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By Flavelle IV

A survey is made of changes in the technical status of a number of western world copper extraction and refining operations over the past 20 years. Specific developments in pyro- and hydro-metallurgy and refining practices are identified together with factors in the changing environment of the industry which has influenced their adoption. Nickel extraction and refining is similarly discussed.The replacement of traditional technology by more attractive alternatives has occurred in a considerable number of operations. The develop-ment and status of new continuous smelting processes, advances in hydrometallurgy and refining innovations which emerged during the 1960s and early 1970s is discussed. The varying experience in commercial acceptance of these new technologies is noted.Finally some possible future directions are canvassed for both operators and the research and development institutions.

Jan 1, 1985

By Peter J. Nicholson

Since the reintroduction of soil mixing to the United States over 10 years ago, the work installed by soil mixing technology has grown dramatically. From an annual turnover of less than ten million dollars per year the volume of soil mixing put in place has grown to an estimated $40 million per year in the year 2000. The majority of work done to date has involved walls, either for excavation support, permanent retaining structures or hydraulic cut-off walls. The other major use for soil mixing has been for mass stabilization of soils whether for isolation of contaminants or for retaining structures. This paper will discuss the uses of and costs of typical soil mix structures. BACKGROUND Soil mixing is defined as the in-situ combining of reagents, typically cement, with native soils, the purpose being to modify or improve the ground. This history of soil mixing covers only the use of cement slurry, aggregated with soil in-situ by mechanical mixing methods only. Soil mixing by use of high-pressure hydraulic means, also known as Jet Grouting, will not be discussed. In addition this will not cover ex-situ (above ground) mixing, or mixing dry reagents with soil. Only mixing applications for building, civil and heavy construction applications will be discussed, with only passing reference made to uses of soil mixing for environmental remediation work.

Jan 1, 2001

By Daniel Su

This paper describes recent ground control challenges encountered at the longwall recovery areas of one of Bailey Mine?s two longwall faces and the proactive measures taken by CONSOL management and engineering to mitigate them. The challenges derived primarily from the following causes: (1) irregular roof coal and draw slate thickness, (2) presence of thick sandstone at the recovery area and extremely weak rocks below the sandstone, (3) close proximity to a regional anticline, (4) low shield set pressure and tip load, and (5) ineffective primary roof support that led to progressive failure of the headgate roof. The presence of the anticline contributed to extensive fracturing of the sandstone. Excessive pot-out in advance of the shields frequently occurred near mid-face due to the presence of thick draw slate and irregular roof coal near the recovery area. This, in turn, resulted in face heights that exceeded the maximum reach of the shields. Subsequently, during longwall meshing, when the advance rate slowed considerably, fractured sandstone would often break loose, causing the shields to yield, thereby reducing the height and inhibiting shearer movement. To improve the headgate and face conditions within the longwall recovery area, several actions were taken, including: (1) assessing site-specific roof geology by conducting in-mine roof coring around the recovery areas and by mapping immediate draw slate and roof coal thicknesses within surrounding entries, (2) increasing pump pressure and thus shield set pressures (3) diligently monitoring shield set pressures and longwall extraction horizon, (4) installing additional cable bolts and roof screening to prevent progressive failure of the immediate headgate roof, (5) fully-grouting supplemental cable bolts to improve headgate support stiffness, and (6) gluing the headgate roof within the recovery areas with polyurethane. As a result of these collective efforts, longwall recovery delays at Bailey Mine were reduced from 21 days in 2006 to nearly zero in 2009.

Jan 1, 2009

By Khaled Morsy

In the past two decades, high horizontal stress has been attributed to many ground control failures. Most believe that entries parallel to the high horizontal stress is most stable and least stable when perpendicular to it. Entry stability decreases when the angle between entry and horizontal stress increases. The concept of 2-D stress shadow has been proposed for selection of proper panel orientation, often with mixed results. In this paper 3-D finite element modeling was used to analyze the stress distribution at the headgate of a longwall panel subject to high horizontal stress at various angles. It was found that the directions of induced principal stresses at the longwall face and headgate are independent of the panel orientation. The induced principal stresses concentrate or relief at headgate based on the panel orientation with respect to the directions of the induced principal stresses. Accordingly, only 3-D modeling can fully account for the effects of high horizontal stress on panel orientation. The paper illustrates in details the changes in orientation and magnitude of all three principal stresses around the longwall face and T-junction area as panel orientation changes.

Jan 1, 2006

By Yifan Ding, Shemek Oginski, Patrick Finn

The Manhattan section of the New York Water Tunnel No. 3 constructed by the Schiavone/Shea/Frontier-Kemper Joint Venture is a $668 million project. The contract includes a tunnel drive of 8.85 km (29,045 feet), tunnel lining of 14.77 km (48,468 feet)and construction of nine shafts ranging in depth from 143 m (469 feet) to 169 m(555 feet). Construction methods for excavation of the shafts are presented including raise bore, ground freezing, soil excavation, blasting, slashing, muck handling, rock support and shaft final concrete lining.

Jan 1, 2007

By M. E. Alam

In the present study, 1.1 volume percent of nano size copper was incorporated into pure tin using hybrid microwave sintering assisted powder metallurgy route. Microwave sintered samples were extruded both at room temperature and at 230 °C. Microstructural characterization studies were conducted on the extruded samples to investigate the distribution characteristics of secondary phase and grain morphology. Room temperature tensile test results revealed that hot extruded Sn-Cu samples exhibited higher strengths (~ 41%, in case of 0.2% yield strength and ~ 38%, in case of ultimate tensile strength) and ductility (~ 15%) when compared to room temperature extruded samples. On the contrary, the tensile properties of pure tin remained independent of extrusion temperature. An attempt is made in this study to correlate the effect of extrusion temperature on the microstructural evolution and tensile properties of Sn-Cu solder.

Jan 1, 2009

By D Mnller, J L. Mauk

The Oblaga Cu-Au skarn deposit and porphyry prospect is located in the south-eastern edge of the Gobi Desert in western Inner Mongolia. The deposit occurs within metamorphosed middle Paleozoic volcanic, plutonic and sedimentary rocks.   Ivanhoe geologists recognise eight main rock types in the area. Calcareous sediments include conglomerate, interlayered siltstone-sandstone, and limestone. Covering the calcareous sediments is a slab of thrusted biotite granite, and above it is rhyodacitic lithic tuff which, in places, is overlain by alluvial sediments. Various plutonic rocks and related intrusion breccias have intruded these units. Monzodiorite, quartz-monzonite and monzonite tend to form thin, high-angle intrusions and the youngest andesitic intrusions are generally wider and subhorizontal.   The Oblaga Cu-Au skarn, which occurs in the calcareous sediments, shows typical prograde and retrograde mineralogy. Petrographic studies show that prograde skarn minerals have been overprinted by retrograde skarn minerals, and original host rock minerals have been texturally obliterated and completely replaced. The mineralogy of the Oblaga skarn deposit is very similar to other Cu-Au skarn deposits worldwide.   Sericitic and minor chloritic alteration occurs throughout the study area and may relate to porphyry-style mineralisation. Generally, this alteration is not intense and most rocks have retained their original texture. Geochemical analyses suggest that K-metasomatism is not widespread at Oblaga. XRD analyses suggest an upward and outward transition from sericitic to chloritic alteration.   Comparisons between Oblaga and other porphyry Cu-Au deposits worldwide show that Oblaga has very similar characteristics to deposits that have undergone sericitic alteration. However, Oblaga is special because it also has relatively intense chloritic alteration, which is uncommon in other porphyry Cu deposits described in the literature.

Jan 1, 2005

This paper reviews the development and operation of a small underground tin mine in NE Tasmania. Tin mineralisation was discovered in the Lottah area in the 1880s with early alluvial and eluvial workings leading to the development of large low grade open pit operations. Apart from short lived activities operations ceased in 1915. Intensive exploration in 1978 - 1981 outlined substantial tonnages of low grade tin mineralisation (0.2% Sn) of open pit material. An underground ore body was also located (800 000 tonnes 0.6 per cent Sn). Spectrum Resources Australia Pty Limited acquired a 98 per cent interest in the property in 1988. Mine and mill development began in early 1989 based on an underground mine utilising trackless mining using room and pillar with fill stoping. The milling circuit involves primary jaw crushing, Barmac secondary crushing to 1 mm, Mogensen and DSM screens with jigs and tables to make a wet concentrate. Final tin concentrates are produced by high tension and magnetic separation. Planned production rates are 500 t/day with a mine life of six to seven years.

Jan 1, 1990

By D. Rahal, I. Shah, B. Hines, S. Reddick

"The development of stirred milling technology has proven to be an enabling technology in fine grained metallic deposits. The increased grinding efficiency allows for the economic size reduction required to produce saleable concentrates. This improvement has opened the door to retreatment projects such as reprocessing of historic gold mine tailings. Recently a VXP2500 stirred mill was installed at Casmyn Mining Zimbabwe Turk mine to allow the reprocessing of historic mine tailings. After commissioning, an extensive joint research project between Casmyn and FLSmidth Minerals was conducted to optimize the performance of the mill. This paper outlines the challenges encountered in the optimization program and the outcomes from the joint research project.INTRODUCTION The development of stirred mills has opened up many new opportunities to recover valuable minerals from refractory ores. Stirred mills have already been reported as an enabling technology for the processing of fine grained ores in lead/zinc applications (Pease, Young and Curry, 2005). Historically, conventional ball mills were unable to economically grind material fine enough to produce the required recovery or concentrate grade. This often resulted in the loss of valuable materials to the final plant tailings. The advent of stirred milling has now provided an opportunity which has both economic and environmental benefits, the reprocessing of historic mine tailings. Many tailings stockpiles now contain economic concentrations of gold because of the ability of stirred mills to efficiently and economically grind the tailings to liberation sizes. The primary advantage of reprocessing historic tailings is very low cost processing. Recovering the tailings is usually as simple as pumping the material into the reprocessing circuit. The disadvantage of reprocessing tailings is the low feed grade and greater difficulty in recovery valuable minerals at the same size distribution. The material has already been previously processed so fresh surface area or an increase in metal exposure is required. These are both provided by regrinding the tailings material."

Jan 1, 2014

Prof. A. Ledebur, Freiberg, Saxony :* Mr. Sauveur has presented and enriched with original observations a valuable summary of the theories advanced hitherto concerning the hardening of steel; but in one particular, it seems to me, his statements call for correction. He says:

Jan 1, 1898

By A. G. Doll

"Multi-stage crushing plants, including high pressure grinding roll (HPGR) circuits, require more materials handling equipment than SAG and ball mill circuits. A temptation exists to neglect the energy consumption of materials handling when doing desktop comparisons of HPGR versus SAG milling circuits because estimation of materials handling power requirements can demand significant general arrangement drafting that is not available when performing preliminary scoping or ""desktop"" studies.The largest component of materials handling power is consumed by conveyors when lifting material between stages of crushing, meaning that a simple potential energy model can be used to evaluate conveying specific power consumption. This potential energy consumption for conveying can then be factored to provide overall materials handling specific energy consumption suitable for desktop studies of HPGR and other multi-stage crushing circuits. The technique also permits different crushing circuit flowsheets to be evaluated, at a preliminary level, by simply counting the number of times a conveyor must ""lift"" ore from ground level up to a bin or other equipment mounted up high.INTRODUCTIONTrade-off studies of multi-stage crushing plants involving high pressure grinding rolls (HPGRs) versus semi-autogenous grinding (SAG) mill circuits typically focus on the operating cost savings of crushing plants versus the capital cost savings of SAG mill plants. Very high-level (or desktop) studies of this type do not include a great deal of engineering work, meaning that the details (and costs) of ancillary systems are often not captured when doing the comparisons. The more complicated nature of the multistage crushing plants means there are more ancillary systems than a SAG mill plant, risking a skewed analysis of the operating costs, benefiting the HPGR option.One of the ancillary systems that may be overlooked is the more complicated conveying systems inherent in multi-stage crushing plants. Due to the mass of material being handled in large mining operations, these conveyors become a significant portion of the operating costs. A simple way to estimate the specific energy consumption of conveying systems without requiring engineering drawings and a site layout would allow high-level studies to capture this operating cost."

Jan 1, 2015

By W. R. Reed

The National Institute for Occupational Safety and Health (NIOSH) uses light-scattering dust monitors (nephelometers) in its research to develop dust controls to reduce respirable silica dust overexposures in miners. Recently, the model 1500-pDR, an active nephelometer, was introduced by Thermo Scientific. Testing was completed to ensure compatibility with the metal/nonmetal mine dust personal sampling unit (M/NMDPSU). Results of testing demonstrated that gravimetric concentrations measured from the 1500-pDR are comparable to the gravimetric concentrations measured using the M/NMDPSU, without need for correction, under commonly observed dust loading conditions.

Jan 1, 2012

By Alun J. Davies

This paper describes a design-build project for the construction of a tanker wharf for 150,000 dwt vessels. The tankers deliver oil from offshore oil fields to a Transshipment terminal on the south coast of Newfoundland. The project described is an expansion to a previously constructed facility, adding an additional berth. The first berth was designed conventionally as concrete structures supported on groups of independent, single piles. The second berth was awarded to Peter Kiewit Sons' Co. Ltd. based on an alternate design which utilized a "jacket" concept whereby prefabricated steel frames are placed on the seabed and serve as permanent templates and also give lateral support to the piles, thereby increasing their load capacity. This led to economies and time savings. Discussed herein is the design process and the field installation, covering the jackets, driven pipe piles, and the rock anchors.

Jan 1, 2000

By J. Rogans

This paper discusses the comparative performances of the three activated carbon adsorption circuits at the West Wits operations of Anglogold. These circuits consist of two pump-cell circuits (at Two Plant, formerly Elandsrand and at Three plant) and a conventional counter-current adsorption circuit (at Mponeng plant). The implications of the improved performance of the pump-cell plants are discussed.

Jan 1, 2002

By Christopher Mark

The first International Conference on Ground Control in Mining opened with the topic of pillar design. Two classic papers were presented, one by Bieniwski and the other by Wilson. Unfortunately, the two methods were so radically different from each other that it was nearly impossible to reconcile them. Adding to the confusion were the many other pillar strength formulas (such as the Salamon-Munro, the Holland-Gaddy, and the Obert-Duvall, just to name a few) that were also available. Little wonder that discussions of pillar design in those days often ended with anguished cries of “but which formula is the right one?” The past 25 years have seen substantial progress in the science of coal pillar design. Indeed, one testament to the improvement is the relative scarcity of papers on the topic at recent Conferences. Two factors have been largely responsible for the progress that has been made. The first has been the collection of large data bases of actual case histories of pillar performance in a variety of settings, from shallow room-and-pillar mines through deep cover longwalls. These have made possible the development of empirical design procedures that are closely linked to real world experience. The second important factor is the development of sophisticated computer models that can accurately simulate pillar behavior and roof/pillar/floor interactions. Together, these two lines of research have led to a new understanding of pillar mechanics that identifies three modes of pillar failure: • Sudden, massive collapse, accompanied by airblast, for slender pillars (width/height<4) • Squeezing, or slow, non-violent failure, for most room and pillar applications (4<w/h<10) • Entry failure or bumps for deep cover and longwall applications (w/h>10) It is particularly satisfying that the insights gained from numerical models broadly support those obtained from the empirical studies. While far less controversial than in the past, pillar design problems continue to arise. One recent example is pillar design for highwall mining. NIOSH has just released a software package, called ARMPS-HWM, which employs a number of modern pillar design concepts. Since highwall mining web pillars are long and slender, the greatest danger is that of a sudden collapse. ARMPS-HWM suggests two possible prevention strategies, one which

Rb-Sr measurements on total-rock samples of granitic rocks from the Mount Isa region have confirmed the existence of two periods of granite-forming activity. The Kalkadoon Granite, together with the Ewen Granite and possibly an older phase of the Sybella Granite, has been shown to belong to the earlier age-group at 1760 m.y.; the Wimberu Granite and a pegmatite associated with the Sybella Granite have been dated at 1540 m.y. The initial Sr ratio suggests that the Wimberu Granite may be new material of deep-seated origin.Further Rb-Sr measurements have confirmed previously-reported K-Ar results upon biotites from these rocks, whilst showing that, in this metamorphic terrain, biotites have lost varying amounts of radiogenic Sr and Ar, and therefore yield ages which are younger than the true age of the second event.

Jan 1, 1966

By F. Mendaña

The characteristics of the igneous and metamorphic bedrock, extra-hard and abrasive, of the Guadarrama Tunnels, a bi-tube project of length 28.4 km without any intermediate attack, are first commented upon. Next, a detailed discussion is given of the most relevant aspects of the performance of the four double shield type TBMs. The experience of this leads to various recommendations to be borne in mind in future designs of TBM having to work in rock of similar characteristics.

Jan 1, 2007

By James Pirie

"The major Archean gold deposits in the Red Lake greenstone belt, which have produced over 374 million grams of gold since 1930, occur near the top of the lower komatiitic to tholeiitic mafic to ultramafic metavolcanic sequence. The upper calc-alkalic mafic to felsic rocks form three discrete and separate ediftces overlymg this lower sequence.The gold deposits are classified according to their stratigraphic or lithologic associations into:1) mafic-volcanic-hosted deposits;2) felsic-intrusive-hosted deposits; and3) stratabound deposits.Group 1 and to a lesser extent Group 2 deposits occur within zones of alteration several square kilometres in extent. The nature of this pervasive alteration can be characterized by comparison of petrochemical data from the altered rocks and their fresher equivalents some distance away. The altered rocks have substantial addition of SiO2> CO2, K2O, As and Sb and subtraction of Na20, CaO, MgO and total Fe. Cr, Ni, Co and Zr appear to have been relatively immobile. Hydrothermal alteration and gold deposition probably accompanied early fumarolic activity and continued during subsequent deformation the metavolcanic sequence, with gold eventually being mobtltzed and concentrated into major vein structures to form the present orebodies. The smaller Group 2 deposits formed by emplacement of felsic intrusions into already altered, anomalously gold-bearing mafic metavolcanics, with the heat from the intrusions setting up parasitic hydrothermal systems which mobilized the gold and deposited it along with minor sulphides in fractures in the cooling intrusions."

Jan 1, 1982

By M. K. G. Whateley, W. Hatton

Paper presented at the conference: Risk assessment in the extractive industries, held in Exeter, UK, 23-24 March 1994, and first published London: IMM, 1994, preprint volume, 20pp., 31 refs. Estimates of coal tonnage on UK open cast mining sites often vary from the recoverable tonnage. This is because the estimates depend on the geological variability of the coal measures. Geological parameters, such as thickness, quality and disturbance of the seam, have a direct control upon this variance. Risk analysis techniques have been applied using commercially available software to combine each parameter's variability into a cumulative variance, resulting in a tonnage distribution. Sensitivity modelling has also been used to identify the geological parameters which have the largest influence on the variance of the simulated tonnage distribution. An understanding of the relationship between the tonnage and geological variability has helped to focus exploration more efficiently. A cost to risk relationship can now be monitored, helping management to avoid negative consequences on site

Aug 1, 1995

By K. Bartholomew

The Functional Performance Equation for ball milling circuits provides plant staff with a new means to improve circuit performance. However, successful execution of a plant processing performance improvement project, with verifiable improvements, requires a significant number of accompanying steps beyond using this equation. In order to identify and articulate all these steps, a study was undertaken with the metallurgical staff from two milling operations and process application specialists from a grinding media manufacturing company. “Task analysis” of improving plant grinding performance was carried out. This analysis identified the required steps, and ultimately yielded a “Plant Grinding Circuit Processing Performance Management/ Improvement System.

Jan 1, 2015