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By Frank C. Morris

It is generally recognized that the productivity and ultimate recovery of an oil well may be reduced as a result of reduction in permeability of the sand at the well bore by invasion of filtrates and clay particles from drilling fluids. As a means of determining whether a sand has been "damaged" from these sources, several investigators2 3 4 5/ have developed methods of analysis based on the rate of increase in bottom-hole pressure while a well is shut in. Because of growing recognition of the importance of completion practices as related to the quantity of oil that may be recovered from wells, the Bureau of Mines has studied completion practices in California and the Midcontinent area. Well-interference and pressure-buildup tests were completed Ear seven wells in the Scurry Reef field to determine the effective permeability in the reservoir.6/ Also, a study was made of the pressure-decline curves obtained from 35 water-input wells in 5 different production areas of northeastern Oklahoma and eastern Kansas.7/

Jan 1, 1957

By K Afewu, R Dunne, W P. Staunton

The treatment of preg-robbing gold ores has always been a technical challenge in the gold industry. Early solutions included removal of preg-robbing carbonaceous material by flotation, the addition of kerosene to æblindÆ/passivate the surface of the preg-robbing component, and the most effective of all options, roasting the ore. Unfortunately gold ores have become more complex and roasting has environmental challenges, so other methods of treatment have had to be found. This paper will review methods of characterising preg-robbing gold ores, method of treatment and cite examples of actual application in the industry.CITATION:Dunne, R, Staunton, W P and Afewu, K, 2013. A historical review of the treatment of preg-robbing gold ores - what has worked and changed, in Proceedings World Gold 2013 , pp 99-110 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By Ken Santini, Ronald R. Bauer, Joseph R. Copeland

Wollastonite, named after W.H. Wollaston, an English chemist and mineralogist, is a calcium metasilicate having the chemical formula CaSiO2. Although it is a unique mineral, wollastonite has a short history of industrial use. Wollastonite is the only naturally occurring, nonmetallic, white acicular mineral. Its acicularity is the main reason for its ascendancy in the late 1970s and 1980s as a reinforcing filler and as a replacement for short-fiber asbestos and short-fiber milled fiberglass. Wollastonite is used in applications ranging from bowling balls to automobile fenders, from ceramic tile to automobile brakes, and from thermal insulation board to protective industrial coatings. The United States is the largest producer of wollastonite, with China, India, and Finland as the other three major sources. The United States, Europe, and the Far East are where most of the production is consumed. Geology Mineralogy and Physical and Chemical Properties Wollastonite, a member of the pyroxenoid mineral group, has the theoretical composition of 48.3% CaO and 51.7% SiO2. Iron, manganese, magnesium, or strontium may substitute for some of the calcium. Commonly associated minerals include garnet, diopside, calcite, quartz, epidote, apatite, and sphene. Some of the physical properties of wollastonite are listed in [Table 1]. Wollastonite is largely chemically inert; however, it can be decomposed in concentrated hydrochloric acid. Some wollastonite will fluoresce under shortwave or longwave ultraviolet light, or both, with colors ranging from pink-orange to yellow-orange and, more rarely, bluish green. In addition, wollastonite may show phos¬phorescence. Because of its unique cleavage properties wollastonite breaks down during crushing and grinding into lath-like or needle-shaped particles of varying acicularity. This particle morphology imparts high strength and is therefore of considerable importance in many of the markets for wollastonite. The acicularity of particles is defined by their length:width, or length:diameter, ratio (i.e., aspect ratio). Individual particles, even the smallest ones, commonly ex¬hibit an aspect ratio of 7:1 or 8:1 and have an average diameter of 3.5 gm. Low aspect ratio products (powder wollastonite, or milled grades) with 3:1 to 5:1 aspect ratios are used as general fillers, in ceramics, and in metallurgical fluxing. High aspect ratio products with ratios of 15:1 to 20:1 are used as functional fillers for rein¬forcing thermoplastic and thermoset polymer compounds and as a replacement for asbestos. The dry brightness and whiteness of wollastonite are also important in determining its suitability for certain filler and ceramic applications. When pure, the mineral is brilliantly white, but impurities may color it cream or gray. Brightness is determined by measuring the reflectance of finely ground powder against a stan¬dard that is assigned a brightness of 100. Magnesium oxide and barium sulfate are the two standards used. G.E. brightness, a term used in North America, refers to brightness measured with a Gen¬eral Electric reflectometer. Commercial wollastonite products usu¬ally have a G.E. brightness ranging from 85 to 95. The Hunter method is also used to measure the brightness of wollastonite. Loss on ignition (LOI), another important property in determining applications for wollastonite, is the amount of volatile matter driven off when the mineral is heated to 1 000°C. Com¬mercial wollastonite products have an ignition loss ranging from 0.5 to 2.0%. Wollastonite's naturally high pH of 9.9 (10% water slurry) is of major importance to its use in the coatings industry. Coatings formulators use milled grades as a pH stabilizer in interior and exterior PVA (polyvinyl acetate) and acrylic latex paints. There are two polymorphs of calcium silicate: wollastonite, a low-temperature form, and pseudowollastonite, a high-temperature form. Conversion of wollastonite to pseudowollastonite occurs at about 1 120°C and results in an increase in the coefficient of expansion and a color change. Pure white wollastonite may change to a cream tint or to various shades of red or brown. This color change is thought to be due to the presence of iron and/or strontium.

Jan 1, 1994

By Robert E. Green, T. Hinton

The velocities of the three possible modes of elastic-wave Propagation have been calculated for single-crystal aluminum at 1-deg intervals throughout the standard steveographic triangle. The results are presented as isospeed contours. The deviations between the direction of maximum energy propagation and specirzen axes are presented as arrows drawn within the standard triangle. The orientation factors associated with dislocation nzotion on the primary slip system only and also on all twelve slip systenzs have been calculated for all three elastic waves. The orientation factors associated with a longitudinal standing--7aue resonant specivnen hazle also been calculated. The relevance of these results to ultrasonic attenuation measurements is discussed. DUE to the widespread use of ultrasonics in the investigation of the properties of solids a number of authors15 have discussed in detail the theory of elastic-wave propagation in solids. In this paper the modes of wave propagation are evaluated according to the procedure suggested by reeen' for the case of single-crystal aluminum at 1-deg intervals throughout the standard stereographic triangle. The wave speeds are presented in the form of contour diagrams within the standard triangle. The deviations between the direction of maximum energy propagation and the normals to the wave fronts are presented as arrows drawn within the standard triangle. The orientation-de pendent factors (orientation factors) associated with dislocation damping as derived in the preceding paper6 have been calculated for the case of aluminum at 1-deg intervals throughout the standard triangle. The orientation factors for dislocation motion on the primary slip system only and on all twelve slip systems are presented in the form of contour diagrams, for both the traveling- and the standing-wave conditions. The relevance of these results to ultrasonic attenuation measurements is discussed. ELASTIC-WAVE PROPAGATION Three waves can be propagated in a linear elastic homogeneous anisotropic medium. The velocity of propagation v of each of these waves in a medium of density p can be obtained from the determination of the eigenvalues and eigenvectors of the matrix equa- The A's are a series of moduli which are functions of the elastic constants cij and the direction cosines 1, m, and n of the specimen axis. In the case of cubic single crystals where there are only three nonzero elastic constants cll, c12, and C, the A's are, The solution of Eq. [I] will give the wave speeds (eigenvalues) and the direction cosines a, 0, and y of the particle displacements (eigenvectors). To obtain the direction of maximum energy flux requires the calculation of the energy-flux vector ET with com- w is the angular frequency, A, the amplitude, and v the velocity of the wave. The direction cosines a, b, and c of the energy flux vector are then given by

Jan 1, 1967

By Nayara Ferreira Nunes

O presente trabalho tem como objetivo promover, através da técnica de elipsometria, a caracterização de propriedades ópticas e dielétricas do nióbio metálico e, além disto, medir a espessura dos filmes finos de óxido de nióbio formados. Devido a grande variedade de aplicações em importantes setores, o nióbio se tornou um elemento de grande importância para o desenvolvimento tecnológico em áreas estratégicas e o Brasil destaca-se neste contexto por deter as maiores reservas mundiais. Logo, conhecer o máximo de informações sobre este material é de grande importância para direcionar estudos às aplicações tecnológicas a fim de se agregar valor ao nióbio e seus compostos. Após a realização das medidas de parâmetros elipsométricos, e modelagem apropriadas, foram geradas satisfatoriamente as propriedades ópticas e dielétricas do material. Sendo também medida a espessura do óxido formado de forma natural sobre o substrato de nióbio metálico.

Aug 17, 2017

By Jogeshwar P. Singh, Mohamed Ashour

The Soil-Foundation-Structure-Interaction (SFSI) problem involves Kinematic Soil- Foundation Interaction occurring during large (cyclic and permanent) ground deformations as well as Inertial Foundation-Structure Interaction occurring during shaking all of which take place while the soil and possibly structural properties degrade with time. The design of the deep foundations for liquefaction induced lateral spread loads include estimation of passive pressure applied by the liquefied material as well as the amount of anticipated displacement. Coupled analyses for SFSI problems that account for liquefaction induced lateral spread and their interaction with the deep foundation system can be performed using sophisticated numerical modeling techniques based on finite element and/or finite difference methods using computer programs such as FLAC or OPENSEES. Such complete SFSI analyses are very tedious and expensive and not feasible for most projects. In 2011, California Department of Transportation (Caltrans) released guidelines for foundation loading and deformation due to liquefaction induced lateral spreading. This simpler prescriptive approach combines empirical and analytical methods through decoupled analyses using computer programs such as LPILE and SLOPE-W together with liquefaction induced lateral spread estimates based on published empirical equations. Pile group effects and pile caps are accounted for using a concept of super-pile. In this paper, we discuss the solution of the same lateral spreading related SFSI problem using computer program CGI-DFSAP (CGI-Deep Foundation System Analysis Program) based on the strain wedge theory that can account for liquefaction, lateral spreading, pile groups, pile caps and nonlinear behavior of piles in a more coupled manner to analyze the foundation system under the lateral spread loadings. CGI-DFSAP can be used to analyze piles in sloping ground conditions as well as piles beneath the abutments near a free-face slope. We have included Strain Wedge Model (SWM) solutions using CGI-DFSAP of several field and laboratory case studies of lateral spreading related to pile foundations. Finally, we have also included the SWM solution of one of the Caltrans (2011) example problems.

Jan 1, 2015

By Daniel Mesquita Duarte

A configuração física de equipamento do sistema de desenfornamento do laminador Morgan na unidade Resende, que é preparado para laminação em dois veios, torna o controle de GAP entre barras muito complexo. O sistema de controle original era suscetível a variações, acarretando na limitação do GAP mínimo na entrada do laminador em cinco segundos. Tendo como base as fontes de variação do projeto original, foi desenvolvido um novo sistema de controle que reduziu as variações em até 1700 %, reduzindo o GAP mínimo de cinco para dois segundos. No que tange à questão do GAP mínimo, o novo sistema de controle garante uma tolerância de 0,1 segundo. Este novo sistema pode ser dividido em duas partes: o controle e correção do GAP entre o forno e a primeira gaiola, e a correção de GAP no trem desbastador.

Jul 30, 2018

By John V. Beall

The Mining Engineering Handbook is written primarily for persons interested in the economic extraction of minerals. Not everyone referring to this book will be knowledgeable about mining and, therefore, this section is intended to explain to interested persons the scope of mining as well as fulfilling the title of "Mining's Place and Contribution" among the industries of society. 1.1-MINERALS, ROCKS AND ORE In the year 1971, the number of known elements amounted to 104. Fifteen of these have been made only in the laboratory, others may have persisted from the primitive atmosphere, but, by and large, elements originated from magmas or igneous rocks of the outer rocky shell of the earth. Only eight elements constitute 98% by weight of the earth's crust. These are oxygen, 47%; silicon. 28%; aluminum, 8%; iron, 5%; and sodium, magnesium, potassium and calcium, less than 4% each. These common elements and the other less common ones are the building blocks of minerals, of which there are over 2,000 varieties. According to Webster: "A mineral is an inorganic substance occul.ring natura!ly in the earth and having a consistent and distinctive set of physical properties and a composition that can be expressed by a chemical formula. The term is sometimes applied to organic substances, such as coal." Thus, minerals are precise combinations of elements. Rocks, as distinct from minerals, are composed of assemblages of minerals. When minerals are found in sufficient concentration to warrant extraction by mining, the mineralized area is considered an ore deposit. The definition of ore is mineral that can be extracted from the ground at a profit. The economic connotation is implicit in the word ore. Since most of the useful elements compose such a small percentage of the earth's crust, the occurrence of ore deposits as we know them would not have transpired had not geologic processes concentrated the elements (see Sec. 4). 1.2-DEFINITIONS OF MINING TERMS Extensive coverage of the many descriptive terms used in mining may be found in a good mining glossary, such as is available from the Superintendent of Documents (see Sec. 35), but for convenience a number of the more common definitions are given here. Mining may be defined, as by A. B. Cummins, as the act, process or work of extracting minerals or coal from their natural environment and transporting them to the point of processing or use. Mining techniques are applied to extracting metallic minerals, such as ores of gold, copper, lead or zinc; to fuels, such as coal, anthracite, lignite and tar sands; and to nonmetallic minerals, such as lime-

Jan 1, 1973

By THOMAS LEONBRD WATSON

I. INTRODUCTION. THE results embodied in this paper are based on a careful field- and laboratory-study of the lead- and zinc-deposits of the Virginia-Tennessee district, begun in the latter part of the summer of 1904 and completed in the spring of 1905, preparatory to the publishing of a State report .on them. A separate description of the individual deposits in Virginia is purposely omitted, since I have already described them in considerable detail in a State report. The Tennessee deposits are described here in some detail for the reason that no detailed record of them has yet been published. Practically, this paper summarizes the results obtained from a study of the geology of the ore-deposits of the district as, a whole. (I had the pleasure of visiting the deposits of Virginia and Tennessee with Dr. H. Foster Bain of the U. S. Geological Survey, in April, 1905. Figs. 21 and 22 are from photographs taken by Dr., Bail.) II. HISTORICAL. . The first authentic records of lead-mining .in Virginia date hack more than 150 years; and the old lead-mines at Austinville, on New river in Wythe county, V a., were the first to be worked. Colonel Chiswell, a native of Wales, and one of the earlier adventurers in southwestern Virginia, was one of the first operators of the Austinville mines. Chiswell's operations at Austinville commenced in the year 1750, and closed shortly after the beginning of the Revolutionary War, in the' year 1776, covering a period of about 25 years. From that time to the present, mining has been carried on almost continuously in the Virginia area. For many years after the Virginia mines were operated, mining was confined exclusively to the lead-ores. The zinc-ores

Mar 1, 1906

By John A. Johnson

"INTRODUCTION The use of wet drilling with adequate ventilation has largely controlled production of dust in drilling rock; however, in some operations, such as shaft sinking and modern tunnel driving, when each of a number of drills is operating in a small cross-sectional area, it is at times difficult to ventilate well enough to keep the dust concentration within desired limits.Some chemical compounds, known as wetting agents, when added to water in small quantities reduce the interfacial tension and make it possible for the solution to wet dust particles more effectively than water alone.This report presents results of tests on the effectiveness of two wetting solutions in reducing the amount of dust produced by wet drilling in basalt.ACKNOWLEDGMENTSThe tests were conducted the Bureau's Mount 'Weather Testing Adit,Mount Weather, The author acknowledges the assistance and cooperation of Wing G. Agnew, superintendent; Marvin M. Revelle, mining-engineering aide; and the rest of the crew at Mount Weather in conducting the tests. C. W. Owings, mining engineer, Safety Division, assisted in conducting some of the first tests and gavel valuable advice and guidance throughout the work and in preparing this report."

Jan 1, 1943

By D. E. Shanks

This U.S. Bureau of Mines (USBM) research simplified an earlier hydrogen chloride (HCI) leach-sparge process developed by the USBM to recover reduction-grade alumina from domestic kaolin clay. Improvements were made by decreasing the initial leaching acid concentration from 25 to 20 pet, decreasing the leaching time from 1 to 2 h to 15 to 30 min, eliminating the solvent extraction step for Fe removal, and eliminating the step to recover the AI content of the bleedstream circuit. A 10-cycle bench-scale experiment of the simplified process showed that the ferric chloride (FeC13) concentration built up to 9.3 g/L in the recycle stream. This did not interfere with any of the unit operations or final alumina product purity because Fe forms stable soluble chloride complexes when sparged with HCI and is easily washed from the large aluminum chloride hexahydrate (ACH) crystals. The reduced leaching time and acid concentration did not decrease Al extraction.

Jan 1, 2010

By Fredrick L. Johnson

In 1987, the U.S. Bureau of Mines began a study of the 4.0 million acre Toiyabe National Forest located in eastern California and western Nevada. This report is a compilation of published, company, and field data for part of the Paradise Range, Nevada. The information is intended to aid the U.S. Forest Service in their long range management of minerals and augment the USBM data base. The Paradise Range study area, located 60 air mi northwest of Tonopah, NV, encompasses about 100,000 acres of which approximately 71,000 are administered by the USFS. The area is in the Basin and Range Province and consists of an east tilted block of sedimentary, metamorphic, and volcanic rocks which have been intruded by granitic rocks. Three major mining districts, the Ellsworth, Gabbs, and Fairplay are in, or extend into the study area. The earliest recorded mining activity occurred in the Ellsworth district in the early 1860's. Commodities produced from the study area include gold, silver, copper, lead, zinc, mercury, tungsten, iron ore, magnesite, and brucite. The Phelps Stokes Iron mine has produced about 1.1 million tons of iron ore, the Baxter-Hancock mine has produced over 10,000 stu WO3, and the Gabbs Brucite-Magnesite mine has produced millions of tons of brucite and magnesite. Numerous other mines have produced, but quantities are relatively small. According to company information the Gabbs mine, currently producing, has brucite-magnesite reserves that will last at least 50 years at current mining rates. One hundred thirty one million tons of identified copper-molybdenum resources exist at the B.C. Springs prospect according to company information, but molybdic oxide (Mo03) prices would need to double or triple from the current $3.00-3.10 per lb before mining of the deposit would be economical. Most company exploration activity in the study area is now focussed on precious metals. Active, or recently active mining claims appear to cover more than one-half of the 100,000 acres studied.

Jan 1, 1991

By Engelmann. William H.

In pursuit of innovative methods to improve mining productivity, the Bureau of Mines is investigating the use of inorganic salts as drilling fluid additives for penetration enhancement. Laboratory diamond drilling tests were performed on Westerly Granite with aluminum chloride solutions and on Sioux Quartzite with aluminum nitrate and aluminum, calcium, sodium, and zirconium chloride solutions as drilling fluid additives. These drilling results were compared with the average drilling performance using distilled, deionized water on Sioux Quartzite (12 replicate tests) and Westerly Granite (3 replicate tests). Maximum in-creases in penetration per given time and bit life were obtained when drilling with zero point of charge (ZPC) concentration solutions of each additive. For Sioux Quartzite, maximum increases in penetration and bit life ranged from 96 to 115 pct and 64 to 99 pct, respectively. For Westerly Granite, maximum increases in penetration of 155 and 165 pct and bit life of 109 and 136 pct were obtained at or near ZPC aluminum chloride concentrations of quartz (7.3 x 10-7 mol/L AIC13) and alkali feldspars (1.1 to 1.5 x 10-6 mol/L AIC13), respectively. This simultaneous increase in penetration per time together with extended bit life should result in increased productivity and reduced bit costs.

Jan 1, 1987

By Andrew Allan

[Research conducted by the Bureau of Mines hrinq the last 5 years on the uce of machines for 7!naer:rolmrl ?.eve loym~nt in pi.t,c hlng anthracite beds l~a~ provide? data ?howin? that ?:;panrt of thc roof an9 str?eg of thes? oTen - jnqs requires almst half of' the PRS? workin? time. The possibilitie~ of i!rinz a mvable,. te1.ee*co@. c tpr? 3f ?tee1 ~h-!.oltl at the face in~tetcrl of conventional wood a*ti~yorts w?r? si:~q~eteil by engineers engaqad on the~ work If ~uch a shi~l8 COLI.~,~. be ~sve~.~yad, it tnillil man that face workera w~uld be provi8ed with mulrnu.m prot?ct+on from falls of' roof and ribs mi! the en- tire ehift could he I~W? Lo ~lro,J.~:ce cocl. Fermanent tim3er coald be p'l.acnA behind the shielR independently of the 'face work as the face advanced.]

Jan 1, 1953

By John W. Walkiewicz

The U.S. Bureau of Mines has conducted studies to utilize rapid microwave heating to stress fracture ore samples. Iron ores containing hematite, magnetite, and goethite were subjected to microwave energy in batch operations at 3 kW and heated to average maximum temperatures between 840 and 940 °C. Standard Bond grindability tests showed that microwave heating reduced the work index of iron ores by 10 to 24 pct. In a microwave chamber designed to simulate a continuous throughput operation at 3 kW, the grindability of a taconite ore was improved by 13 pct at a bulk temperature of 197 °C. Because stress cracking occurred at a lower temperature, less energy was consumed. To further improve the economics of microwave fracturing, higher powers up to 16 kW were used to rapidly heat samples to relatively low temperatures in a continuous, belt-fed applicator. A significant improvement of grindability was obtained with a larger rod mill feed size in comparison to a minus 6-mesh Bond feed.

Jan 1, 2010

By Maurice Guillaud

The most striking innovations on diaphragm-wall construction plant are those associated with continuous real-time trajectory monitoring of the excavating tool (either a grab or a hydro-cutter). The recent equipments are fitted with clinometers and gyrometers to control deflection, rotation or deviation from the vertical, thus allowing to install diaphragm-walls with a verticality accuracy of less than 0.3%. One of the greatest advantages of extensive use of on-board IT systems on the Hydrocutters and hydraulic grab machines is that it aids quality control by automatically producing complete real-time reports of all excavating data (verticality, depth, type of ground, rate of progress, stoppages, etc.). These reports are available to the Engineer, providing the total transparency required for Works Supervision and the Quality Assurance Plan. They also provide the Contractor with input data for databases used for optimising efficiency and progress criteria on future jobs.

Jan 1, 2002

By E. P. Youngman

The rapidly growing demand for titanium pigments has aroused new interest in actual and potential sources of supply of titanium- bearing ores , which only a comparatively few years ago were almost unmarketable . This paper , which supplements a general circular entitled " Titanium" ( Information Circular 6365 ) , represents a summary of current trade literature and Government reports , together with some hitherto unpublished material that has accumulated in the files of the Bureau of Mines . The purpose of this pamphlet is simply to indicate the commercial possibilities of the deposits , and the discussion is confined almost entirely to the three commercial ores , ilmenite , rutile , and magnetite ( titaniferous iron ore ) .

Oct 1, 1930

By M. Gauthier, A. C. Brown

"Monometallic zinc mineralization associated with marbles of the Grenville Supergroup in the Mont-Laurier Basin of Quebec is found to be stratiform and to occur (1) within limited zones of dolomitic marble and (2) more precisely along contacts between these marbles and adjacent metaclastic units. Massive sphalerite with accompanying pyrrhotite and pyrite is the prime exploration target, and commonly gives rise to good geochemical anomalies, but generally weak and ambiguous geophysical responses. Disseminated sphalerite in dolomitic marbles may signal proximity to interesting massive mineralization, although, due to weathering, this broadly disseminated mineralization may not be detected easily on outcrops. It is concluded that the western and possibly the eastern margin of the Mont-Laurier Basin constitute favourable areas for continued exploration.IntroductionThe Grenville Supergroup marbles of Ontario, Quebec and New York State host numerous occurrences of zinc mineralization (Fig. I) , several of which have been periodically mined since the beginning of this century (Fig. 2). The Balmat Edwards district of New York is the giant of this depo sit-type, with the production since 1915 of some 20 million tons of ore grading 10% zinc, and acknowledged current reserves of approximately equal tonnage and grade. At present, there is renewed interest in the potential for similar mineralization throughout the Grenville Supergroup, and this paper outlines some of the geological, geochemical and geophysical guidelines that may be employed in the search for new ore. The geologic guidelines are derived especially from lithologic and stratigraphic features which survived intense, multiphase deformation and metamorphism.Although major portions of the extensive Grenville Supergroup hold potential for zinc mineralization, the present study is confined to a known zone of mineralization in the Mont-Laurier Basin of Quebec. Concurrently, we are compiling information on the regional metallogeny of the basin so that our conclusions can be applied to areas of similar Grenville Supergroup host-rocks elsewhere."

Jan 1, 1980

By Ergin Arioglu, Werner Burger

"SUMMARY The Istanbul Strait Road Crossing Project includes a 3.34 kilometer subsea tunnel excavated by TBM with an excavation diameter of 13.71 m. The tunnel will incorporate two road decks, each employing two traffic lines and shoulder with the daily capacity of 100,000 light vehicles. The tunnel alignment crosses full face rock sections with heavily fractured zones due to tectonic events as well as a long central stretch of difficult mixed face and very variable soft ground conditions. The demanding ground conditions and the large diameter in combination with realized face pressures well above 10 bar required a highly specialized and well adapted TBM. The paper describes the project challenges and the related technical solutions incorporated within the TBM design as well as the real site experience. INTRODUCTION In 2013, a 13.71 m diameter Mixshield was manufactured in Germany for the Istanbul Strait Road Crossing Project. The delivery of the TBM in late 2013 was a major milestone for the Istanbul Strait Road Crossing Project, also known as the Eurasia Tunnel Project. The Eurasia Project (www.avrasyatuneli.com.tr/en) consists of a 14.6 km route including a 5.4 km tunnel segment in its central part crossing the Bosphorus. The 3.34 km subsea section of the tunnel was excavated in closed mode using a Mixshield TBM. The remaining tunnel length is constructed by sprayed concrete lining (SCL) method followed by a cast in place (CIP) lining or by cut and cover (CC) structures for the TBM transition boxes (Figure 1, right). Other project sections on the European and Asian side consist of upgrading and widening surface access roads towards the tunnel. Conceptual ideas of connecting Asia with Europe via a tunnel crossing the Bosphorus have been around for an extended time and only became realistic towards the end of the 20th century based on significant technical developments in mechanized tunneling. Feasibility studies for a new Bosphorus crossing in 2003 and 2005 confirmed and suggested a road tunnel in its present alignment as the preferred solution. Following an international tender process the Ministry of Transport, Maritime Affairs and Communications of Turkey assigned ATAS, a special purpose company formed by Yapi Merkezi (Turkey) and SK E&C (South Korea), to design, build and operate the Eurasia Tunnel Project. The Implementation Contract was signed in February 2011. In 2012, Herrenknecht AG was selected as the supplier for the 13.71 m Mixshield TBM."

Jan 1, 2016

By Tairine Berbert Tavares

A eletro-obtenção constitui em um importante processo na recuperação dos principais metais produzidos através de processos hidrometalúrgicos (i.e. Cu, Ni, Au, Co, Zn), pois permite a obtenção de depósitos catódicos de elevada pureza a partir de soluções aquosas contendo o metal. O presente trabalho investigou a eletro-obtenção de zinco, a fim de avaliar a influência da gelatina, um aditivo orgânico, na eficiência de corrente e na qualidade do metal depositado no catodo de alumínio. A caracterização dos depósitos de zinco através do MEV revelou que, na presença de concentrações crescentes de gelatina até 40mg/L, houve diminuição da quantidade de poros ocasionados por evolução de hidrogênio na superfície do zinco depositado, contudo, em concentrações de 80mg/L, os poros voltaram a aparecer. Além disso, notou-se que diferentes concentrações de gelatina não alteraram a forma dos cristais de zinco, porém provocaram redução do tamanho de suas plaquetas hexagonais, à medida que a concentração de gelatina aumentou, mostrando efeito de refino de grão, em comparação à solução livre da adição de gelatina.

Aug 17, 2017