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By J. Ndlovu, R. Hundermark

Keywords: Anglo Platinum, Polokwane Smelter, pyrometallurgy, metallurgy, platinum, platinum group metals, PGM, base metals, nickel, copper, sulphide smelting, electric furnace, Söderberg, electrode, matte, slag, flash drying, matte casting, crushing, granulation Anglo Platinum?s Polokwane Smelter is situated outside Polokwane, in the Limpopo Province of South Africa. Wet concentrate is received from various concentrators along the Eastern Bushveld Complex, with 60% of the total concentrate received being from UG2 reef and 40% from Merensky reef. The concentrate grade differs from 35 g/t to 110 g/t, and from this a PGM-rich nickel-copper matte is produced. The furnace matte produced is sent to the ACP converter in Rustenburg. The Anglo Platinum concentrators, from which concentrate is received, are Lebowa, Potgietersrus, Amandelbult, and Union, as well as the joint venture Modikwa. The concentrate is fed to two flash dryers that utilise coal-fired, fluidized-bed hot-gas generators to produce the hot gas that will drive off the moisture, leaving a fine bone-dry concentrate to feed to the furnace. The dry concentrate is pneumatically transferred to a storage silo before being transferred to the feed bins situated above the furnace. Lime, if required as a flux, may be transferred separately to the furnace feed bin by a pneumatic system. The concentrate and lime is fed from the feed bins onto airslides and into the furnace. The feed rate is automatically controlled, and the system is set up to optimize the power to feed ratio. The electric furnace is nominally rated at 68 MW and the power is transferred into the furnace using six 1.6 m diameter Söderberg electrodes. Concentrate is melted by energy generated when electric current passes through the electrodes and resistive slag layer. On melting, two immiscible phases form: slag and matte. Furnace matte, containing the bulk of the base metal sulphides and PGMs, is denser than slag and collects naturally at the bottom of the furnace. The furnace is constructed of a combination of refractory brick and water-cooled copper coolers. The furnace sidewalls and hearth are cooled by air drawn through the area by cooling fans. The hearth and matte zone are constructed from refractory bricks. The copper coolers reside only in the slag zone of the furnace along the entire perimeter of the furnace. One staggered row of plate coolers is installed above the waffle coolers along the perimeter of the furnace. Matte is tapped periodically through one of the two matte tapholes into 35-ton refractory-lined ladles, and cast into matte ingots on a casting machine. The cooled matte is discharged onto a concrete slab for cooling and then transferred by front-end loaders to the crushing plant. The matte is first crushed in a jaw crusher and then a Rhodax cone crusher to a size of 2 mm before it is loaded into tankers and sent to the ACP. The low-grade slag is tapped from the furnace through a water-cooled copper insert into a short water-cooled copper ?hot launder? which discharges into a granulation cold launder. The granulated slag slurry flows to three rake classifiers, from which the coarse slag is discharged onto a conveyor to dewatering silos. The dewatered slag from the silos is dumped. The water overflow from the classifiers reports to two thickeners where the water is clarified, and the thickener underflow is returned to the rake classifiers. The smelter is a zero-effluent plant and all the water from the slag silos where the slag is dewatered, as well as the storm water, is pumped to the process water dam from where it is pumped back into the plant for process water use. The off-gas from the furnace is drawn through a forced draught cooler and into a high temperature baghouse. The dust collected in the baghouse is pneumatically transferred into bins above the furnace and is fed via the concentrate airslides. The cleaned off-gas is then vented through the main stack.

Jan 1, 2006

By A. A. Toprac

The recurring problem of joint failures in ofjshore structures, coupled with the catastrophic collapse of many of these structures during Hurricane Hilda (1964), hay forced reconsideration of techniques presently used to design sfuctural joints. This paper presents results of studies conducted for this reconsiderat?on. Only right-angled T-joint,s and cross-joints where a brace was welded directly to the undisturbed surface of another tube (the chord) were considered. Tests were performed on seven T-joint and 12 oross-joint specimens of two types which were designed to give a broad but practicd range to the geometrical parameters believed to be of significance to the problem. These paramefers were expressed in dimensionless form. Each specimen of the T-joints was instrumented wirh both electrical resistance strain gauges and deflection dials. After the elastic tests were concluded, each specimen was loaded to failure by applying an axial tensile load to the brace. The cross-joints were tested to failure without measuring elastic strains. Theoretical solutions for the stresses in a cylindrical shell due to a distributed radial load over portions of its surface were numerically evaluated. The experimental results are compared with calculated values obtained using Bijlaard's and Dundrova's theoretical analyses. INTRODUCTION During the last IS years a large number of structures were built for the offshore exploration of oil both in the Gulf of Mexico and dong the Pacific Coast.' In all these offshore platforms, the tubular shape was extensively used since this shape provides outstanding strength in proportion to its weight, compared to other shapes, when all directions (x, y, z) are considered. Past use of tubes was hampered because of connection details. But with the advent of welding, it became no more difficult to connect tubular shapes than to connect rolled shapes. However, some problems have been encountered in actual construction in making welded joints that are adequate and yet economical. In trying to connect tubular members, designers have used a varied number of methods; consequently, some of the joints seem to be very expensive in detail while others appear weak and underdesigned. An inspection of offshore platforms owned by different companies indicates the use of a large number of joint arrangements and configurations. Such a variety of joint types in current service indicates the wide divergence of opinion that exists on how such joints should be designed, stiffened and strengthened. Fig. 1 shows the various types of connections that have been used in practice. This paper reviews the present state of art on tubular joints of the T and cross type, and presents results of experimental and analytical work being conducted at The U. of Texas and elsewhere. It is believed that such information will be of great help to designers for the formulation of proper design procedures for joints. CONNECTION PROBLEM Recently, cracks have been observed in several welded connections in offshore structures. Fortunately, until about 1 1/2 years ago, these failures have been localized and have not resulted in the collapse of structures or loss of life. For example, one platform installed in Louisiana during 1955 in about 60 ft of water had been subjected to four tropical hurricanes. This platform successfully withstood these forces and was later removed because operations at this location had been completed. Many joint failures were observed during the removal.

Microprocessor-based balances are helping Keffler & Rose Coal Preparation Co. to test and ship coal faster than the competition. They provide a high level of accuracy in meeting Environmental Protection Agency standards and customer specifications .and help minimize "bad" coal. The combination of speed and accuracy has helped increase K&R's sales, while improving the company's reputation for meeting precise client requirements. The quality of coal that is assured by the company's testing-at an in-house lab using fast, precision weighing, and a computerized sulfur test-has assured K&R of a good price for its products. Recent EPA standards have strained the testing capabilities of coal suppliers. Companies involved with high-sulfur coal often use outside laboratory services that can take three to four days to report test results. Since the coal business moves much faster these days, some coal companies cannot afford that kind of time. Too much coal not up to specifications could be produced within a three or four day period. Keffler & Rose took a novel approach to this problem, installing its own in-house laboratory. The test situation immediately improved with this step. However, one bottleneck persisted for a time: the weight measurement procedure for ash, moisture, and energy content. The company first employed a mechanical balance that required time for setting up and taring. The balance provided readings on a conventional scale that was not very precise and allowed for error through subjective readings by the operator. The balance bottleneck was broken when K&R applied new technology to meet its needs: microprocessor-based weighing. The result has been a 75% reduction in weighing time and a sharp increase in accuracy. This has contributed to the test speed needed to keep up with 227-t/h production and precise K&R coal specs.

Jan 11, 1980

By Mirza A. Beg

The Piedmont physiographic province of east-central Alabama lies in a humid subtropical climatic zone. Such an area with mature land forms underlain by rocks rich in feldspars provides conditions condusive to development of gibbsite, a major source of alumina; a raw material for which the United States relies on foreign suppliers for 85 percent of its needs. Gibbsite occurs in the northern and inner sections of the Piedmont Province of Alabama in Coosa, Clay, Randolph, Chambers, Elmore, Tallapoosa and Lee Counties in soils and saprolite derived from amphibolites, granites, feldspathic hornblende gneiss and other gneissic rocks. The major occurrences of gibbsite are in areas underlain by hornblende gneiss in Chambers and Randolph Counties. This region provides the proper physiographic and mineralogical setting for large areas containing up to 25 percent of saprolitic gibbsite. These areas provide potential sources of alumina that could be used to meet the United States future needs. Narrow zones and pockets rich in gibbsite also occur in soil and saprolite derived from areally restricted feldspar rich zones of narrow linear amphibolites in the inner Piedmont and feldspathic zones in various granites distributed throughout the Piedmont.

Jan 1, 1982

By R. P. Stahura

Conveyors are the lifeline of mining and processing operations. They continuously supply materials to and carry finished products and waste away from operations. When conveyors are running at less than maximum efficiency, the operation's productivity is in trouble. Inefficient conveyors suffer carryback, leading to the buildup of materials on idlers and other expensive components. They spill and leak material at loading zones and conveyor transfer points. This causes accumulations that can damage the belt, wear moving components and increase both clean-up labor and maintenance expenses. They wander or mistrack, spilling material and endangering personnel and conveyor components. And through these inefficiencies, they multiply the operation's hidden costs. These added expenses occur in lost production, increased downtime for service and maintenance and replacement costs for prematurely worn equip¬ment. In addition, the attitude that inefficiency is "good enough" is recognized elsewhere in the organization. As a result, other departments relax or operate at less than peak performance. Quality goes down along with employee morale. Costs of inefficient conveyors A key to efficiency is handling a product as few times as is necessary. That means conveyors should be loaded, track true to the unloading point and then be unloaded, all without material escape or waste motion. An inefficient conveyor is often signaled by accumulations of DURT - material that has escaped from the system and is now at large in the plant. This DURT adds costs to an operation that are uncounted and, perhaps, uncountable.

Jan 1, 1992

By R. E. Head, E. L. Tucker

Previous investigations of E. L. Tucker and R. E. Head' related in particular to the effect of cyanogen compounds on galena, sphalerite, and pyrite, and their behavior in the presence of such compounds. The present contribution deals with the floatability of the copper minerals and of pyrite. All experiments were performed on minus 200-mesh material, the method of preparation being the same as that described in the previous article. Flotation tests were made in a small mechanically agitated machine of 50-gm. capacity designed in this laboratory by Gates and Jacobsen.2 General Naval Stores pine oil No. 5 and potassium xanthate were used in constant amount in all of the experiments; these agents were selected because of their present wide use in the flotation of copper minerals. Time additions were varied to secure four final hydrogen ion concentrations, namely, neutral, 0.0005 per cent. CaO, 0.003 per cent. CaO, and 0.02 per cent. CaO. The variation in lime addition was introduced to include the range of alkalinities employed in actual flotation practice. The minerals employed were the purest obtainable. Their analyses are shown in the following tabulation: Table 1.—Analyses of Minerals Employed in Experiments mineral Cu Fe Cao S MgO Insol. Chalcocite .............. 77 02 0.49 0.29 21.70 0.08 0.28 Chalcopyrite............. 34.50 29.20 0.23 34.10 0.07 1.42 Bornite................. 64.30 9.30 0.12 23.70 0.10 1.95 Pyrite....................... 36.90 1.12 49.70 .... 1.51

Jan 1, 1926

By B. Ladanyi

The design philosophies for piles in unfrozen and frozen soils are compared, and their similarities and differences are underlined. It is shown that in frozen soils, the long term behavior of a pile is difficult to predict, because of inadequate knowledge on the behavior of adfreeze bond with time, and on the value and variation of the lateral normal stress acting on the pile. Both of these problems are discussed in the paper on the basis of laboratory tests and theoretical analyses.

Jan 1, 2010

By Hargraves A. J, Smith J. W

Experiments conducted at Tahmoor Colliery, Sydney Basin, have demonstrated the variability in chemical and isotopic composition of seam gases issuing from boreholes in the Bulli seam and desorbing from lump coal from the same source.From this work it appears that an immediate preferential release of methane accompanies the physical disturbance of the coal seam by penetration with development or drilling or by detachment. In addition, both early released methane and carbon dioxide are depleted in 13C relative to later desorbed gases, therefore the analyses of gas samples taken after such events may not reflect the true bulk composition of the undisturbed seam gas in situ. A method for overcoming this problem by taking gas samples at depth in the "steady state" is proposed.

Jan 1, 1987

By B. Denby

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993. The design and scheduling of open pit operations are consistent problems encountered by the surface mining industry. Numerous techniques and algorithms have been developed to assist the mining engineer in the creation of optimum development strategies. Virtually all the practical techniques that have been produced have concentrated on one of the aspects (limit definition or scheduling) at the expense of the other. It has long been recognised, however, that the two activities are intrinsically linked and thus solving either problem independently of the other can only ever produce sub-optimal results as a whole. This has been termed the "circular reasoning problem". It has also been recognised that, for all practical-sized situations, solving both problems simultaneously is virtually impossible using conventional techniques due to the massive size of the search space involved. A technique is presented which is based on a self-learning genetic algorithm, which provides a combined pit limit and extraction schedule simultaneously in order to maximise the NPV (net present value) of the extraction. The theory is developed in two-dimensions and a number of examples of its application are presented. It is proposed that this approach is a highly efficient, heuristic technique offering the potential to transcend the circular reasoning difficulties of separate pit limit and extraction scheduling systems. Extension of the technique into three-dimensions and its application to realistic problem sizes are discussed

Apr 1, 1994

By Kenji Koga

In order to derive the population distribution of gold nanoparticle morphologies as a function of size, highresolution electron microscopic (HREM) observations and structural analyses were done for over 4000 particles (3-18 nm) grown by an inert gas aggregation (IGA) source using helium. To obtain structural features threedimensionally and not to skip high-contrast images, twenty photos were taken for each particle by changing tilting angle of a specimen holder in combination with the through-focus procedure. For the reliable structural determinations, HREM images and their tilting sequences were directly compared with multislice-simulation results for icosahedral, decahedral and face-centered cubic morphologies, and finally the population distribution of each morphology was obtained as a function of size. In the present sample, icosahedral particles were dominantly populated over the whole observed size range and decahedral particles with non-spherical truncated bi-pyramid shape were secondly dominant. Even though a large number of sampling has been done, few crystalline particles were observed.

Oct 1, 2003

By Daniel L. Hanson

This paper presents a case history of the design, installation and performance of a tied-back tangent caisson retaining wall which was constructed as part of the Third Harbor Tunnel project currently underway in Boston, Massachusetts. The Third Harbor Tunnel project consists of a large multi-lane transportation tunnel which is being constructed by the sunken tube method. In this type of construction, the tunnel alignment, slopes and bedding are excavated and installed underwater and the tunnel sections floated over the proper alignment and sunk in place. The tangent caisson retaining wall discussed in this paper was constructed to provide support of the upper portions of the tunnel excavation at the East Boston Portal where the tunnel exited from below the harbor and continued underground on shore. A portion of the tangent caisson retaining wall was also utilized to provide earth support for the barge unloading facility where spoil from the tunnel excavation was transferred to surface vehicles for removal from the site. PROJECT BACKGROUND The tangent caisson retaining wall was constructed by The Millgard Corporation (TMC) as a subcontractor to the Boston Third Harbor Tunnel Contractors, a Joint Venture which consisted of the firms of Morrison-Knudsen Corporation, Interbeton Inc., and J.F. White Contracting Company. The entire project team is listed below on Table 1. The design of the tangent caisson wall system was performed by Hanson Engineering, P.C. (HE) acting as design consultant to TMC. The retaining wall system incorporated a single row of pressure injected earth anchors (tie-backs) as part of the design. The earth anchors were designed and installed by Drill Tech as a subcontractor to TMC.

Jan 1, 1994

By Ad. Breyre

[Internal-combustion engines have been used in Belgian mines for a long tine. As early as 1899, the use of these engines underground was considered, but the general policy was to prohibit such an application unless ministorial permission was granted' in special instances. At that time only gasoline engines were available, and a few of these were installed as stationary engines, although in general they were replaced later by electric or compressed-air motors. However, the number of gasoline locomotives continued to increase. Regulations governing the use of these locomotives soon were formulated and as early as 1920, when a now set of regulations was promulgated, the use of gasoline locomotives in mines could be authorized by the Provincial Inspection Department and no longer depended on obtaining a ministerial decision. Since 1931 this authorization may be given by the Chief Inspector of Mines, Director of the Mining District. Since 1920, safe practices have boon incorporated in the regulations.]

Jan 1, 1940

By John W. Brown

Electrical resistivity surveys were conducted at three sites in Wyoming in an attempt to detect underground rubble zones in oil shale and to determine their size and resistivity contrast. The zones were detected at Rock Springs sites 4 and 5, but none were detected at Green River site 1. The resistivity of the rubble zones at sites 4 and 5 is greater than that of the surrounding rock. The zones at sites 4 and 5 are concluded to be roughly ovaloid in shape, with a horizontal diameter of 33 m and a vertical thickness of 24 m. Both rubble zones and the blasting that created them are considered to be centered at a depth of 24 m.

Jan 1, 1972

Industries in the Kwinana area have embarked on a journey of improving the eco-efficiency of Western AustraliaÆs primary heavy industry area. The Kwinana Industrial Area has some unique characteristics that provide both opportunities and barriers. The Kwinana Industries Council and the Chamber of Commerce and Industry are working with the industries to identify a range of projects that can deliver improvements for both environmental and economic æbottom linesÆ, and to progress these projects using internal and external resources. The evolution of the process, its relationship to the ethos of operating companies, and the availability of resources to pursue projects, is an interesting study with lessons for others interested in taking the same course.

Jan 1, 2002

By C. G. Dunn, F. W. Daniels, M. J. Bolton

IN recent investigations1. a data on relative grain boundary energies in silicon iron have been obtained. The present investigation is a continuation of this work along similar lines for the purpose of obtaining additional information on boundary energies. One aim has been to extend the data for a (110) series, which was formerly studied,' to small differences in orientation, since a recent theory3,4 based on a dislocation model of grain boundaries predicts a E. ? (A-ln ? )* form of energy curve for small differences in orientation. Another aim has been to provide data for a (100) series—all grains having (100) planes parallel with the surface of sheet speci-mens—and to compare the results with the predicted form of energy curve. Finally, information on the nature of approach to equilibrium conditions was to be obtained through observations on the movements of grain boundaries. Recently published papers2,3,5 have treated the mathematical problem of expressing equilibrium conditions for grain boundaries for the general case when boundary energy depends upon boundary orientation. The equilibrium equations, which relate equilibrium angles and grain boundary -free energies, contain additional terms that express the variation of energy with boundary rotation. It has been necessary in the present investigation, however, to neglect these additional terms since no data for their evaluation were available. Dropping the additional terms leads to the following approximate equations which were used: E12/sin ?3 = E18/sin?2 =E28/sin?1 or those of the form: E28 + E13 cos ?3 + E12 cos ?2 = 0 Experimental Procedure Except for sample F1, all specimens were made from two lots of silicon iron called C and L respectively. The compositions of these are listed in table I. In the preparation of 12 three-grain specimens for the present investigation, a controlled grain growth technique, which has been described previously,' was used. After preparation, the specimens were notched at the boundaries to shorten them as a means of providing more rapid approach to equilibrium in the anneals. Initial grain boundary angles were determined from micrographs taken at X500. Seven anneals, totaling about two days at 1300°C and two to four days at 1400°C, were run in an atmosphere of pure dry argon as described in a previous paper.' Boundary changes generally could be followed without metallographic surface preparation, because thermal etching occurred during the anneals. These observations indicated angle changes of as much as 35" in some instances, with the major changes occurring during the first anneal. Annealing was discontinued when the angles reached stationary values. Fig. 1 gives a schematic diagram for purposes of defining crystallographic and boundary directions for three grains with common plane parallel with the sheet. Differences in orientations (expressed by A) are the angles between [00l] directions. They can be calculated with the aid of the ?'s. The grain boundary angles can be calculated from the w'S. Results Results are given in table 11. Types of crystal-lographic planes refer to those parallel with the sheet. Orientations are given in terms of [00l] direc-tions as shown in fig. 1. Except for grain 3 of specimen H6, which was unintentionally tilted 7" out of a (100) plane, all grains generally were within 1" or 2" of the plane specified. The directions of boundaries were measured generally to within 1" on both upper and lower surfaces, and the average direc- tions were determined for use in calculating the grain boundary angles. Variations in grain boundary directions refer to deviations from average directions. Boundaries near the junction point for all specimens generally were very close to perpendicu-

Jan 1, 1951

By John Stroiazzo, Bernard C. Aubé

Brenda Mines, located 22 km Northwest of Peachland in British Columbia, Canada was an open pit copper- molybdenum mine which closed in 1990 after 20 years of operation. The primary concern in Brenda's tailings and waste rock drainage is molybdenum at a concentration of approximately 3 mg/L. The mine drainage is alkaline and contains little or none of the typically problematic heavy metals. Given that the waters downstream are used for municipal water supply and some irrigation, a discharge limit of 0.25 ma molybdenum was imposed with specific water quality guidelines in the receiving creek. A review of all existing and potential molybdenum removal methods was undertaken prior to mine closure. The chosen process is a two-step iron co-precipitation with clarification and sand filration at a slightly acidic pH. A 4,000 usgpm (912 m3/h) treatment plant was constructed and commissioned in 1998, at a cost of $10.5M. The successful removal of molybdenum from the drainage water is explained with details on some design innovations and operational challenges encountered during plant start-up. Investigated sludge disposal options are discussed although the long term disposal scenario has not yet been finalised.

Jan 1, 2000

By H. W. Fleming, R. R. Brooks

The Clearwater Deposit, a small occurrence of massive-sulphide mineralization enclosed in an envelope of disseminated-sulphide mineralization, was discovered as a result of an aeroelectromagnetic survey in New Brunswick in 1955. Subsequently, additional flights were made over the deposit and various ground follow-up methods were employed to ascertain the nature of their response. All methods proved to be capable of indicating the occurrence with varying degrees of precision. This paper is a presentation and a discussion of the magnetic and electromagnetic data, both airborne and ground, and the self-potential data obtained over this deposit. The attention of Canadian mining exploration companies was initially focussed on New Brunswick by the discovery, in 1953, of the Brunswick ore body. Ground electromagnetic surveys were of considerable assistance in locating and developing this deposit. In the following year, 1954, the Heath Steele base-metal deposits were discovered by employing an airborne electromagnetic device and ground electromagnetic surveys to follow-up the airborne indications. These discoveries demonstrated clearly that both airborne and ground electromagnetic techniques were applicable for locating the near-surface deposits of massive sulphides present in this region. Airborne electromagnetic equipment became available on a contract basis through Aeromagnetic Surveys Limited early in 1955 and was used extensively thereafter throughout a large portion of northern New Brunswick. It was as a result of one of these surveys with Aeromagnetic Surveys Limited equipment in the summer of 1955 that the Clearwater Deposit was detected. The airborne anomaly was located on the ground by means of an electromagnetic survey using a Swedish Slingram unit. During 1956, the region was investigated more thoroughly- in the hope that other sulphide bodies might be located. Airborne electromagnetic coverage was extended and the Clearwater Deposit itself was used as a testing ground for the various methods and types of equipment currently in use in New Brunswick. In this paper com prative data are presented for the airborne magnetic, airborne electromagnetic, ground magnetic and ground electromagnetic surveys over this deposit. The ground electromagnetic instruments used were the McPhar vertical-loop unit and the Slingram and Boliden horizontal-loop units. Self-potential surveys were carried out with a McPhar unit. From the geophysical point of view, all ground electrical methods employed indicated the presence and the extent of the massive-sulphide mineralization with a good degree of accuracy. The horizontal-loop methods however, defined the contacts more precisely as is to be expected when dealing with a flatly-dipping

Jan 1, 1961

By Jheison Lopes dos Santos

Sistemas de blindagens multicamada têm sido estudadas pela sua ótima capacidade de proteção, devido à combinação de diferentes materiais que constituem seus componentes. A primeira camada é constituída por um componente cerâmico, cujo objetivo principal é fragmentar o projétil, dissipando grande parte de sua energia. A camada intermediária compreende tecido de aramida ou matriz polimérica com fibras naturais, que também dissipa energia tanto do projétil quanto do cerâmico e opera retendo os fragmentos cerâmicos. Neste trabalho, pela primeira vez, o sistema cerâmico Al2O3-Nb2O5-LiF tem seu comportamento dinâmico avaliado balisticamente. Este composto cerâmico foi submetido a impactos balísticos de projéteis 7,62 mm, para testar este cerâmico do primeiro componente de um sistema de blindagens multicamadas. Os resultados obtidos mostraram que a adição de LiF ao composto cerâmico Al2O3-4%p. Nb2O5, sinterizado a 1.300 ºC, obteve desempenho comparável ao obtido por Al2O3-4%p. Nb2O5 sem LiF, sinterizado a 1.400 ºC. Os resultados revelaram que, ao serem submetidos a esses impactos balísticos, apresentaram valores comparáveis aos esperados de pressão e de velocidade de partícula na interface de impacto projétil-cerâmico. Dessa forma, a adição de fluoreto de lítio ao composto cerâmico alumina-nióbia possibilitou a redução em 100 ºC na temperatura de sinterização, sem comprometer o desempenho balístico e exibindo parâmetros de choque comparáveis, e redução de custo.

Oct 30, 2017

By Carlos Guillen Morales

Como parte del proyecto de estudio de impacto ambiental presentado por la Compañía Minera Antamina (Ancash), el presente trabajo describe la reutilización de las aguas residuales de los procesos mineros realizado en Huarmey. El estudio plantea el transporte el concentrado de mineral desde la mina hasta el puerto de embarque en Huarmey a través de camiones utilizando una carretera que facilitaría el desplazamiento de los mismos. Una vez llegado el concentrado al puerto de embarque, se separaría el agua del concentrado y el agua sería tratada para luego descargarla en el mar. Sin embargo, por análisis posteriores, se optó por otra propuesta más ecológica, donde se traslade los concentrados de cobre y zinc en suspensión acuosa a través de un minero ducto, y el agua tratada remanente del transporte de mineral, sería disipada mediante una plantación forestal, evitando la descarga al mar, generando empleo y una extensa área verde en el desierto de Huarmey. De forma que se innova en la minería a través de la reutilización de las aguas y se desafia las condiciones extremas del desierto costero para desarrollar una superficie vegetal que consumiera esta agua.

Sep 12, 2005

By John A. Dal Pino

This paper describes two independent building underpinning projects during the construction of the Los Angeles Metro Rail System. The first project involves pinpile underpinning of a building along the Red Line which is the main heavy-rail portion of the system. Vertical and inclined friction pinpiles were constructed, using drilling equipment in a low-overhead height space, to support underpinning grade beams. This underpinning permitted the demolition of the building caissons so that the subway tunnels could pass beneath the building unimpeded. One of the piles was statically tested in compression. The second project involves the use of traditional pit piers for the underpinning of historic buildings along the Pasadena Blue Line, which is one of the light-rail branches from the Red Line. The piers were designed for various loading conditions and to minimize differential settlement of adjacent foundations. The piers will be internally braced with steel struts to be designed by the contractor.

Jan 1, 1996