Search Documents

By N. Economou

Temporary local seismic networks were installed in western Crete, in central Crete, and on Gavdos, an island south of western Crete, in order to image shallow seismically active zones of the Hellenic subduction zone. Data acquisition was divided in four campaigns through the years 1996 to 2001. More than 4000 events in the magnitude range between 0.5 and 4.8 were detected and localized. The resulting hypocenter distribution allows the localization of seismically active zones in the area of central Crete from the Mediterranean Ridge to the Cretan Sea. The comparison of the hypocenter distribution and the structure has allowed intraplate and interplate seismicity to be distinguished. A southwards dipping zone of high seismicity within the Aegean lithosphere is found south of central Crete in the region of the Ptolemy trench. Between 20 and 40 km depth beneath central Crete, the Aegean lithosphere appears to be seismically inactive. Especially for the year 2001, 1560 events were localized, by the seismic network installed on Messara, central Crete. Most of the seismic events were located, as expected, in the South region of central Crete. National Observatory of Athens (NOA) maintains a permanent seismic network in Greece. In this work a comparison of the earthquake epicenters obtained from both the NOA network and the BOCHUM-TUC network is presented.

Jan 1, 2006

By William Priestley

IN THE manufacture of gun forgings and other steel parts that, in service, are subject to sudden high stresses and shocks, it is most desirable to use steel possessing the greatest toughness and ductility possible without sacrifice of strength. In order to obtain this condition, it is necessary to procure steel that shows the highest possible elongation and reduction of area without lowering the tensile strength and elastic limit. Proper heat treatment of the steel can control this condition within certain limits. When heat treatment has failed to produce the desired results, metallurgists have used steels containing molybdenum, zirconium, vanadium, chromium, tungsten, etc. The purpose of this paper is to describe a method by which these desired physical properties may be procured-by the elimination of certain impurities that inherently exist in steel made by the open-hearth process, and without the use of expensive alloys. DESIGN OF GUN FORGINGS In the manufacture of gun forgings, a certain elastic limit is fixed by the designer, and the walls of the gun are made of the proper thickness, allowing a suitable factor of safety for the high stresses and sudden shocks that occur during gun firing. The elastic strength of the gun is about 1.4 times the stress set up at any point along the bore of the gun during firing with the maximum powder charge.

Jan 12, 1921

By Z. C. Song

[THIS PAPER WAS TRANSLATED FROM CHINESE TO ENGLISH BY S. S. PENG, WEST VIRGINIA UNIVERSITY] Immediately after coal extraction, the pressure that causes the movement of the surrounding strata is called mine pressure. Through the strata movement, certain features such as supports taking load arise. This is called "manifestation of mine pressure". The existence of mine pressure is ab¬solute whereas its manifestation is relative and conditional. The visible movement of the surrounding strata occurs only when the applied pressure exceeds the plastic breaking strength. Me support begins to take load only when it offers resistance to the strata movement. The key to investigating mine pressure and its control hinges on understanding the rules and conditions for the manifestation of mine pressure. Since the face moves continuously, the mine pressure and its manifestations are also constantly changing. 'Therefore, it should not only emphasize to obtain its instantaneous magnitude, but more importantly the rules of development changes and their relations to the movement of overlying strata. Once this is resolved, one can estimate the movement of the overlying strata through mani¬festation of mine pressure and predict the time and magnitude of incoming roof weighting. Consequently the location and timing of rib excavation can be correctly selected and thus solve several major problems in the design of mining operation.

Jan 1, 1982

By Theo. A. M. Salet

The historic centre of one of the most beautiful cities in Northern Europe -Amsterdam - is being excavated to accommodate the new North/South metro line. This new line is due for completion in 2012, and will link the Buikslotermeerplein district north of the harbour, underneath the Central Station and the old city with its gables and picturesque canals, to the commercial centre in Amsterdam Zuid/WTC. Three underground stations are being construction in the old city at Rokin, Vijzelgracht and Ceintuurbaan. The logistics of working in the middle of an historic city are demanding -maintaining tram, vehicular traffic and pedestrian access along narrow streets, providing suitable protection for the public alongside the working areas, arranging adequate delivery routes, as well as monitoring the old and mostly historical buildings for potential settlement. Safety of both the public and adjacent properties is paramount. Diaphragm walling - 1.2m & 1.5m thick and up to 48m deep - was chosen as the support system for the three deep metro stations. Challenging engineering as well as state-of-the-art equipment to construct the diaphragm walls was needed in order to meet the tight working specifications, in the narrowest locations imaginable. Extreme conditions call for innovative solutions.

Jan 1, 2006

By P Benjamin, H Bohannan, C Farr

Geoffrey Blainey's historical account of the mining activity on the west coast of Tasmania, æThe Peaks of LyellÆ documents the changes over 130 years of activity in the region. Commissioned by the Mount Lyell Mining and Railway Company, emphasis is placed upon the development of the Mount Lyell Mine in Queenstown. Chapter 19 æWidening HorizonsÆ details the review the Mount Lyell Company undertook in 1904/05 to ensure the future of the operation, following the pessimistic outlook regarding diminishing reserves and poor grade ore. The analogies documented between the Mount Lyell Company at that time, and Gold Mines of Australia 90 years on are remarkable, with both companies demonstrating a commitment to the Mount Lyell area through active exploration, the proactive search for alternative technology and the recognition of the valuable human resource. As Blainey writes (Blainey, 1993), æwith its expanding chemical works, its huge Tasmanian mines, its railways and smelter, its coke works and its mine crusade, Mount Lyell was probably one of the nation's five great industrial companies in 1906 or 1907. This brief phase of industrial and mining expansion had its seed in the threat of extinction . . .Æ After a number of reprieves, the Mount Lyell mine did stop production in 1994, but that only provided an impetus for a review and rebirth.

Jan 1, 1998

By J. J. Beeson

For the past fifty years or more, the structural features of the Cordil-leran mountain system of western United States have presented some most interesting problems. Any geologist or engineer living in this region, or even making occasional examinations of the mines, will lose much of interest and importance if he is not familiar with the literature. Some of the greatest works on geology have been the result of studies carried on in sections of this region. Among the more important of the earlier works are those of Dutton,l King,2 Gilbert3 and Powell;4 of the more recent Lindgren,5 Ransome,6 Spurr,7 Butler8 and others have contributed much. Many of the papers are largely of scientific interest but even these lay the foundation for the commercial application of the broader features of the geology. I have read many of these works with the keenest interest and pleasure; in fact, some have been read until some of the more important findings seem to be my own. In this paper, however, it is my aim to accept credit for little more than the labor of assembling some of the ideas of others. This is done with the hope that an interesting and valuable discussion will be the result. If some of the ideas presented should

Jan 1, 1927

By J. J. Beeson

Fox the past fifty years or more, the structural features of the Cordilleran mountain system of western United States have presented some most interesting problems. Any geologist or engineer living in this region, or even making occasional examinations. of the mines, will lose much of interest and importance if he is not familiar with the literature. Some of the greatest works on geology have been the, result of studies carried on in sections of this region. Among the more important of the earlier works are those of Dutton,1. King,2 Gilbert,3 and Powell;4 of the more recent Lindgren,5 Ransome,6 Spurr,7 Butler,8 and others have contributed much. Many of the papers are largely of scientific interest but even these lay the foundation for the commercial application of the broader features of the geology. I have read many of these works with the keenest interest and pleasure; in fact, some have been read until some of the more important findings seem to be my own. In this paper, however, it is my aim to accept credit for little more than the labor of assembling some of the ideas of others. This is done with the hope that an interesting and valuable discussion will be the result. If some of the ideas presented should

Jan 9, 1925

By J. R. McWilliams

Several of the current concepts of brittle fracture involve consideration of the existence of defects or flaws. Griffith 1 observed that the tensile strength of brittle materials was several orders of magnitude less than might be expected from the calculated strength of the molecular bonds. He was able to show that the stress concentration at the tip of an elliptical crack is sufficient to raise the local stress level many fold. He therefore proposed that real materials do contain such stress risers in the form of minute cracks and that this accounts for the rather large difference between theoretical and actual strengths of brittle materials. The degree of stress magnification depends to a great extent upon the orientation of the crack with respect to the general stress system, and to the general geometry of the crack.

Jan 1, 1967

By M. B. Shongwe

Pt-based alloys are being developed for high-temperature applications with the aim of replacing some of the currently used Ni-based superalloys (NBSAs) in the highest temperature applications. The Pt-based alloys have a similar structure to the NBSAs, and since Pt is more chemically inert than nickel and has a higher melting point, they can potentially be used at higher temperatures, up to 1300°C, and in more aggressive environments. Several experimental Pt-based alloys were studied at Mintek, and an optimum composition was found to be Pt84:Ahi:Ru2:Cr3 (at.%). On the basis of hardness and microstructure, a later study identified a new optimum: Ptr8:A111:Ru5:Cr6 (at.%). There are at least two Pt3A1 allotropes, and the high-temperature cubic structure has better properties than the lower temperature tetragonal form, and so needs to be stabilized. This work describes the latest results obtained in transmission electron microscopy (TEM) studies of the quaternary Pt-based superalloys. These results are both interesting and important, because the samples have a higher precipitate density compared to those from earlier work. The precipitate morphology is mainly cubic, with minor areas having irregular-shaped precipitates. The high volume fraction of the precipitates is a major breakthrough, since the objective of this work is to improve the alloys. A prior disadvantage was that the proportion of the precipitates was too low in samples before this work, especially compared with the work from Germany on Pt-Al-Cr-Ni¬-based alloys as well as the NBSAs. TEM -Pt3A1 diffraction patterns were studied, and for each diffraction pattern, many possible lattice point combinations were tried, with the angle between the lattice spots as well as interplanar spacings being calculated for each phase (cubic or tetragonal) to match the measured results. An overall analysis of the diffraction results indicates that the cubic phase fitted the experimental lattice points with much lower errors compared to the tetragonal phase. Thus, with the close match achieved with the cubic structure, the structure of -Pt3A1 precipitates is likely to be cubic. X-ray diffraction has been carried out on selected samples, and the results confirmed the presence of cubic -Pt3A1 and (Pt). Different X¬ray diffractometers were used to further verify the results, and the results were also compared with those from TEM.

Jan 1, 2012

By M. Massinaei, S. Abasi, M. Oliazadeh

Reliable measurement and control of the pulp-froth interface (froth depth) in the flotation columns is critical to achieve the desired metallurgical performance. Shallow froths result in a reduction of grade because of particle entrainment and deep froths reduce recovery because of the drop back of entrained and weak hydrophobic particles to the pulp zone. The cleaner circuit at Miduk copper concentrator consists of three parallel MicrocelTM flotation columns 4 m in diameter and 12 m in height. The interface level of the flotation columns is measured by two pressure sensors located at 1.4 and 2.4 m from the cell lip (in the collection zone). In this study the performance of the level detection system at different operating conditions was evaluated. A calibrated float-ultrasonic location system was used for measuring the actual froth depth. The results indicated that the existing level control system was subject to considerable error. The absolute error was found to be 33.27 cm. This was mainly attributed to the constant set-point value assigned to the froth density (ρf=0.3 g/cm3), which actually varies with the operating conditions. The actual froth density at different conditions was calculated and its average value (ρf=0.12 g/cm3) was re-set in the control system. This resulted in substantial reduction in the level-detecting error. Recommendations for more accurate measurement of the interface level were presented. INTRODUCTION Froth flotation is a complicated process because of many involved variables. One of the most significant controlled variables in the flotation process is the pulp-froth interface (froth depth). The froth depth has a profound influence on the metallurgical performance parameters (i.e. grade and recovery). Shallow froths result in grade reduction because of particle entrainment and deep froths reduce recovery resulted from the drop back of entrained and weak hydrophobic particles to the pulp zone (Finch and Dobby, 1990). Various techniques have been developed for measuring the interface level of the flotation cells in the last few decades. These techniques can be classified as: Techniques based on hydrostatic pressure measurements (Finch & Dobby, 1990), Techniques based on the density gradient (float) (Moys & Finch, 1988), Techniques based on conductivity measurements (Uribe-Salas, 1991), Techniques based on temperature measurements (Moys & Finch, 1989).

Jan 1, 2019

By G. A. Irons, D. Colbert

Several electric arc furnace (EAF) shops have increased the zinc and lead grades of EAF dust by reinjecting it into their furnaces; however, the kinetics of this operation are poorly understood. To understand the kinetics, EAF dust was injected into 70 kg heats of iron or steel in an induction furnace. Supplemental additions of carbon and oxygen to overcome the heat load on the system were also investigated. In all cases, the dust was chemically transformed, and the zinc content increased from 16% Zn to 60 - 80% Zn. About 50% of the zinc in the EAF dust dissolved in the iron or steel. The zinc oxide in the dust is thought to be reduced by carbon and the zinc vapour subsequently dissolved in the iron. A kinetic model for the dissolution process is proposed, and the implications for EAF dust recycling are discussed.

Jan 1, 2000

By Ernest A. Curth

The Bureau of Mines studied pressure changes in coal pillars by using encapsulated hydraulic pressure cells to measure relative changes in stress developed during mining. The data indicate that (1) abutment stresses were detected when the pillar line is within 42 to 100 feet, (2) vertical pressure increases as coal is mined in the pillars, (3) at first pressure is higher at the edge of the pillar than in the core, but as mining progresses, the higher pressure is measured in the core of the stump, and (4) in the two instances where lateral pressures were measured, they remained lower than the vertical pressures during pillar extraction. The data also indicate that the mean vertical pressure increase, 6P, in a pillar is roughly related to the percent of pillar extracted, A, by the empirical parabolic equation

Jan 1, 1967

By D. A. Poulter

The stability of a liner system is influenced by many factors which can be compiled into four basic groups. They are: 1. the liner system components and physical characteristics; 2. the geometry and slope of the liner system; 3. the loading conditions on the liner system; and 4. the foundation conditions under the liner system. Failures in the liner system that are due to one or more factors from the first three groups usually result in movement relative to the plans of the liner system. Failures associated with factors in the fourth group result in deformation(s) across the liner system section beyond its design limits. For purposes of these discussions a failure in the liner system refers to displacements or movements resulting in physical damage to the liner system such that it can no longer function.

Jan 1, 1995

By Muhammad Zia-ur Rehman, Sajjad Ahmad Baig, Gao Lei Fu, Muhammad Mohsin, Sobia Naseem

The environmental sustainability is linked back to human sustainability; the sustainability development comprises the environment, society, and economics. This study mainly focused on mining sustainability and its impact on the environment of Pakistan. For measuring the level and environmental mining sustainability nature to Environmental Impact Assessment (EIA) of the world’s second largest salt mine “Khewra,” Folchi and Phillips environmental sustainability mathematics (PESM) models are applied. The results indicated that Khewra was deemed to be potentially sustainable for the environment and quality of salt. The results suggest the delicate balance of maintaining sustainability successfully, regarding the mining process in Pakistan which has been affecting the local environment and community so badly. The paper lays emphasis on the potential significance of the model’s application for the attainment of sustainable mining goal. This study is essential for researchers,

May 11, 2020

By F. R. Koeberlin

ABOUT thirty miles south of the port of Coquimbo, Chile, nestling in one of the western outliers of the main Andes range, lies the little mining town of Andacollo, a place whose history and traditions make up one of the most romantic pages in the life story of this southern republic. The beginning of Andacollo is shrouded in the penumbra of the pre-Columbian era, but its first mining activity probably dates from about the years 1440 to 1460. It was in the middle of the fifteenth century that the Inca Tupac-Yupanqui, grandfather of Atahualpa, conquered this part of Chile. His domain extended even as far south as the present site of Santiago, and perhaps farther, but was maintained with increasing difficulty against the fiercely independent and indomitable tribes of Araucanian Indians of the South.

Jan 1, 1938

By J. Marts

Underground longwall coal mining sections are operated as sealed gobs if the coal is prone to spontaneous combustion. Sealing along the gate roads during longwall face retreat limits the flow of fresh air (oxygen) into the gob and, thus, deprives the spontaneous combustion reaction of oxygen. In a project sponsored by the National Institute for Occupational Safety and Health (NIOSH), researchers at the Colorado School of Mines have used computational fluid dynamics modeling to simulate the flow of gases in sealed longwall gobs. The models were validated using measurements and observations from the field and demonstrate that targeted injection of nitrogen along the gate roads inby the face can be used to control the size and location of explosive methane clouds within the gob and to minimize or eliminate the explosion hazard resulting from the formation of flammable methane-air mixtures.

Sep 1, 2013

By Y. Maeda

Kosaka Smelter is a copper smelter located at the nothern part of Japan? and has been treating. complex sulfide concentrates using flash smelting technology for a long time. The flash smelting technology has an advantage in the point of controllability of matte grade and heat balance in the reaction shaft. But the disadvantage of this process, is that the dust generation ratio is high compared with other smelting process such as injection smelting technology. This reason why is that the flash smelting process is the oxidation process for the fine sulfide concentrates applying flash reaction in the oxygen enriched stream In addition of this disadvantage, the sulfide concentrates contains much volatile impurities is resulted the dust; eneration ratio more. This paper outlines the recent improvement of the flash reaction in the furnace and the behavior of impurities in Kosaka Smelter.

Jan 1, 1998

By Xiaojie Gao, Jingshe Li, Chengsong Liu, Haiyan Tang

In order to clarify the reaction between MnO-SiO2 oxides with low FeO content and Fe-Mn-Si alloy, two diffusion couples were produced by the new method using confocal scanning laser microscopy (CSLM). The interface of the alloy and oxide, content of Mn and Si in the alloy near the interface, size distribution and composition of the particles which precipitated in the alloy were observed and analyzed using the electron probe microanalysis (EPMA). Results show that though the FeO content in the oxides decrease to 1% which is lower than the equilibrium with the molten steel at 1873K, the diffusion of oxygen from oxide to alloy still exists during the heat treatment at 1473K and causes shorter Particle Precipitated Zone (PPZ) and Manganese Depleted Zone (MDZ) normally for the reduction of diffusion flux of oxygen.

Jan 1, 2015

By F. Hashiuchi

In 1996, the Saganoseki custom smelter & refinery successfully shifted to a single flash smelting furnace operation and increased the copper production capacity to 450,000mtpy in 1998. As the next step, Saganoseki planned to further increase the productivity, especially in the area of P.S. converters and acid plant. As the results of modifications and operational improvements, the gas washing & cooling sections of the Saganoseki acid plant were consolidated from 3 to 2 lines, and increased the gas treatment capacity. The S02 converters in the acid plant were also modified to increase the acid production. By increasing the matte grade from 65 to 68%, six PS converters have been successfully integrated into four, while maintaining the production capacity and reducing the environmental burden in 2005. This paper discusses recent operational conditions and the results of implementation of technological improvements.

Jan 1, 2007

By M. Portal, L. Goicochea

This study is carried out in the Zenit mining concession, which is located in the city of San Pablo in the department of Cajamarca in Peru. The Project has 33 mineralized structures and according to laboratory analyzes we have the presence of gold and silver. The geostatistical evaluation provides an analysis on the distribution of precious metals in the vein. This information is used to improve the efficiency of metal extraction and to reduce costs. The general objective is to evaluate the polymetallic veins (Au and Ag), for which the classification of resources (measured, indicated, and inferred) has been carried out, taking into account the parameters of minimum distance from the composite, corresponding volume and tonnage calculation. In addition, an inventory of estimated geological resources was carried out with the block grades obtained to generate the tonnage-grade curves.

Feb 1, 2024