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By Felipe De Lucio Pezet

El presente texto describe la importancia del oro como metal precioso -en tanto sus propiedades permiten que se lo convierta con facilidad, pulverizar y se lo vuelve fundir, a diferencia de otros metales que requieren de instalaciones complicadas para extraerlos. Asimismo, su distribución es homogénea ya que sus yacimientos no están concentrados en pocos países como sucede con el cromo o estaño. De otro lado, el brillo, color y la forma de esta metal genera una belleza particular entre los hombres. En cuanto su uso en la minería , solo una séptima parte es industrial o cotidiana, mientras que el resto es guardado en las bóvedas del banco. Finalmente, la producción del oro en el Perú proviene de una cuarta parte de los lavaderos de Madre de Dios y de una quinta parte de la fundición de La Oroya que lo rescata al fundir minerales de muchas minas que tienen el oro como subproducto.

Jan 1, 1985

Coal bursts are one of the least understood yet the most critical hazards in underground coal mines. The ground motions induced by seismic events can trigger unstable failure of coal and rock mass and degrade the surroundings of an excavation. Therefore, the characteristics of ground motions should be fully investigated for an improved burst risk management. This paper analyzes ground motion features of a longwall panel from a typical underground burst-prone coal mine in China. The results showed that most of the ground motions on roadways were hardly initiate coal bursts due to insignificant energy input to the damage. The intensity of ground motions in near-field zone were nearly 20 times higher than those in far-field zone. The strongest vibration on roadway was induced by a coal burst with energy of 28,600 kJ, which can cause ground motion of 0.77 m/s and equivalent dynamic stress of 14.69 MPa. The findings of this paper can improve the assessment of seismic risks and its management.

Jan 7, 2020

By T. A. Rickard

The key-note of good writing, as of good manners, is B natural. Sincerity is the first requisite for effective writing. When a man says what he knows or believes, he is likely to be interesting, because each human being possesses an individuality, a point of view, or a range of sympathy that makes him different from his fellows. To say or to write what you do no6 think, for the mere sake of talking or writing, is a verbal exercise that must be performed with extraordinary skill if it is to be attractive. Affectations are rarely attractive, rarely effective. To be natural is to be yourself, not a poseur; to give the reader the best of yourself, instead of re-warming the baked meats of yesterday. Quotations-which are second-hand thoughts-will serve occasionally when the thing you want to say has been said so well by another that it would be waste of energy to try to say it better; but, as a rule, the utterance of the writer himself is more interesting than the quotation, because the writer brings something of himself to bear on the subject, and for the moment is more in touch with the reader than any dear departed author. Therefore, say things as best you can in your own way, neither in borrowed words nor in the phraseology that mimics another. Write as if you were speaking to a person whom you desire to persuade or convince. You will then write better than you speak, because, in the first place, you can be more deliberate, and, secondly, you can revise what you have written. Speaking and writing are similar mental acts, with a difference: the difference between eating food raw and eating it cooked. Some kinds of food gain nothing by being cooked; likewise some kinds of utterance are not bettered by being written down first; but most expressions of thought, especially

Jan 1, 1931

By A. H. Lang

Introduction The recent uranium discovery at Theano point, lake Superior, is probably a rediscovery of the first reported Canadian uranium occurrence. A description of material from the original discovery was published in 1847 by J. L. LeConte, and many attempts have been made to relocate the deposit. Such attempts have in the past been unsuccessful because of vagueness in the original description of the locality. Besides being a prospect that seems to merit development work, the Camray discovery is important because it reaffirms the occurrence of pitchblende in the eastern part of the Precambrian shield. Much staking followed the announcement of the discovery, and some additional finds have been reported. Location The Camray discovery is at the shore of Theano point, lake Superior, about seventy miles north of Sault Ste. Marie (see Figure 1). It is in township 29, range XIV, district of Algoma. The showing is two miles from Highway No. 17, and is reached by a rough trail that leaves the highway at mileage 72.9 from Sault Ste. Marie. There are no towns of any size nearer than Sault Ste. Marie.

Jan 1, 1949

Pese a tener cajas sólidas en su estructura, algunas vetas desarrollan un relleno frágil, ocasionando problemas futuros de sostenimiento para el "corte y relleno" de los mismos. Por ello, se utilizó el método de los "Square Sets", donde además de ser costoso, implicaba eliminar una proporción de la roca encajonante y diluía el contenido metálico de los filones. En ese sentido, el objetivo del texto es señalar la viabilidad del "método Cornish"como método alternativo, económico, de rendimiento óptimo y que no presenta riesgos para el personal o la labor realizada. Este método es aplicable en aquellas vetas uniformes no falladas, que tengan desde una potencia pequeña hasta aquella que sea posible apuntalar, así como en aquellas que requieran sostenimiento del techo en la veta mima o donde se realizen Shrinkages. El proceso del método se basa en la preparación de los tajeos, luego en la explotación(perforación y disparos), enmaderado, relleno del tajeo, recuperación de madera, las variantes en la preparación del tajeo y la recuperación del mineral. La única desventaja que ofrece este método es su peligrosidad, dado que si se aplica en zonas inadecuadas o sin la supervisión que garantice el cumplimiento de las normas preventivas, es preferible el uso de los "Square Sets". Sin embargo, la aplicación del método resulta mucho más productiva en rendimiento teórico puesto que alcanza de 7 a 10 toneladas por tarea de 8 horas y responde satisfactoriamente siempre y cuando las condiciones de las vetas lo permita.

Jul 20, 1957

By Charles Camsell

Few persons ever stop to consider how vital an influence minerals, and especially metals, have had upon human history, how they have affected the every-day life of the individual or how at different periods they have altered the course of nations and determined their progress. Students and writers of history have dealt very fully with political history and have given us a great deal of detail about the careers and policies of kings, parliaments and nations, but frequently have not touched the economic causes that have been the real forces influencing the development and carrying out of these policies. So far as minerals are concerned there is no single work from which one can get a concise and consecutive account of the growth in the use of minerals, nor of the diverse ways in which the. geographical distribution, the .search for, the development and the use of mineral resources have affected human progress from the beginning of man's history. The reason for this is quite plain, and when one takes a little time to think of it he begins to appreciate the magnitude of the job and he will realize that the story of minerals and mineral resources touches a tremendous range of human activity, not only of mining .and metallurgy, but the whole field of agricultural and industrial growth, of exploration and colonization, transportation and commerce, monetary system, commercial policy, in short, almost every phase of economic life.

Jan 1, 1926

By AIME AIME

TRANSFER to the Bureau of Mines of the responsibility for conservation and production of helium, and announcement that a proposal has been made to the President for commercial operation of the Los Angeles has attracted new attention to the helium program of the Government. The matter is one in which mining engineers, and the mining industry in general, have a peculiar interest. Helium is a byproduct of the petroleum and natural gas industry. It is found in certain of the natural gases which have themselves been discovered, in the main, in the search for oil. If it is to be produced on a large scale, the conservation and development of the fields will necessarily be done by the men of the oil and gas industry. There is no known or expected source of supply of quantities of commercial importance save in the natural gas fields. Not all gas wells supply helium and none of them supply it in important percentages. If it were necessary to prospect a field, develop it, lay pipe lines and build production plants for the helium alone, the cost would be prohibitive. On that basis helium would necessarily be restricted to essential war uses, where cost is subordinate to need. As a byproduct of the natural gas in certain, at least, of the fields in the United States there is distinct reason for anticipating that it may be produced in amounts and at a cost that will permit its regular use in commercial airships.

Jan 1, 1925

By Oluwatosin A. Aladejebi, Apsara S. Jayasekara, Raymond J. Longbottom, Mark Reid, Marc in het Panhuis, Brian J. Monaghan

The coke analogue is a new research tool that has been developed to quantify and characterize the effect minerals in coke have on coke reactivity. The analogue material is made from a number of different carbon or carbon containing materials and minerals to in part replicate real industrial coke’s reactivity behavior. Elucidation of the effects of minerals on coke reactivity has proved difficult due to the complex and heterogeneous nature of industrial coke and the potential non-additive effects of minerals on coke reactivity. The coke analogue addresses this complexity and heterogeneity through control of its mineralogy, mineral size and mineral dispersion through the analogue, porosity and carbon structures. Initial studies using the analogue were focused on coke dissolution kinetics in liquid iron but recent work has focused in characterization of its porosity, carbon structure and rate of reaction.

Jan 1, 2014

By Gennaro G. Marino

The Bureau of Mines and the University of Illinois investigated surface characteristics and damage to structures from mine subsidence over a room-and-pillar coal mine in Hegeler, IL. Data on three adjacent subsidence sags and associated structural damage were collected, summarized and evaluated. The subsidence sags developed over a 10-year period and took place above a modified room-and-pillar operation mining the Herrin (No. 6) coal at a depth of 130 to 135 ft. Surface vertical displacements of 3.0 to 3.5 ft resulted from extracting 6.1 to 6.4 ft of coal. Ground movements associated with sag formation severely damaged three houses and a radio station building, broke numerous utility lines, and structurally distorted three radio transmission towers. The radio station was remodeled and the towers repaired, but the three houses were subsequently demolished. Surface waters collecting in the subsidence depressions caused failure of radial ground transmission systems. The following subsidence profile characteristics were determined at the radio station and one of the houses, respectively: profile slopes, 0.02 and 0.07; maximum curvatures, 2.3 x 10-4 ft-1 and 3.0 x 10-4 ft-1; and angular distortions, 6.6 x 10-3 and 62.0 x 10-3. Although the house was more severely damaged than the radio station, both structures are classified as severely to very severely damaged.

Jan 1, 1986

By Christopher J. Pacitto

This paper presents a case history of an engineered, monitored, and tested program that provided an effective and satisfactory basis for the completion of pile foundations for Twin Dolphins 1 at La Peninsula Condominiums located in the Isles of Capri in southwest Florida, U.S.A. An 8-story building (withl-story parking underneath) along with recreational facilities (such as a swimming pool and tennis courts) had been planned for final construction. Following an evaluation of various foundation alternatives, a precast prestressed concrete (PPC) pile-supported system was selected. The building foundations were designed for pile capacities of 445kN (50 tons) and 890kN (100 tons) in compression and 133kN (15 tons) in uplift. A test pile program was performed to provide site-specific pile driving data, verify design assumptions, determine production pile lengths, and evaluate pile driving criteria. A total of 24, 356 mm (14-in.) square, 19.8 m (65 ft) PPC concrete piles were driven and dynamically load tested utilizing a Pile Driving Analyzer (PDA) within the building limits. Dynamic monitoring during probe pile installation and restriking was performed to estimate the ultimate capacity of the piles and to evaluate driving stresses during installation. CAPWAP analyses were preformed on PDA data to better estimate pile capacity, resistance distribution, and predict pile freeze (increase in pile resistance with time) and thus optimized the production pile lengths. Upon completion of probe pile installation, 12 of the probe piles were tested using the Pile Echo Tester (PET) function of the Pile Integrity Sonic Analyzer (PISA). PET testing was performed to evaluate the integrity of piles which had exhibited high driving stresses during PDA testing. Information gathered during the probe pile driving program was effectively utilized as part of the overall quality control program to install a total of 539 PPC piles (including 24 probe piles) within the building limits at the project site to depths ranging from 9.1 to 19.8 m (30 to 65 ft) below the existing ground elevation as part of the foundation support system. Prior to installation of probe or production piles, a termination criterion was established using 1-dimensional wave equation analyses in addition to the design pile embedment requirement. The predicted pile capacities compared very well with the capacities from the CAPWAP analysis for probe piles. Use of geotechnical instrumentation and PDA assisted technology enabled each foundation support element to be constructed to its optimum capacity and at optimum cost. Furthermore, by using PDA the consultant was able to quantify a difficult to measure geotechnical phenomenon termed "pile freeze" which eliminated costly overdriving and unnecessary splicing of piles.

Jan 1, 2002

By Chas. F. Jackson

The annual reports of the supervising engineers of the nine sections comprising the Mining Division are assembled here and constitute the annual report of the division. In planning activities the aim is to adapt them to changes in conditions, in the needs of the mining industries, and in the public interest; those that contribute most to solving the present problems are emphasized, investigations of less immediate importance being recessed if necessary. The strategic minerals investigations of the bureau afford an example of this change in emphasis to problems of immediate and urgent interest, and during 1941 they comprised, upon the basis of appropriations and expenditures, more than 90 percent of the work of the division.

Jan 1, 1941

The annual reports of the supervising engineers of the nine sections comprising the Mining Division are assembled here and constitute the annual report of the division. In planning activities the aim is to adapt them to changes in conditions, in the needs of the mining industries, and in the public interest: those that contribute most to solving the present problems are emphasized, investigations of less immediate importance being recessed if necessary.

Jan 1, 1941

The 1981 Review: In the late 1970s there was an upsurge of interest in the prospecting and mining of this countryÆs mineral resources. That upsurge of interest was accompanied by a mounting public concern over the damage mining operations might do to the environment. Concern was also expressed about what some people perceived as inadequacies in the legislation which regulates mining and the grant of mining privileges, and inconsistencies in the relationship of that legislation to other legislation regulating land use and the use of resources.

Jan 1, 1984

By E. Don Dilling, W. F. Holbrook, Lloyd R. Michels, James W. Pennington, Dwight L. Harris, Wm. F. Hergert, Cyrus L. Blogett, H. A. Doerner, Ernest A. Reige

"IntroductionA process for production of magnesium by carbothermal reduction was developed at Padentheirm, Austria, by the Austro Americanische Magnesit Corporation& an independent investigation of this and other processes was started in 1937 by the Bureau of Mines at Pullman, Wash., with the cooperation of Washington State College. 10/ A preliminary study of the Radentheirm pro¬cess, as revealed by the meager information then available, demonstrated the following two major disadvantages,The use of hydrogen for shock cooling requires an enormous volume of gas - about 1,000 cubic feet for condensing each pound of metal as a pyrophoric dust which must be completely separated from this gas. Then if the gas is to be recycled for repeated use, the CO produced by the reduction reaction must be separated from the hydrogen. These separations are costly from the standpoint of equipment and operation. 11/The condensate is an impure, pyrophoric metal powder that must be purified and converted to coherent form. This is accomplished by distillation or sublimation of the metal. Distillation on a large scale involves difficulties inherent in the high boiling point (1,107° C.) and the chemical activity of the metal. To avoid these difficulties, the metal is sublimed at 600° C. and of very low pressure. This is quite easily carried out as a batch operation but is a costly procedure. A continuous sublimation process has not been accompli shed."

May 1, 1945

By Anselmo Monteiro Ilkiu

No presente trabalho será apresentado um modelo matemático para a análise da instabilidade plástica de um cilindro de parede fina sujeita a pressão interna, considerando o material com anisotropia normal R no estado plano de tensões. As equações foram obtidas, com base nas teorias elásticas e plásticas, considerando o critério de escoamento de von Mises no estado plano de tensões em termos da anisotropia normal, e de acordo com os trabalhos realizados por Johnson & Mellor [1], Chakrabarty [2] e Al-Qureshi [3].

Aug 16, 2017

By K. H. Luo, J. Y. Liu

An experimental study on interparticle breakage of three iron ores was carried out by compressive stressing of particle-bed in a piston-die device. The feeds to the particle-bed stressing were five narrow size fractions in the size range of 0.2~3.2 mm respectively and a wide size fraction of 0/4.0 mm. The pressures applied were in the range between 30 and 360 MPa. The results show that the energy absorption of the particle bed increases linearly with the pressure; the increase of the product fineness with the pressure declines as the pressure goes up; and the product size distributions resulting from interparticle breakage of different narrow size fractions have no self-similarity. Using data obtained from the piston-die compressive stressing test, the suitability of a previously-developed material-characterization model for interparticle breakage was verified for these ores. It is shown that the particle-bed compression test conducted with piston-die device in lab-scale may provide a cost-effective way of studying and modelling size-reduction of ore materials by interparticle breakage.

Jan 1, 2014

By G. Cordingley, A. Mwanza

Lumwana is an open pit Copper mine located in the Northwestern Province of Zambia approximately 80 km west from the provincial capital of Solwezi, approximately 300 km northwest from the Copperbelt and 700 km northwest from the national capital of Lusaka. The mine has two major Copper deposits: Malundwe and Chimiwungo. Copper mineralization includes Chalcopyrite, Bornite and Chalcocite. In addition to Copper, these deposits also contain the undesirable element Uranium contained in vein hosted and disseminated Uranite. The processing plant was designed using conventional technologies: semi-autogenous grinding (SAG) and ball mill for grinding, and mechanical cells for rougher and cleaner flotation. Soon after commissioning in early 2009, it was recognised that two stages of conventional cleaning were unable to produce plant final Copper concentrates with the desired Uranium grades. Studies have shown that a significant quantity of liberated and fine Uranium particles (up to 80-90%) is recovered with the concentrate by entrainment. Lumwana Operations sought the use of the Jameson Cell technology after observing successful implementation at other sites in rectifying similar issues. In late 2009, Jameson Cell pilot-plant test work was conducted at the site and this quickly led to the installation of a full-scale B5400/18 model into the existing cleaner circuit. Inclusion of the Jameson Cell resulted in the plant being able to effectively produce clean and saleable concentrate with Uranium contents consistently below acceptable levels. Initially designed to be used as a cleaner scalper cell at the head of the existing conventional cell circuit, subsequent operational issues with the existing recleaner cells forced reconfiguration of the cleaner circuit and reintroduced the Jameson Cell for the recleaning duty. This paper reports the Lumwana Operation from the first two years of operation where it struggled to produce a saleable concentrate with Uranium grades below 150 ppm, which is the maximum allowable limit set out in the smelting contracts, to steps taken in the subsequent years to implement a satisfactory solution. The plant can now consistently produce a clean Copper concentrate with Uranium grades well below 130 ppm and the overall improvements implemented at site have seen the overall plant recovery improve by 1.3%.

Jan 1, 2014

By L. Bichler

Lightweight magnesium alloys are gaining in popularity for applications in the automotive and aerospace industries, Their use, however, remains limited due to their relatively low strength and creep properties. Lost Foam Casting (LFC) is a new casting process and the strength of foam cast magnesium alloys has not been investigated in great detail thus far, In this research, magnesium alloy AZ91 E and three new alloys were cast by the LFC process to study the effect of varying aluminum and manganese content on the alloy's tensile properties, The study reveals, that the tensile strength of the magnesium alloy is closely related to the relative amount of aluminum in the system. Formation of ß-Mg17Al12 phase was seen to significantly affect the yield strength and ductility of the alloy, Furthermore, formation of manganese intermetallic compounds was seen to effectively increase yield strength of the base alloy, Individual alloy morphologies were analyzed via optical and SEM techniques.

Jan 1, 2004

By Mohammed Y. Fattah, Wissam H. S. Al-Sudani

"During installation of pile, a soil column is formed inside the pile. For small depths, the height of the soil column typically equals to the penetration depth (full coring state). As the penetration depth increases, the developed internal shear stresses become larger and reduce the amount of soil to penetrate. At the same time, the soil in pile at the bottom is compacted. This will continue until at a given moment, the soil column is a soil plug, and does not stop moving relative to the pile. This is because the shear stresses developed in the interior of the pile are greater than the load-bearing capacity of the ground.This paper presents the results obtained from 40 model pile tests carried out to assess the effect of soil plug on the model pile capacity. The piles are embedded in sand of different densities with different lengths of piles and types of pile-ends. The model tests are divided into two parts according to the type of end of the pipe pile used in the model pile test. The first part consists of 32 model open-ended piles with different lengths of soil plug inside the pile. The second part consists of 8 model closed-ended piles.It was concluded that open-ended pipe piles behave as a closed-ended if the soil plug formed inside piles in state partial plug or full plug. Length of soil plug depends on the type of installation and relative density. The pile load carrying capacity in dense sand is several times greater than those in medium sands especially in cases of closed ended piles or open-ended since the pipe pile can produce external and internal skin friction in addition to end bearing resistance that makes the total pile capacity close to that of closed-ended pile. Whether open-ended piles are driven or pressed in the fully coring - fully unplugged mode or in the partially plugged mode, the plug does contribute to static pile base capacity."

Jan 1, 2014

By R. Karl Zipf, Francois E. Heuze

Stress analysis programs such as MULSIM/NL, LAMODEL, MinSim 2000, and EXAMINETAB are used in the mining industry to analyze stresses and displacements in coal mines, platinum mines, gold reefs, and tabular-type deposits. These relatively simple numerical models can efficiently simulate yielding and failure of a rock mass near a mine opening and subsequent stress transfer. The main input parameters for these models are a family of nonlinear stress-strain curves for the in-seam material. For many applications of these models, such as in coal mining, extensive field measurements and observations exist from which to estimate these stress-strain curves and calibrate the numerical models; however, such measurements are lacking for other types of mines. A three-step method is presented to determine nonlinear stress-strain curves for boundary-element (BE) programs used in many mining applications. The method requires a suite of laboratory-scale strength tests at various confining pressures. Note that this analysis uses laboratory-measured strength and modulus properties of alluvium. The dependency of the mechanical properties of alluvium on scale has not been established, although more tests are being planned. However, it is believed that the relative comparisons performed are valuable regardless of scale effects. First, the FLAC2D computer program is used to model the laboratory tests and determine cohesion (c) and friction angle () for a Mohr-Coulomb material model. Second, another FLAC2D model uses the c and values to calculate vertical stress and strain around a single opening in the rock mass. This model calculates the stress-strain path of points at various distances from the opening boundary. Finally, based on these stress-strain paths, the stress-strain curves needed for a BE analysis are derived. This three-step method was demonstrated in a large, flat-lying underground test facility in very weak rock. The BE analyses agreed well with observations of failure at the test facility and provided a basis for evaluating the behavior of alternative layouts.