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By M. Pekguleryuz, S. A. Argyropoulos

"The recovery of additions in light metals is an important parameter influencing consistency of the finished product, which ultimately means cost. Recovery is a function of many parameters such as assimilation speed, addition density, addition practice, liquid metal processing conditions, etc. In liquid metal processing operations, it is desirable to have the maximum possible recovery at the shortest possible time.In this paper a new index will be presented, namely, the rate of recovery (RR). This index quantifies the addition recovery and introduces the time dimension in the recovery increase. As such, the RR equips the liquid metal practitioner with an accurate picture of addition assimilation in liquid metals. Results will be presented on how this index is applied to a variety of additions in liquid aluminum. IntroductionThe data on addition assimilation kinetics offer a valuable parameter describing how fast a given addition enters the metal bath. These data may be expressed as gr m-2 s-1 of additive for a set of experimental conditions which might include bath temperature and degree of bath agitation among others. However, the liquid metal processing practitioner is more interested in the recovery of additions. In other words, the point of interest is the percentage of the used addition entering the metal bath. Ideally, the addition recovery can reach the 100% level. However, in practice, the addition recovery never or rarely reaches that level. Many factors can contribute to this. Some of these factors can be slow assimilation kinetics, addition density, addition practice, turbulence of the melt, etc. In some cases, sloppy addition practices can contribute to low recoveries, or even worse, to erratic recoveries.In this paper a new parameter is introduced. This parameter relates the maximum addition recovery observed over the time needed to achieve this maximum recovery."

Jan 1, 2002

By Jom Gentry

Acrylamide chemical grout (C3H2NO) has been successfully used for over 50 years to control groundwater and stop infiltration. This paper will address three unique projects involving the control of groundwater with each study providing special circumstances and geological conditions: encapsulation of radioactive hazardous waste in the United States, a tailings dam for a large copper/gold mine in Argentina and 27 miles of leaking subway in Canada. The primary reasons for selecting acrylamide grout were based on the following characteristics: thinnest chemical grout on the market, a true solution grout which contains no suspended solids in the blended product, flexible gel set times, and a 362 year half-life in soil as determined by the U.S. Department of Energy.

By Syd S. Peng

Coal mine ground control is the science of the application of rock mechanics principles to coal mining operations. More acceptance of ground control techniques by the US coal mining industry has been seen in the 1980s. It has been demonstrated many times that a proper ground control design is key to a successful coal mining operation. However, numerous in-mine applications of various ground control techniques by the author indicate that cur¬rent techniques need improvement. The biggest problem in coal mine ground control is that miners are dealing with materials of rapidly varying properties and occurrence. And only the exposed surface can be identified positively. Thus, in attempting to solve the ground control problems, many unknown factors are assumed. Some of these problems deriving from such assumptions are discussed here. Coal pillars There are two types of coal pillars - barrier and chain pillars - depending on the purpose. Barrier pillars are those located between panels or sections or mines. Their objective is to isolate the mined-out effects of one from the other. Chain pillars are characteristic of room-and-pillar mining. They are designed to support the overburden load and protect the surrounding entries and crosscuts. Pillar design is the most popular and, frequently, the only ground control technique employed by coal operators for mine design. There are many pillar design formulae available (Bieniawski, 1983; Peng, 1986). Nearly all consider both size and width/height effects. Specifically, pillar strength decreases with increases in pillar size and increases with increase in the ratio of width to height. However, the manner of those changes varies with investigators. Consequently, the pillar size determined varies considerably from investigator to investigator. And the variation grows much more pronounced as the seam depth increases (Fig. 1). The question, then, is which one should be used? One may say each formula is developed for a particular coalfield. A particular formula may have been used to design a pillar, which has not failed. Does that mean it was over designed? Not necessarily, because no one can confirm its stated "safety factor." Recent case studies (Peng, 1986; Tang and Peng, 1988) show that all pillar formulae are too conservative for chain pillar design in room-and-pillar mines due to the following two problems: • Uncertainty about in situ pillar strength. All formulae employ uniaxial compressive strength of selected samples tested in the laboratory and scaled to that for underground pillars. The scaling factors are not well proven. In situ testings by Bieniawski (1969) suggested that 1.5 m (5 ft) pillars are representative of in situ pillars that, after being tested in various US coal mines, are not universally applicable. • Uncertainty about the actual loading on the pillar. The most frequently used tributary loading theory defines the loading as total overburden weight tributary to each pillar (from roofline to surface). This is too conservative when it applies to coal measure rocks. The overburden consists of layered strata of different stiffness. Many stiffer strata will self-support over small roof spans. Depending on the location of these strata above the coal seam, it will reduce pillar loading in various proportions. It follows that total structural analysis using, for instance, finite element method is more appropriate. It can take into account the interaction of roof and floor strata with coal. This has been demonstrated by Peng et al. (1986,1988) on several case studies. However, the validity of the finite element structural analysis depends on the accuracy of in

Jan 1, 1989

By Rafael Henrique Alves Gomes

A automação em processos industriais agrega qualidade, padronização e segurança aos produtos e pessoas envolvidas. Entretanto, as demandas de mercado, custos agregados e a concorrência exigem melhorias que podem ser alcançadas através de métodos de otimização. Este artigo apresenta algumas metodologias e ferramentas para otimização de processos industriais que visam desvincular a obrigatoriedade de que Técnicas de Controle Avançado em métodos de otimização são a única solução capaz de oferecer resultados satisfatórios para aumento de produtividade. Os recursos expostos abordam a gestão de malhas de controle, gestão de alarmes e o cálculo do indicador global de eficiência, o OEE.

Aug 17, 2017

By John S. Burton

Mineral policy in Canada has been in a state of transition and change over the past several years. 1976 has witnessed some settling of troubled waters and the pattern of the currents of change is becoming more clear. The provinces play a key role in this process and have provided much of the thrust for new initiatives. On the other hand, the federal government in Canada in recent years has taken a much more active interest in mineral affairs than previously and has asserted its powers on a number of key policy questions. Some of the initiatives from the two levels of government in Canada have come into conflict with each other and, thus, contributed materially to a state of affairs that includes change, uncertainty and conflict.

Jan 1, 1976

By P. J. Clifford, A. B. Brown

The development of computerised mine planning has been hindered by the cost of processing the large data bases associated with mineral deposits and the inherent inconvenience of performing an interactive process on a time-shared computer. A dedicated computer is ideally suited for the purpose but reasonably priced micro/mini-computers have not had the capacity to store the volume of data or the processing capability required. Hardware development has cleared the way for the development of truly interactive mine planning software, covering the complete range of activities associated with mine planning, from geological assessment to short-term scheduling of operations, incorporating them into a single system using a common database. The integrated system, comprising software and dedicated hardware, adds previously unattainable speed, flexibility and clarity to the planning process because it has been tailored exclusively for that purpose.

Jan 1, 1983

By D. M. MacHunter, M. K. Palmer

Refinement of design parameters and features has resulted in the development and commercialization of spiral separator models that offer enhanced performance for a number of application areas. Examples of recently developed spiral separator models include the enhanced performance (EP)spiral and the HC (high capacity) series. Comparative performance data for appropriate applications are presented for each of these new model spiral separators. The utilization of spiral separators providing improved performance offers significant cost and operational benefits for process plants. Examples of process flowsheet changes that have resulted from the incorporation of recently developed spiral separators include the reduction of the number of process stages and the achievement of high density tailings by the utilization of a dewatering arrangement in the spiral tailings splitter system.

Jan 1, 2003

By Wagner da Silva Lima

Um Sistema Piloto de alimentação de biomassa foi instalado em paralelo ao sistema de alimentação de coque em uma caldeira leito fluidizado circulante movida a coque de petróleo na Unidade Fabril da Votorantim Metais em Niquelandia, GO. Quatro experimentos foram realizados utilizando os alimentadores de coque (limitados a capacidade de mistura da pá-carregadeira) e o sistema piloto instalado que tem capacidade de 30 m3/h de cavaco de eucalipto. A substituição energética chegou a 19%, bem acima dos 10% determinados pelo fabricante utilizando o sistema atual de alimentação de combustível na caldeira. O potencial de redução de custo do vapor varia de 4 a 7%.

Aug 17, 2017

By Britt H. Hatfield, Jiu-Chiuan Chen, Wen-Ruey Chang, David C. Christiani

Occupational exposures to whole-body vibration (WBV) at different frequency domains may differentially affect human comfort and the musculoskeletal system. Under this presumption, a frequency-based weighting scheme has been adapted in many widely accepted standards for WBV measurement. However, there is very little human data showing a direct link between WBV frequency and musculoskeletal disorders. We conducted an epidemiologic study to examine the association between WBV frequency and prevalence of low back pain (LBP) and to identify determinants of specific frequencies associated with LBP in urban taxi drivers. Methods The WBV frequency data were collected from 247 professional drivers (aged 44.6±8.3) who participated in an exposure validation study 1 of the Taxi Drivers’ Health Study (TDHS) in 2000. 2 In accordance with the ISO 2631-1 (1997) methods, we measured the frequency-weighted acceleration over drivers’ seat surface, under conditions representing randomly assigned destinations. We developed a WBV record-replay system at the Liberty Mutual Research Institute (LMRI) in Hopkinton, MA, USA. This system includes two tri-axial accelerometers (PCB Piezotronics, NY, USA), one RD-130T PCM data recorder (TEAC, Tokyo, Japan), and one LMWBV meter 2.0 (LMRI, MA, USA). Only the vertical axis of seat-surface WBV frequency was used in this study. To characterize the WBV frequency curve, we manually identified the presence of any peak within each of the following frequency range: <4, 4-10, 10-20, and >20 Hz. Information about the operating vehicles and driving environment was either collected from the vehicle registration record (manufacturer, year of make, transmission, engine size, etc.) or directly measured (wheel-base length, seat inclination, etc.). Structured interviews were conducted by an occupational physician to gather information on LBP that had led to medical attention or absence from driving in past year. We used multiple logistic regression to estimate the prevalence odds ratio (OR) associated with the presence of each index peak frequency, adjusting for age, body mass index, professional seniority, daily driving hours, seat inclination, and the intensity of predicted root-mean-square WBV exposure in m/sec2. For any revealed WBV frequency that was associated with LBP, we constructed a multiple logistic regression model to identify the personal and vehicle characteristics associated with the presence of WBV peak within the indicated frequency range.

Jan 6, 2006

By G M. Volkmann

Pipe umbrella support systems – also called canopy tube systems – have been used successfully for tunnelling in challenging ground conditions since the 1970s. Historically, the drilling unit was the limiting factor for pipe umbrella installations – less attention has been paid to pipe couplings and their influence on labour time and load-bearing capacity.This contribution investigates the influence of the type of pipe connection on the load bearing characteristics of a connected pipe and discusses associated influences on design calculations and installation performance. Standard thread connections reduce the effective cross-section and thereby load-bearing capacity in the connection area. To achieve design parameters, over-dimensioning of the un-weakened pipe section is the only way to overcome this limitation. Recently, two new, alternative connection types were designed and developed for connected pipe umbrella pipes. The first one is the nipple coupling, consisting of fitting with a threaded connection that is pressed and welded into the ends of standard tubes. The second type is the squeezed connection, which mechanically connects non-threaded pipe ends, achieved by force-fitted squeezing from the drill rig. Both coupling types have technical as well as operational advantages compared to the common thread couplings, which are the weakest point in the support system.In the following sections significant technical differences are explained, design values given and a site example presented to illustrate the operational advantages of the newly developed coupling?type.CITATION:Volkmann, G M, 2014. Development of state-of-the-art connection types for pipe umbrella support systems, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 333–338 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Webster Smith

El cobre se encontró en Cornwall al mismo tiempo que el estaño debido a que ambos elementos se encuentran asociados en las minas. En ese sentido, el presente texto señala las primeras minas de cobre en Inglaterra, como las primeras prácticas de fundición de este metal, las fuentes medievales de cobre inglés, las fuentes de mineral más antiguo del extranjero, la expansión del cobre en la antigua China y en la antigua Grecia y Roma.

Jan 1, 1969

By Daniel W. Kappes

Testing ores for heap leach operations traditionally follows a progression of bottle roll tests, bucket and column leach tests, and very expensive large field leach tests. Enough data is now available to streamline the procedures. Data from five different operations shows that recoveries from large field leach tests can be predicted from the bucket tests. Initial recovery times in large field leaches are longer than in bucket tests- a typical response is eight days versus twenty days to the same recovery percentage; but the ultimate percent recoveries (after 60 days) are normally very close. Methods of mining and stacking can radically affect recoveries from clay-rich ores. Leaching of uncrushed ores provides special testing problems, since accurate samples smaller than several tons cannot be taken.

Jan 1, 1981

By Yoneji Kanoh, Masahiko Ohtsuka

In Japanese tunneling history, it has commonly been accepted that the long-round driving is difficult due to the complicated geological condition. Therefore, the maximum past record has been less than 3 m per round. A new record of advance was established in the 99 m2 headrace tunnel of Imaichi Water Power Station Project with an advance of 239.5 m in a month by drilling 3.9 m deep blast holes. The geology of the headrace tunnel composed of pyroxine andesite (ie. 960-1770 kg/cm2, VP3.1-4.3 km/s) which had several clay seams and open cracks and was moderately weathered. Automatic shotcrete machine was used for shotcreting. Rock support was specified according to the N.A.T.M. with each different rock type. The contractor achieved a remarkable tunneling advance not earlier experienced in Japan.

Jan 1, 1983

By Alexandre de Freitas Gomes de Mendonça

São crescentes as exigências por confiabilidade nos processos siderúrgicos. Nesse contexto, a Usiminas tem direcionado esforços em suas aciarias na busca da melhoria contínua dos processos garantindo a maior estabilidade operacional. O lingotamento contínuo é responsável pela solidificação controlada do aço líquido. A solidificação inicia-se no molde pela formação de uma pele que sustenta o núcleo líquido ao longo da máquina. O rompimento dessa pele representa um dos maiores problemas no processo de lingotamento contínuo por vazar o aço líquido no interior do veio e atingir as partes eletromecânicas da máquina. Essa ocorrência oferece risco de dano às pessoas, promove a interrupção do lingotamento no veio, sucateamento de produtos e indisponibilidade momentânea do equipamento. Visando reduzir a frequência de rompimentos, a Usiminas repotencializou o sistema de exaustão de vapor, adequou o sistema de detecção de rompimento de pele e criou uma equipe multidisciplinar para análise de cada evento. Essas ações reduziram significativamente a frequência dos rompimentos de pele na Aciaria 2 da Usina de Ipatinga, a ponto de registrar 539 dias sem esse evento.

Aug 17, 2017

By Wilbert J. Huff, Raymond H. Moore

"Black powder is employed widely in peace and war. Its properties are therefore of considerable interest to many. The Bureau of Mines frequently is asked to furnish information on its use and safe handling in the mining and mineral industries in times of peace and is now engaged in studies of its application to the arts of war.Black powder has been the agent in many accidents - some very disastrous - and its handling and use are deemed very hazardous. The belief is widespread that the hazards are due principally to the ease with which the powder is ignited by a hot spark or flame in contradistinction to high explosives; these usually are ignited only with difficulty, and some burn incompl0tely and to a certain extent are self-extinguishing. Primary precautions, .therefore, should be taken to prevent the access of heat, spark, and flame.In black powder manufacturing operations a frequent source of disaster is the initiation of fires and explosions in the wheel mills in which the sulfur, charcoal, and nitrate are incorporated. Long experience has indicated that the wheel mill probably will fire if the powder is not kept moist enough; manufacturing supervision calls for the maintenance of a minimum moisture content, at least during the milling. Accidents occur elsewhere in the manufacturing line, and in an endeavor to minimize these, particularly those happening in corning mills, one of the writers suggested many years ago that a suitable humidity be maintained in other operations in the hope that it would serve protectively as in the wheel mill. The experience of one company for many years with this practice was favorable. It seemed desirable therefore, to explore the question experimentally."

Nov 1, 1944

By G. R. St. Pierre, A. J. Wilhelem

In connection with the reduction of hematite or magnetite to metallic iron, it appeared desirable to study the rate of reduction of each oxide to the next lower oxide under conditions which excluded all other condensed phases. For this purpose, pellets of Fe,O,, Fe,O,, and oFeOo were prepared. A gas train for the preparation of Ar-Hz-H20 mixtures was employed to establish a continuous flow of a controlled atmosphere over a pellet suspended on a balance. In this manner the following individual reduction steps could be studied: For example, pellets of hematite were reduced solely to magnetite by adjusting the gas atmosphere such that it was oxidizing to wustite. In other words, the reaction was complete when the hematite pellet had been totally converted to magnetite. The pellets were prepared from Baker Chemical ferric oxide. The ferric oxide powder was moistened and handrolled. Air sintering at 950°C produced Fe,0, pellets with a density of 3.65 g per cm3. The pellets ranged in size from 0.6 to 1.2 cm diam. The magnetite and

Jan 1, 1962

By JO Choi

Jet-grouting method is a useful technique to reinforce foundations on relatively soft or vulnerable soil layers such as fractured zone and stratum with cavities. Although jet-grouting has been widely applied to various field works, a reliable design standard has not been established yet. A number of model tests were performed to investigate end bearing behaviors of piles reinforced by jet-grouting. It was concluded that end bearing capacity was increased in proportion to uniaxial compressive strength of grout column. Based on the test results, the design criteria for the end bearing capacity were suggested.

Jan 1, 2006

By Seiji Mizutani, Hirofumi Taguchi, Makoto Yoshida, Hidenori Takahashi, Naotoshi Shinkawa, Kazuo Konishi, Yoshiyuki Morikawa, Masaya Kawata

"The lattice-shaped cement treatment method has been used to improve the seismic performance of liquefied sandy soil in Japan. The efficacy of the method has been confirmed by the huge earthquake in Japan. In the present study, a new method to improve sandy ground by using the lattice-shaped cement treatment method is proposed as a liquefaction countermeasure. It is the floating-type and lattice-shaped cement treatment method, where cement treated soil is not fixed to an un-liquefiable stratum. In this method, a fixed-type structure such as treated soil should be formed at the side of the floating-type treated soil to reduce its lateral displacement. In the study, one-dimensional dynamic response analyses were firstly conducted to confirm the mechanism of the new method. Secondly, a series of centrifuge model tests were performed to demonstrate the effect in a proto-type scale's stress condition. The analyses and model tests confirmed the effect of liquefaction countermeasure of the new method.INTRODUCTIONLiquefaction induced by an earthquake generates sand boiling and ground settlement. Other problems have also been reported, including a decrease in bearing capacity and an increase in the horizontal earth pressure against retaining walls. To prevent these problems caused by liquefaction of the ground, various countermeasures have been proposed, such as cement deep mixing and high-pressure jet mixing methods. These methods have the big advantage of being applicable to ground that contains soil with a fine-grain fraction. Furthermore, the unnecessary displacement caused by the construction can be reduced. In Japan, a lattice-shaped cement-treatment method has frequently been used at many construction sites to prevent liquefaction, where cement-treated piles are intersected to form a lattice, as shown in Fig. 1. The lattice-shaped walls can reduce the shear stress generated by an earthquake, restricting the liquefaction at that location. However, the construction cost of the cement treatment is relatively high compared to other methods such as the sand compaction pile (SCP) method, and needs to be reduced. Therefore, decreasing the total volume of the cement treatment is necessary to reduce the construction cost."

Jan 1, 2015

By Arash Khosravifar, Ali N. Ibrahim

"Large areas of Iraq are covered with collapsible soils namely gypsiferous soil which is often used as the foundation soil for structures. In particular, the Mosul Dam foundation is comprised of high contents of gypsiferous soils. Intrusion of water through the foundation soil dissolves gypsum which acts as the binding material between soil particles. This phenomenon results in the formation of collapsible soils which can cause serious damages to the dam structure. The failure of Mosul Dam, with a reservoir as large as 11 billion cubic meter of water, can be catastrophic. In the past, Mosul Dam Authorities have been remediating the soil foundation by injecting cement mortar. This method has been proved not economic; therefore, new, more efficient, methods are desperately needed.This research study focuses on finding practical methods to remediate collapsibility of gypsiferous soils by improving their geotechnical properties. This study presents remediation of collapsible gypsum-rich soil by grouting. Three types of stabilizer materials were used to make the grout; (1) sodium silicate (Na2 O3 Si) which is a well-known chemical soil stabilizer, (2) bentonite slurry, and (3) silicone oil. The purpose for using these stabilizer materials is to provide an impermeable layer (waterproofing coat) around the gypsiferous soil particles and to fill the voids that may occur in the soil as a result of gypsum dissolution when subjected to water.A series of double oedometer (collapse) tests and direct shear tests were carried out on gypsiferous soils before and after remediation by grouting. The results show that the soil compressibility decreases in the grout-treated gypsiferous soil by reducing volumetric strain. Consequently, the potential for collapsibility decreases too. It was also shown that grouting, increases the shear strength of the soil at confining stresses smaller than 250 kPa by increasing the cohesion combined with a slight reduction in the internal friction angle.INTRODUCTIONGrouting is one of the ground improvement techniques which is often used to improve the loose foundation soils. Bruce (2003) provides step-by-step procedures on using grouting techniques for sealing dams and other water reservoirs. Grouting can be classified as permeation grouting, compaction grouting or hydraulic fracturing. Permeation grouting is an effective way to send the grout into the ground without disturbing the soil structure, i.e. free flow of grout into the soil voids where grouting is accomplished by injection of a fluid-like material that is capable of forming a gel and binding the soil particles together. Grout materials may be solution grouts or suspension grouts. The permeation grouting technique is generally used to minimize ground permeability and to control ground water flow, but it can also be used to strengthen and harden the ground (Raman et al., 2012)."

Jan 1, 2017

By Jeffrey M. Listak

The National Institute for Occupational Safety and Health (NIOSH) conducted field tests to evaluate the effectiveness of a wet head continuous mining machine for reducing dust exposure for continuous miner operators. Wet head technology delivers water via sprays to the continuous miner&apos;s cutter head as opposed to traditional standard sprays located on the boom and body of the mining machine. The sprays, positioned directly behind each bit on the cutter head, deliver water at the point of attack, serving to cool the bits during mining to reduce the potential for frictional ignitions. The sprays also flood the coal with water to potentially suppress dust generation. Dust surveys were conducted at several mines to evaluate the wet head&apos;s effectiveness to control respirable dust exposure at the continuous miner operator location and in the immediate return. Results show that the wet head miner improved air quality at both locations to varying degrees in some cases and not in others when compared to a continuous miner with a standard spray system.

Jan 1, 2010