Search Documents

By Albaniza Alves Tavares

Neste estudo, a influência do tipo de argila como nucleante heterogêneo para o PP foi avaliada. As argilas organofílicas MPH e MPTH, provenientes do Laboratório de físico-química da UAMG/UFCG, e C20A da Southern Clay Products, em teor de 1% em massa, foram misturadas com o polipropileno (PP) compatibilizado com 15% em massa de polipropileno enxertado com anidrido maleico (PP-g-MA), em misturador interno do reômetro de torque Haake visando a obtenção de concentrados que posteriormente foram diluídos com o PP em extrusora. As amostras preparadas foram caracterizadas por medidas de calorimetria exploratória diferencial (DSC) e difratometria de raios-X (DRX). Os resultados obtidos mostraram que embora as três argilas tenham atuado como agente nucleante para o PP a MPH foi a mais eficiente.

Aug 8, 2018

By Donald E. Wakefeld

"The pace at which mining will occur in Northern regions and Arctic lands will depend on the answers to a number of questions. Who are the local aboriginal participants? What land uses are they pursuing? What are their objectives? What is their understanding of the process of mining development? This paper will focus on the last question, communicating the process of mineral development to local aboriginal communities.IntroductionIn the environmental impact hearings for the BHP-DiaMet diamond mine, the smaller Dene Treaty 8 Nation argued for the settlement of its Land Claims as a pre-condition to development. However, the larger Dene Treaty 11 Nation were prepared to permit the mine to proceed on the basis that their people would receive benefits during the construction and operation of the mine.Wherever mining is the significant basis for tax revenues and economic development expectations may be encouraged beyond the realities of the situation. Izok Lake has been known for several decades as a significant mineral deposit but because of its size and the transportation costs involved, it is now a “frozen” ore body. The extent of its mineralization at current metal prices will not support the mining and processing costs without substantial government support for infrastructure and roads. At the opposite side of Canada, Voisey’s Bay clearly satisfies all technical criteria but, nonetheless, two Inuit groups, the Innu, and Métis, have all made LandClaims relating to the mine area.Contrasting the mineral deposits at Voisey’s Bay and Izok Lake emphasizes that the timing of production is dependent on factors such as the grade and amount of reserves, their market price, location and availability of government support. Nonetheless, it is this author’s thesis that given an economic orebody the next most important factor is good communications. It is his view that Arctic mineral development will occur quickly only where good communication has resulted in the trust and mutual respect necessary to implement the mammoth cultural changes required."

Jan 1, 1996

By Lionel Loïc Limol

Polymeric materials, such as polyurethanes and rubbers, are widely used in the mining industry because of their moderate cost and excellent mechanical properties. Such polymers have been used mainly in transportation (conveyor belt systems and pipes coatings) and screening, for their appreciable abrasion wear resistance. Studies revealed the complex influence of test parameters, such as grit size and applied normal load, on the abrasion wear process for polymers. In this study, the abrasive wear behavior of several polyurethanes and rubbers were investigated at room temperature according to a rotary drum abrasion method (DIN 53516). Wear tests were carried out at 26 cm/s test speed and load value of 5 N and 10 N. Corundum paper grit varying from 60 to 400 mesh were used as an abrasive surface. After each test the mass loss of the pin was recorded and the wear rates were calculated from wear volume. The wear surfaces were investigated by scanning electron microscopy.

Jul 31, 2018

By AIME

WE got our chance to talk with Arthur J. Blair at the Annual Meeting at the Pennsylvania Hotel. By two o'clock Wednesday afternoon things had quieted down enough so we had our interview in the foyer to the Ball Room. There were the usual questions. Where were you born? In La Salle County, Ill., on March 26, 1885. Where did you go to school? Northwestern University, B.S. degree in 1906. Where did you start work? For E. J. Longyear right after leaving school. One's ability as a geologist was measured by one's ability to wield a brush hook and ax. He stayed on the job as geologist for three years and then got to thinking about the advantages of a warmer climate. The advantages stacked up favorably, so off he went to Birmingham, Ala., just about the time U.S. Steel took over the Tennessee Coal, Iron and Railroad Co.

Jan 1, 1948

By L. L. Oriard

In order to predict the influence of blasting on slopes, one must first understand the action of explosives, the manner in which rock is broken or displaced, and how seismic waves are transmitted, and the nature of these seismic waves. In this paper, the author describes the action of high explosives on rock masses, beginning at the source of the explosion, extending through the zone of rupture to a distance where only elastic waves of low energy persist. The paper describes the relationships between explosives charge quantities and distances, including the character and intensity of the seismic waves in various types of terrain. In looking at the analysis of slopes subjected to seismic waves, it has been common practice to assume a simplified model in which the anticipated acceleration is applied horizontally to the slope as an equivalent static force, or a model in which there is a rigid base subjected to mechanical shaking. Such models do not accurately portray blasting activity taking place within or near the slope in question. In dealing with blasting effects, it is important to under- stand seismic wave types, wave lengths, attenuation and transmission paths, as well as vibration intensity. In most cases, those slopes that are the least stable under static loading will also be the least stable under dynamic loading, although there may be rare exceptions. Thus, the more that is known about a slope statically, the better will be the assessment of it dynamically.

Jan 1, 1983

By W. W. Adams

Three hundred and twenty-eight mines and quarries, representing 36 States, took part in the twelfth yearly accident-prevention contest conducted by the United States Bureau of Mines and known as the National Safety Competition. Four underground mines and one open-cut mine (which represents the quarry and open-cut mine group), each the leader in its group, were awarded the ?Sentinels of Safety? trophy. Relative standing in the contest" was determined by the number of days lost from accidents in proportion to the total number of man-hours worked. Since 1925, when the National Safety Competition was inaugurated, an increasing interest has been taken in it by mining and quarrying companies as a means of stimulating mine and quarry safety by competition among similar plants. Each participating plant can, on a basis of its standing and record in the contest, determine to what extent its safety program is succeeding or to what extent it needs strengthening. With this information, each company that has a low standing in the contest can intensify its safety-promotion efforts the following year to obtain a lower rate and possibly win the trophy or achieve honorable mention in the competition. Except for 1929, the National Safety Competition of 1936 represented more man-hours of employment than any other year since the yearly contests began.

Jan 1, 1937

By Robert B. Hopler

Reefs, exposed rocks, and fast currents made the Hell Gate section of New York's East River a treacherous passage ever since man attempted to sail through the area. As the harbor's importance grew, attempts to improve the channel were made, starting in 1851. This paper discusses the first major organized effort to clear the area, which began in 1869 and culminated in a single large blast in September 1876.

Jan 1, 1981

By Grant D. Nicholas

This paper compares an integrated evaluation approach to decision-making with more traditional sensitivity analysis and Monte Carlo simulation. The primary objective is to highlight the differences in NPV that can arise from using these evaluation methods in a top down and bottom-up approach. Results from three resource scenarios, derived from sampling a "virtual" ore body (reality) on grid spacings of 75m, 50m and 25m, are analyzed and compared.

May 1, 2007

By E. Garab, M. Pillalamarry, E. Develo

"Recent geological exploration at Rosh Pinah mine revealed that the mine’s major production is shifting towards the western orefield, which will increase the demand for air flow to be supplied to this area. A snapshot of the ventilation survey carried out in December 2014 at the western orefield drill drive B (WOF-DDRB) showed that the air flow was well below the required standards. In order to improve the existing conditions, possible options were considered and simulated using Ventsim™ software.The best option found was to replace the existing western orefield fans with the larger fans from the inactive southern orefield workings, to increase the air flow in the DDRB district. Simulation showed that as much as 20 m3/s of air can be received at the working faces of WOF 30, compared to the previously received amount of 1.37 m3/s. The economic analysis indicated that the above option can reduce the ventilation cost by N$1.9 million annually. It was also noticed that after implementing this option together with other projects, the ventilation conditions in the mine were greatly improved and currently give no cause for concern. IntroductionA good mine ventilation system should be capable of providing adequate quantity and quality of air to all working faces, and is critical to the occupational health, safety, and comfort of underground employees (Luxbacher and Ramani, 1977; Exikis and Kapageridis, 2006). No ventilation system can remain adequate indefinitely; as the mine workings are extended, the ventilation characteristics such as system pressures, air volumes, leakages, and airway resistances change considerably. Continuous improvement of the ventilation system is needed to ensure compliance with health and safety regulations (Lovejoy, 2010). It also ensures that the right quality and quantity of air is delivered to all the necessary areas at the lowest possible cost. This can be achieved by identifying inefficient airways and poorly ventilated areas in the mine and planning how best to upgrade them.The latest geological exploration shows that the focus of production at Rosh Pinah mine is shifting towards the western orefield (WOF). As mining progressed, the working areas have advanced away from the main fans, which increased the resistance to air flow drastically and resulted in increasing demands being imposed on the main fan in order to supply an adequate air flow. This process also created more leakage paths between the fan and the working areas, which has caused the air to short-circuit before it can reach the faces. Consequently, a much larger quantity of air has to be circulated by the fan so that the stipulated quantity reaches the face, which increases operating costs (Singh et al., 2004)."

Jan 1, 2016

By S. E. Khalafalla

In support of its goal to maintain an adequate supply of minerals to meet national economic and strategic needs, the Bureau of Mines has investigated a novel hydrometallurgical system with sulfur dioxide. Differential leaching with dissolved SO2 of manganese, nickel, and cobalt from their hydrous oxides was found to be very rapid and efficient--almost instantaneous and quantitative. In this method a given weight of mixed oxides previously ground to minus 200-mesh is slurried with a leach solution containing a specified quantity of dissolved SO2 for 10 minutes at room temperature and ambient pressure. An empirical leaching parameter, R, is defined as the ratio of the number of SO2 moles in the leaching solution to the weight of the metal oxide charge. Plots of the variation of metal extraction with the ratio R generate a series of sigmoidal-shaped curves, each of which is characteristic of a specific metal extraction. A threshold value of R is required to initiate the leaching of a given metal from the mixed oxides. Once this threshold is reached, the metal recovery can increase to more than 95 pct in very short times. For increasing values of R, the extractability of various metals by SO2 follows the order: Mn > Ni > Co >> Fe, Al, Cu. Differences in the threshold R values permit a variety of metal separations to be made simply by adjusting the quantity of SO2 in the contacting solution. Success in this leaching system depends upon comminuting the sea nodules to less than 0.149 mm (100-mesh). Above this critical size, leaching is slowed due to the inaccessibility of inner particle reacting groups to the SO2 leaching agent. This results in nonselective extraction and less extraction of preferred metal values. At or below 0.149 mm, leaching by SO, is possible with all its attributes of selectivity, sensitivity, and rapidity. Leaching with HC1 solutions of the same pH level as dissolved SO2 yielded mixed, slow, and incomplete metal extractions. This observation rules out any interpretation based on hydrogen ion as the leaching agent. The leaching curves resemble the complexometric titration curves of heavy metals with specific coordination species.

Jan 1, 1981

By Dermot M. Winters, Brent T. Wahlquist, C. Y. Chen

The enactment of the Surface Mining Control and Reclamation Act (SMCRA) in August 1977 addressed subsidence resulting from underground mines, in addition to creating the requirements for reclamation of surface coal mines. Subsidence control regulations pursuant to SMCRA were initially promulgated in March 1979. Several revisions have since been made. In addition, due to court challenges some regulations have been remanded and others are still on appeal. In the meantime the Secretary has agreed to initiate rulemaking on some issues. It is yet to be determined how the prohibition of certain areas from surface coal mining operations under Section 522(e) of the Act applies to subsidence. This presentation discusses the status of the regulations and issues related to or affecting the subsidence regulations.

Jan 1, 1986

By Charles E. Glass

The purpose of this report is to demonstrate the flexibility of rte sensing techniques for providing data with which to implement mined-lands reclamation in an efficient and cost-effective manner. An operational program is presented for using satellite remote sensing data, collateral data, and automated image analysis to provide: 1) an inventory of coal and copper mines and mine waste in Arizona, 2) techniques for periodic monitoring of mining areas using multitemporal classification and image prediction techniques, and 3) delineation of high priority areas for future reclamation and current land-use planning of Arizona mining areas based on environmental hazards indices computed using classified scenes and collateral data.

Jan 1, 1980

By Jack A. Simon, M. E. Hopkins

GENERAL GEOLOGY Coal is defined as a combustible rock that had its origin in the accumulation and physical and chemical alteration of vegetation. Coal can be ignited and burned like the wood that was man's earliest fuel, but coal gives more heat than the same amount of wood and has many industrial uses. Unlike wood, coal is not generally found on the surface of the ground but is mined from the solid rock of the earth. Before taking up the occurrence, formation, and the somewhat unique character of coal in the rock sequence, let us briefly consider the general character of all rocks in the crust of the earth. Relatively little is known about the very earliest history of the earth, although a number of logical theories have been developed. Manned exploration of the moon and the rocks being returned to earth will, we hope, provide some answers to questions concerning the earth's origin and history. The period of earth history with which we concern ourselves here begins after great areas of water had evolved on earth and substantial land areas of once molten (igneous) rock existed. Weathering and other processes that attacked the surface of the rocks reduced them to small particles. Water provided by rainfall transported this material, ultimately, to large bodies of water where it was deposited. Thus was initiated the geologic sequence of sedimentary rocks that lie above the once molten igneous rocks. The crust of the earth is not completely stable, and throughout the geologic past portions of the crust have moved laterally and vertically. Even today, many coastal areas are slowly rising or sinking. More sudden earth movements are recognized by the earthquakes they cause. Throughout geologic history, rises in sea level or the sinking of the land areas have many times permitted the oceans to cover much of what are now the areas of the continents. Only relatively small parts of the present continents appear to have been above sea level throughout geologic time. Great

Jan 1, 1973

By E. P. Klier, Taylor Lyman

THE structures formed when austenite is quenched to subcritical temperatures and allowed to transform isothermally have been the subject of intensive study since the work of Davenport and Bain.1 Isothermal transformation diagrams summarizing the results of many of these studies have become widely familiar to metallurgists. Of particular interest to metallographers are the dark-etching, acicular products of transformation formed by isothermal reaction below the temperature of maximum velocity of the austenite to pearlite reaction. These products, the bainite structures, can be formed in a wide variety of steels. However, the constitution of bainite is not well understood and divergent views have been expressed as to its mode of formation. In this investigation a combination of dilatometric, microscopic and X-ray methods has been brought to bear upon the problem in the hope of some elucidation of the bainite reaction as it occurs in hypoeutectoid steels. MECHANISM OF BAINITE FORMATION Davenport and Bain1 considered the mechanism of bainite formation to consist of two steps-an allotropic transformation followed by precipitation of carbide. The separation in time of the two processes was considered to be very slight in the upper temperature range and very marked at temperatures just above the martensite range. This concept has been restated by Vilella, Guellich and Bain2 in the form of a definition of the acicular mode of transformation as: The successive, abrupt formation of flat plates of supersaturated ferrite along certain crystallographic planes of the austenite grains; this supersaturated ferrite begins at once to reject carbide particles, (not lamellae), at a rate depending upon temperature. In effect, this is the acicular mode of transformation, even though the temperature be such as to limit the actual life of the quasi-martensite to millionths of a second. The investigation of isothermal decomposition of austenite in certain alloy steels (notably those containing chromium or molybdenum) has revealed that there may be a range of temperatures between the pearlite and bainite reactions in which the austenite decomposes at a relatively low rate.3-6 Further, it is characteristic that in the second region of fast reaction the decomposition of the austenite is incomplete by one reaction but goes to completion by a second reaction. These observations led Wever7 to a description of the bainite reaction as follows: I. The reaction takes place by initial precipitation of a martensitic intermediate structure. 2. In the upper temperature range this structure readily decomposes into ferrite and cementite. In the lower range carbon separates in an unknown form. 3. In the upper temperature range the precipitated carbide nucleates the precipitation

Jan 1, 1944

By Earnshaw Cook, J. A. Fellows, Howard S. Avery

Heat-resistant alloys of the higher nickel and chromium ranges have been empirically developed through the practical experience of the past two decades to a position of significant industrial importance. Few quantitative metallurgical data have been published, however, that could be related directly to engineering specifications and design. Inadequate information led to the inauguration, in 1934, of a research directed toward a better understanding of the properties and performance of these steels at temperatures between 1400° and 2000°F. Investigation was concentrated upon the 26 per cent Cr:I2 per cent Ni type, which owes its extensive application to an excellent combination of economy, strength and surface stability at elevated temperatures. The requirements of the oil-refining industry have been prominent in influencing the scope and evolution of the program. Creep strength at the maximum allowable deformation ranges has been employed to evaluate the merits of these alloys. Permissible elongation rates vary from 1.0 per cent in one million hours for turbine blades to I .o per cent in ten thousand hours for tube supports and heating-furnace equipment. Throughout this paper, the limiting creep stress (L.C.S.) for a given temperature has been defined as the stress that will produce a uniform elongation rate (stage 11) of one per cent in ten thousand hours as extrapolated from rates per hour for tests of less than two thousand hours duration. Certain current specifications require a minimum L.C.S. of 1600 lb. per sq. in. at I800°F., of 3600 lb. per sq. in. at 1400°F., and include a tensile acceptance test at room temperature, after aging for 24 hr. at 1400°F., as a measure of embrittlement in service. An elongation of 4 per cent is considered satisfactory for general use, while a minimum of 9 per cent is prescribed on occasion. Many differences of opinion concerning the properties and performance of these alloys appear to result from their sensitivity to unappreciated variations of chemical analyses which, for example, may change their L.C.S. from 3500 to 350 lb. per sq. in. at 1800°F. Within broad chemical limits, it is possible to balance the six or more important elements present to attain desirable properties with a number of different combinations. One method for adjusting the composition has been described under the sponsorship of the Alloy Casting Institute,' in which, by maintaining a substantially austenitic* alloy, optimum creep strength and minimum tendency to embrittle after aging are expected. Unless, however, the limits are undesirably close, it has not been possible to ensure a moderate range of strength and of ductility by any chemical specification alone. There is a definite need

Jan 1, 1942

By J. A. Fellows, Earnshaw Cook, Howard S. Avery

Heat-resistant alloys of the higher nickel and chromium ranges have been empirically developed through the practical experience of the past two decades to a position of significant industrial importance. Few quantitative metallurgical data have been published, however, that could be related directly to engineering specifications and design. Inadequate information led to the inauguration, in 1934, of a research directed toward a better understanding of the properties and performance of these steels at temperatures between 1400° and 2000°F. Investigation was concentrated upon the 26 per cent Cr:I2 per cent Ni type, which owes its extensive application to an excellent combination of economy, strength and surface stability at elevated temperatures. The requirements of the oil-refining industry have been prominent in influencing the scope and evolution of the program. Creep strength at the maximum allowable deformation ranges has been employed to evaluate the merits of these alloys. Permissible elongation rates vary from 1.0 per cent in one million hours for turbine blades to I .o per cent in ten thousand hours for tube supports and heating-furnace equipment. Throughout this paper, the limiting creep stress (L.C.S.) for a given temperature has been defined as the stress that will produce a uniform elongation rate (stage 11) of one per cent in ten thousand hours as extrapolated from rates per hour for tests of less than two thousand hours duration. Certain current specifications require a minimum L.C.S. of 1600 lb. per sq. in. at I800°F., of 3600 lb. per sq. in. at 1400°F., and include a tensile acceptance test at room temperature, after aging for 24 hr. at 1400°F., as a measure of embrittlement in service. An elongation of 4 per cent is considered satisfactory for general use, while a minimum of 9 per cent is prescribed on occasion. Many differences of opinion concerning the properties and performance of these alloys appear to result from their sensitivity to unappreciated variations of chemical analyses which, for example, may change their L.C.S. from 3500 to 350 lb. per sq. in. at 1800°F. Within broad chemical limits, it is possible to balance the six or more important elements present to attain desirable properties with a number of different combinations. One method for adjusting the composition has been described under the sponsorship of the Alloy Casting Institute,' in which, by maintaining a substantially austenitic* alloy, optimum creep strength and minimum tendency to embrittle after aging are expected. Unless, however, the limits are undesirably close, it has not been possible to ensure a moderate range of strength and of ductility by any chemical specification alone. There is a definite need

Jan 1, 1942

By Arunsiva R., Sivaranan S., Venugopal B., Kumaran M.

Being a rapidly developing country, India is undergoing a massive infrastructure phase change remarkably. The construction industry is already set to boom, but the time and space constraints necessitate the employment of heavy plants and machinery to take the foundations deeper than ever. Operating such machinery on soft or poor ground conditions without a good working platform leads to uncertainties with massive loss of men and machinery. Plenty of such cases can be observed on construction sites across the globe. Unfortunately, forming a temporary working platform is given least to no importance in the construction industry, particularly ground engineering. This glitch can only be addressed through standard guidelines or codal recommendations on designing and implementing temporary working platforms issued by regulatory bodies. The present paper highlights the importance of providing the working platform, existing design method for working platforms such as TWf 2019:02 of Temporary Works forum, Building Research Establishment BR470 and a brief discussion on the design and construction of the geosynthetic reinforced working platform with a case study is also included. A pitch has been made on the importance of Indian codes/guidelines for the design and construction of temporary working platforms. These guidelines will ensure the safety of the men and heavy machinery and, in addition, increase the productivity of foundation construction irrespective of weather conditions and also become part of the regular construction scope.

Sep 1, 2022

By Martin Berman

Tables of 28 positions for all the transitions for nine common analyzing crystals for first, second, and third order reflections were compiled by the Bureau of Mines to facilitate elemental X-ray fluorescence analysis on multi-element systems. The tables are based on a compatible set of wavelengths for 2,346 observed X-ray transitions of the elements lithium to americium. The results are tabulated in order of increasing wavelength as well as by increasing wavelength for each element.

Jan 1, 1969

By Zetti Gavelán

Globalization and the search for new ore deposits inevitably lead to investment in foreign markets. Investors need to be aware of the effect of their venture on regional, social and economic issues when they invest. Decades of detailed statistics from various sources can be integrated and analyzed to predict the social-economic impact of investment, thereby mitigating risk. To this end, the correlation among variables such as foreign direct investment into mining (FDIM), reserves, and socio-economic indexes is examined. The investigation focuses on South America from 1992 to 2000. Throughout the past decade, South America has benefited from capital investment from more developed countries. This huge investment by the mining industry has impacted the South American economies and can be measured directly using the FDIM. Other economic variables investigated include mining gross domestic product, direct employment, and human development indexes. The correlation is based on data compiled from the World Bank, international risk assessment agencies, the United States Geological Survey (USGS), and the information agencies of various South American countries. Initial analysis of the economic data suggests various expected outcomes. For example, foreign investors may disregard a measured, highly negative country risk in deference to the quality of its mineral resources. It is important to note that the standard measures of country risk published by investment analysts are not industry or investor-specific. In the case of the investor, the level of accepted risk is based on their managed investment portfolio. It is noted that arguments for level-playing fields may be the antithesis of globalization. The discovery and exploitation of ore bodies in a globalized environment necessitates the development of economic measures that standardize mining-specific risk variables and trends. The latest published information on the security of mineral investments in South America is investigated by integrating databases of economic, geologic, production, human indexes, and risk ranking.

May 1, 2003

By M. Narasimha

The flow in a hydrocyclone classifier is highly turbulent complex nature of multi-phase structure, which has led designers to rely on empirical mathematical models for predicting the performance. A number of classifying cyclone models have been developed and successfully used in mineral comminution circuit simulators over the past four decades (Plitt, 1976 and Nageswararao, 1978). However, most of the mathematical models currently available to describe hydrocyclone classifier performance are based on single average mineral density component behavior. In industrial comminution circuits, the feed to the cyclone composed of a mixture of particles of varying degrees of liberation and sizes. The behavior of multi-component particles in a hydrocyclone is poorly understood and unaccounted for in most of the mathematical model equations available in the literature. There is evidence from a number of experimental data sets indicating the significant influence of the multi-component particles on measured cyclone performance. A concept for modeling the performance of hydrocyclones based on multi-component behavior is proposed in this paper. A set of semi-empirical model equations for cut-size, sharpness of separation are presented and the corresponding model parameters evaluated from the measured data are given.

Sep 1, 2012