occurrences, unnecessary as they generally are, unfairly indict the industry when only a small segment thereof is involved. As a result of a rather recent disaster, which might not have happened if good escape routes had been provided, the Bureau of Mines decided to delve into the escape procedure to determine (1) what is being done in the industry and (2) what might be done at reasonable cost.

Jan 1, 1962

By H. W. Gillett

CLYDE WILLIAMS has reminded me that in the fall of 1929, gave, in MINING AND METALLURGY, an account of the hopes and aspirations of Battelle Memorial Institute, which was then just swinging into initial operation; and that therein I remarked that B.M.I. should stand, as well, for Better Metallurgical Industries, since helping to better them was the Institute's aim. So he has suggested that some of the betterments of the past fifteen years might well be listed. A yearly summary of progress comes pretty close to the ultimate in futility, for everything proved of value in that year had its inception in earlier years, and everything really new has still to be proved. Plenty of things hailed as wonderful achievements for that year, by some enthusiasts invited to contribute to the summary, turn out in later years to be inglorious flops. But over a decade and a half, betterments that are really such become self-evident, and recounting some of them can be done without guesswork or wishful thinking. An inventory of what was known and utilized in 1929 compared to what is now known and used is not too hard to make. Perhaps the most clear-cut picture of what is known and used at a certain date is drawn by the handbooks, textbooks, and equipment catalogs of that date, with scientific periodical literature forecasting what knowledge may later be used when it is verified and assimilated. The tools available for production or for research limit the application of old and the finding of new knowledge.

Jan 1, 1945

By H. M. Lewis

The current status of the international zinc market is summarized, and a supply /demand outlook is presented for the next five years. A number of technical problems facing the industry are outlined. Introduction ZINC has sometimes been called the unknown metal. Considering that on a world basis it ranks third among non-ferrous metals in production and consumption, zinc retains a certain modesty. It has no distinctive colour like copper, lacks the low density of aluminum or magnesium and is not always easy to identify as a product. The 'spangle' of galvanized steel is probably zinc's most distinguishing feature. The purpose of this article is to develop an over-all review of zinc. Starting with the current position of the metal, the major factors that will shape its future will be described so that an assessment of the outlook for zinc can be made.

Jan 1, 1978

By A. Kazemi, M. A. Ahmadi

Pressure tunnels are constructed nurously in related with powerhouse. In some cases, according to high internal water pressure, rock mass around tunnel can seldom suffer this pressure. So installation of concrete lining which interacts with rock mass and suffers parts of this pressure and transfers the rest of the pressure to the rock. In this paper hydromechanical interaction between rock and lining is investigated. With using empirical and numerical methods concrete lining for Symareh waterway is designed. Initial support of 10 cm reinforced shotcret with wire mesh and rock bolts pattern of 2.5*2.5 m with length of 4 m is suggested. By using FLAC package final lining with paying attention to axial force and momentum in reinforced concrete was designed. Reinforced concrete with 60 cm thickness and two rows of bars, 18 mm diameter and 20 cm spacing are designed. Also for preventing cracks in concrete which caused by the change of temperature and shrinkage, bars with 10 mm diameter and 25 cm spacing, and also bars with 8 mm diameter and 10 cm as minimum shear bars are suggested. Plusieurs galeries en pression se construisent en liaison avec les centrales électriques. Dans certaines galeries, suite à une haute pression interne de l'eau, le massif rocheux autour de la galerie ne peut pas supporter cette pression. L'installation d'une couche de béton a l'intérieur de la galerie donc réagit avec les roches et support d'une partie de cette pression et transfère le reste de la pression aux roches. Dans ce papier, l'interaction hydromécanique entre la roche et la couche en béton a été étudiée. En se basant sur les méthodes empiriques et numériques le système de support de galerie de passage d'eau de Saymareh a été conçu. Un soutènement initial d'une épaisseur de 10 cm de béton étant renforcé par un grill métallique et une maille de boulon (2.5 * 2.5 m) d'une longueur de 4 m a été proposé. En utilisant le logiciel de FlAC, la couche finale en béton selon les forces dans le béton a été conçue. Le béton renforcé d'une épaisseur de 60 cm et deux ranges d'armateurs (18 mm de diamètre) avec un intervalle de 20 cm a été conçu. De plus; pour éviter des fissures dans le béton suite au changement de la température et de l'extraction, des armateurs de 10 mm de diamètre et de 25 cm d'intervalle pour augmenter la résistance au sciesiement du béton ont été proposes Unter Druck stehende Tunnels werden hauptsaechlich im Zusammenhang mit Kraftwerken gebaut. In einigen Faellen, wo der Wasserdruck zu hoch ist, Kann selten die Felsenmasse diesen hoehen Druck allein aufnehwen. Deshalb werden sie mit Betonauskleidung versehen, die wegen guter Wechelwirkung mit der Felsenmasse einen Hauptanteil des Druckes aufnehmen Kann, wobei der Rest an die Felsenmesse weitergeleitet wird. In dieser Arbeit wird die hydromechanische Wechelwirkung zwischen der Gesteinmasse und der Auskleidung untersucht. Mit Hilfe empirischen und numerischen Verfahren sowie Kombination der beiden wurde eine Betonauskleidung fuer die Symareh Wasser Kannal koustruiert. Als erstes wurde ein 10Cm dicker armierter Beton mit einem Mashengitter von 2.5*2.5 sowie den gleichen Felsbolzenabstaenden und einer Laenge von 4 m vorgeschlagen. Mit Hilfe des FLAC Programms wurde die Hauptauskleidung unter Beruecksichtigung von Axialkraeften und Momenten im Stahlbeton koustruiert. Der 60 Cm dicke Stahlbeton wurde mit zwei Reihen von Stangen, 8 mm im Durchmesser und in Abstaenden von 20 Cm koustruiert. Ferner im Sinne der Vorbeugung gegen Rissen im Beton, die durch Temperatur aendeungen und Schrumpfungen bedingt sind, wurden Stangen mit 10 mm Durchmesser und 2.5 Cm Abstaenden zur Erhoehung vor Scherfestigkeit des Betons vorgeschlagen.

Jan 1, 2003

By W. S. Weldon, R. M. G. Machunter

The use of spiral separators for the beneficiation of fine coal typically in the size range - 2+0.lmm is now well established process technology. Developments during the mid 1980's resulted in the production of cost effective, efficient large diameter coal spiral separators. Recent developments and research have been geared to optimise metallurgical performance, materials handling and equipment geometry of large diameter coal spiral separators.

Feb 24, 1997

By S. S. Peng, C. T. Holland

Mountain Top Removal (MTR) mining started in West Virginia nearly thirty years ago. This surface mining method can extract multiple coal seams as thin as a few inches thick with total recovery and minimum rock dilution in very steep mountainous terrain. It is highly efficient even if coal seams are in close proximity and small in aerial extent. Consequently, MTR has been widely used in the Central Appalachian Coalfield (mainly Kentucky, Tennessee, Virginia and West Virginia) for the past thirty years with great success. In that respect, there has been no demand for research and little scientific research has been performed to investigate its impacts on the surroundings in the history of MTR mining. However, in the past two years the debate over the MTR mining has grown quickly and in times become very intensely. This paper describes chronologically the issues raised by various parties, legal actions, its impacts on mining permit application and research projects developed to address the issues.

Jan 1, 2000

By S. D. Hill, G. E. McClelland

To maximize productivity and improve minerals processing technology, the U. S. Department of the Interior, Bureau of Mines, is investigating a particle agglomeration technique as a means of increasing the percolation rate of leaching solutions through heaps of clayey or finely crushed, low- grade, gold-silver ores. Bench-scale and pilot-scale experiments conducted on different ores indicated that the percolation rate of cyanide leaching solution was enhanced markedly by mixing the ore with a binder, such as lime or portland cement, moistening the mixture, then mechanically agglomerating and aging the feed prior to heap building and leaching. In addition, the rate of silver and gold extraction markedly increased without sacrificing total recovery of values. The use of concentrated cyanide solution instead of water during the agglomeration procedure substantially decreased the leaching time required to obtain maximum recovery. Results from bench-scale and pilot-scale experiments using the particle agglomeration technique are discussed.

Jan 1, 1981

By D Hill

In the Ngakuru area zeolite deposits occur in late Quaternary lacustrine vitric tuffs of the Ngakuru Formation and two of the deposits are being mined. The Ngakuru Formation overlies the Ohakuri Ignimbrite dated at c. 240 ka, and is overlain by younger alluvial sands and gravels. Individual zeolite deposits contain 50 - 80 per cent zeolite over a thickness of up to 45 m in thinly stratified vitric tuffs and are localised along NE-trending normal faults. Glass shards in the tuffs are replaced by the silica-rich zeolites mordenite and clinoptilolite. Amorphous silica (opal A), opal-CT, Kfeldspar and smectite are also present. The zeolites and other minerals are very fine grained (<10 8m), with open meshes of crystals that result in high porosities (52 - 70 per cent) in mordenite-rich tuffs. Zeolitic tuff samples typically have cation exchange capacities of 80 to 110 meq/100 g and internal surface areas of 25 - 58 m2/g, which combine to give high liquid and odour absorption capacities. The first zeolite deposit (Mangatete) was found in 1992, and this and the Twist Road deposit are worked by quarry benching into the side of hills. The zeolitic tuffs are dried and crushed to produce a variety of products including adsorbents for soaking up oil/chemical spills and animal wastes, animal feed supplements, water treatment, and sports turf and slow release fertiliser. The Ngakuru zeolite deposits formed at shallow depth (<100 m) along fault zones from reaction of glass-rich tuff beds with groundwater-diluted geothermal water during the late Quaternary, and are as young as 8500 yr BP from 14C dating of plant material in sinter associated with the Mangatete deposit.

Jan 1, 2005

Effect of Iron on ash fusion temperature and waterwall deposits FeS, H2S on tube material corrosion and erosion [ ]

Jan 1, 2005

By Marcel Bielefeld, Joost Bakker, Rob van Dorp

Pile load testing can be performed by a static, rapid or high strain dynamic (generally designated as dynamic) testing method. The static load test is often considered the “gold standard” of testing with the other methods merely ‘alternatives’. However, the rapid load test, as a quasi-static test, has all the positive elements of the static alternative: the direct measurement of loads and displacements. Moreover as stress wave phenomena have no influence, the interpretation of rapid load test results is more straightforward than that of dynamic testing, and also independent of the person performing the interpretation. This paper will explore the Rapid Load Testing method and illustrate the advantages and limitations through a case study in Rostock, Germany

May 1, 2022

The small scale alluvial gold mining industry in Papua New Guinea (PNG) is c.irrently the only form of small scale mining carried out in this country. It already contributes significantly to the economy with current production estimated at 2 000-2 500kg per year. Until recently, small scale alluvial gold mining has been confined to simple panning and sluicing of high grade alluvial and colluvial deposits. Traditionally the small scale miner in PNG has only worked gravels with gold grades in excess of 500mg/m3. Grades of this order are required to justify the hard physical labour involved ~n hand operated small scale mining methods. .he introduction of higher throughput technologies such as trommels fed by hydraulic excavators has the effect of altering what constitutes an economically viable deposit. Mechanised techniques allow for the consideration of grades of almost half that level. The potential and opportunities for utilising this type of small scale mechanised mining in PNG are enormous with large areas of ground with gold grades running in excess of 250mg/m3 and often up to 2000mg/m3 throughout the country. An assessment of the current operating economics of this technology in the PNG context is the principal objective of this paper. Small to medium scale mechanised mining can potentially contribute significantly to the PNG economy particularly as it lies within the react-, of many PNG businessmen. Its potential is currently somewhat limited by a general lack of infrastructure and is also constrained by socio-political factors.

Jan 1, 1991

The following paper describes the refining practice for the production of lead, silver and gold at the works of The Broken Hill Associated Smelters Pty. Ltd., Port Pirie, South Australia.The refinery is situated on the wharf frontage and is built parallel with it. The refinery occupies an area of approximately 3380 square yards. (Fig. 8)There are two buildings, one containing the softening and de-silverising sections, measuring 225 ft. x 57t ft., while the other building, which measures 225 ft. x 90 ft. covers the de-zincing, lead moulding, retorting, cupellation, and dore parting sections. (Fig. 1)The retorting, cupellation, and dore parting sections are completely isolated from the rest of the plant by strong small-mesh wire gratings welded to steel uprights. The dore parting plant and generator room are further isolated by a brick wall, built up to the roof. The two main buildings are steel structures, with outer walls and roof of "Robertson" corrugated sheeting; the side and end walls are open for some distance above the ground, and this, coupled with the high roof which is 50 ft. from ground level, ensures the free access of air and light. Conditions are such that operators work in a clear atmosphere.

Jan 1, 1937

By AIME AIME

THE American Engineering Council, which is the working body of The Federated American Engineering Societies, held its first meeting in Washington, Nov. 18 and 19, 1920. The Federated American Engineering Societies was formed in Washington in June and is composed of engineering and technical societies, national, state, local and regional. These Member Societies elect delegates to the American Engineering Council, which is the administrative body of the Federated. The meeting was called to order by Richard L. Humphrey, Chairman of the Joint Conference Com¬mittee, and the program (which is printed below) was carried out without substantial change by E. S. Carman, who was elected temporary chairman. Under the Constitution, the Council appoints an Executive Board, the members of which are chosen according to the proportional membership of the vari¬ous Member Societies in their respective districts. Under this plan, with the present membership, 'the national societies will have 14 members and the local societies 6 members on the Executive Board.

Jan 1, 1920

Variations in delay timing can have a marked influence on blasting effectiveness and, hence, on total production costs. In single-row bench blasts, delay firing is invariably more effective than simultaneous initiation. In single-row delayed blasts, there is an optimum inter-hole delay above and below which inferior blasting results are obtained. This optimum delay is equal to the time required for each charge to just effectively detach its quota of the burden. The inter-hole delay should seldom be less than 4 ms.m-l of burden.In multi-row blasts in which holes in a given effective row are fired on the same delay, the entire burden on any effective row should be detached from the rock mass just before charges in the next effeotive row detonate. Delays shorter than this give inferior blasting results and an increased likelihood of environmental and slope stability problems. If the inter-row delay is too long, cut-offs can occur, especially where the delay unit is located outside the blasthole. For a surface delay system, the optimum inter-row delay usually varies between 4 ms.m-l and 8 ms.m-l of effective burden. The number of rows that can be fired effectively with surface delay systems (in a single blast) is limited by the threat of cut-offs. Greater interrow delays and a larger number of rows per blast can be fired to advantage with down-the-hole delay systems.There are practical limits to the timing accuracy of all available delay systems. The existence of delay time variability should be recognized and duly considered in the design of blasts.The relationship between delay timing and blasting vibrations is not discussed.

Jan 1, 1977

By Whiteman P. C, Stacey G. S, Hunter G. D

Processing of lead-zinc and copper ores by Mount Isa Mines Limited produces large quantit- ies of concentrator tailings waste which is pumped as a slurry to special dams where the solids are allowed to settle and dry out. These areas are unattractive and show no signs of encroachment by plant life even though the surfaces of some dams have remained undisturbed for more than a decade. During 1970 Mount Isa Mines Limited commenced a long term research program in conjunction with the Department of Agriculture, University of Queensland to deter- mine possible methods of establishing a plant cover on this material. Research has defined the major factors limiting plant growth in the tailings medium. Modification of the edaphic conditions through fertilizer inputs, particularly of phosphorus and nitrogen, and alteration of "soil" physical properties by incorporation of mulching mater- ials, provided conditions which allowed plant growth. The outstanding "soil" amendment treatment was incorporation of fly ash, a waste product of the company's coal fired power stations. A range of crop and pasture species have been selected which have grown well with adequate irrigation under the amended conditions in the field. Further research is assessing a range of native plant species and agronomic techniques to provide a stable plant cover on the tailings dams.

Jan 1, 1974

By P Steinier

Most operations, when considering their comminution circuit, are primarily concerned with achieving the desired particle size distribution to obtain adequate liberation for the separation process, at minimum cost. Invariably, the effect the grinding media has on the subsequent separation process (ie flotation, leaching) is not taken into account when selecting the media. This choice is driven by cost rather than metallurgical outcomes. Maximising valuable mineral recovery, with optimum selectivity against gangue minerals, is about good particle preparation. And, particle preparation is strongly related to achieving adequate mineral liberation with the correct pulp chemical conditions. However, the pulp chemistry of a system is largely ignored and relies heavily on pH control and the addition of appropriate reagents (collectors, frothers, activators, depressants). The changes effected by the addition of the various reagents are obtained through conditioning the ground pulp prior to or during the concentration stage, subsequent to grinding. Frequently, reagents are added during grinding with good effect, but the impact of the grinding media on down stream processing is usually overlooked. A number of case studies examining the effect of grinding media on pulp chemistry and subsequent flotation performance were completed on several different sulfide mineral systems (for example, lead/zinc, copper, refractory gold). The evidence suggests that a change in grinding media type from forged to high chrome (ie conditioning the pulp during grinding) resulted in a shift in pulp Eh to less reducing conditions, an increase in the dissolved oxygen content of the pulp and a reduction in the iron species present. The changes have a positive impact on flotation behaviour. The results of the case studies are discussed.

Jan 1, 2004

By KEITH BARRONI

In the proposed criterion for coal a distinction is made between brittle and "psuedo-ductile" failure. This criterion is the basis for the development of new equations for coal pillar strength, including a transition from brittle fracture to pseudo-ductile yielding. In addition the equations obtained allow the critical minimum pillar dimensions to be calculated to avoid "catastrophic" and "ultimate failure".The validity of these formulae can be tested by comparing their results with pillar case histories derived from the literature.

Jan 1, 1988

By Scott W. Hazen

COMPREHENSIVE summary is presented of results of several years of research at the Bureau of Mines Mining Research Center at Denver on adapting and applying techniques of statistical analysis in mine and mineral-deposit sampling and in computing grade and tonnage of ore for a mineral deposit. In addition to elementary statistical theory the material presented in the bulletin includes: (1) Certain special statistical techniques that have been found useful in mining applications; (2) problems, implications, and limitations that may be encountered in applying these techniques in mine sampling and evaluation; and (3) numerous examples to demonstrate application of the theory and techniques.

Jan 1, 1967