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By H. F. King

In 1982, the result of a 3-year study was published as "A Guide to the Understanding of Ore Reserve Estimation". The principal conclusions were that computation formed only part, and perhaps not the most important part, of an estimate and that the estimate should recognize that geological, mining engineering and metallurgical judgements formed an essential part of the eventual result. Subsequent expectation/realization studies of several mines have produced case histories which form the principal basis of the paper. These imply that geology is even a larger factor than thought earlier.

Jan 1, 1985

By S. Fuentes, J. Cáceres

"During the past fifteen years, mines utilizing the block caving method have improved performance and systematically reduced total mining costs.This paper describes improvements in mine design, mine planning, and mine management, including methods enabling the Chilean and international mining industry to ensure cost savings and productivity growth while using the block caving method. These improvements have encouraged the re-evaluation of underground operations at operating and closed open pits, and challenge surface mining applications as the only low-cost mining method. This paper describes a strategy to estimate the optimum open pit to underground transition time during the life of a mine. IntroductionDuring the last fifteen years, block caving mines have experienced huge changes in designs, planning and administration. These changes have permitted operators to drastically reduce costs, improve equipment productivity, and improve overall business performance. As a consequence of this situation, the block/panel caving mining system is challenging actual open pit operations to maximize the net present value (NPV)."

Jan 1, 2004

By J Player, P Mikula, G Sweby

A numerical modelling back-analysis exercise was carried out at a WA gold mine at which early signs of seismicity (rock noise, scatts from active faces) were becoming apparent as depth of mining increased towards the 500 m mark. Some strain bursting had occurred and it was necessary to discover what the implications of this were for greater depth. The aim of the modelling was to: 1. Establish a correlation between observed ground conditions and model predicted damage, in overstressed areas of the mine. 2. Use this correlation to forecast rock mass damage and ground control requirements for proposed future stoping panels at greater depth. Good correlation has been achieved between observed rock mass damage, and a 3D Finite-Element RS3 model, run in elastic mode. Two candidate stress field orientations were modelled. The model parameter best fitting the observations was the Strength Factor (SF), the ratio of strength/stress. The good match (correlation coefficient of 0.7) between observed and modelled suggests that the elastic approach is justified for the depth range and rock mass properties analysed. The correlation also enabled a link between observed damage and installed ground support performance. Using the linear best-fit between observed and modelled, a forecasting exercise was carried out using the same RS3 model, modified to include future stoping. The resulting damage and ground support categories were obtained from the modelled SF for each proposed stoping level. Also, a series of generic geometries was assessed to investigate the impact of varying stope face lead/lag distance, sill pillar height and stope pillar size, on ground conditions. The key finding of the generic geometries were: • Ground support schemes have been defined for the expected conditions. • All ore drives are expected to have significant damage in the backs and rehabilitation. • Lead/lag distance not to exceed 10 m. • Sill pillar/level intervals of less than 20 m require an increase in ground support scheme. • Pillar sizes for maintaining footwall and hanging wall stability should be at least 10 m × 5 m.

Nov 29, 2022

By William D. Mayercheck

Beginning in 1974, the Bureau of Mines, U.S. Department of the Interior, sponsored R & D efforts related to further development and use of continuous face haulage in underground coal mines (Cowan, 1975). The U.S. Department of Energy continued this effort as of October 1977. This paper represents an update of an article previously published in Mining Engineering magazine (Mayercheck, 1979). Development progress is summarized for a variety of prototype systems or components now being built, surface tested, or tried underground.

Jan 1, 1981

By M. M. Fine

"INTRODUCTION One of the principal activities of the Bureau of Mines during the recent war was to help to increase the supply of strategic and critical minerals. Fluorite was one of the most critical of the nonmetallic minerals because of the increased demand for it as a flux in basic open-hearth and electric steel furnaces and as a raw material for the production of artificial cryolite used in the aluminum industry. Wartime developments in the technology of hydro-fluoric acid, such as the use of the anhydrous acid as a catalyst in high-octane-gasoline production and the use of organic fluorides as carriers for insecticides, also increased the demand for acid-grade fluorspar. 2/ In 1943 the consumption of acid-grade fluorspar was advancing at a more rapid rate than production and was only slightly less than production during the latter half of the year.The outlook for the postwar market for fluorspar is encouraging. Steel production is expected to remain high until the domestic demand for commodities not manufactured during the war is satisfied. The uses for hydrofluoric acid also are expected to increase under the impetus of war-initiated research. In consideration of these and other factors some authorities predict a new peacetime demand for fluorspar equal to 60 to 75 percent of the war production, 5/ 6/ and others believe that the fluorspar industry will be permanently expanded. 7/"

Dec 1, 1947

By Cecil H. Desch

THE progress of metallurgical practice and the demands made by the engineering industry on our foundries and mills have made the crystalline structure of metals a subject of far more than academic interest. Metals and alloys are made up of crystals. Even if we accept the view, so ably maintained by some metallurgists, that the crystals are separated from one another by an amorphous layer, it remains true that all but a very minute fraction of any metallic mass is crystalline. The conditions which affect the growth of crystals are therefore of importance in metallurgy. It is not only castings whose properties depend on the arrangement of their crystals, for the more we learn of the behavior of forged, rolled and drawn metals, the more certain it becomes that it is profoundly influenced by the size and arrangement of the crystals in the original ingot, deter- mining a structure which may persist in a modified form through a long series of mechanical operations and annealings. This is mainly due to the concentration of much of the impurities in the last portions of the liquid to freeze, so that the boundaries between single crystals or groups of crystals are marked out by a zone of segregated material, differing in properties from the mass, and offering a barrier to diffusion and equalization of composition throughout the whole. The importance of this fact has been fully recognized by steel manufacturers, who have to deal with ingots which are sometimes very large, and are cast at a high temperature, containing impurities which have a marked effect on the properties even when present in very small quantity. For this reason the Iron and Steel Institute has set up a committee to examine the whole question of the heterogeneity of steel ingots,(l)f and a report has been issued, containing an account of the structure of 16 ingots, ranging in weight from 15 cwt. to 172 tons, each of which was sectioned and examined by chemical analysis and by etching. A valuable body of data concerning segregation has thus been collected. The work of the committee is being prosecuted with great activity, and at the same time researches are in progress to determine the physical

Jan 1, 1927

By Adam Bedell, Paul Derby, Brad Crenshaw

Modified contact grouting was introduced almost 15 years ago as a methodology combining traditional contact grouting and consolidation grouting to address groundwater infiltration into hard rock tunnels that utilize cast-in-place concrete as permanent tunnel support. This process has been used on additional tunnels (since initially presented) as a measure to mitigate both groundwater infiltration and exfiltration. During this time, self-sealing grouts have been developed and have been added to the process to further reduce groundwater infiltration that occurs through cracks and discontinuities within the concrete liner itself. This modification is presented and additional results from the grouting process are discussed.

Jun 13, 2021

By George T. Faust

The petrographer engaged in examining the products resulting from the beneficiation of ores and rock minerals is constantly required to develop new means and methods of assaying microscopically the results of such operations. From time to time investigators have published descriptions of apparatus that have aided in solving problems in processes f physical separation. Thus, in 191.9, Coghill and Bonardi 31 published a paper covering the application of the binocular microscope and camera lucida to the microscopic analysis of pulverized ores. Similar work has been published by Schneiderhohn 4/, Schwartz 5/, and Head and his associates6/, 7/, 8/. The present paper goes further and considers application of the polarizing comparison-microscope to problems directly concerned with mineral dressing where it is desirable to compare analogous products, and in addition it suggests new uses in various related fields. This work was conducted under the cooperative agreements of the Southern Experiment Station of the Federal Bureau of Mines and. the University of Alabama.

Jan 1, 1940

By H. A. Watson

Laboratory tests on three commercial methane detectors, two combustion-type detectors and one interferometer-type detector, were made by the Bureau of Mines to determine their response to certain single and multiple flammable gases mixed with normal and abnormal air atmospheres. Although both types of detectors responded accurately to methane-normal air mixtures, they did not show correct concentrations for other single flammable gases in air. Uniquely, the response of the interferometer-type detector to hydrogen was in a negative direction. The effects of individual gases in multiple flammable gas mixtures were approximately additive. In oxygen-deficient atmospheres the methane response of the interferometer-type detector erred on the high side, but only in very low oxygen concentrations were the combustion-type detectors affected-showing low, erratic methane readings.

Jan 1, 1966

By Paul Hewitt, Tim Smirnoff

Design and construction of the Epping to Chatswood Rail Line tunnels in Sydney, Australia required an innovative approach to define hydrogeological properties of the Sydney Hawkesbury Sandstone and provided an insight into the hydraulic behaviour of fractured sedimentary rocks. To meet restrictive water inflow and infiltration criteria both the pre-treatment of zones of fractured or highly jointed rock, and waterproofing using an interior spray on membrane for the finished drained tunnels and stations was required. Methods typically used to address the interaction of groundwater and tunnels in the Sydney Basin are demonstrated by case histories from major design-build tunnel projects.

Jan 1, 2005

By Sergio N. Monteiro

Polymeric matrix composites with dispersed hard particles are being as wear resistant tools in industrial polishing operations. In the present work, the microstructure of epoxy composites with different amounts of embedded diamond particles, up to 30 wt.%, was investigated for the effect on fracture characteristics. It was found that the introduction of diamond particles promoted an increase the porosity of the epoxy matrix. Moreover, the particle morphology associated with a non-uniform distribution within the matrix was responsible for the nucleation of cracks that caused rupture of the composites.

Jan 1, 2006

By James H. Allen

The air lift method of pumping water is discussed. A review of several large diameter hole drilling projects that used reverse circulation air lift techniques is presented. Proposals are made for reverse circulation flow rates for slow rates of bit penetration (5 fph) as well as reverse circulation flow rates for faster rates of bit penetration (10 fph). The Ingersoll- Rand air lift equations are modified for rotary drilling operations. By establishing minimum reverse circulation flow rates and utilizing the modified air lift equations, the establishment of minimum circulation equipment sizes and a more definitive requirement for improved bit body design should result.

Jan 1, 1976

By R. S. Adhikari

The changes in defects patterns or in element condition index during visual inspection of bridges are primary concerns for inspectors. This paper presents a new approach for change detection of defects in bridges by identifying changes in texture patterns through spectral analysis of digital images. The commonly used method for change detection is image differentiation. This subtraction method requires images to be of same size, scale, and rotation. However, no two images are same in real practices. Thus, image registration is required to align images and to produce change maps. This process is tedious and it is difficult often to achieve a good registered image. But, the change detection task can be readily modeled in frequency domain for texture patterns discrimination and also for quantifying their properties. This paper proposes a novel approach for change detection by transforming digital images into Fourier spectrum. In new coordinate system, 1-D signature functions can be drawn which facilitates easy comparison of textures in different directions. The proposed methodology provides useful tools for comparison of inspection history graphically and quantitatively. In practice, expensive sensors are used to detect subtle change in defect patterns. The proposed method can be used to detect any subtle change in defect patterns using digital images at much lower cost.

Aug 1, 2013

By James M. Baugher, Donald W. Conrad, William J. Wiehagen

This report describes a process for quickly developing information that is useful for skills training. The process is called job training analysis (JTA). Its main use is to structure skills training at the jobsite. JTA supports structured skills training by identifying the job duties, tasks, and steps and the reasons why those job components are important. The outcome of the JTA process is a worksheet—a training outline based on the knowledge and expertise of experienced workers. Time invested in developing a JTA will result in significantly more time saved when it is used appropriately by skilled trainers. Like a roadmap, JTA saves time and energy. Experimental work at several mine sites helped document, refine, and validate the JTA process. JTAs for two mining jobs—roof bolting and lift truck operation—at two different mine sites are used to illustrate some of the concepts and the specific JTA process described in this report. The work at these two sites was influenced by cooperative work between the Mine Safety and Health Administration (MSHA) and the National Institute for Occupational Safety and Health (NIOSH) at several other mine sites and prior collaborative work with the U.S. Navy. The mining JTA process is grounded within the military research on the design of instructional systems. MSHA and NIOSH worked to simplify and apply the military training development model for mining industry use through collaborative work at several mine sites. The JTA process involves three activities: (1) planning, (2) a 1- to 3-day workshop where the JTA is developed using facilitated work with subject-matter experts, and (3) followup. Guidelines and considerations for each of these activities are included. Results indicate that the JTA process has been well received and valued by mining industry participants. It blends aspects of health and safety, production, maintenance, and crew coordination.

Jan 8, 2006

By B. Anameric, S. K. Kawatra, K. B. Rundman

The iron nugget process is an economical, environmentally friendly, cokeless, single-step pig iron making process. Residence time dependent process requirements for production of pig iron nuggets at a fixed furnace temperature (1425 C) were investigated. Three chemically and physically different products were produced after complete reduction to iron, depending on the residence time in the furnace. These products were direct reduced iron (DRI), transition direct reduced iron (TDRI), and pig iron nuggets (PIN). The increase in the carbon content of the system as a function of residence time was detected by optical microscopy and Microhardness measurements. Sufficient carbon dissolution for the production of pig iron nuggets was obtained after 40 minutes residence time. The pig iron nuggets produced had chemical and physical properties similar to blast furnace pig iron. They were liquid state products and slag was completely separated from the metal.

Jan 1, 2005

By Steve Kral

President Bush’s National Energy Program and his Clear Skies Initiative both emphasize the use of coal to help meet the nation’s growing energy needs. And why not? Coal is currently responsible for more than 50 percent of the nation’s electricity generation. That fact, though, seems to be lost on policy makers, the environmental community and the public. Critics of coal advocate the increased use of renewable energy sources and the increased use of natural gas. Renewables, though, are only capable of generating a tiny fraction of the power required. Natural gas is expensive. And natural gas production cannot keep up with demand, especially given the nation’s increasing energy needs.

Jan 1, 2003

A line of nine self-aspirating W emco cells, part of the Rougher circuit at Division Salvador, Codelco Chile, was retrofitted to allow operation with forced air. Each cell could be operated self-aspirated or with compressed air supplied through a 4-inch line equipped with a mass flow meter. Gas dispersion was characterized for the two modes of operation. Metallurgical performance was compared under self-aspirated conditions and with different gas profiles under forced air conditions. Cell characterization demonstrated that with forced-air the cells could not evenly distribute air across the cell volume. Bubble size increased with gas velocity, as expected, with no difference between self-aspirated and forced-air operation. A systematic increase in bubble size down the bank was found. Cumulative bubble surface area flux down the bank showed no major differences between surveys. However, grade-recovery curves revealed that the highest recoveries were invariably obtained with forced air operation. Plotting concentrate mass recovery vs. enrichment ratio showed that the line performance could be controlled over a wider range when forced air was used.

Jan 1, 2007

By Vinícius Cunha de Souza

Dispositivos atuatores com componentes de ligas de NiTi podem ter seu desempenho modificado quando submetidos a distintas taxas de aquecimento e/ou resfriamento resulte numa transformação de fase. Por outro lado, por norma, as temperaturas de transformação de fase (início, pico e fim) devem ser estabelecidas a partir de taxas fixas de 10ºC/min (tanto no aquecimento como no resfriamento) através da técnica de Calorimetria Diferencial de Varredura (DSC), sem levar em conta a dinâmica do material durante a transformação em aplicações reais. O presente trabalho procura observar a transformação de fase do material avaliando a capacidade de resposta do mesmo, quando submetido a ciclos em um DSC sob diversas taxas de resfriamento e aquecimento, entre 1 e 10ºC/min em uma liga de NiTi rica em Ti, com formação de fase R durante o resfriamento e/ou aquecimento. Os resultados de DSC foram submetidos a um tratamento de dados com o intuito de melhor determinar as temperaturas de transformação de fase associadas as frações transformadas. Pode-se verificar que valores de taxas de resfriamento e de aquecimento superiores a 7°C/min permitem que ocorra uma tendência para um incremento do intervalo entre as temperaturas de início e fim das transformações direta e reversa.

Aug 16, 2017

By M. J. Slater

Ion exchange using resins is one of the few processes capable of reducing ionic contaminants in effluents to very low levels. Continuous fluidized-bed ion exchange is an advantageous technique for processing dirty effluents and thin slurries. It also reduces resin inventory and equipment cost compared to fixed packed beds. A simple continuous fluidized-bed unit has been investigated for treating effluents and its performance is described. Breakthrough curves were first obtained from static fluidized fixed beds; these data were then used to determine the required operating conditions for a periodic-flow, countercurrent fluidized-bed ion exchange system. A waste stream, containing about 56 ppm copper, was treated in the continuous system using an extraction fluidized bed depth of 203 cm and a flow rate of 1.22 cm3/ cm2s (900 gph / sq.ft) to yield an effluent containing less than 0.02 ppm copper. A generalized design method is proposed for similar chemical systems.

Jan 1, 1978

By Frank M. Howell

Creede, one of the younger major mining camps in Colorado, grew spectacularly to a town of eight or ten thousand people in the early 1890's following discovery of rich ore in the Amethyst and Last Chance mines. Gross metal production in gold, silver, lead, copper and zinc rose to a maximum of four million dollars a year in 1893. Annual production dropped to much lower figures and ranged between one hundred and five hundred thousand dollars per year during the period from 1914 to 1940. Production reached a gross of eight hundred thousand to one million dollars per year by the mid-1950's. In the years 1953 to 1957, Steven and Ratté conducted geologic investigations which were carried on as part of a cooperative program of the U. S. Geological Survey and the Colorado Metal Mining Fund Board. In a preliminary report on the Creede District, Steven and Ratté suggested that the Bulldog Mountain Fault Zone appeared to be a favorable structure to prospect. On the basis of that recommendation, augmented by independent work done by Manning W. Cox, the property was acquired, transferred to Bulldog Mountain, Inc. and financed by an O. M. E. loan. Late in 1963 Homestake Mining Company, under a Lease and Option Agreement, backed the venture by furnishing additional funds plus management.

Jan 1, 1969