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By Kazem Oraee

In underground coal mining, particularly room-and-pillar methods, the coal pillars play a significant role in roof stability. If the pillar dimensions are increased, the pillar bearing capacity also increases, but more coal remains in the pillar and therefore the recovery of mining operation decreases. Therefore, determining the optimum pillar dimension based on technical, economical and performance parameters is important. In this paper, the coal pillar is designed by using the concept of ground reaction curve (GRC). For this purpose, the GRC for coal pillars is drawn and then the elastic and plastic zone of coal pillar behavior is determined. Based on elastic and plastic zone, different equations are presented to draw a pillar reaction curve and the process of coal pillar design based on GRC is explained. As a case study, this new technique is applied to study the coal pillar state in Tabas coal mine of Iran. The results show that the presented new approach is successfully used in the design of the optimum coal pillar dimensions, and also determines the elastic and plastic behavior limit, which is important especially for the logical design of yield pillars.

Jan 1, 2009

By D. Washington

The US economy and the demand for nonfuel minerals grew at lower rates in 1995 than in 1994. Demand for major metals, such as aluminum, copper and steel, was mixed but relatively stable. The building industry, including highway construction, helped to support modest overall growth in demand for industrial minerals. The value of processed materials of nonfuel mineral origin produced in the United States during 1995 was estimated to be $395 billion, an increase of almost 10%compared with 1994 (Fig. 1). The estimated value of US raw nonfuel minerals production during 1995 was $38billion, about 7% more than in 1994. The value of US minerals production has increased in 30 of the last 35years.

Jan 1, 1996

By M. J. Allan, D. J. Barratt

This paper reviews current testing methods for sizing autogenom and semiautogenom mills in the North American context with comments on the necessity for test work and requirements for different circuits and equipment selection. The economics of testing and the value received are discussed.

Jan 1, 1987

By Virgil J. Stachura

The Bureau of Mines conducted a series of delayed blasting experiments at a West Virginia contour coal mine that resulted in smoother highwalls. The 17; were smoother due to reduced overbreak and inherently safer A, to reduced likelihood of rockfall. Reduced overbreak was accomplished by an increase in the highwall hole delays, which changed the effective delay pattern geometry and the direction of burden movement. The blast delays in the highwall holes were 50 to 100 ms longer than the mine's nominal design pattern (flat V, 17- by 42-ms surface delays, 200-ms in-the-hole delay). The burden movement was effectively changed from a 45* angle to 90* with respect to the highwall. The results of the blast delay changes were evaluated using terrestrial photogrammetry to generate vertical profiles at regular intervals. This evaluation showed that delay changes produced generally smoother vertical profiles.

Jan 1, 1984

By E. J. Murphy, John C. Holtz

"INTRODUCTION Toxic gases in the products from the detonation of explosives are one of the hazards in blasting underground. Investigations by the Bureau of Mines 4/5/ have shown that the oxygen balance of the explosive is an important factor in the control of toxic gases. This balance is considered in determining the composition of modern metal-mining explosives for blasting underground, and application of the concept has reduced the volume of toxic gases generated.The chemical nature of the material being blasted also influences the composition of the toxic gases produced. Under some conditions of blasting in massive pryrite, unsafe concentrations of sulfur dioxide and hydrogen sulfide have been found.Experiments with the O-J apparatus 8/ have shown that there is an increase in the volume of carbon monoxide in the gaseous products when permissible explosives are detonated in contact with coal dust. Thus, reactive materials of a reducing nature adjacent to explosives loaded in drill holes may decrease the effective oxygen balance of the explosive and cause the volume of toxic gases to increase.Several blasting accessories of reducing nature have been introduced recently for use in coal or metal mines or tunnels. In practice these are loaded adjacent to the explosive where conditions favor reaction with the products of detonation. The effects of this loading on the gaseous products obtained from the shot are indicated in this report. Broad consideration was not given the efficiency, usefulness, or over-all safety of these devices, but the practical significance of the hazard resulting from increased volume of carbon monoxide is discussed."

May 1, 1942

By R. R. Klimpel

This paper demonstrates, using the results of an unusually complete industrial test sequence, what the various interactions are between grind size, collector dosage, and frother type. While particle size is universally acknowledged to be important in optimizing industrial copper sulfide rougher flotation circuits, many of the various interactions that do occur at the industrial level with particle size are still being identified and/or quantified. This study also presents, in a consistent manner, the changes in flotation kinetics that occur as a function of particle size, in a typical industrial circuit along with some insights as to how flotation operators can optimize rougher circuit performance.

Jan 1, 1993

By M. Mentser

The exchange of oxygen between carbon dioxide and carbon monoxide that occurs reversibly on carbon surfaces was studied at temperatures of 750° to 850°C and a pressure of 1 atmosphere. Carbon-14 was used to detect and measure the exchange reaction. The extent of oxygen exchange was a linear function of com- position of the gas mixture, and this relationship was used to evaluate the forward and backward rate constants of the reaction. Equilibrium constants, directly determined for oxygen exchange in this study, agreed well with values in the literature that were derived only by indirect procedures. This result establishes the validity of oxygen exchange in the mechanism of carbon gasification by CO2. Rates of carbon gasification were less than an order of magnitude slower than rates of oxygen exchange. Activation energies for these two processes were 58 and 53 kcal/mole, respectively. The closeness in the activation energies argues against any change in the rate-controlling step over a wide temperature span at atmospheric pressure. The role of CO as a retardant on the CO2-C reaction, and the nature of the carbon-oxygen complex are also discussed in view of the data obtained.

Jan 1, 1973

By Earl Cook

A high-energy economy based on fossil fuels is in fundamental conflict with an ideal of clean air, clean water, undisturbed scenery, and maintenance of fragile ecosystems. There is an inevitable trade-off between the material standard of living of a modern society and the conservation of its environment. During the past four years, some of the costs of environmental protection have been internalized in the energy-flow system of the United States. The cost of bituminous coal and fuel oil usable under new air-quality standards has doubled or more. The cost of mining coal underground has risen because of a 20-30 percent reduction in productivity resulting from new environmental health and safety legislation; the economic impact of proposed surface-mine regulation may be equally severe. The cost of producing electric power has been rising at a 12 percent annual rate because of environmental costs, and would be climbing still more steeply were it not for the continued forced subsidy of natural-gas consumers by natural-gas producers. The efficiency of the automobile, already a monument to the triumph of self- indulgence over economy, is being further decreased by addition of anti-pollution devices. Part of the recent sharp rise in agricultural costs stems from the fact that five energy units of fossil fuel go into U.S. agriculture for every energy unit of raw food that leaves the farm; further large injections of fossil-fuel energy occur in the transport, processing, and refrigeration of farm products.

Jan 1, 1974

By Willem P. C. Duyvesteyn

"Scandium International Mining Corp (SCY) has been involved in the commercial development of its Nyngan Scandium Project for about ten years. Various studies at a variety of global R&D organizations have been carried out in an attempt to define the deportment of scandium in both the limonite as well as the saprolite phases of Nyngan ore to assist with process development. Technologies such as sulfuric acid baking, high pressure acid leaching, sulfuric and hydrochloric acid atmospheric leaching and heap leaching have been extensively investigated both at the bench and pilot scale level to arrive at the most economic process flow sheet that will be discussed in some detail in this paper. Solvent extraction, ion exchange and other refining technologies have been tested and an optimum configuration has been established for the Nyngan project which is expected to be the first primary scandium mine and metallurgical plant in the world.Because of a lack of product availability the current scandium market is limited to less than 20 tons per year. Technologies have been identified to produce product with different specifications for aluminum alloys and solid oxide fuel cell applications. Preliminary economics have identified that Nyngan will be a robust and low capital cost project that can readily be expanded as the size of the scandium market increases."

Jan 1, 2016

By Richard T. Newcomb

This paper considers the many problems involved in estimating rates of technical change via productivity indexes. In mining, declining ore grades complicate the measurement of progress considerably. The estimates discussed in this article were made for the United States iron mining industry by means of two techniques: a simple model of production with two inputs, and multiple regression. The results can be used to explain the relation existing on U.S. iron ranges between rates of exhaustion, technical change, output per man and the increase in capital proportions observed since World War I. Similar ob-servations can be made on the mining sector trends in the United States, Canada, and Japan. Formidable problems confront the economist attempting to estimate the influence of technological changes on the progress of mineral industries. Peculiar to these industries is the problem of how to adjust any measure of technological progress for the offsetting influence of exhaustion. Exhaustion has long been recognized in the mining industry as a critical dimension. Empirically, it is usually treated as a problem of declining grades of ore either in production or in reserves. There are studies of the trends in mining industries attempting to relate changes in input requirements to changes in grade and technology over time. Most frequently, the measure used to indicate technological progress is average labor productivity, e.g., output per man-hour. However, although such an approach has the merit of being simple and direct, it ignores the influence of other important factors of production such as capital. Without defining both the nature of technological change and of production, it can be very misleading to identify increases in labor productivity with tech-

Jan 1, 1969

By Dan Ifrim

Soft ground tunneling poses major challenges to the underground industry. Most of soft ground tunnels are in highly urbanized areas, often include limited cover, and include a strong trend of increasing diameters. Therefore, soft ground tunneling works can sometimes cause inevitable ground movements and settlements that may lead to damages to adjacent buildings, roads, structures or utilities; many of these being “lifeline” infrastructure assets. Tunneling operations, Tunnel Boring Machine (TBM) advance rates, and face pressure control can significantly increase or decrease such risks, depending on how well the TBM and operational parameters are applied to the ground conditions. Additionally, the risks of impacting existing infrastructure are heightened in many parts of North America because of cobbles and boulders. To date there is no standardized guideline that determines appropriate tunneling rates nor operator’s guidelines, to ensure safe tunnelling in soft ground. The paper analyzes tunneling records from completed soft ground tunnels to determine a relation between ground conditions, tunnel cover, TBM cutters maintenance and TBM advance rates. The records are discussed to draw several mitigation measures to be adopted during tunnelling, to reduce risks of settlements, over excavation or sinkholes.

Jun 13, 2021

This paper presents an overview of the current status of mine water management in South Africa. The regulatory framework within which mine water management operates is set out, based on the principles and policies embodied in the relevant legislation. The status of the gold and coal mining industries, with regard to water management, is presented on the basis of studies that have been undertaken to develop water and salt balances for these industries. While the data is not available to quantify the status of ARD in South Africa, the range of typical mine water quality problems faced by South African gold and coal mines is presented. The status quo, problems and challenges relating to mine water management are presented and discussed. It is shown that, while there have been major strides in the last decade, and mine water management and treatment in South Africa has moved onto the forefront of mine environmental management, important problems still persist. There is still a significant amount of improvement required, particularly in the field of prediction of water quality deterioration and the application of such predictions to the identification of management actions that can be applied to prevent or minimise mine water pollution in the shortmedium- and long-term.

Jan 1, 2003

The paper concerns an unconventional, yet promising, use of waste magnesite dust and fines. In India a significant amount of this dust is generated from some of the integrated iron and steel industries, refractory and cement plants, during calcination of raw magnesite. However. it is possible to utilize this dust, which is normally a waste, conveniently and economically for the production of magnesium. chemicals. A bench scale study was carried out to determine the rate of formation of sulfated com¬pounds of Mg.Ca,and Fe, inter alla, present in the dust system containing MeO constituents (in which Me=Mg.Ca,Fe,Si,Al etc.) Effects of various process parameters, which affect the reaction rate as also the purity of the product ,were also studied. Some work carried out to develop the process flow charts involving the salient steps to produce magnesium chemicals commercially is reported in the paper .

Jan 1, 1992

By A. M. Johnson

Dewatering is a major operational cost at some mines. Under certain conditions, costs associated with water disposal may continue beyond the productive bye of the mine. For mines with mineralized waters, this is of special concern. Since 1974 experience has been gained from examination of a number of closed underground metal mines that exhibited drainage problems. It was observed, in certain cases, that had appropriate steps been taken prior to closure, the resulting drainage problems could have been largely avoided. Reclosure steps would have involved alteration to the 'plumbing system" of the mines; i.e., the drifts and crosscuts interconnecting the mine workings. This could have best been accomplished by the placement of bulkheads and/or selective drifting. In addition to reconfirming that hindsight is 20-20, a lesson learned from these case studies shows that a relatively simple hydrologic evaluation prior to mine closure may avoid a troublesome and costly drainage problem.

Jan 1, 1985

By M. Evertsson, E. Hulthén

"In aggregate production and mining the operators are responsible for controlling and monitoring the process to maintain high plant throughput and safe operation. Operators have to make different decisions to control the process due to changed demand on the operation from both management and conditions of the process. The quality of the response and the time it takes for an operator to respond to altered demand relies on what information is available and the experience of the operator. In this work a dynamic simulation platform has been developed to be used for operator training. Models for representing production units and process control for plant simulations have been developed and implemented in MATLAB/SIMULINK to simulate time-dependent plant behavior. Stochastic and scheduled events are included using the discrete events simulation toolbox SimEvents. The human-machine interface was developed using the human-machine interface software ICONICS. The operators’ cognitive process, in interpreting the plants semantic, has been studied by observations and with informal interviews with operators. This was done to get information about the daily operation and the problems that occur in the process. By interacting with operators that experience different physical interactions with the process; more qualitative e-learning software for supporting operator training in a dynamic operator environment could be developed. The quality of the operator training environment was evaluated with a usability study that was performed with operators and others within the production."

Jan 1, 2014

By Ma Fangyuan, Li Min, Xu Bing, Xian Yushuai, Zhao Tonglin

The study explored a new combination amine collector (XK-28) that can obtain better flotation index and defoaming rate for magnetic iron ore. A pure quartz mineral test indicates that dodecylamine, XK-I, or XK-II has good collection effect on quartz and their best flotation pH is in the range of 6–7. The experimental results of a combination collector (XK-I:XK-II = 2:8.) show that the separation effect for quartz and magnetite is better than that of a single collector. The single factor for actual mineral test shows that when the combined reagent is used as the collector, the best conditions are pH = 7, 90 g/t dosage, and XK-I:XK-II = 2:8, which is consistant with the pure mineral test. The difference for dodecylamine as a collector is that the optimal dodecylamine dosage is 60 g/t. Under the best conditions of actual ore test, dodecylamine and XK-28 are respectively used as the collector to compare the flotation indexes. Study results indicate the magnetite grade using XK-28 as the collector is higher by 3.02% than that of using dodecylamine, recovery is increased by 1.92% over that of using dodecylamine. Based on the measurement results of zeta potential, uses of XK-28 can slightly increase the zeta potential difference of quartz and magnetite to enhance the flotation effect. The mechanism of action between the XK-28 collector and the actual ore from the Gongchangling plant is physical adsorption, and this adsorption also has hydrogen bond formation. Contact angle results shows that XK-28 improves the hydrophobicity of quartz better than dodecylamine. Compared with dodecylamine, XK-28 is more sparsely arranged on the surface of the foam. The foam produced by the XK-28 collector has better air permeability and it is more likely to merge and disappear with bubbles.

Jul 21, 2021

Principles of management in ore preparation before process of enrichment of chrysotile ores are discussed. The formulas, which were tested in industrial conditions, are offered, which may be used for averaging of chrysotile-asbestos fibres by content in ore and grade.

Dec 6, 2010

By V. O. Murray

Safety, from the Latin word "Salvus" -Safe. 1. The condition or state of being safe; freedom from danger or hazard, exemption from hurt, injury, or loss. 2. Freedom from whatever exposes one to danger or from liability to cause, danger, or harm; safeness: hence, the quality of making safe or secure, or of giving confidence, justifying trust, insuring against harm or loss. (From Webster.) The meaning of the word "Safety" by Webster is very explicit, clear, and plain. It is not obscure or imperceptible. What man, woman or child is not familiar with this word? A mere word by itself, but indifference to its significance means the difference between life, death, permanent or partial disability, or injury. There is no question about a safety program being expensive. It is-it produces no commodity-but when properly organized and with a definite goal in view it will pay 'a dividend by increasing the efficiency of the human worker.

Jan 1, 1930

By W. D. Dietzman

This Bureau of Mines report presents a continuation of statistics pertaining to distribution of petroleum reservoirs (or fields), wells, and production by depth and producing rate classification in the United States. These statistics show the change that has occurred since results of a similar study were published by the Bureau of Mines in 1967. Data are presented in tabular form by State for the 18 principal oil-producing States and by subdivision for the two largest oil-producing States, Texas and Louisiana. Tabular summations and graphical illustrations are presented for the Nation. The data are classified by 4-barrel-of-oil-per-day rate increments up to 36 barrels and one increment of greater than 36 barrels of oil per day and by 2,000-foot depth increments up to 8,000 feet and one depth increment of greater than 8,000 feet. The overall average producing rates for States and the Nation have been published for many years, and although such rates are useful, they are very general descriptions of producibility. A breakdown of production, wells, and reservoirs by various depths and rates and by State or by State subdivision provides a more detailed description of producibility.

Jan 1, 1975

By Rafael Fagundes Ferreira

Aços Bake Hardening são aços laminados a frio com envelhecimento controlado. Estes aços caracterizam-se pela boa conformação e por apresentarem aumento de resistência mecânica devido ao envelhecimento, que ocorre por tratamento térmico. Nesse trabalho, corpos de prova de tração do material BH220 foram submetidos à pré-deformações que variam de 0 a 9% por tração uniaxial, posteriormente à tratamento de envelhecimento realizado em temperaturas que variam de 140°C a 210°C em tempos de aquecimento entre 5 minutos a 45 minutos. Foi confirmada que as temperaturas de envelhecimento, na faixa estudada de 140°C a 210°, alteram a variação do limite de escoamento devido ao fenômeno de difusão que é termicamente ativado. Nos resultados encontrados verifica-se que o tempo de aquecimento, dentro do intervalo testado, não é significativo.

Aug 16, 2017