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By M. Ashraf Mahtab

In Louisiana salt mines a sudden erruption or outburst of salt and gas occurs when the heading face approaches a pressure pocket (altered salt with high pressure gas). The resulting cavity is semi-ellipsoidal, reaching lengths of 50m or more. Potential risks from the outbursts include loss of life and equipment. A gas outburst is initiated by "disking" of the salt in biaxial compression and propagates by spalling of the cavity walls and further disking. The outburst is terminated by a combination of dilatancy hardening, increase in stress along the cavity axis, and enlargement to boundaries of the pressure pocket.

Jan 1, 1982

By L. Adler

Existing classifications of mining and construction equipment have had major deficiencies. They often lack organization, balance, and have remained obscure. Particularly when proceeding to great.er resolution these deficiencies have proven crippling. By adopting "Classes", "Groups" f "Types" and "Kinds" at successive degrees of refinement, a "Taxonomy" is developed based on clear visual differentiation or on a "Morphology??. This symbiotic application, adopted from the Biological Sciences, yields clear, simple and unambiguous results. Supporting this effort are guidelines for easily and credibly sketching equipment which are also distinctive. Numerous illustrative examples are provided. Communications are improved and the engineer obtains a confident feel for the equipment at hand.

Jan 1, 1989

By R. J. Roman

Controlled and uniform distribution of the leach solution to a heap is of primary importance to achieving the desired rate of metal recovery and PLS grade from the heap. The step used to engineer the irrigation system are the same whether drips, wobblers or sprinklers are to be used. The mining rate, leach cycle time and heap height influence the heap cell size which along with the irrigation method selected controls the design of the irrigation system. The steps in the design procedure are explained as are the advantages and disadvantages of each irrigation method.

Jan 1, 1996

By T. P. Meloy

Like our wives, the comminution of brittle solids is easy to recognize but difficult to describe. However, describing it we must. Describing the fracture mechanism of brittle solids permits the eventual mathematical quantification of the results, process optimization and control strategies. This paper presents a physical model of brittle solid comminution that explains why the slope of the log-log size distribution curves have a slope of one or less in the smaller particle sizes. To develop the hypothesis, modifications of the Gaudin Meloy physical model are made. In brittle solids, comminution takes place by cracks propagating through the material. These cracks may bifurcate as they move. Cracks may terminate either on the original surface of the material, or on a secondary crack within the material formed earlier in the comminution process.

Jan 1, 1994

By Johann Knecht

Due to lower specific investment and operating costs the tendency towards large scale equipment will remain. For the design engineers not only the stresses in the mill structure and manufacturing are of importance but also transportation to and erection on site. A scale up of the design of smaller sized units on the pantograph principle may not always give the best approach to the job in this respect. This paper covers recent developments in the design of large size equipment where the huge dimensions call for designs being different to the well known ball and SAG mill concept with cast conical endwalls. The first part describes the features of the biggest ball mill in the world, whereas the second part provides some details of the largest shell supported SAG mills being currently in the manufacturing process.

Jan 1, 1993

By William C. Peters

"A large proportion of the earth's surface is blanketed by young sedimentary formations and by recent lava flows. How many Guanajuatos lie concealed beneath the rhyolitic capping of the Sierra Madre of Mexico? How many Kirkland Lakes are under the drift cover of the Canadian Shield? How many Wilunas are still hidden by the alluvium of the desert of Western Australia? How many ore deposits lurk underneath the basalt-covered plateaus of the Columbia River region? If erosion at Goldfield, Nevada, had stopped 100 feet higher, probably no ore would have been exposed. How many Goldfields are still awaiting discovery?" --Hugh Exton McKinstry, 1948

Jan 1, 1969

By G. K. Wilson

This paper will discuss some of the more important aspects to be considered when selecting pumps for mill discharge, cyclone feed or other severe-duty applications Included will be the selection of the pump based on such factors as particle size, particle distribution, head, flow, temperature and pH Other specifics to be covered: The relationship of impeller speed, head and wear factors as they affect pump performance and wear life; the importance of selecting a pump whose performance curve best suits the application; and how the addition of service factors applied to the actual operating conditions can lead to severe operational problems such as premature wear, pump running out on curve, and exceeding horse power limitations.

Jan 1, 1996

By Denis McDermott

This paper describes the process used at three mines to devel­op safety and training programs. The mines are located in Australia, New Zealand and the United States of America. The aims of the programs were to promote and reinforce safe and healthy behaviour, increase productivity and efficiency and to provide a fair and objective basis for the payment of wages. There were common aspects to each of the projects: • mandatory legislation required employers to provide employ­ee training in work performance • employees had little previous involvement in the design and development of the training provided • training had been unstructured with employees relying on the "buddy system" to acquire new skills; the degree of skill acquired by an employee depended on the knowledge and teach­ing capacity of the worker to whom the novice was assigned • appointments and promotions had been based on judgements by supervisors and these were not generally understood by employees • employment conditions for employees were covered by an industrial agreement between management, unions and employ­ees. The degree of sophistication of the industrial agreements varied however none provided a description of work performed in each classification, nor the career or promotional path for an individual • supervisors with the responsibility to train, develop, motivate and reward employees expressed concern that there were no structured processes ( eg work standards or wage progression cri­teria) to support their role.

Jan 1, 1998

By John L. Burnett

Field criteria are needed to help the prospector recognize a potentially expansible shale, clay, or slate. Certain criteria have proven useful in California even though the physical-chemical mechanisms of expansion are not thoroughly understood. Three conditions must be satisfied before expansion can take place, The raw material must partially fuse at a low temperature (1800-2000°F.), Concurrently a gas must form. The raw material must be sufficiently impermeable to trap the gas within the particle. Low temperature melting, which is controlled by bulk chemical composition, is difficult to assess in the field but most common shale, clay, and slate is suitable in this respect, The presence of organic carbon, the most common source of an expanding gas, is indicated by dark color of the rock, A large proportion of clay-sized particles promotes impermeability; fine grain-size is indicated by conchoidal fracture, The shape of the expanded particle is commonly indicated by the texture of the raw material. Rocks with well-developed slatey cleavage produce accordion-shaped particles; massive rocks tend to form rounded particles. Undesirable materials commonly present with expansible shale include: weathered shale; sandstone and other coarse-grained sediments; and limestone, Weathering, which is indicated by color, reduces or eliminates expansion; therefore, surface samples seldom are representative of the shale found at depth. Sandstone does not expand and will increase the average weight of the finished product, Limestone or particles of carbonate minerals can be actively harmful because they are converted to free lime (CaO) during the firing process, If free lime is present in concrete, hydration will cause expansion of the lime particles which result in surficial ?popouts.?

Jan 1, 1963

By J. F. Strunk Jr., K. M. Maestas, Y. Chai, R. Legrand, R. L. Henry

"Groundwater with elevated sulfate and metals was treated using a sulfate-reducing pilot PRB consisting of a series of six 55-gallon drums filled with ZVI (Fe0), wood chips, brewer’s grain, limestone, and emulsified vegetable oil (EVO). Sulfate was reduced from >3000 to <250 mg/L and Cd, Cu, Mn, Ni, and Zn concentrations declined up to 3 orders of magnitude in 2 months. After 6 months of operation at a 7.5-day retention time, sulfate broke through. The system was then rejuvenated by injecting EVO in each drum and operated for 5 more months at a 9-day retention time. Sulfate-reducing bacteria in the pilot system grew by 3 to 4 orders of magnitude in 2 months. Some cementation of the PRB media was observed in the first 2 drums after processing 25 pore volumes of water, due to preferential upstream precipitation of sulfides; this can be avoided through operational modifications. Resulting permeability losses were estimated at 0.1% to 1% per year. Absorption/desorption was tested at bench scale to evaluate the use of various oil-soaked sorbents as a slow-release source of dissolved carbon. The tests show that oil sorbents can increase the useful life of a PRB between oil refills to over 100 pore volumes. INTRODUCTION High sulfate concentrations, low pH, and dissolved metal exceedances are common characteristics of mining-influenced water (MIW). Above-ground such MIW is commonly treated using biochemical reactors (BCR). In a BCR, water generally flows vertically downward through a layer of biomass, such as wood chips, manure, etc. The dissolved organics resulting from the decay of this material are oxidized first by microbes using oxygen; when oxygen is exhausted, other bacteria can use nitrate, and then sulfate to oxidize organics. Sulfate-reducing bacteria (SRB) reduce sulfate to sulfide, which quickly reacts with metals to form largely insoluble and stable metal sulfides. These reactions can be summarized as follows:"

Jan 1, 2016

By George D. Tikkanen

The world supply of zinc and lead is reviewed. The nature of zinc and lead deposits, production constraints, current production and reserves, new developments, possible future developments, and closures are considered. Lead sup- plies for the future are adequate. Zinc supplies are expected to tighten in the longer term due to growth in zinc consumption and orebody depletion.

Jan 1, 1986

By F. Segobia, M. Portal, F. Ysla, L. Goicochea

It is our responsibility to promote responsible and sustainable mining with new generations, promoting a culture of equality and respect. To fulfill this commitment, we are working with the SME UNC Student Chapter team, Newmont Yanacocha, BRG Women and Allies and the Museo de Agua y Tierra (MAT) to carry out the “Building our future” project. It is our responsibility to promote responsible and sustainable mining with new generations, promoting a culture of equality and respect. To fulfill this commitment, we are working with the UNC SME Student Chapter team, Newmont Yanacocha, BRG Women and Allies and the Museo de Agua y Tierra (MAT) to carry out the “Building our future” project. This project seeks to instill in new generations the importance of mining, integrating sustainable development objectives. We have the participation of Newmont Yanacocha and external professionals, who share their life stories and inspire participants from rural and urban educational institutions to pursue their dreams and aspirations. We believe that this project is important because it will help new generations understand the importance of mining and its role in the development of the country, covering the economic, environmental and social spheres. Since its inception in 2022, the project has positively impacted more than 500 participants.

Feb 1, 2024

By Ronald O. Harma

Iron ore pellets made from concentrates produced from low grade iron ores are the primary iron bearing feedstock for iron making in North American blast furnaces. Steelmakers are demanding increasingly higher quality to provide for improved blast furnace productivity, efficiency, product quality and environmental compliance. Unfortunately, this higher quality iron ore product must be produced from the vast deposits of low grade iron ores that are becoming increasingly poorer in quality with regard to mineral liberation and ease of concentration. Since some of these low grade iron ores require grinding to as fine as 90% -500 mesh (25 microns) for liberation and since more of the silicious gangue and other minor undesirable constituents must be removed to provide the higher quality, we have come to depend on flotation to do the added work. Flotation technology and other preflotation unit operations must improve to meet these increasing demands. In many cases, flotation equipment, reagents and circuit operating performance have improved little during the last two to three decades. Mechanical flotation cells have grown from 14 cubic meters (500 cubic feet) to over 84 cubic meters (3000 cubic feet) to help reduce capital and operating costs; however, flotation metallurgical performance has not improved, Column flotation has only recently shown promise in improving metallurgical performance for iron ore rougher flotation. Previous column flotation success was mainly in scavenger and cleaner flotation steps for treating minerals other than iron ore. Although some new flotation chemicals have been developed for removal of silica and other minor constituents under widely varying mineralogical scenarios, recovery of iron mineral has not improved. The operation and control of flotation circuits have become more challenging because of the increasing workload on flotation. Better sensing, process control and operation of flotation circuits are essential as we go forward. Iron ore upgrading by flotation can be classified into either anionic or cationic methods. Anionic flotation of either iron oxide or silicious gangue is accomplished by collector type, pH control and selective chemical activation . Similarly, cationic flotation of silica or iron oxides is accomplished by collector type, activation and/or pH control. Removal of other minor constituents is achieved by using specialty chemicals under controlled conditions for preflotation, co-flotation or post flotation steps. Generally, anionic flotation is used for floating cleanly liberating crystalline oxidized iron ores such as hematite, specularite and martite. Earthy and hydrated oxides such as hematite and geothite can be upgraded with either anionic or cationic collectors after controlled dispersion of slimes or prior removal of slimes. Anionic flotation of silicious waste can be achieved by calcium activation of silica. For magnetic iron ores small amounts of locked silica particles (middlings) can be removed by cationic silica flotation, which is the only method in commercial use in North America today. Historically the efficiency of these iron ore flotation processes has been restricted by the loss of fine iron particles (minus 500 mesh) to the tailings product. New technology is required to overcome this loss and improve overall flotation performance. Development of technology for more selective separation of silica and other minor undesirable constituents from iron ore will provide both quality and cost benefits to the iron and steel producers. Development of future iron ore production in North America will face stiffer technical challenges. These new and undeveloped iron ore deposits are largely oxidized (non-magnetic) and by nature contain more slimes and other undesirable constituents. Unless other new technology evolves, flotation will be the major treatment process required to upgrade these difficult low grade iron ores.

Jan 1, 1993

By Ottmar Burghardt

Sintering of iron ore has undergone a dramatic development world-wide. Today, the annual world production amounts to approximately 600 million tons. At present, the sintering process in competition with pelletizing, seems to offer certain advantages inasmuch as it allows the use of solid fuels. Also, its charging behaviour in the blast furnace is, in general, considered as being better than that of pellets. This is true, in particular, for the charging behaviour and the gas permeability in relation to the grain size. Moreover, instead of charging limestone into the blast furnace, for instance, the basic components which are necessary for the burden materials can generally be supplied in a simpler and more cost-effective way by using basic sinter instead of basic pellets. While in sintering, with basicity rising to the range of 1.6 to 1.8 CaO : SiO2, the capacity increases and the sinter quality shows improvements in most of its characteristics, the pro¬duction of basic pellets generally requires a higher fuel rate, when compared to acid pellets, while production capacity decreases and some of the quality characteristics deteriorate.

Jan 1, 1982

By Gerald H. Luttrell, Jaisen N. Kohmuench, Michael J. Mankosa

A new separator, known as the Hydrofloat cell, has been developed to overcome limitations of traditional flotation cells in recovering coarse particles. In this process, small air bubbles are introduced into a hindered "teeter" bed of fluidized solids to create light bubble-particle aggregates that can be separated based on differences in density. Laboratory tests conducted with coarse phosphate feeds indicate that the Hydrofloat cell is capable of increasing BPL recoveries by nearly 20% over conventional flotation methods. Based on these encouraging results, a pilot-scale Hydrofloat cell was fabricated and installed at a central Florida phosphate plant. Test data collected using the pilot-scale unit suggest that the BPL recovery of the plus 35 mesh plant feed can be increased by more than 40% through the application of this new technology. This improvement is particularly beneficial due to the very high grade (-73% BPL) of the plus 16 mesh particles in the Hydrofloat concentrate. This article describes the theoretical basis for the development of the Hydrofloat cell and provides an overview of recent laboratory and pilot-scale test results.

Jan 1, 1999

By Brian H. Zelenko, Patricia M. Perry

INTRODUCTION The environmental requirements of the next section of Washington, D.C. METRO subway tunnels present unique challenges to the Contractor. The 14th Street Tunnels contract includes twin 975 m (3200 linear ft) soft ground tunnels. A stringent environmental soil and groundwater monitoring and free product recovery program was specified by the owner. A project-wide dewatering program hinges on satisfactory completion of the environmental requirements. Implementation of the Contractor&apos;s environmental program is discussed, including the pros and cons of the program, as they relate to progress of the project. Environmental issues on tunneling projects have become an important part of the urban tunnel construction process. Delays associated with environmental issues can have a major cost impact on tunneling projects. This paper will discuss the first of five Washington Metropolitan Area Transit Authority (WMATA) tunnel and station contracts awarded in 1994. These contracts are part of WMATA&apos;s Fast Track Plan to complete the original 166 km (103 mile) system by 2001. As such, stringent environmental requirements have been specified as a part of these contracts to limit delays associated with local regulators in order that the tunnels may be constructed on schedule.

Jan 1, 1995

By Zhang Youdi

A two-step approach has been developed for surface mine short term planning by the authors. The first step is mid term control and planning by the use of Goal Programming. This step gives optimal results for mid term planning (i. e. yearly or quarterly mine plan) as well as a macro control for short term planning (i. e. monthly or weekly plan.) The second step of the approach deals with short term production scheduling by the application of CAD technique and Systems Simulation. An interactive color character graphic design system has been developed with a software package. The menu-driven and module- structured package provides sufficient functions for surface mine short term planning and makes the model very flexible and user-friendly. This model has been applied to a large surface coal mine for short term planning optimization. Satisfactory results have been obtained. It is concluded that for complicated mining conditions this two-step combined approach gives an optimal control of mid term planning, makes the short term planning easier to avoid blindness; it has been proven that the Goal Programming is a powerful tool for solving multi-objective decision-making problems; guided by GP mid term planning, the CAD technique and simulation software package for short term planning are able to be concentrated on their practicality and flexibility.

Jan 1, 1992

By Z. Nivolianitou

This article aims at highlighting the importance of technological innovation, namely the potential use of Virtual Reality (VR) technology, as a Sustainable Development Indicator for the minerals industry. Nowadays, VR is regarded as a mature technology for real world representation, and it has been already applied in various domains such as architecture, topography, aeronautics, medicine, and lately in the process industry. Several industrial sectors already use VR tools, as the car industry for improving car ergonomics and design and the aviation industry for both pilot and maintenance crew training. It is well known that the mining industry, as well as the process industry, requires people to work in hazardous environments and situations, often inadequately trained owing to limitations in time and resources, building thus the potential for minor or major accidents.

Jan 1, 2007

By Bruce C. Trent

The need for effectively evaluating the potential for surface subsidence due to under- ground mining has been widely documented. As the emphasis within the coal mining industry changes to reflect the increasing demand of this resource, the potential for damage due to differential surface subsidence will certainly become more acute. The present state-of-the-art of predicting ground motion due to underground excavations is, at best, primitive when one considers the immense complexity of possible geological inter- actions. For the most part predictions have been limited to empirical evaluations based upon earlier case histories. While the tools of the subsidence engineer are limited, they are important and serve to provide reasonable bounds for possible ground motion. As underground mining becomes more extensive, however, there will be many instances where excessive subsidence will be most undesirable and yet there may be few, if any, case histories similar to the operation in question.

Jan 1, 1982

By J. J. Kellar, W. M. Cross, J. D. Miller

Infrared spectroscopy has been one of the most useful experimental techniques for the analysis of surface reactions in flotation systems, including surface alteration and surfactant adsorption reactions. With the advent of Fourier transform infrared (FTIR) spectrometers, many low-energy throughput IR experimental techniques previously unused by flotation researchers have come into greater use. In particular, internal reflection spectroscopy (IRS) is the most often used technique for in-situ studies. To date, three IRS methods have been used for in-situ measurements. These techniques are evaluated for use in characterization of surface reactions in flotation systems. The method using mineral crystals as reactive internal reflection elements (IRE) is of particular interest because it allows surfactant adsorption densities to be calculated directly from in-situ spectral data in real time. Application of in-situ FTIR/IRS with reactive internal reflection elements will be demonstrated for collector adsorption reactions in each of the major flotation systems. The alumina (A1203)/sodium dodecylsulfate system is used as an example for insoluble oxide/silicate flotation, while the fluorite (CaF2)/oleate system serves as a paradigm for semisoluble salt flotation. For sulfide flotation, sphalerite (ZnS) is used as the reactive IRE with potassium amylxanthate and potassium ethylxanthate as collectors. In the case of soluble salt flotation, sylvite (KC1) is used as the IRE with n-octylamine as collector. Finally, the use of reactive IREs in the near-IR spectral region and in spectroelectrochemical research is discussed.

Jan 1, 1989