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By P. K. Koh, H. A. Lewis, H. F. Graff

New data on the distribution of silicon between slag and carbon-saturated iron at 1600Oand 1700OC are presented which, in combination with previously published data, permit the determination of silica activities over a broad range of compositions in the CaO-Al2O3-SiO2 system. The distribution of silicon between graphite-saturated Fe-Si-C alloys and blast furnace-type slags in equilibrium with CO has been described in previous publications.1"3 In this past work the silica-silicon relation was established at temperatures of 1425" to 1'700°C for slags containing up to 20 pct A12O3. This paper presents the results of additional studies at 1600" and 1700° C which extend the silicon distribution data at these temperatures for CaO-A12O3-SiO, slags over a range from zero pct Al2O3 to saturation with Al2O3, or CaO.2Al2O3. The upper limit of SiO2 is set by the occurrence of Sic as a stable phase when the metal contains 23.0 or 23.7 pct Si at 1600" or 1700°C, respectively. The activity of silica over the expanded range is determined directly from the distribution data.3 Recently4-7 other investigators have studied the activities of SiO, and CaO, principally in the binary system, using different methods and obtaining somewhat different results. EXPERIMENTAL STUDY The experimental apparatus and procedure have been fully described in previous publications.1, 3 Six new series of experimental heats have been made, four at 1600° and two at 1700°C. Master slags of several fixed CaO/Al203 ratios were pre-melted in graphite crucibles, and these were used with additions of silica to prepare the initial slag for each experiment. Slag and metal were stirred at 100 rpm and CO was passed through the furnace at 150 cc per min. The initial sample was taken 1 hr after addition of slag at 1600°C or 1/2 hr after addition at 1700°C. The run was normally continued for 8 hr at 1600°C or 7 hr at 1700°C, and the final sample was taken at the end of this period. Changes in Si and SiO2 content indicate the direction of approach to equilibrium, and in a series of runs where the approach is from both sides this permits approximate location of the equilibrium line. Fig. 1 shows the results of such a series of 15 runs at 1600°C for slags of CaO/Al,O3 = 1.50 by weight. Figs. 2 and 3 record other series at 1600°C and Fig. 5 a series at 1700°C with fixed CaO/Al0 ratios. The results of the experiments at 162003°C have been reported in part in a preliminary note.3 In the experiments recorded in Figs. 4 and 6, the slags were saturated with A12O3 (or with CaO.2A12O3 within its field of stability) by suspending a pure alumina tube in the melt during the course of the run. The final slag analyses were used to establish the liquidus boundaries8 in the stability fields of CaO.2Al2O3 and of Al20,. ACTIVITY OF SILICA The free-energy change in the reaction has been calculated by Fulton and chipman2 from recent and trustworthy data including heats of formation, entropies, and heat capacities. The more recent determination by Olette of the high-temperature enthalpy of liquid silicon is in satisfactory agreement with the values used and therefore requires no revision of the result which is expressed in the equation: SiO2 (crist) + 2C (graph) = Si + 2CO(g.) [1] &F° = + 161,500 - 87.4T The standard state for silica is taken as pure cristobalite and that of Si as the pure liquid metal. Since the melts were made under 1 atm of CO and were graphite-saturated, the equilibrium constant for Eq. [I] reduces to K1 = asi /asio2. The value of this constant is 1.77 at 1600°C and 16.2 at 1700°C. Through K1, the activity of silica in the slag is directly related to the activity of silicon in the equilibrium metal.

Jan 1, 1960

"The richest hill on earth" had its start as a placer gold camp in 1864. The gold was quickly worked out but then silver was discovered in the copper ores in Butte Hill. After ten years as a silver camp, rich copper ore was found in 1881 and the future of Butte was assured. In the early 1960's, the Anaconda Company began the shift from underground mining at Butte to open pit mining of the enormous, low-grade copper deposit surrounding the old high-grade veins which had been worked for over eighty years. Their first primary crusher was a 66 in. by 84 in. (168 m by 2. 13 m) jaw crusher. The pit was expanded at such a rate, however, that its location became endangered. Additionally, the new Clyde Weed concentrator had been built at Butte; and in 1969 construction of a new gyratory installation was started. The primary crusher at the Clyde Weed concentrator is one of the most unusual primary crushers ever put into operation. At times, the ore from the Berkeley pit contains large amounts of timber, pipe, rails, and so forth left in the ore body from the old underground mining operations; and the crusher installation had to be designed so this tramp material could be readily removed ahead of the crusher. Ore is delivered by 100- and 150-ton trucks to two side-by-side dump pockets, each with a capacity of 400 tons. Originally, a hydraulic grapple was installed on the dividing wall between the dump pockets; but it was found that oversize boulders large enough to block the discharge opening at the bottom of each hopper were rapidly covered with other material, and the grapple was unable to reach and remove the large boulders causing the blockage. In addition, the grapple was located in a quite vulnerable position; and it sustained damage from being struck by rock dumped from the trucks. Oversize boulders are now blasted. Underneath each pocket is a vibrating grizzly feeder with the grizzly bars set at 4 in. (102 mm). These feeder-grizzlies are 84 in. (2. 13 m) wide and 32 .ft (9. 75 m) long, with grizzly sections 16 ft (4. 88 m) long. Approximately 75% of the ore passes through the grizzlies and grizzly oversize then drops onto two parallel 6 ft (1. 83 m) wide picking belts. The belts are 3 in. (76 mm) thick and rest on idlers supported by air- filled rubber shock absorbers. At the side of each picking belt is a hydraulic grapple which is used to remove timbers too large to be removed by hand. At times, four men are used to remove timber and tramp iron. Timbers are dropped onto a transverse belt conveyor which discharges into a truck stationed outside the primary crusher building,

Jan 1, 1978

By Musa Karakus

In an attempt to explain the phenomena of lead entrainment during Cu drossing of lead bullion, two different synthetic lead bullions were heated to 1050°C, cooled slowly to various temperatures, and then quenched. The morphology and composition of dross particles that form when Mn is used to desulphurize bullion also were examined. Polished sections of these pyrometallurgical products were examined by process mineralogical techniques to identify the impurity phases, determine their chemical compositions, examine the morphology of the impurity phases and evaluate the potential for lead entrainment in such crystals, and characterize pre-quench and quench-generated phases. The phases crystallized were metallic lead, metallic copper, galena, chalcocite, albandite, Cu14.4Pb2S9. and 5.5Pb2S3.5. Metallic copper formed isometric skeletal crystals, chalcocite formed platy and skeletal crystals, and 1formed crystals and eutectic intergrowth with chalcocite and Cu14.4Pb2S9 or Cu5.5Ph2S3.5. The pre-quench crystals are larger and usually exhibit skeletal forms; the quench-generated phases are only a few micrometers across and disseminated throughout the lead matrix. Skeletal crystals of metallic copper and chalcocite form three dimensional networks that entrain large amounts of metallic lead.

Jan 1, 1989

By D. A. Norrgran, J. A. Wernham, D. E. Walsh

A qualitative test program was sponsored jointly by the University of Alaska and Eriez Magnetics, in order to study placer gold nugget recovery using an eddy-current separator. Various gold nuggets from Alaska, ranging from 6.4 mm to 63.5 mm in size, were tested. All testing was performed using an Eriez Laboratory ESC, Model REA, fitted with 2000 gauss, surface field strength magnetic rotor. The belt speed was set to 91 meters per minute and the rotor speed was set to 2500 rpm in the forward direction. The splitter was adjusted to just reject the largest pieces of rock that measured an average 76 mm x102 mm x 127 mm. Based on the results of this limited test work, it can be recommended to placer gold mine operators, that Eriez Magnetics ECS technology is a viable and practical concentration technology for coarse gold recovery. Silver and platinum were also tested.

Jan 1, 2003

By George Wilson

When pumping abrasive slurry mixtures, special attention must be given to pump design and construction. The second article in this two-part series describes some design features to consider when selecting centrifugal slurry pumps. Hydraulic Design Most centrifugal pumps are conventionally designed to achieve the desired hydraulic performance at the highest efficiency and lowest cost when handling clear fluids in reasonably clean environments. Manufacturing limitations are not imposed on the configuration of the pump, since conventional materials such as cast iron, bronze, and stainless steel are used. Manufacturers and buyers usually select the highest specific speed commensurate with the lowest cost attainable. Part life is almost infinite. When a centrifugal pump is designed for slurry service, the important factors in pump design are wear and materials of construction; size and efficiency assume lesser importance. The pump must operate at low rotational speed and the impeller has to be a truly radial flow design. These factors immediately determine that the pump must be of a low specific speed design in the range of 600 to 1800. The specific speed is a type number that is constant for all geometrically similar pumps; it designates the geometry of the impeller and casing. [ ] where n = rpm, Q = flow (US gpm), H = total head (ft), and Ns = specific speed. Since wear is a function of velocity it can be shown that for a given head and capacity, wear will increase with increased Ns. Centrifugal Pump Casing The casing has a profound effect on performance. If designed incorrectly it can destroy a large part of the energy given to the flow by the impeller, resulting in low efficiency, high hydraulic forces, and excessive wear on both the casing and impeller. In a conventional spiral volute, the static pressure around the impeller is uniform only when there is a free vortex velocity distribution in the volute, i.e., when the spiral flow from the impeller coincides with that of the volute spiral. This occurs only at the best efficiency point (BEP), between the pump's best operating zone and over capacity zone. Departure from the free vortex velocity distribution in the volute at partial or over capacities produces circumferential pressure gradients at the impeller periphery, which is directly proportional to the specific gravity of the mixture being pumped. At partial or over capacities, the flow will not tolerate the abrupt deflection at the tongue and severe energy losses and wear are created near the casing throat and on the impeller. Concentric and semi-concentric volute designs produce uniform static pressures at the impeller periphery and make the pump, much less sensitive to "off"' BEP operation. Hydraulic forces and wear are considerably reduced-eliminating the tongue prevents abrupt deflection of the flow, turbulence is minimized, and the velocity in the casing volute and throat is reduced. Good efficiency is sustained over a wider operating hand. Casings of this design are easy to cast. • Spiral volute (conventional)-Radius to the outer periphery of the casing and the volute area constantly increases. • Semi-concentric casing-Radius to the outer periphery of the casing and volute area remain constant within a certain angle. • Concentric casing-Radius to the outer periphery of the casing and volute area remain constant through 360°. The degree of concentricity must be reconciled with efficiency, hydraulic radial load, and wear for each specific speed chosen. Up to 1200 Ns the casings can be fully concentric without sacrificing too much efficiency. Above 1200 Ns, the casings can be semi-concentric. The angle of concentricity

Jan 10, 1981

By S Piercey, M Doublier, B Eglington, D L. Huston, S Pehrsson

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The distribution of volcanic-hosted massive sulfide deposits through time is episodic, involving relatively short time intervals of apparent high productivity and long intervals of low productivity. This distribution is principally related to the geodynamic evolution of the Earth. The vast majority of these deposits is associated with the assembly of supercontinents and form along convergent margins, generally in back-arc basins or rifted arcs. This contrasts with the distribution of black smoker deposits, which presently form along both convergent margins, particularly in the western Pacific, and divergent margins at mid-ocean ridges. However, the latter environment is rarely preserved deep into the geological past.There also appear to be systematic patterns in a number of other features of volcanic-hosted massive deposits through time. Deposits hosted by mafic-dominated successions are dominant in Archean to Proterozoic rocks, whereas deposits hosted by felsic-dominated successions are most common in Phanerozoic rocks. Geochemical characteristics of felsic rocks within the host successions and ore lead and sulfur isotope data of the ores have also changed with time. This suggests changes in the process of subduction and/or changes in the characteristics of the over-riding plate with time, consistent with isotopic and geologic evidence for greater reworking of pre-existing crust during the Phanerozoic.Other secular changes that are reflected in characteristics of volcanic-hosted massive sulfide deposits include the redox state and salinity of coeval oceans. As an example, both the abundance of sulfate minerals and sulfur isotope patterns reflect the development of periods of anoxic conditions over time, with major intervals of anoxia reflected by a virtual lack or low abundance of sulfate minerals in volcanic-hosted massive sulfide deposits in the Mesoarchean to the Palaeoproterozoic, and shorter intervals since.CITATION:Huston, D L, Eglington, B, Pehrsson, S, Piercey, S and Doublier, M, 2015. Secular variations in the abundance and characteristics of volcanic-hosted massive sulfide deposits – implications for evolution of convergent tectonics and ocean geochemistry , in Proceedings PACRIM 2015 Congress, pp 475–480 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By F. C. Langenberg, J. Chipman

New data on the distribution of silicon between slag and carbon-saturated iron at 1600oand 1700oC are presented which, in combination with previously published data, permit the determination of silica activities over a broad range of compositions in the CaO-Al2O3-SiO2 system. The distribution of silicon between graphite-saturated Fe-Si-C alloys and blast furnace-type slags in equilibrium with CO has been described in previous publications.1"3 In this past work the silica-silicon relation was established at temperatures of 1425" to 1700°C for slags containing up to 20 pct Al2O3. This paper presents the results of additional studies at 1600" and 1700° C which extend the silicon distribution data at these temperatures for CaO-A1203-SiO2 slags over a range from zero pct A12O3 to saturation with A12O3, or CaO.2A12O3. The upper limit of SiO, is set by the occurrence of Sic as a stable phase when the metal contains 23.0 or 23.7 pct Si at 1600" or 1700°C, respectively. The activity of silica over the expanded range is determined directly from the distribution data.3 Recently, 4-7 other investigators have studied the activities of SiO, and CaO, principally in the binary system, using different methods and obtaining somewhat different results. EXPERIMENTAL STUDY The experimental apparatus and procedure have been fully described in previous publications.1, 3 Six new series of experimental heats have been made, four at 1600° and two at 1700°C. Master slags of several fixed CaO/A12O3 ratios were pre-melted in graphite crucibles, and these were used with additions of silica to prepare the initial slag for each experiment. Slag and metal were stirred at 100 rpm and CO was passed through the furnace at 150 cc per min. The initial sample was taken 1 hr after addition of slag at 1600°C or 1/2 hr after addition at 1700°C. The run was normally continued for 8 hr at 1600°C or 7 hr at 1700°C, and the final sample was taken at the end of this period. Changes in Si and SiO2 content indicate the direction of approach to equilibrium, and in a series of runs where the approach is from both sides this permits approximate location of the equilibrium line. Fig. 1 shows the results of such a series of 15 runs at 1600°C for slags of CaO/Al2O3 = 1.50 by weight. Figs. 2 and 3 record other series at 1600°C and Fig. 5 a series at 1700°C with fixed CaO/Al2O3 ratios. The results of the experiments at 162003°C have been reported in part in a preliminary note.3 In the experiments recorded in Figs. 4 and 6, the slags were saturated with A12O3 (or with CaO.2A12O3 within its field of stability) by suspending a pure alumina tube in the melt during the course of the run. The final slag analyses were used to establish the liquidus boundaries8 in the stability fields of CaO.2Al,O3 and of A120,. ACTIVITY OF SILICA The free-energy change in the reaction has been calculated by Fulton and chipman2 from recent and trustworthy data including heats of formation, entropies, and heat capacities. The more recent determination by Olette of the high-temperature enthalpy of liquid silicon is in satisfactory agreement with the values used and therefore requires no revision of the result which is expressed in the equation: SiO, (crist) + 2C (graph) = Si + 2CO(g.) [1] &F° = + 161,500 - 87.4T The standard state for silica is taken as pure cristobalite and that of Si as the pure liquid metal. Since the melts were made under 1 atm of CO and were graphite-saturated, the equilibrium constant for Eq. [I] reduces to K1 = asi /asio2 The value of this constant is 1.77 at 1600°C and 16.2 at 1700°C. Through K1, the activity of silica in the slag is directly related to the activity of silicon in the equilibrium metal.

Jan 1, 1960

By J Merrells

Fluor, together with our clients, has yielded significant reductions in the total cost of mining projects by employing a systematic and methodical process of cost reduction. This paper outlines this structured approach to reducing the total cost of projects through the gathering of information, the evaluation of the zero base design, and the development of the execution strategy for the project in the study phase.Over the recent iron ore boom the cost of growth projects escalated rapidly due to a variety of factors including the engineering cost of re-designing facilities, construction in remote areas and an increase in the ‘perceived’ capital requirements for maintainable and operable facilities.Fluor has made strategic steps towards safely reducing the capital intensity of projects, by working with clients to develop zero base designs which utilise the minimum technical requirements in order to meet the function of the plant and then add cost for safety, maintenance and operability only where clearly justified.This paper has set forth a structured three phased approach to focus the team on reducing capital cost while maintaining a low increase in engineering effort.The initial ‘gather’ phase focuses the team on acquiring information and identifying decisions that will need to be made so that the team can prioritise and focus the attention on areas that will provide the greatest benefit. Within this phase the identification of zero base design requirements, review of lessons learnt and analysis of capital cost levers, allows the team to identify the key decisions on the project that will affect the capital cost.In the subsequent ‘evaluation’ phase the team established the zero base design, using the hierarchy of cost reduction as a guide to focusing the team’s attention on high yielding cost saving opportunities.In the final phase the team develops the execution strategy which will yield the least cost using strategies and tools such as modularisation, standardisation, replication, strategic sourcing and 3D design.CITATION:Merrells, J, 2017. Reducing total project cost in the study phase using zero base design, in Proceedings Iron Ore 2017, pp 621–626 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Bruce Geller

Attending the Prospectors and Developers Association of Canada (PDAC) meeting and exhibit has become an annual tradition for many in the mining industry. Similar to last year’s synopsis, this report is an overview of the 2003 conference from the eyes of a consulting mineralogist. It is supplemented by conversations with other participants. And it examines the conference handouts. Certain segments of the mining industry have seen improvement throughout the year in terms of metal prices, stronger demand and renewed interest by the investment community. Other segments continue their decline due to depressed commodity prices, higher oil prices, a continued weakness in the global economy and war uncertainties. SARS was known to the world, but it was not a Toronto epidemic during PDAC. In short, this year’s PDAC was permeated by an air of anxiety about the Middle East.

Jan 1, 2003

By S. Castro

Molybdenite flotation is strongly depressed at pH higher than 9.5 in the flotation of Cu-Mo ores in sea water. Chemically sea water contains mainly Na+ and Cl- ions, but also some secondary ions, such as SO42-, Mg2+; Ca2+, HCO3-; etc., which are not necessarily indifferent for the flotation of molybdenite. The natural floatability of molybdenite in sea water and in NaCl solutions containing different secondary ions is investigated by micro-flotation tests. The tests indicate that the floatability of molybdenite in alkaline media in 0.6 M NaCl solutions is not affected by the presence of anions, such as, SO42- and HCO3-, at concentrations similar to those occurring in sea water. However, a strong depression of molybdenite at pH ranging from 9.5-10.0, is produced by the alkaline earth metal cations (Ca2+ and Mg2+ ions), dissolved in distilled water or in 0.6M NaCl solutions. It was found that effect of Mg2+ions is significantly stronger than Ca2+ ions. Effect of both ions is attributed to hydrolysis and adsorption of MOH+ hydroxy-complexes. This is followed by subsequent precipitation of hydrophilic colloidal hydroxides at the molybdenite/solution interface, and in bulk solution.

Sep 1, 2012

By Charles M. Means

A thoroughly modern coal-handling system has been installed at the Pittsburgh Terminal H. H. &. Coal Co.'s new No. 8 shaft, or Cover-dale mine, about 11 mi. (17.7 km.) from Pittsburgh on a spur of the Montour R. R. The Pittsburgh scam, which is the one worked, is reached at a depth of 342 ft. (104 m.). Power is delivered to the mine at 22,000 volts over a transmission line of the bow-arrow type of construction. A private telephone line connecting the various mines and the main office in Pittsburgh is carried on the same poles. The high-tension line is brought to an outdoor, step-down, transformer substation, where three 833-kv.-a., single-phase, 60-cycle, oil-insulated, self-cooled transformers reduce the potential to 2300 volts. The transformers are protected by electrolytic, aluminum-cell lightning arresters, horn gaps, and choke coils. High and low-tension busses, together with fuses, choke coils and air-break horn-gap switches with thcir remote-control operating mechanism are mounted on a substantial structural-steel tower 25 ft. (7.6 m.) in height. Mine Substation The transformer substation is adjacent to a. pressed-brick building that houses direct-current substation equipment together with switchboards, etc., for the control and distribution of power. This building also contains the hoist for the men and supplies. Main Switchboard The 2300-volt circuit is carried underground in a conduit from the transformer substation to an oil switch in the substation and supply hoist building. This is the main switch controlling the 2300-volt busbars mounted back to a twelve-panel black-slate switchboard. From the switchboard, 2300-volt circuits are carried to transformers feeding the street and house lighting systems and to other transformers furnishing power for the elevator and lighting circuits in the store building. Other 2300-volt circuits run from this switchboard to the main hoist building, fan house and auxiliary or man-and-supply hoist. High-tension wiring,

Jan 1, 1922

By M. H. Marvin

This report presents the results of a program to develop backfilling techniques to mitigate undesirable effects of hydraulic borehole uranium mining. Large underground cavities, formed during the borehole mining process, can be backfilled to prevent ground subsidence and to allow mining of adjacent uraniferous sandstone. Three backfilling techniques were tested in the laboratory and in the field: bulk dumping of slurry into the borehole from ground level, slurry injection under water, and slurry injection above the cavity water level. These techniques were tested with sand and with sand and one percent cement (by weight) mixtures. The project was accomplished in four tasks: equipment preparation and transport, mining operation to generate a full-sized cavity, backfilling operation, and assessment through core samples and subsidence checks. The concentrations of cement mixed with sand proved to be inadequate to bond the sand. Bulk dumping resulted in a 30-degree angle-of-repose, much too steep to completely fill the cavity. Both slurry injection techniques filled the cavity satisfactorily. However, underwater injection is the recommended backfilling technique because the borehole water level does not need to be pumped down during backfilling. The borehole itself was filled by bulk dumping of slurry. In conclusion, backfilling of borehole mining cavities is entirely feasible, and the preferred method is slurry injection under water.

Jan 1, 1979

By C M. Rebagliati, J G. Payne, K Roberts

The Pebble deposit, located in south-west Alaska, is one of the largest Copper- Gold-Molybdenum (Cu-Au-Mo) porphyry systems in the world, with a current resource of >8 billion tonnes which contain 73.7 billion pounds of copper, 87.1 million ounces of gold and 4.16 billion pounds of molybdenum. The Pebble deposit formed at ~90 Ma, during emplacement of subduction-related hornblende granodiorite porphyry intrusions emplaced into Jurassic-Cretaceous sedimentary, volcanic and subvolcanic intrusive rocks of the Kahiltna Terrane. The Pebble West and Pebble East Zones represent two thermal and fluid centres in a single large magmatic-hydrothermal system. The West Zone extends from surface to about 500 m depth, has thin zones of oxide and supergene mineralisation overlying hypogene chalcopyrite mineralisation, and is amenable to open pit extraction. The East Zone extends to at least 1700 m depth, is higher grade, occurs beneath an eastward-thickening cover of younger sedimentary and volcanic rocks, lacks oxide and supergene mineralisation, and is being evaluated for underground block-cave mining. Most Cu-Au-Mo was introduced with early K-silicate alteration and related quartz-sulfide veins. In the East Zone, a structurally-controlled overprint by advanced argillic alteration significantly increased Au and, to a lesser extent, Cu grades. Exploration potential at Pebble and its surrounding district remains high. Several other porphyry, skarn and epithermal deposits have been discovered in the district, but only limited exploration has been conducted. The eastern, higher grade part of the Pebble deposit remains open in several directions, with significant potential for resource expansion by ongoing, aggressive drill exploration. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Gordon T. Austin

The combined production value of natural abrasives, which consist of tripoli, special silica stone, garnet, and emery, decreased in 1986. Shipments of processed tripoli increased slightly in quantity and 20% in value. Production of garnet, a common iron- aluminum-silicate mineral, decreased 12% in quantity and value. There was a 4% increase in the quantity and an 11% increase in the value of refined garnet shipped when compared with 1985 shipments, a new record high. Production of crude special silica stone decreased 7% in quantity and slightly in value, and shipments of finished special silica stone products decreased slightly in quantity and increased 229% in value. Production of emery, an impure aluminum oxide, increased 77% in quantity and increased 269% in value of product mined and shipped. [ ]

Jan 1, 1988

By David Hopkins, Steve Klein, Bradford Townsend, Ed Sum, Derek Penrice

INTRODUCTION The Transbay-Caltrain Downtown Extension (DTX) Project involves the construction of an approximately 1.5-mile rail line that will extend Caltrain commuter service and the future California High Speed Rail system into downtown San Francisco. The underground rail extension will be constructed by mined tunnel and cut-and-cover methods. Tunneling challenges include difficult ground conditions, low rock cover, the presence of historic buildings along the alignment, and the large tunnel span, ranging from approximately 50 to 65 feet. Three mined tunnel construction methods were evaluated: the Stacked Drift Method, the New Austrian Tunneling Method/Sequential Excavation Method (NATM/SEM), and Tunnel Boring Machines (TBM). This paper describes the challenges presented within the mined tunnel section, and summarizes the evaluation of tunneling methods that led to the selection of NATM/SEM. PROJECT OVERVIEW The existing Transbay Terminal opened in downtown San Francisco in 1939. This facility is antiquated, and does not meet current building seismic safety standards or the transportation needs of the Bay Area. For these reasons, San Francisco voters approved Proposition H in 1999, which proposed to construct a new or rebuilt regional transit center at the site of the existing terminal and extend Caltrain commuter rail ser-vice to the new transit center. The new transit center is the hub of the Transbay Transit Center (TTC) Program, which will greatly enhance regional transit service by providing connectivity for six Bay Area transit providers at one facility. The program will be the largest inter-modal centerwest of New York City. The TTC Program is comprised of two major projects, the Transit

Jan 1, 2007

By Bengt Fellenius

The conventional wave equation analysis without control of the representativeness of the parameters to the actual conditions does not provide accurate results. However, the representatives can be vastly improved by means of using the results of monitoring the dynamic response in a pile during driving. Dynamic monitoring displays the interaction of independent strain and acceleration measurements having directly propor­tional response to impacts, but inversely proportional response to re­flections from the soil. Examples are given and the CAPWAP method used to calculate from the measurements the dynamic pile and soil para­meters and mobilized soil resistance is outlined. The dynamic monitoring technique and analysis has been accepted internationally and been incor­porated into Building Codes. The prediction is offered that in five year's time, no major piling project will be undertaken without dynamic monitoring and analysis.

Jan 1, 1984

By M. M. Hassan

This report describes the analysis tools developed at West Virginia University which can be implemented to optimally design coal mine electrical systems. The basic analytical tools for all power systems are the load-flow and short-circuit analysis. Well known programs have been developed for analysis of ac transmission and distribution systems, but they are not applicable to a system which has combined ac/dc distribution, such as a coal mine power system. Furthermore, the topology of a coal mine electrcal system changes continuously due to the movement of the locomotives on the track. In the first section of this report, algorithms for carrying out load flow and short-circuit analysis of a coal mine electrical system are described. Results from the study of a typical coal mine system are presented. In the second section a method is described to optimally size power cables for cyclic loads. The method is based on the development of a thermal-electric model for a low-voltage power cable. Results from experimental verification of the model are also presented. These techniques are useful in the safe, efficient, reliable and economical design of the coal mine electrical power systems.

Jan 1, 1979

Possibilities and Working of the Specific Agglomeration of Fibrous Materials and Residues Plant based fibrous materials are becoming of increasing interest in a multitude of industrial applications. Main advantages are the specific lower energy demand and virtually closed CO2 cycle, excellent mechanical properties based on low density as well as a high level of recyclables. In contrast, processing and handling of such materials is associated with a number of challenges. These challenges are mainly related to specific morphological characteristics in correlation to fibre length and structure (branching and splices). Specific problems in further processing steps including transport, dosage or storage for natural fibre compounding, result from form-locking bonds leading to burling, clusters or plaits. Technologies of fibre processing are well known, but other than textile based technologies they generally result in intermediate goods which do not allow direct industrial application. The investigation to be presented is based on results of recent research activities and shows two possible technical solutions of innovative fibre agglomeration procedures. These methods allow the conversion of middle to long fibres into a form, which eases further processing and dosage significantly and therefore allows free flowing too. The procedures are based on the working principles of rolling and winding technology. Within the work, both of the patented methods and their respected lab-scaled devices will be described. Further, results will be shown for an up-scaled rolling agglomeration unit applying the developed principle and consisting of multiple process zones. Possible variations of the resulting product characteristics and the impact of different process parameters will be discussed based on the trials with natural fibre (hemp and flax) agglomeration. As a main outcome of the research, product qualities can be supplied according to the requirements of the specific application in correlation to agglomerate strength, porosity or form. In conclusion, recent developments for specific methods of characterization will be depicted.

Sep 13, 2010

By S. Bellec

A leaching model for gold ore that takes into account the impact of cyanide and oxygen concentrations as well as gold surface exposure on leaching performance is developed. Cyanide consumption is estimated by an empirical model that is a function of ore particles size distribution as well as cyanide, copper and sulphur concentrations. The proposed model has been validated by data from laboratory leaching tests on the Sleeping Giant gold mine ore. Keywords: gold leaching, modelling, exposure surface.

Jan 1, 2009

AT the Non-ferrous Metallurgy session on Wednes-day afternoon, R. M. Roosevelt, vice-president of the Eagle-Picher Lead Co., presided. The paper "Sug-gested Improvements for Smelting Copper in the Rever-beratory Furnace," by G. L. Oldright and F. W. Schroeder, was presented by. Mr. Oldright. It was brought out that lessening of dusting of the charge would increase the life of the arch at present operating temperatures, but will not allow much higher tempera-tures to be used unless dusting can be entirely elim-inated. The best opportunity for improving rever-beratory practice lies in the use of still higher tempera-tures but this requires the development of refractories superior to those now used. There was an interesting discussion of the facts brought out. The paper. on the "Formation and Decomposition of Zinc Ferrite," by

Jan 3, 1928