Search Documents

By Manuel Rapiman, Ricardo Sepulveda

The feasibility study of Escondida Norte (ENorte), recommended a slope angle design for the Final Pit. But, according to the experience obtained with the slope adjacent to the West wall of ENorte, in which Compañia Minera Zaldívar (CMZ) gained in its phase 4, a slope of similar geotechnical characteristics will be exposed in the West Wall of Phase 1 (Premine) and of the Final Pit, with an interramp angle 53º and with very good stability results. In this regard, Minera Escondida Ltd. (MEL) performed a study of the slope angles for the phases mentioned and according to this delivered the results of this evaluation, the recommendations and/or the necessary conclusions in the design to ensure that the slopes are stable enough and may enable safe operational management of them.

Jan 1, 2006

Enhancing the Flotability of Gold-Bearing Ores by a Mixture of Collectors

Sep 13, 2010

By Robert J. Dompe

The objective of this program was to develop a cost effective microprocessor-based electronic image sensor system for monitoring pit slope displacement to detect and/ or predict impending slope failure in surface mines. A background study and data analysis yielded a performance specification for candidate Video Slope Monitoring Systems. A design concept was developed based on using a pair of solid state video cameras located on precision pointing assemblies. The digital images from the cameras are compared and, using electronic triangulation, slope topology is calculated. The current and past locations of operator selected features are compared to determine pit slope displacement. A proof-of-concept test was performed using a laboratory model of a pit slope. Based on the successful results of that testing it is recommended that an in-mine evaluation be performed using a full-scale prototype Video Slope Monitoring System.

Jan 1, 1982

Media Type Effect on Grinding Efficiency

Sep 13, 2010

In the estimation of reserves the known values of the variables of interest from surrounding drill holes are used to compute or estimate the unknown value of the orebody over a given region or at a given point of interest. The classical means of doing this are: 1. The Polygonal Method û where the region is divided into polygons centred on bore holes, each variable is then assumed to have constant value over each polygon. 2. Inverse distance methods, where the variable is assumed to vary linearly with the distance between the known values of the drill holes. 3. Inverse distance squared method û a quadratic variation is assumed for the variables between the bore holes.

Jan 1, 1983

By S. Suwansawat, D. J. Maconochie, C. C. Chang

This paper describes the overall delivery of the tunneling for the Mass Rapid Transit Authority of Thailand’s Chaloem Ratchamongkhon Line in Bangkok and the constraints provided by the alignment. Eight earth pressure balance tunnel boring machines were employed under two major civil works contracts to drive approximately33 kilometers of tunnel in soft saturated ground beneath the crowded streets of Bangkok. Responsibility within the contract for building damage provided an inherent control for ground movement arising form tunneling when the right of way was narrower than the influence zone. These limits affect the earth pressure balance requirements and permissible ground loss. The methods adopted to limit ground movements and deal with the various obstacles to tunneling influenced the design and operation of the machines. The challenges provided by the need to tunnel through numerous lines of piled foundations of canal bridges and overpasses crossing the alignment are described.

Jan 1, 2001

By Rob Farnfield, Yuill Gavin

The rock blasting industry continues to be under pressure to reduce the level of vibration induced by the use of explosives. In recent years much research and development has been directed to minimizing vibration levels by controlling the delay period between blast holes. The most commonly applied technique is known as Linear Superposition. This technique takes the vibration produced from a single-hole test shot and simulates the vibration that would be produced from a full-scale production blast. The simulation can be run with various delay periods and the optimum delay chosen. The success of the Linear Superposition technique depends to a great extent on having accurate delay detonators and on the single-hole test shot reliably indicating the vibration signal produced from each hole in a production blast. A quarry-based case study is given illustrating how these assumptions are not always valid. In this case the use of electronic detonators has controlled frequency but not vibration level. The paper goes on to describe a series of single-hole test shots in an U.K. limestone quarry. The vibration 2 signals recorded are examined in terms of variations in free-face provision, blast geometry, explosive properties, etc.

Jan 1, 2001

By D. Whittles, C. J. Lea, T. X. Ren, A. Kelsey

A methodology for the simulation of methane drainage combining geotechnical modelling and computational fluid dynamics (CFD) will be described. Geotechnical modelling was used to predict the development of stress and strain due to mining. The results from the geotechnical modelling were combined with empirical expressions for the variation in permeability with stress of coal measure rocks and assumptions on fracture behaviour. This allowed the permeability, as affected by mining, to be specified in CFD simulations. Flow of methane through strata, with and without methane drainage, was then simulated to examine the effects of methane drainage.

Jan 1, 2003

By T. J. McKeon

Partition curves are used to evaluate the separation performance of gravity-based concentrators. The partition curve is used to identify the nominal density cutpoint and relative sharpness of the separation. In addition, the graphical representation makes it possible to quickly identify the root cause of misplacement based on the characteristic shape of the partition curve. Partition curves have been traditionally constructed using data obtained from float-sink tests using heavy organic liquids. These toxic liquids are environmentally unfriendly and have been banned in several countries. Another method of establishing the partition curve is to introduce density tracers into the feed and plot the distribution to the lights and heavies. For heavy mineral separations, this approach is generally impractical due to the fine particle size. In addition, the partition data obtained using these existing techniques do not account for secondary factors such as particle shape that may influence the separation. In light of these problems, a methodology was developed for constructing partition curves using experimental data obtained from microscopic grain-counts. This technique, which essentially uses the different mineral species as density tracers, provides a powerful tool for evaluating heavy mineral separations. A case study is provided to demonstrate how this analytical approach can be used to assess and improve the separaton performance in an industrial upgrade plant.

Jan 1, 2005

By C A. Feebrey, R A. Duncan

The Ebor Volcano in north eastern New South Wales is an eroded example of a central-type intraplate volcanic-intrusive complex. It is of Miocene age (19 - 20 Ma) and has similarities to other central-type volcanoes in eastern Australia which may represent manifestations of sub-lithospheric hotspot activity. Thick lava flows are exposed around the Great Escarpment and are dominated by a tholeiitic basaltic suite, ranging from ol-tholeiite to qz-tholeiite to icelandite with ages of 19.2 - 19.6 Ma. On its western edge, the tholeiitic lava suite probably overlies remnants of basanite flows belonging to the Eocene (~48 Ma) Doughboy province, but elsewhere, minor alkaline basaltic lavas may be coeval with the tholeiitic suite. Several felsic bodies were emplaced into the volcano at ~19.0 - 19.2 Ma and include subalkaline and peralkaline types. The Crescent Complex is a Miocene-age, strongly differentiated mafic to felsic intrusion in basement rocks and centrally located in pre-erosion reconstructions of the Ebor Volcano. It is interpreted to be a major feeder for the tholeiitic lavas based on age and composition. Evolution of the dominant tholeiitic suite proceeded from a parental ol-tholeiite magma, through qz-tholeiite, icelandite and small volumes of felsic rocks by fractionation of plagioclase, olivine, clinopyroxene and titanomagnetite, accompanied by enrichmentof SiO2, SFeOlMgO, alkalies and HFSE.

Jan 1, 1995

By J. Duran

Mining at Newmont Mining?s Phoenix?s Mine is currently done by surface operation in the Fortitude and Bonanza pits at a combined rate of approximately 100 kt/d (110,000 stpd). A portion of the orebodies targeted by these pits was mined previously by underground mining methods, dating back to the mid-to late-1800s. Most of the underground workings (voids) are located in the west central area of the Bonanza pit. The surface operation requires excavation through voids, and there is a risk of pit floor subsidence that has to be addressed. This article presents a review of the risk mitigation measures that were implemented to reduce risks to people and equipment working in the area.

By G H. Clark

Batu Hijau is a porphyry copper-gold deposit located onSumbawa Island in the western Banda Arc of Indonesia. The deposit has been evaluated from 54 000 m of drilling in 105 diamond drill holes over a surface area of 1.2 km2 and to a depth of 1000 m below surface (412 m below sea level). A provisional plan is being evaluated to mine 642 million tonnes at an average grade of 0.61% Cu and 0.55 g/t Au (variable cut-off) from an open pit in the higher grade portion of the resource.   The deposit is associated with a calc-alkaline intrusive complex that was emplaced in a thick sequence of andesitic pyroclastic rocks. The oldest and most widespread intrusion is porphyritic to medium-grained, equigranular, quartz hornblende diorite. At Batu Hijau the western diorite contact zone was intruded by two phases of tonalite. The older tonalite is a stock increasing from 200 m diameter at surface to 500 m at sea level. It consists of quartz, plagioclase and hornblende phenocrysts set in a groundmass of similar composition. A younger tonalite intrudes the tonalite stock, quartz and plagioclase phenocrysts are more abundant and it has a finer groundmass than the older tonalite. Brecciation occurs near the older tonalite contacts but there are no breccia pipes or late-stage features such as pebbledykes or postmineralisation intrusive rocks.   Hydrothermal alteration of Old Tonalite and adjacent rocks is centred on the Old Tonalite and is zoned from a core of pervasive potassic alteration grading to an outer propylitic halo. At depth a propylitic assemblage is developed in the low grade core in the Old Tonalite. Phyllic alteration, late stage and mainly fracture controlled, overprints both potassic and inner propylytic zones. Intermediate argillic alteration overprinting is widespread, particularly on the eastern side of the hydrothermal system, where advanced argillic alteration overlies argillic alteration.   Ore grade mineralisation is cylindrical in shape, up to 800 m in diameter, and is centred on the Old Tonalite. A high grade shell (>0.75% Cu) forms an upward tapering cone in and around the Old Tonalite and reaches the surface in the centre of the deposit. Lower in the shell >l g/t Au and >2 g/t Ag accompany >1% Cu. Below 75 m above sea level mineralisation in the Old Tonalite rapidly decreases as a weakly mineralised core develops, but the limb continues to contain mineralisation to at least 412 m below sea level. Fracture and vein-controlled chalcopyrite and bornite are the dominant hypogene copper minerals and are the hosts for most of the gold mineralisation. Gold occurs free and in the lattice of the copper sulphides, and has been observed in quartz.   Weathering, especially where argillic alteration is developed, has produced a strongly leached cap, up to 147 m thick, below which is an irregular copper enriched supergene zone. Where leaching is not developed, such as over the centre of the deposit, an irregular oxide zone and a weakly developed supergene zone may be present.

Jan 1, 1995

By L. M. English, Y. J. Wang

When plotted as head vs. volume, fan curves start high and decrease in head with increasing volume while mine head curves start low and rise with increasing volume. Their intersection is the system operating point. But wait a minute: Isn't head loss a negative number, a debit? And isn't fan head an energy addition, a credit? This, as every ventilation instructor knows, is often a stumbling block to student or audience comprehension. It is possible to use the intuitively correct curves - pressure losses as negative values and energy additions as positive values-and still obtain the correct operating point: adding the two curves produces a third curve that intersects the x-axis at the operating point, the point at which the fan energy input exactly matches air circulation energy loss. Using this technique also makes it easier to account for outside influences on the system, such as natural ventilating pressure; with the standard approach it is quite easy to add or subtract such influences to the wrong curve. This approach can be extended to the graphical solution of any series/parallel circuit or ventilation network. The results are the same, and the approach is logically consistent and less confusing.

Feb 24, 1997

A Mechanistic Model of Batch Grinding in Ball Mills

Sep 13, 2010

By K. Terhaar, K. Prisbrey

The objective was to determine operating protocols for a lead and silver column flotation cleaner, being considered for installation at Sunshine Mining & Refining Co.’s Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause and effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feedgrade. The results were that xanthate, zinc sulfate, and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences were useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training, and provide a foundation for future on-line control.

Jan 1, 1999

Delivery of effective plant shutdowns is primary to the business success of mining and processing plant operations. This paper sets out a methodology that starts with understanding the business objectives of the shutdown and promotes rigorous detailed planning, effective communication, appropriate governance and effective participation of plant operations personnel. The result is delivery of business effective outcomes.

Jan 1, 2004

By A. F. Colombo

Bench-scale research was undertaken to determine if adding ammonia to cyanide leaching solutions would enhance the extraction of copper from an argillaceous Michigan copper ore. Two leaching techniques, (1) rolling using a tumbling bottle and (2) aerating using a modified Buchner funnel, and variations in pulp temperature; were employed in evaluating the effect of ammonia concentration on copper extraction. Under these experimental conditions, the extraction of copper was shown to be independent of ammonia concentration and entirely dependent on cyanide concentration.

Jan 1, 1968

By C. B. Webber, W. A. Grell

"Sherritt Gordon's Ruttan Mine is a copper-zinc operation located approximately 600 miles north-west of Winnipeg. Open pit mining began in 1973 at 10,000 Tpd., with a change over to underground mining in 1981 producing 7,500 Tpd. Ore is crushed to -3/4"" followed by rod and ball mill grinding (two ball mills in series), differential copper-zinc flotation, and dewatering. The copper and zinc concentrates are trucked 75 miles to Lynn Lake, where they are shipped by rail to the HBM&S smelter at Flin Flon.This paper describes a method used to predict the effect of grind particle size on metallurgical performance, as well as details on the copper and zinc metallurgical performance due to fine grinding in actual plant operation.Initial statistical studies on historical data (including ore source, head gr3de, grind, etc.) indicated that copper and zinc recoveries increased with fineness of grind, in the range of 50 to 65% -200 mesh.In order to extrapolate beyond 65% -200 mesh, and to develop expected nonlinear relations between grind, Cu concentrate grade, and recovery, the assays of screen fractions of copper concentrate and tailing were used to determin8 the relation between net smelter return (a function of grade and recovery) and grinding cost. The optimum economic grind would be that grind at which the net smelter return less grinding cost reached a maximum."

Jan 1, 1982

By Didier Kasongo NYEMBWE

The paper circumscribes the base metal casting industry in Southern Africa. It essentially consists in the founding of copper and zinc alloys. The challenge related to the scarcity and the unaffordable quality patterns and dies faced by the industry is discussed. New manufacturing technologies for foundry tooling called Rapid Prototyping that can possibly be used to alleviate the above mentioned challenge are then presented and their benefits assessed.

Jan 1, 2007

Organization Place Date 1917 American Electro-Chemical Society Detroit; Mich. May 2-5 American Waterworks Association Richmond, Va. May 7-11 American Institute of Electrical Engineers New York City May 18 America' Society of, Mechanical Engineers Cincinnati, Ohio May 22-25 American Iron and Steel Institute New York City May 25-26 ' Interstate Oil Mill Superintendents Association. Augusta, Ga. May (last wk.) Electric Power Club Hot Springs, Va. June 11-14 Society for the Promotion of Engineering Education .... Evansville, Ind. June 19-22. American Institute of Electrical Engineers Hot Springs, Va. June 25 American Society for Testing Materials Atlantic City, N. J. June 26-30

Jan 5, 1917