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By A. L. Wilder

Coeur d'Alene Mines Corporation's newest precious metals property is located in the old Rochester Mining District approximately twenty-five miles northeast of Lovelock, Nevada. Built at an elevation in excess of 6 000 feet, the Coeur-Rochester gold silver heap leach property encountered cold weather operational problems typical of most northern Nevada heap leach properties, soon after the start-up of operations last fall. Due to the size of the heap area under leach at Rochester, it was decided that 1 the usual practice of spraying to an "ice field" and waiting for the spring thaw was impractical. Further, the delivery schedule for a solution heating system of the size required was unacceptable. Accordingly, Rochester personnel embarked on a program to seek out a leach solution distribution system that would enable an operation through the winter and yet be cost effective. The findings of this program were rather dramatic and, as a result, the whole perception of heap leach solution application at Rochester has changed forever.

Jan 1, 1988

By I. Iwasaki

The effects of autogenous grinding and conventional grinding on the floatabilities of copper-nickel sulfides were investigated as a part of a pilot-plant development project on the differential flotation of Duluth gabbro. At the same mesh-of-grind copper, nickel, and cobalt recoveries were higher and residual sulfur in the flotation tailings was lower with the autogenously-ground pulps. With the ball-mill-ground pulps the residual sulfur in the tailings could not be lowered to the level attained by the autogenously-ground pulps even at increased levels of the collector addition. From mineralogical examinations of concentrate and tailings samples, an electrochemical interaction between grinding media and sulfide minerals was thought to have a greater effect on sulfide mineral flotation behavior than the breakage characteristics of the ore samples in these two types of mills.

Jan 1, 1981

By Slobodan Vujic, Goran Cirovic, Dragan Radojevic

Mine production systems (MPS) are characterized, more or less, by the following properties: uncertainty, subjectivity, impreciseness, polysemy, instability, indefiniteness and lack of data. From modern study aspect these MPS mathematically belong to the class of fuzzy systems. With this in mind, the usage of fuzzy sets is recommended as a methodology that treats impreciseness, indefiniteness and complexity of mine production systems in a satisfactory manner. Fuzzy modelling, discussed in this pa- per, is applied as a mathematical implement. The objective of the paper was to show production optimization in practice on the ex- ample of bauxite open pits where fuzzy linear programming (FLP) was used following the criterion per income. The variables in criterion function are linguistic variables while both variables and variable restrictions are presented by triangular fuzzy numbers (TFN). The term "satisfactory income" presented through triangle fuzzy numbers was introduced instead of "maximizing the income". sensitivity of the obtained solutions has been analysed

Jan 1, 1996

By Kevin Lofftus

The rest potentials of molybdenite electrodes are measured as a function of pH in absence and presence of flotation reagents. The chemicals used include sodium ethyl xanthate, kerosene, dextrin,sodium hydrosulfide, hydrated sodium molybdate, sodium sulfate, and hydrated sodium thiosulfate. The effect of dissolved oxygen is also noted. The obtained data are correlated with the results of micro-flotation tests obtained under similar chemical conditions.

Jan 1, 1984

By Klaus Grebe

Recent investigations by Mannesmann Research have shown that disintegration of sinter with widely varying quality levels is subject to a much more complex set of influences than was previously assumed. It was confirmed that disintegration at temperatures between 300 and 600 °C is triggered by the degradation of hematite. The specific tendency of hematite to disintegrate is, however, not constant: sinters containing the same amount of hematite can show widely differing disintegration tendencies depending upon structural homogeneity, porosity and gangue quantity. Especially sinters with heterogeneous structures transmit stress to the hematite phase and this favours disintegration. Another factor is the brittleness of the glassy silicate phase, which can be influenced even by small modifications of minor gangue constituents.

Jan 1, 1981

By R. Hogg

The sedimentation and dewatering characteristics of flocculated slurries are determined by the size and density of the flocs. Studies of the formation and growth of flocs reveal that floc size is limited by breakage of the agglomerates due to shear in the suspension. Floc density measurements indicate that there is an inverse relationship between size and density. This relationship appears to be determined primarily by the nature of the solid particles, especially the size distribution, but it appears that agitation of the suspension can lead to some densification of the flocs, in addition to breakage. It follows that both size and density can be controlled to a significant extent by regulating the physical conditions (agitation, method of flocculant addition etc.) during flocculation. The use of physical floc conditioning to control the sedimentation and dewatering (filtration) behavior of flocculated, fine-particle suspensions is evaluated in terms of its effects on floc size end density.

Jan 1, 1986

By Regina N. Tempel, Laurie S. Balistrieri, Lisa L. Stillings, Lisa A. Shevenell, Maggy F. Lengke

Dexter pit lake, within the townsite of Tuscarora, Nevada, has been in existence since 1990 and provides a natural laboratory for the study of cycles of trace elements associated with ore deposits (e.g. As, Cu, Pb, and Se). Our goal in this study is to develop and calibrate methods of geochemical modeling that may be applied to estimating the concentrations and fluxes of trace elements in pit lake systems. Our initial modeling work considers limnology, hydrology, wall rock mineralogy and geochemistry, benthic fluxes, and colloid composition. Results from our work may be useful in evaluating water quality in the arid West.

Jan 1, 2000

By Saied S. Navid, Michael A. Piepenburg, Richard F. Escandon, Robert C. Lindsay

INTRODUCTION Phase I of the Los Angeles Metro Rail Project, known as MOS-1 (Minimum Operable Segment-1), is the first phase of the 27 km± (17 mi) subway starter line. MOS-1 is currently under construction and involves approximately 6.4 km (4.4 mi) of subway, five stations, yards and shops routed through the downtown area of Los Angeles. The project will form the initial heavy rail backbone of a more extensive light and heavy rail transit system planned for the greater Los Angeles area in the future. Construction Contract A-171 is one of 4 tunnel contracts within MOS-1 and involves construction of twin tunnels running from the downtown metropolitan area west to MacArthur Park. The heavily populated and developed downtown area, potentially gassy ground conditions, and the possibility of undocumented abandoned oil wells in seismically active southern California made the design and construction of Contract A-171 a uniquely interesting project. This paper summarizes the construction history to date (December, 1988) including design geotechnical considerations, tunnel support design, as-built geologic conditions, shield tunneling performance through soft ground, and ground response. The findings presented herein may aid in the design and construction

Jan 1, 1989

The segregation process has been known for many years and applied industrially for the treatment of various refractory copper ores. The principles of the process are briefly reviewed; the process was tested in the laboratory on two copper-cobalt oxide ores from Gecamines, Shaba Province, Zaire. Various parameters of the process, such as segregation temperature, dosage of reducing and chloridizing agents and flotation conditions were inyestigated. Experimental results have shown that the segregation of copper could proceed satisfactorily at low temperature (1000° K) but that of cobalt required higher temperature and higher additions of reducing and chloridizing agents.

Jan 1, 1992

By Philip K. Chan

Batu Hijau is a new copper and gold mine located on the island of Sumbawa in the Republic of Indonesia. This paper details the design and construction of the Batu Hijau overland conveyor, one of the most challenging efforts of the project. The 1.8 m wide, 5.6 km long conveyor has a design capacity of over 10,000 mtph and carries primary crushed ore through the steep mountains of Sumbawa, which necessitated a 160 m vertical downhill section, a 75 m vertical uphill section, ten vertical curves and one horizontal curve.

Jan 1, 2000

By Y. H. C. Wang

A detailed study of carrier flotation of kaolin clay using calcite showed the major beneficiation mechanism to be enhanced aggregation between anatase and calcite under intense agitation conditions. In order to develop an understanding of this selective aggregation, surface charge characteristics of kaolinite, anatase and calcite were studied under simulated flotation conditions. Zeta potential of all these minerals tended towards a constant negative value in ole- ate solutions under certain conditions possibly due to adsorption or precipitation of oleate on them. However, whereas the zeta potential of anatase in the oleate solutions was not influenced by the agitation level, that of kaolinite was found to be strongly dependent on the agitation intensity. The effect of oleate on zeta potential of kaolinite was reduced by an increase in agitation intensity. It is suggested that oleate is much more firmly bound to the surface of the anatase and that this preferential attachment is responsible for the enhanced selective aggregation of the anatase with calcite. Agitation level plays a major role in carrier flotation since intense agitation is considered to en- hance both the chemisorption of oleate on anatase and preferential detachment of calcium oleate precipitate from the kaolinite surface, all of this producing a large difference in the surface properties of anatase and kaolinite, and hence in their tendency to aggregate with calcite.

Jan 1, 1981

By Celeste Powell

Liquid carbon dioxide can be used as a replacement for organic solvents in the extraction of anionic PGM complexes from an aqueous phase. This can be achieved only if highly carbon dioxide-soluble chelating agents are developed because conventional chelating agent-metal complexes, such as trioctylamine-gold chloride, are not soluble in liquid carbon dioxide (although trioctylamine is CO,-soluble). Our novel CO,-soluble chelating agents have a fluorinated tail and a conventional amine head group. Both the chelating agent and the chelating agent-metal complex are soluble at ambient temperature at pressures between 7-35 MPa. Equilibrium constants in the 105 range have been measured (in Freon 113, a low pressure screening liquid for carbon dioxide), indicating that these compounds will strongly bind the metal chloride. For example, 93% of Pt-chloride was extracted into Freon 113 using a 3.5:1I ratio of a double-tailed fluoroalkyl amine chelating:metal chloride. 88% recovery of Pt-chloride into liquid carbon dioxide was achieved using the same chelating agent at a 3.5:1 ratio.

Jan 1, 1999

By V. Králová

The TESCAN Integrated Mineral Analyzer (TIMA), an automated mineralogy system, enables fast and quantitative mineral analyses of rocks, ores, concentrates, tailings, leach residues or smelter products. It combines BSE and EDX analysis for identification and measurement of mineral concentrations, particle size distribution, and liberation/locking parameters. In addition, it can provide bright particle searches for PGM, gold-silver ores, and/or REE. With the newly developed Automated Loading System (AutoLoader), the TIMA has become the world?s first automated mineral analyzer which permits robust, continuous and unattended sample loading. With the AutoLoader (robotics) system, the TIMA has emerged as a powerful plant support instrument. It increases the sample throughput, minimizes manual labor and enables 24/7 operations. As such, it can be used in daily, continuous mineralogy for mine geology/ore control, concentrators, leach operations, and smelter support. It will also increase the capabilities of technical service centers for mining companies, commercial laboratories, large drilling programs or pilot test campaigns. In combination with a highly automated sample preparation lab (sizing, potting and polishing), TIMA technology can establish high-throughput and fast-turnaround automated mineralogy lab modules for mine-site production support.

Feb 23, 2014

By A. L. Mular

Se revisan brevemente varios procedimientos para el cálculo de coste de capital; no obstante, se discute en preferencia el método del factor estimado. Se proporciona una tabla de costes frente a los datos de parámetros de equipo, de donde los costes pueden ser adaptados a partir de los valores actuales de los índices de costes M&S para minería y molienda. Las ecuaciones de costes son utiles para preparar los programas de computador que realizan cálculos de coste de capital. Se ilustra la utilización del metodo del factor estimado.

Jan 1, 1982

By C. I. Wilmot

The paper presents an update of the Paradise Peak mill after the first year of operation. Process revisions, equipment modifications and additions, and personnel requirements are discussed with a comparison to original design. All areas of milling are discussed including crushing, grinding, leach/countercurrent decantation (CCD), precipitation, refinery, and heap leach.

Jan 1, 1987

By D. S. McAllister, P. M. Rice, M. E. Fowler

The Westside Light Rail Project, a major 19.3-km (12-mile) extension of Portland, Oregon's light rail system, includes 4.6 km (2.8 miles) of twin 5.8-m (19-ft) diameter running tunnels, a binocular type station which, at 80 m (260 ft) below the ground surface, will be the deepest mass transit station in North America, two 9.4-m (31-ft) diameter station access shafts, and a 5.2-m (17¬ft) diameter ventilation shaft. The tunnels are being excavated by TBM and conventional rock, soft ground, and mixed-face methods. Geologic conditions, alignment, underground opening design, excavation method selection, and payment provisions for excavation and initial ground support are discussed.

Jan 1, 1995

By P. A. Plunkert, D. E. Morse, L. McCartan, S. F. Sibley

Following the recession of 2001, restrained consumer spending, declines in domestic manufacturing and industrial output, and increased unemployment led to a lack-luster year in the domestic economy. In 2002, the U.S. real gross domestic product (GPD) grew only 2.4%. Significant production declines in the U.S. metals industry were registered by copper, lead and zinc producers. Steel producers, despite a slight improvement in shipments, continued to face strong foreign competition, higher energy costs and lower prices for their products. Homebuilding and other domestic construction sectors— major consumers of nonmetallic mineral products such as cement, brick, glass and stone — remained strong enough to help raise the output of industrial mineral materials slightly above 2001 levels. A strong U.S. dollar relative to other national currencies continued to weaken the competitive stance of U.S. metal and non-metal mineral materials companies alike against foreign producers in markets at home and abroad.

Jan 1, 2003

By Behzad Khorshidi

"The ultimate objectives of the post-tensioned strands are to connect the precast segments into a ring and provide pre-stress in the tunnel circumference. The method involves inserting the strand through the preliminary embedded duct in the precast concrete segments and then tensioning the strand by jack and fastening it. The post-tensioned strand eliminates the necessity of bolt connections between the segments and may reduce the labor cost and increase speed of lining construction. Pre-stressing of the segmental lining reduces the steel reinforcement or fiber volume in precast segments and/or thickness of the precast segments which would result in reducing the manufacturing cost of them. Pre-stressing would reduce cracking and increase water tightness, and would provide smooth intrados due to eliminated bolt joints and pockets in the tunnel lining. Pre-stressing would increase resistance to internal pressures as well. Further, this system could work very well structurally in tunnels with squeezing rock or tunnels with high seismic loadings. INTRODUCTION OF THE METHODPost-tensioning is commonly used in the construction of bridges, large buildings, nuclear power stations, and water tanks but its utilization in tunnels is still in its infancy.The precast pre-stressed concrete segmental lining can be used for shield tunnels. It provides a reinforced lining ring by the following construction stages and as shown in Figure 1:1) Segments to be assembled by TBM to complete a full ring2) Steel strand to be inserted through embedded duct (sheath) within the segments3) The strand to be tensioned by Jack after anchorage of the other end4) The strand to be fastened after reaching required tension load5) The horizontal strands (if necessary) to be installed, tensioned and fastened6) The recesses and gap between strand and duct to be filled by groutingFurther, Figure 2 shows an unbonded post-tensioning strand model; Figure 3 shows an anchor sample (Xanchor); Figure 4 shows a duct (sheath) and anchor within reinforcement; Figure 5 depicts the posttensioning of a strand by jack; and Figure 6 is an image of the Midorigaoka Trunk line tunnel in Sagamihara, Japan which was constructed using this system."

Jan 1, 2016

Geostatistics is well known as a tool for ore reserves calculations at the exploration stage. The goal of this paper is to show geoscatistics can also contribute to productivity gains, allow better selection of the mining methods and better control of the grades during production. The first two examples show how geostatistics can provide sophisticated models, using conditional simulations and the use of them for simulations or optimizations of mining processes. A third example will show how to use geostatistics for short term planning in a large polymetallic vein type mine.

Jan 1, 1983

By Lars Olaf Höglund

MiMi has been set up to be i) visionary, ii) strategic and iii) long-term. The planning as well as the executive phases involves industry, academia and authorities in close co-operation. MiMi focuses on improved, economically efficient management of mining waste, a challenge that requires combined and integrated research efforts across discipline boundaries. The MiMi programme is financed by the Swedish Foundation for Strategic Environmental Research (MISTRA) with support from the mining industry. The first programme phase covers the period 1997 - 2000, with intentions for additional phases. Planning, experience and results from the first programme period are highlighted. INTRODUCTION Most of the mining activities in Sweden takes place in the No

Jan 1, 2000