Search Documents

By Jorge Madias

Neste trabalho se leva a cabo uma revisão da literatura sobre defeitos em beam blanks. O foco é no mecanismo de formação e as soluções propostas para diminuir sua ocorrência. Os defeitos superficiais incluidos são as trincas longitudinais e transversais, bleeding, pinholes e escória. Os defeitos internos levados em conta são os blowholes, as trincas centrais e as trincas nas pontas das abas. A revisão incluie as técnicas utilizadas para pesquisar os defeitos: caracterização metalográfica, CFD, modelagem termodinâmica e termomecânica, etc. As medidas adotadas estãorelacionadas a mudanças no sistema de lingotamento (por exemplo o design da vâlvula submersa), design do molde, mudanças e regulação do resfriamento secundário, suporte dos veios.

Oct 30, 2017

By Q. M. Huang

In 1979 our company undertook the project of infra-structural work of White Swan Lake Hotel, (International class ) Guangzhou. Visit to the site showed that it was situated at the riverside, covering an area of 54,000 M2 with 30,000 M2 of which reclaimed from Pearl River. The material used for reclamation was black sand which was dredged from the nearby riverbed. The sand had the properties of high permeability and very low internal friction. The basement of the building was 6.2 m below ground level and 3 m lower than the riverbed. Apart from the pile foundation, a diaphragm wall was to be constructed prior to the commencement of excavation work for basement. A feasibility study was carried out to determine the method of construction which would maximize utilization of the plants and equipment that were available in the execution of the aforesaid foundation works. This report concerns only the construction of the diaphragm wall and the performance of the plants employed. A detailed delineation of the construction method is herein discussed

Jan 1, 2010

By I S. Lowndes, K. Moloney

Diesel powered equipment is currently used extensively in mining and tunnelling operations around the world due to its mobility, flexibility and through selective application to enhance productivity. However, the increased use of diesel equipment has exacerbated the pollutant load (including heat, humidity, exhaust gases and particulates) placed upon the environmental systems of many underground operations. This expansion in the use of diesel equipment has prom pted researchers to evaluate m easure ment and control technology. This paper reviews the recent research conducted in various countries.

Jan 10, 1996

By D. G. Leddy, J. B. Johnson, L. D. Gratz, S. T. Bagley

"Studies have been conducted at Michigan Technological University (MTU) for over twenty years on methods for characterizing and controlling particulate emissions from heavy-duty diesel engines and die resulting effects on regulated and unregulated emissions. During that time, control technologies have developed in response to more stringent EPA standards for diesel emissions. This paper is a review of: 1) modem emission control technologies, 2) emissions sampling and chemical, physical and biological characterization methods and 3) summary results from recent studies conducted al MTU on heavy-duty diesel engines with a trap and an oxidation catalytic converter (OCC) operated on three different fuels. Control technology developments discussed are particulate traps, catalysts, advances in engine design, the application of exhaust gas recirculation (EGR) and modifications of fuel formulations. Methods for dilution tunnel sampling, particle size analysis, chemical analysis with emphasis on polynuclear aromatic hydrocarbons (PAH) and nitro-PAH, and biological characterization using mutagenic activity (Ames) assays are described, along with statistical approaches to experimental design and data analysis.In studies at MTU, both particulate traps and an OCC have been shown to be effective for the reduction of total particulate mauer (TPM), with the OCC being better al reducing all forms of hydrocarbon emissions, including PAH and nitro-PAH, and with the traps being better at removing the solids (SOL). The use of low sulfur fuel (0.Ql % by mass) has led to additional reductions in TPM; the low sulfur fuel has been shown to reduce the number of small, nuclei-mode particles for one of the engines tested. PAH, nitro-PAH, and mutagenic actively levels generally decreased with use of either the traps or the OCC.INTRODUCTIONDuring the 1980s and the early 1990s there have been significant advancements in the development of technology to control diesel particulate emissions. Efforts have been focused on internal control of the engine by design, the use of after-treatment devices, and improvements in fuel formulations to reduce all the diesel emissions. The research and development activities have been driven by the need to meet the US EPA heavy-duty vehicle standards shown in Table 1. The important standards for new technology are the 1994 heavy-duty vehicle 0.1 gm/bhp-hr particulate, the new urban bus 0.05 gm/bhp-hr particulate standard for 1996 and the heavy-duty vehicle 4.0 gm/bhp-hr NOx standard for 1998."

Dec 1, 1995

By Pratt Rogers, Aaron Young

This paper considers the mining industry’s need for digital transformation (DT) and presents a three-part review of the foundational components of the DT process: ubiquitous data, connectivity and decision-making. It also provides a discussion on the future of DT in mining as well as a research direction, which identifies the need of academia to provide support for mining companies in the form of both research and the education of digitally literate, dynamically capable mining engineers into the coming decades.

By Pratt Rogers, Aaron Young

Digital transformation (DT) is the process by which entities adapt themselves to modern technology. As digital technology becomes more prevalent (automation, cameras, sensors, touchscreens, artificial intelligence, etc.), there will be increased pressure on companies to leverage it for additional gains. For many companies in the mining industry, this will involve overcoming a steep learning curve. Furthermore, as the long-term success of the mining industry is dependent on a labor force with new skills (data management, analytics, digital literacy, etc.), new curriculum will need to be appended to the mining engineering discipline. This paper considers the mining industry’s need for DT. Then, it presents a three-part review of the foundational components of the DT process–ubiquitous data, connectivity, and decision making. Finally, it provides a discussion on the future of DT in mining as well as a research direction, which identifies the need of academia to provide support for mining companies in the form of both research and the education of digitally literate, dynamically capable mining engineers into the coming decades.

By A. T. Jakubick, A. MacG. Robertson

This paper reviews key issues related to the placement of dry (soil) covers on extremely weak, compressible fine tailings. The design and construction of soil covers on such tailings often presents a formidable challenge to the geotechnical as well as the environmental engineer due to the low shear strength, poor traffic ability, and high settlement of under consolidated tailings at the time of reclamation. The geotechnical issues to be considered include: (1) consolidation of near-surface tailings to achieve strength gains, improve traffic ability, and allow safe placement of initial cover layer; (2) stability of tailings slopes during dewatering of tailings ponds and/or cover placement; and (3) long-term settlement of tailings and its impact on cover integrity and final surface shaping. The environmental issues to be considered include: (1) management of contaminated (free) pond water; (2) management of contaminated pore water expelled during tailings consolidation; and (3) management of (uncontaminated) surface water on top of the cover. This paper summarizes recent experiences gained in a large uranium tailings reclamation project. It is concluded that a careful consideration of both geotechnical and environmental issues during the planning stages greatly reduces the costs and environmental risks associated with fine tailings reclamation.

Jan 1, 2000

By P Craig, M Holden, C Zhang, D Foster, J Oh, S Saydam, J Liu, H L. Ramandi, S Akdag

High stress in rock masses can cause significant instability problems such as squeezing deformation in soft rock and rock bursts in hard rock. The support system applied in burst-prone areas in high-stress conditions is required to be able to carry high load and accommodate large deformation of the rock mass without experiencing any serious damage. Yielding support systems are promising to provide support for both squeezing and burst-prone rock mass encountered in mining or tunnelling at depth. They are ideally strong and stiff initially and then ductile after yielding (Potvin and Hadjigeorgiou, 2020). With respect to support design, a ground support system has to create a safe working environment under both static and dynamic loading conditions by providing the functions of reinforcing, retaining, holding and connecting elements (Cai and Kasier, 2018). Rigid rock bolts and cable bolts perform reinforcing and holding functions of a ground support system. In highly fractured ground or with large excavation spans (eg at roadway intersections or in caverns), unstable ground depth can exceed the length of typical rigid rock bolts (ie greater than ~3.0 m). In such cases, flexible cable bolts are needed to tie the reinforced and retained rock mass back to deeper and more stable rock. The flexibility of cable bolts allows anchor lengths greater than the tunnel opening that would otherwise restrict rigid bolts. Cable bolts also offer higher strength to weight ratio, with tensile strengths 2–3 times that of standard rebar bolts. This high strength comes at the cost of lower strain tolerance, typically around 5–7 per cent at break. Despite the lower strain tolerance, cable bolts are often used as dynamic support in demanding burst-prone ground conditions. The lower strain tolerance is compensated by allowing sufficient free length for stretching or incorporating a yielding device. There are a number of dynamic cable bolts available on the market and a number of testing campaigns have been undertaken to quantify the dynamic performance of these cable bolts. This paper reviews the existing range of dynamic cable bolts and discusses the potential areas for improvement and further research.

Nov 29, 2022

By Ebrahim Ghasemi

Problem statement: One of the most challenging safety problems in room-and-pillar coalmines is controlling roof falls during retreat mining. Roof falls not only cause both fatal and non-fatal injuries to miners, stoppages in mining operations, and equipment breakdowns, but also results in the inefficient recovery of coal reserves. Approach: Sufficient awareness of effective parameters related to roof falls is an important factor in roof control. In this study, the major contributing parameters on roof falls during retreat mining are introduced based upon experience and judgment acquired from extensive retreat mining case histories and a review of relevant literature. Key findings: The main roof fall parameters in retreat mining can be divided into three categories: geological, design, and operational. Key conclusions: The design and operational parameters can be controlled by the engineer and/or operator. By the appropriate selection of these parameters in the design and implementation stages of retreat mining, the roof fall risk can be decreased to an acceptable extent.

Jan 1, 2012

By T. W. Healy, M. S. Moignard

The use of electrokinetic or zeta-potential phenomena in studies of the properties of mineral sulphides has increased greatly over recent years. This review aims to examine and discuss the body of literature on the subject of electrokinetic properties of sulphides in a comprehensive and critical manner. Although the review covers the period from 1925 to 1975, it is only in the past ten years that researchers have been fully aware of the implications and problems of chemical reactions, notably oxidation and precipitation reactions, on the surface properties of sulphide minerals. These papers are discussed in more detail than the earlier publications. A table containing a list of determinations of iso-electric- points and points-of-zero-charge of mineral sulphides, and the methods employed in obtaining these results, is presented.

Jan 1, 1976

By F. Hörtkorn, Y. Narainsamy

Rather quietly, a new generation of European norms dealing with earthworks has been developed over the past few years, in particular a part of EN 16907 pertaining to extractive waste. Whereas the majority of the parts deal with routine geotechnical aspects, one part deals specifically with tailings dams. The standard is currently in draft form but if this becomes a European Standard, members of the European Union are bound to comply with the regulations. As such, the standard has the capacity to influence mining in Europe and potentially in South Africa. In this paper we review the standard and compare it to the South African standard on mine residues and the recently published Global Industry Standard on Tailings Management (GISTM). We conclude found that although the European norm makes great strides towards increasing tailings dam safety, there is room for improvement. The current South African standard has served well since its inception, but can be improved by using concepts from the European and global tailings standards.

Jun 2, 2022

By Merle L. Bowser, Lawrence W. Scott, John N. Murphy

The environmental status of underground mining operations is critical to the health and safety of the miners; particularly in a large mine, the multitude of interacting parameters that can favorably or adversely affect the environmental status makes the manpower requirement of the routine checking of specific areas and conditions a formidable one. While the concept of environmental monitoring for miners has been considered for some time, until recently the availability of sensors to reliably measure the parameters of interest severely limited the utility of such systems. The status of sensors for mine use and the evaluation of environmental monitoring systems is reviewed.

Jan 9, 1979

By C. I. Huang

The mining industry is an easy target for criticism from an environmentally sensitive society. Recent researches discovered that human activities, including mining. cannot be blamed for all of the pollution observed on earth. Interdisciplinary research is providing diagnostic and remedial solutions to problems such as acid mine drainage and cyanide-polluted streams. Researchers have also found that mercury-bearing hot springs and volcanic eruptions are partly responsible for some pollution. Geochemists, mining geologists, engineers, and environmental scientists can pool their efforts to make the environment cleaner and safer. Remote sensing of the environment and the use of microbes may become much more popular in the near future in the mining-environment arena.

Jan 1, 1988

By John N. Murphy

The environmental status of underground mining operations is critical to the health and safety of the miners; particularly in a large mine, the multitude of interacting parameters that can favorably or adversely affect the environ-mental status makes the manpower requirement of the routine checking of specific areas and conditions a formidable one. While the concept of environmental monitoring for miners has been considered for some time, until recently the availability of sensors to reliably measure the parameters of interest severely limited the utility of such systems. The status of sensors for mine use and the evaluation of environmental monitoring systems is reviewed.

Jan 1, 1977

By Merle L. Bowser, Lawrence W. Scott, John N. Murphy

The environmental status of underground mining operations is critical to the health and safety of the miners; particularly in a large mine, the multitude of interacting parameters that can favorably or adversely affect the environmental status makes the manpower requirement of the routine checking of specific areas and conditions a formidable one. While the concept of environmental monitoring for miners has been considered for some time, until recently the availability of sensors to reliably measure the parameters of interest severely limited the utility of such systems. The status of sensors for mine use and the evaluation of enviornmental monitoring systems is reviewed.

Jan 1, 1980

By B Dold

Western Europe is a dynamic region, with an emerging co-operation between the individual nations both politically, economically, technically and scientifically. The European Union, today with 15 member States and with a range of central European States applying for membership, is a catalyst for this Cupertino, using a combination of EU funds, for financing research initiatives, and legislation to enhance development of technology and environmental performance. Europe is a major net importer of metals but with a large potential for own production, in particular in the accession countries. The metals and mining sector is furthermore identified as having a large potential to generate wealth both in todayÆs EU and in the future, widened Union. This paper provides a chart of examples on the many research initiatives presently underway in Europe, addressing environmental issues related to mining. The list of programmes and projects does not claim to be complete; it is rather an illustration on the wideness of the approach, describing various ways for transboundary Cupertino. The approach taken by many of the programmes goes beyond the strict ARD scientific area and therefore only a limited number of the many programmes can be identified as ARD research programmes. Also national programmes, without EU funding, are operating, eg in Sweden, Germany, and UK. The picture is continuously changing with new programmes being commissioned and old ones being completed.

Jan 1, 2003

By Ing. Alois Adamus, Ing. Václav Pošta, Ing. Lubomír Hájek

This paper reviews experiences connected with the use of nitrogen in the Czech coal industry. Special attention is focused on the first use nitrogen In the Czech Republic, it is probably the first case of fighting a mine fire using nitrogen in all the World. Discussion dwells on the present-day use of nitrogen, its sources, consumption, technological equipment, and the theoretical evaluation of nitrogen flushing.

Jan 1, 1995

By Milton H. Fies

THE writer wishes to acknowledge at the outset his great sense of obligation to those who contributed so broadly and expertly to the preparation of this paper: Dr. Albert DeSmaele, Chairman of the Board of Directors of Socogaz, Belgium; Dr. Julien Venter, Director of the National Institute of Coal Mining, and Coal Utilization Industry, Belgium; Dr. Roger Loison, Chief Engineer, French National Coal Research Board, France; and Dr. Erich Sarapuu of the Sinclair Coal Co., Kansas City, Missouri. Liberal use has been made in this paper of a recent publication on Russian, Italian, Belgian, and French experiments prepared jointly by the Centre d'Etudes et Recherches des Charbonnages de France (Cerchar) and the Institut National de I'Industrie Charbonnière of Belgium (Inichar) .l The writer is particularly indebted to Dr. E. T. Wilkins, of the Fuel Research Station, London, and to Mr. James L. Elder, of the Alabama Under- ground Gasification Experiment at Gorgas, Alabama, for their unfailing patience and effective support. Not only did these experienced and capable men edit and revise this discussion, but much of its content is a direct contribution quoted in full from their memoranda. Without the assistance of all these colleagues, this presentation would not have been possible. It has been a privilege to serve and work with them and to acknowledge repeatedly their loyal cooperation. The recovery of the energy inherent in coal beds throughout the world has been done through the years by methods that today may be justly regarded as primitive. While the techniques of coal mining through the application of machines and the enhancement of information and skills have advanced to an extraordinary extent, particularly during the past 20 years, the underlying means is essentially the same as when man first began to mine coal. Despite this progress in the manner of coal mining, it continues today as a hazardous, toilsome, grimy task. Coal mining per se has advanced at a greater and more rapid stride in the past 25 years than the mining of any other mineral, but the basic method is fundamentally the same as it was the first day a miner took a pick into his hands many centuries ago. This situation presents a challenge to mining engineers everywhere, from

Jan 1, 1953

By J. G. MacGregor

At this, the opening meeting of the Western Quebec Branch of the Institute, it seems fitting that the first paper presented should embrace a survey of the known mineral deposits occurring in the area, and also a review of ?the exploration methods that have brought about their discovery. And since the study of geological structures must always be the guiding principle of an intelligent exploration campaign, it also seems to be the appropriate occasion to review the geological situation from the economic angle, in an attempt to arrive at a re-statement of the known facts governing the deposition of the mineral bodies . . It is not my intention to confine my remarks entirely to the geological problems involved, but rather to pass under review the exploratory methods that have been employed in the past and that are presently being used, and to offer a forecast of the type of exploration campaign that will be largely adopted in the future search for ore.

Jan 1, 1929

By B. M. Larsen

ATTEMPTING to review the fundamental aspects of segregation in steel ingots of all types in a paper of reasonable length, we encounter two difficulties: (I) the fact that a large number of different physical and chemical effects are involved, and (2) rather incomplete and confusing evidence on certain aspects of detail and mechanism in the freezing process in which the segregation effect is involved. The best solution seemed to be to link together most of the underlying factors into a simplified theoretical picture that appears to the writer to explain most of the observed data, in the hope that this will serve as a reasonably good target for discussion and criticism. Segregation effects, especially in steel ingots or castings, are often divided into " microscopic " and " macroscopic," depending on whether the variations in concentration of solutes? or dissolved elements in the iron occur as: (I) a periodic variation over the small distances between the nuclei and the surfaces of the primary grains, or (2) as a larger scale effect involving concentration gradients over distances of the order of several inches, more or less. The reason for this somewhat artificial division is, of course, that it is only the macroscopic scale effect that has much practical importance. About the only effect of practical importance that results from microscopic segregation is the banded structure often left in rolled sections, and even this is relatively harmless in most cases. However, the causes of microscopic segregation also underly the larger scale effect, so we must first consider matters such as the formation and growth of crystal nuclei, selective freezing and diffusion, and others that are fundamental to all segregation effects. UNDERCOOLING AND NUCLEI FORMATION It is probable that although the degree of undercooling is small in iron, as in metals in general, a certain amount of it takes place, and also that the number of crystal nuclei increases very rapidly with increased undercooling below the liquidus tempera¬ture. In practical terms this means that the nuclei number increases very rapidly with increased cooling or freezing rate, thus being dependent on the rate of heat flow out from the zone of crystallization. TEMPERATURE GRADIENTS AND HEAT DISSIPATION DURING FREEZING Each pound of steel evolves about 100 B.t.u. when freezing. In addition to this, the temperature gradient in the solidified portion (required to dissipate the heat as freezing progresses into the axis) necessitates a loss of heat required to cool the solid metal below its freezing range, which is equivalent to an amount of not so much less in magnitude. In a 5-ton ingot, the total would include about one million B.t.u. for freezing alone and about 0.4 to 0.5 million B.t.u. for the gradient, up to the end of the freezing period: Thus the rate of freezing depends primarily on the rate of heat dissipation. In the ordinary ingot shapes, the axial rate of growth of the solid

Jan 1, 1944