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By Charles Stone, Hannes Lagger, Dru Desai

The design methodology of the planned Second Avenue Subway Project (SAS) led to development of the initial support design to estimate cost and quantities in the Preliminary Engineering (PE) stage. Careful selection of the cavern design rules that recognized the impact of rock quality, rock cover, excavation geometry, and excavation sequence helped to overcome the design challenges of large, shallow caverns for the initial ground support. In the course of the design verification process prescribed by the design methodology, the design team was continuously reviewing and updating the support quantities. The design procedure includes methods using different approaches of empirical, continuum, and discontinuum analyses, which are currently advanced in the Final Engineering (FE) stage. The paper is a continuation of the RETC 2005 “Trials and Tribulations” and focuses on the procedures that led to the changes in the initial support as a result of the ongoing design development.

Jan 1, 2007

By V. Svalbonas

When the Trelleborg Divisions of Boliden Allis and Mineral Processing Systems (MPSI) merged, a unique opportunity occurred for two independent mill fabricators to compare design pro¬cedures and the research upon which they were based. Several semiautogenuous (SAG) mill analyses are compared using Boliden Allis and MPSI methods. The differences and similarities are then used in a correlation of critical stress definitions and the acceptable design and inspection criteria. Given the opportunity to compare the total philosophies and methods of several companies involved in the design and fabrication of grinding mills, it was important to first develop the comparison method and ground rules. One option was to compare analytical methods by details such as numerical techniques and accuracies. However, this option was discarded in favor of a more general approach. The question that was finally posed was in two parts. Given an identical mill requirement: • What would be the difference in the analytical design result, and to what aspect of the analytical process could this difference be attributed? • What would be the difference in approaches to obtaining the final hardware in subcontracting, both in specifying and Quality Assurance surveillance? By using this comparative approach, questions of relative conservativeness and reliability would automatically be answered.

Jan 1, 1992

By David L. Kuck

Siderophyle platinum-group metals and sane gold are a thousand times more abundant in metal and chondritic meteorites than in terrestrial or lunar rocks. Type I and II carbonaceous chondrites contain granules of the high boiling point metals W, Re, Mo, Ir and Os. Metal meteorites and the metal fractions of other chondrites contain siderophyle Pt, Pd, Ru, Rh, Os, Ir and Au. Spectra of sunlight reflected from asteroids, when compared with those of meteorites and specific minerals, provide a rough classification and guide to sources of precious platin-group metals.

Jan 1, 1982

By C. Richard Tinsley

Investment activity in the Pacific Rim of Fire has seen a phenomenal surge from epithermal gold exploration. Individual countries are attractive because of lower up-front minerals lease costs (United States, Canada), better geological prospects (Chile, Indonesia), or cheaper equities (Australia). Since the October 1987 stock market crash, large companies are shedding minority joint venture interests to focus on core businesses. Some vertical integration is evident in Japanese coal investments in the Pacific Rim. This article does not cover the aluminum industry oligopoly, which is multinational in character. Nor does it cover the many Canada to US minerals investments. It will be interesting to see if the new US-Canadian free trade treaty will reverse that investment flow. Cross-border investments The following examples should dispel any doubts about the significance of cross-border investment in the Pacific Rim. BHP, Australia's largest public company, has invested $US 4.5 billion in the JS for the following transactions 1984 $2 billion Utah Minerals 1984 $500 million Energy Resources 1985 $745 million Monsanto Oil 1987 $400 million 50.7% Hamilton Oil 1989 $378 million Pacific Resources Placer Dome, mainly through 76% owned Placer Pacific, has the following gold mine developments in hand including the date the project began, Placer Dome's ownership, project name, its location, and capital expenditures: • 1985, 53.1 %, Kidston, Queensland, $A 139 million; • 1989, 37.9%, Big Bell, Western Australia, $A135 million; • 1989, 60.6%, Misima, Papua New Guinea, $C252 million; • 1990,45.5%, Granny Smith, Western Australia, $A95 million; • 1991, 50%, La Coipa, Chile, $US276 million; and • 1991, 25.3%, Porgera, Papua New Guinea, $C1.1 billion. Australia's Western Mining Corp. (WMC), through a foray of off-market acquisitions in late 1987, acquired con¬trol of five Canadian gold companies for a $A488-million outlay ($C452 million) as follows:

Jan 1, 1990

By Thomas P. Meloy

There is much interest in the automation of entire comminution circuits, At the present technological level it is possible to automate a circuit but to date it has not been done, To successfully automate a circuit, a number of problems must be solved. Not all of them are engineering problems. The purpose of this paper is to discuss some of these problems, as certain the implications of these problems and indicate solutions to them. In this paper the term "automation" is used loosely but in the popular sense. Namely, that a plant is automated if a computer is used to control the basic flow of the materials as well as setting the critical parameters in the process. Specifically, the discussion will concern itself with the control of comminution circuits from the dumping of the ore into the primary crusher until the final interface between the comminution circuit and say, the flotation mill in the case of a sulfide ore.

Jan 1, 1965

By Elimame Elaloui, Kais Elghniji, Constantin Virlan, Aurel Pui, Chaima Ouled Amor

Separation and identification of minerals composing the Tunisian silica sands have been conducted by acid etching and hot filtration/sedimentation (HFS) without affecting the quartz component. It was found that the hot acid etching process is an effective method to separate quartz and clay minerals in the silica sand. The SEM micrographs of the silica sand show rough surface and some cracks with irregular shapes. The surface becomes clean and smooth after acid etching process. After chemical dissolution, the clay minerals were recovered by hot filtration following by sedimentation at low temperature. FT-IR, EDS maps, and secondary electron (SE) analyses of separated clay minerals reveal the presence of Fe2O3, montmorillonite, and kaolinite minerals. The LIBS analysis of clay minerals shows the presence of Al, Fe, Ca, Al, and Mg. The sequential etching process can be introduced in the purification methods as an effective way to separate quartz from clay minerals.

Jul 29, 2020

Many of the world?s largest existing mines are considering substantial step changes in production volumes, compensating for declining ore grades while trying to address increases in world demand for resources. The natural configuration of coal deposits allows for many mine development openings along the strike to access the ore body and thus increase volume. Similarly, with iron ore the nature of the deposits means that additional capacity can easily be added by opening up new mesas and providing extensions to infrastructure. On the other hand most of the non-ferrous metaliferous deposits form vertically and additional extraction volume comes from increasing depth. Underground mining from the base of the strata allows for large extraction rates, but block or panel caving operations develop at rates dictated by the geophysics of the overlying strata and the need for massive tunnelling developments to establish sufficient extraction points for high volumes. For really big mine production capacity, open cast mining still allows the easiest development of more massive mining techniques. But there remains the question of whether there are limits to how large an open cut mine can become in terms of throughput?

Feb 27, 2013

By James H. Allen

The air lift method of pumping water is discussed. A review of several large diameter hole drilling projects that used reverse circulation air lift techniques is presented. Proposals are made for reverse circulation flow rates for slow rates of bit penetration (5 fph) as well as reverse circulation flow rates for faster rates of bit penetration (10 fph). The Ingersoll- Rand air lift equations are modified for rotary drilling operations. By establishing minimum reverse circulation flow rates and utilizing the modified air lift equations, the establishment of minimum circulation equipment sizes and a more definitive requirement for improved bit body design should result.

Jan 1, 1976

By T. S. Bomar, C. J. Wood

Heavy media cyclones (HMCs) are efficient, high-tonnage devices suitable for upgrading run-of-mine coal in the 50 to 0.5 mm size range. Unfortunately, industrial HMC circuits are often not optimized due to problems such as incorrect operating pressures, poor feed distribution, excessive media contamination, mismatched components, and improper density control. To avoid these problems, operating guidelines have been provided in this article that are useful for optimizing the performance of HMC circuits. The validity of these guidelines has been assessed by means of density tracer tests carried out at several coal preparation plants.

Jan 1, 2002

By G. R. Laurer, J. W. Neton, C. Pomroy, N. Cohen, M. Eisenbud

INTRODUCTION In uranium miners, a causal relationship between exposure of the lung to high levels of alpha radiation and the consequential induction of bronchial carcinoma is now well-established (Wagoner, et al., 1965). Quantitation of this cause-effect association presents considerable difficulty, however, as the result of various confounding factors such as the contributing effects of smoking and/or arsenic exposure (Archer, Gillam, and Wagoner, 1976), normal metabolic variability and, perhaps most important of all, the absence of accurate radon/radon daughter exposure data. Estimates of cumulative lung exposures suffer from inaccuracy due to critical factors such as 1) unknown ventilation rates; 2) difficulties in obtaining representative mine air samples; 3) the variable character and magnitudes of the exposure sources; and 4) specific differences in metabolism and job histories that exist among miners. It was with considerable enthusiasm, therefore, that investigators readily embraced the idea of using skeletal burdens of the relatively longlived descendants of radon and its short-lived daughters, i.e., 210 Pb and 210Po (Archer, et al., 1968), to provide a measure of cumulative past exposure wherein the body acts as an integrating dosimeter. Early studies considered excretion rates of 210Pb and 210Po in urine, blood and hair (Sultzer and Hursh, 1954; Black, et al., 1968; Jaworowski, 1965; Bell and Gilliland, 1964) as well as their concentrations in bone samples, if and when they became available (Blanchard, Archer, and Saccomanno, 1969). These methods were ultimately complemented by in vivo, whole-body counting techniques using low background, NaI-Csl(T1) detectors (Eisenbud, et al., 1969). By this latter method, it would be possible to measure the skeletal burden of 210Pb directly, thereby avoiding the many difficulties associated with the relation between nuclide excretion rates and body burden. The rationale was simple; by knowing the skeletal burden of 210Pb it should be possible, by the judicious use of an applicable metabolic model, to estimate the cumulative lung exposure to alpha-emitting radon daughters (Fig. 1). Various models that were consequently constructed, however (Fisher, 1969), all suffered from the same limitation, i.e., the assumption that the source of 210 Pb in the skeleton and the source of lung exposure to the short-lived radon daughters were simply related and, if not, were at [ ] least not too variable (Raabe, 1970). By now, the difficulty with this assumption has been recognized and more sophisticated modeling techniques have been attempted which presumably present a more realistic picture of exposure conditions (Holtzman and Rundo, 1981). There is, nevertheless, the pessimistic view that due to the variety and variability (in time as well as in character) of sources that may exist for the origin of 210Pb in bone, it may [never] be possible to estimate past lung exposures accurately by an indirect, predictive model. For example, the origin of 210 Pb in the skeleton may include such sources as: 1) the decay of short-lived 222Rn daughters, inhaled and ingested; 2) the decay of 222Rn dissolved in body fluids and tissues; 3) directly from 210 Pb present in air, inhaled and ingested; and 4) 210Pb from non-occupational sources, e.g., food, water, smoking and endogenous 226Ra. The contribution of each of these sources may vary depending upon specific site conditions such as ventilation and mining operation. On the other hand, empirical evidence seems to indicate a trend reflecting the simplest of direct

Jan 1, 1981

By Lida Sun, Na Wu, Mengyang Huang, Xingxiang Fan, Yan Jiang, Shasha He, Kunbin Yang, Yang Cao

The separation of lead (Pb) and mercury (Hg) from copper (Cu) smelting acid sludge using the carbonization and acidleaching total hydrometallurgical process was investigated. The effects of the excess coefficient of sodium carbonate, excess coefficient of nitric acid, conversion time, conversion temperature, dissolution time, and dissolution temperature on the separation efficiency of Pb and Hg were studied. The test results indicated that when the dosage of sodium carbonate was 2.0 times the stoichiometric ratio, the conversion time was 1.5 h, the conversion temperature was 75 ℃, and the amount of nitric acid was 1.8 times the stoichiometric ratio. Additionally, the dissolution time was 1.0 h, the dissolution temperature was 60 ℃, the ratio of liquid–solid was 5:1, and the separation efficiency of Pb and Hg was 98.72%. This study demonstrated the advantages of a short, simple, and environmentally friendly process for separating Pb and Hg from Cu smelting acid sludge, providing complete separation and introducing a new technology.

May 30, 2024

Adequate ventilation of coal mine working faces is the single most important technique for controlling respirable dust and methane. Choosing the right technique presents some tough questions. Bureau research has shown that to control respirable dust you must contain the dust near the face, keeping rollback (turbulence) to a minimum. For methane the most effective approach has been to use a blowing brattice or tubing and to create turbulence and disperse the face methane, allowing it to pass over the machine and into the return. It is immediately apparent that the two approaches may counteract one another, thus complicating the decision as to which system may be best for a given situation. At present, Bureau research has developed two successful machine-mounted face ventilation systems to meet these different needs and allow deeper cutting. The fan-powered dust scrubber is designed to control dust primarily associated with blowing face ventilation systems. The spray fan controls methane on exhaust-ventilated sections.

Jan 1, 1988

By Stewart W. Daniel

Competitive pressures involving product duality, uniformity and economics are increasing the interest in and accelerating' the adoption of automation by the cement industry. The demands of this industry on instrumentation and control manufacturers for more effective and reliable control of process variables is also increasing. The trend to replacing small grinding mills with a fewer number of larger mills is lowering the investment requirement per unit of capacity both for the mills and for their automation. Cement process control systems of today are more sophisticated than the equipment installed two or three years ago, not because the process itself is more complex but because todays demands require a higher degree of control action and accuracy. Because of increasing labor costs, an important objective of an automation program is a reduction in the process labor content. This can be realized by allowing the operator free time for other duties, by increasing the number of grinding circuits one operator can supervise and by removing to. a large extent the need for the operator to make process' adjustment decisions.

Jan 1, 1965

By Jian Liu

The dissolubility of a natural sphalerite (ZnS) in the entire pH range was theoretically calculated, and its practical dissolution in an aqueous solution at different pH values in an inert environment, together with its surface properties after dissolution, was fully investigated. The results of the investigation indicate that the total concentration of Zn (CZnT) decreases significantly with the increase of pH value, while the pH value is set below 8; however, it reverses when the pH value reaches 8. Such a tendency is similar to that of the theoretical calculations, although the experimental CZnT were much higher than those of the theoretical calculations. The X-ray photoelectron spectroscopy (XPS) of the sphalerite surface after its dissolution under alkaline solution shows that a polysulfide (Sn 2-) surface layer with a binding energy (BE) value of 162.96-163.25 eV is present on the surface, and the percentage of Sn 2- increases significantly with an increase in pH value; the undissolved and dissolved sphalerites under the acidic solution have a negligible difference in S2p peaks. The surface S/Zn ratio of all dissolved sphalerites shows a marked Zn enrichment and S deficiency. An atomic force microscope (AFM) view of the sphalerite surface, after its dissolution under the alkaline solution at a pH of 12, shows that the surface is significantly different in morphology from that of the undissolved one.

May 1, 2012

By D. M. Richards, A. D. MacPhail

Highland Valley Copper currently mines two low-grade ore bodies, Lornex and Valley. The partnership was formed in 1986. As a cost reduction measure, it was decided to use an in-pit crushing and conveying system to deliver the ore from the Valley Pit to the Lornex mill 3 km (1.8 miles) away and 175 m (575 ft) above the pit rim. The system uses two gyratory crushers that feed a series of conveyors to transport up to 130 kt/d (143,000 stpd) to the main stockpiles. This paper describes the performance of the in-pit crushing system as it is currently configured, as well as its evolution to date and future planned moves.

Jan 1, 1995

The 23rd annual American Mining Hall of Fame Awards Banquet sponsored by the Mining Foundation of the Southwest will be held at the Tucson Marriott University Park Hotel, Tucson, AZ on Saturday, Dec. 3, 2005. The Mining Foundation of the Southwest is a non-profit organization. It educates the public about the mineral industries and reports outstanding accomplishments in the fields of mining and the earth sciences. This year’s inductee, guest of honor and featured speaker at the banquet will be Pierre Lassonde, president of Newmont Mining and resident of the World Gold Council. He is one of Canada’s leading gold analysts.

Jan 1, 2005

By F. Warnaars

Historically, this area produced gold and silver from many well-known vein deposits, like Tayoltita, Topia, and San Jose de Gracia. Modern exploration identified three categories of deposits: 1) low grade porphyry golds in shallow level dacite porphyries; 2) batholith-related deposits; and 3) those formed in volcanic sequences of Late Cretaceous to Late Tertiary. At least four porphyry golds have been identified, of which Metates is best known. These are formed by and within dacite porphyries, associated hydrothermal breccias and sometimes within surrounding metasediments. Their ages are from mid-Cretaceous to Early Tertiary. Precious metal deposits associated with batholiths occur as veins, contact haloes in metasediments or volcanics, skarns, tectonic breccias, hydrothermal tourmaline breccias, dacite dikes or as disseminated or stockwork deposits such as La Fortuna. Several new gold discoveries were made in older Early Tertiary Volcanic Sequences and in the younger Tertiary volcanics within prominent structures exceeding 3 to 5 km in lengths. Some of these are open-pittable but most have to be mined by underground methods.

Jan 1, 1999

By Craig Ammar

JAMIE DAVIS: Our next speaker is Craig Ammar. He's director of equipment management for Cyprus Climax Metals Company. He has, prior to this assignment, been responsible for maintenance at Bagdad Copper, Cyprus' Miami smelter, and Thompson Creek. Like Jerry, he's very shy and retiring, and doesn't have any strong opinions about maintenance. INTRODUCTION CRAIG AMMAR: The ultimate goal behind implementing a proactive equipment management process is to provide capacity assurance and ultimately increase an organization's ability to generate revenue while reducing operating costs. Targeting such lofty objectives has brought many an organization to its knees, utilizing new maintenance techniques, concepts, and technology aimed at making our lives better and more organized. The root cause of such frustration generally stems from a lack of understanding or support for the fundamentals of implementing a proactive equipment management process. There are just two types of maintenance programs, reactive and proactive. It's an established fact that you need a little of both to run an effective equipment management process, obviously more of one (proactive) than the other. Here are some telltale signs that your equipment management process is in trouble: -Maintenance is performed as a knee jerk reaction when equipment fails. -Repeated and frequent equipment failures occur, with no focus on eliminating the root cause. -Sketchy, inconsistent, unclear preventive maintenance is performed or there is no support for the preventive maintenance process. -No predictive maintenance technology process is in place, or little support for predictive maintenance exists. -Less than 50 percent of your work is generated by the maintenance group resulting from inspections.

Jan 1, 1998

By Klaus Schönert, Martin Botsch

In common high intensity magnetic separators, the magnetic particles are deposited on ferromagnetic matrices, such as expanded metals, steel balls or grooved plates, inserted into a strong magnetic field. The nonmagnetic material is flushed through the matrix chamber. Discharging the magnetic particles is only possible if the magnetic field is reduced to zero (e.g. high gradient magnetic filtration for the purifying of kaolin) or the matrix chamber is moved out of the field by a rotor (e.g. the Jones Separator). Therefore, these separators perform only in a batch or semicontinuous mode. A real continuous operation requirs transport of the deposited magnetic material to an outlet where it can leave the separation chamber inside the field. One possibility for accomplishing such separation and transport is through the use of a rotating induction body with a certain shape, such as a spiral.

Jan 1, 1995

By H. Schubert

The flotation of sylvite and also some accessory minerals is performed in brines containing very high electrolyte concentrations. Under these circumstances the mechanims of collector adsorption exhibit some characteristics which will be discussed by significant examples: - flotation separation of sylvite and halite with n-alkylammonium salts and n-alkyl sulfates - flotation separation of kieserite and anhydrite with acylamino carboxylic acids - flotation of halite by collectors which are adsorbed by hydrogen bond formation.

Jan 1, 1988