Search Documents

"This paper challenges the traditional notion that mine planners need to plan production so as to incur the lowest mining cost. For a given mine configuration, a mine that increases its mining rate will incur increased mining costs. In an environment in which operations are fixated on cost reduction, a proposal that increases costs will not be readily accepted. Such a proposal requires financial justification—the increase in costs might be recuperated by the additional production. This paper evaluates the net present value (NPV) across a range of copper prices for two underground orebodies located at different depths, using a production rate of 300 kt per quarter and a scenario that introduces additional equipment and costs for 450 kt per quarter. The evaluation was based on the changes of NPV for the orebody located at a shallow depth compared with the orebody at a greater depth. Discrete event simulation combined with mixed integer programming was used for analysis. Unlike traditional sensitivity analysis, this study re-optimizes the mine plan for each commodity price at each production rate. The results show that, for the low mining rate at the final copper price, an NPV of A$1530.64 million is achieved, whereas an NPV of A$1537.59 million is achieved at a higher mining rate. Even though pushing mining rates beyond traditional limits may increase mining costs, this option may be beneficial at certain commodity prices, particularly when prices are elevated. IntroductionA traditional notion among mine planners is that mining rates should be planned in such a way as to reduce production costs. This concept generally relates to the mining rate that results in the highest machine utilization for the selected equipment. Although an existing mine may consider increasing its mining rate by adding equipment to a given mine configuration, this typically increases mining costs. In an environment in which operations are fixated on cost reduction, a proposal to increase costs may be very difficult to argue for. The value of the mine plan is well recognized as varying with the mining rate for a given orebody (Smith, 1997)"

Jan 1, 2017

By Frank J. Klima

Explosives are probably the most widely used and most mysterious large scale' mining tools of modern times. The post black powder explosives were primarily nitroglycerin-based straight dynamites, ammonia dynamites, blasting gelatin, gelatin dynamites, ammonia gelatin dynamites, etc. Of these, the strongest and highest velocity explosive used in industrial operations is blasting gelatin, which is nitroglycerin colloided with a nitrocellulose of medium nitrogen content in proportions which give the product a plastic character, or about 93 to 7. Many variations of the basic groups above were developed by substituting ammonium nitrate and/or sodium nitrate for some of the nitroglycerin. The nitrates being insensitive to caps required a certain percentage of nitroglycerin to sustain detonation in smaller quantities or diameters. Paralleling the development of industrial dynamites was the development of more expensive, highly sophisticated explosives which were developed for specific military purposes. Such explosives as Amatol, RDX, Composition A, Composition B, Composition C, Lead Azide, PETN (Pentaerythritol Tetranitrate), Tetryl, Pentolite, TNT, etc., were primarily military explosives. Amatol, which is a cast mixture of ammonium nitrate and TNT (Trinitrotoluene), and identified by percentage of AN versus TNT as 50-50 Amatol, 80-20 Amatol, etc., was a favorite World War I explosive. RDX, or Cyclonite, was widely used in World War II. Also used during WW II were compositions A. B, and C, which were mixtures of RDX (Cyclotrimethylene trinitramine), TNT, and other nitrotoluenes. These high explosives, along with nitroglycerine, are exact chemical compositions or mixtures of exact chemical compositions which are individually explosive, or in other words, individually capable of explosive chemical decomposition when properly initiated. These chemical decompositions result in the formation of simpler compounds and/or large quantities of common combustion gases, and large amounts of energy in the form of heat. Of these, the most powerful is RDX which, based on the ballistic mortor test, is 1.5 times as powerful as TNT. Chemically, the decomposition of TNT releases about as much energy as the reaction of ammonium nitrate and fuel oil.

Jan 1, 1967

By David Mast, Irwan Halim, Brian Hagan, Kaveh Talebi, Jason Edberg, Amanda Foote

On June 14, 2023 Jay Dee Contractors’ Tunnel Boring Machine (TBM) “Phoenix” holed through and completed mining the second drive of the I-75 Segment 3 Storage and Drainage Tunnel. Completion of the tunnel came only after overcoming several challenges, including a groundwater intrusion event which deposited thousands of cubic yards of wet ground material into the tunnel. This paper will discuss the events which delayed completion of the tunnel by over nine months, the risk management and construction approaches assumed by the Design-Build team during bid, several challenges faced by Design-Build teams when building stormwater resilience tunnels using traditional Department of Transportation standards, and recommendations for improving risk allocation and proposal documents for future similar Design-Build tunnel projects.

Jun 23, 2024

By X S. Li

The modern mechanical excavation machines have enough power for cutting hard rock. The ‘bottle neck’ which limits the use of machines for hard rock excavation is ‘cutting tool’. To cut hard and abrasive rock, CSIRO has been developing Super Material Abrasive Resistant Tools (SMART*CUT). SMART*CUT technology replaces the tungsten carbide (WC) tip of conventional pick with thermally stable diamond composite (TSDC) and attaches the TSDC tip to steel tool body with CSIRO worldwide patented bonding technology. This paper introduces the key features of SMART*CUT, compares its performance with conventional WC tipped tools, discusses the challenges faced by SMART*CUT and the further developments needed for successful application of SMART*CUT to mining industries.

Nov 22, 2011

By Toshio Suzuki, Machiko Ode, Won Tae Kim, Seong Gyoon Kim

"The Ostwald ripening and growth and coarsening of the secondary dendrite arm are studied using a phase-field model. The phase-field parameters are obtained at a thin interface limit proposed by Kim et al. In Ostwald ripening analysis, the difference of the concentration due ·to· the curvature effect is shown. The third power of the average particle radius Rav is proportional to time and the ripening constant shows a good agreement with the value by Deppers et al. The particle radii distribution shows the transition behavior to attain a self-similar stationary shape. The growth and coarsening behavior of the secondary dendrite arm is also analyzed using a phase-field model. The estimated arm spacing and its dependence on time are in good agreements with experimental data.IntroductionThe ripening or coarsening process controls the microstructure during the late stage of solidification. The ripening phenomena are recognized firstly by the Ostwald [1]. The first quantitative analysis for the Ostwald ripening in the limit of vanishing solid fraction was provided by Lifshitz, Slyozov and Wagner (LSW) [2,3]. In their study, that the mean radius grows proportional to the cubic root of time and the size distribution of precipitations shows a ""self-similar"" shape are shown. Most of the studies for the Ostwald ripening confirm or predict these two general rules above. In case of finite solid fraction, the general rules are observed but the ripening constant is larger and the self-similar shape is wider than the LSW prediction respectively [4-6]. To analyze· the high solid fraction system, the theories that consider the solute field correlation are proposed [4,7-8]. In the theory, however, since the particle is treated as the point, the effect of the concentration field deviation from the monopole field should be taken into account. Recently the numerical simulation, in which not only diffusive transportation of solute but also convection effect is considered, has been done using a phase-field model [9]."

Jan 1, 2000

By Valery M. Paretsky

The effect of the degree of nickel oxide reduction and the reaction gas composition on the furnace productivity has been estimated by computations and the established relationship is in good agreement with the practical data obtained in the process of electric smelting at the Severonickel smelter. An increase in the reduction degree within a range of =0.65 - 0.9 results in an increase in the furnace productivity by 19% to 37% and in a decrease in the unit electric power requirement by 16% to 27% depending on the reaction gas composition. The agreement between the computed and practical data has confirmed that the decisive factor for the process of treatment of reduced nickel oxide in an electric-arc furnace under the given conditions is the specific heat absorption, which is dependent on the nickel oxide reduction degree and the reaction gas composition.

Jan 1, 2005

By N. Hosking, M. Nichols

Aluminum alloys are increasingly used for automotive body construction but are susceptible to filiform corrosion or paint blistering in service. Filiform corrosion resistance of two 6000-series aluminum alloys was investigated in this work. Test panels were produced with full automotive coating layers and scribed parallel and perpendicular to the rolling direction. The corrosion exposure comprised an inoculation step with acidified salt solution followed by a 6-week exposure period at 95% relative humidity and either 25°C or 70°C. Greatest corrosion activity was measured on the alloy with higher copper content, AA6111. Higher temperature exposure led to greatly enhanced corrosion activity for AA6111 compared to the lower temperature exposure. The 70°C exposure also led to greater mean corrosion-affected area measurements for the low copper aluminum alloy, AA6022, but the effect was not as stark as that observed for AA6111. Rolling direction affected the propagation direction, and possibly mechanism, of the corrosion effects. Cross-sectional analysis revealed dense corrosion products within the filament, comprising mostly aluminum and oxygen but with traces of chloride and sulphate. Development of varying filament and blister types on a single test panel and the progression of corrosion underneath a filament into the substrate indicate that several corrosion mechanisms can develop on the test panel, testament to the complexity of the corroding surface developed on an aluminum automotive body panel.

Jan 1, 2015

By David C. Grant

A laboratory technique for simulating in-situ uranium mining was developed and used to determine the effects of leaching variables on permeability, uranium recovery, leach solution interaction with the ore-aquifer environment, and post-leach chemical leakage. In particular, ammonium bicarbonate, the commonly-used leach solution, was examined in great detail. Agitation leach tests were conducted to examine the effect on ammonium sorption and desorption of clay content, solution and clay ammonium levels, pH, and the type and concentration of other anions and cations in solution. Initial column tests were performed to determine the degree of ore-aquifer interaction that could be expected for various leach solutions; sulfuric acid, and ammonium, sodium, and potassium bi-carbonates. Subsequent tests examined various methods to restore the ores by lowering the post-leach chemical leakage. The restoration tests examined the use of reducing agents (e.g., ammonium bisulfite, sodium bisulfite; and sodium sulfite), ore blocking and stabilizing agents (e.g., sodium silicate, aluminum chloride, and magnesium-calcium salt).and ammonium displacement agents (e.g., aluminum chloride and lanthanum chloride-sulfate)

Jan 1, 1980

By Christian Heili

In 1991 the Government of the Republic of Zambia passed legislation providing for the privatisation of Zambia Consolidated Copper Mines Limited (ZCCM). The newly formed Mining Companies, established after nearly a decade of difficult and protracted negotiations on such matters as, cash at close; retained percentage interest by ZCCM; equity investment; future investment commitment and tax concessions, were faced with great internal challenges and a harsh external environment. There was a convergence of a number of negative forces that had and will continue to have an impact on the mining environment in Zambia. The most crucial of these being, the competitive pressures of the global economy, fluctuating copper price and the prevailing HIV/AIDS pandemic. In the short period after privatisation, the Industry has seen the collapse of Binani Industries (Luanshya Mine), the withdrawal of Anglo America Corporation from Konkola Copper Mines Plc and the disposal of Chambishi Cobalt and Acid Plants by Anglovaal Mining Ltd. The objective of this paper is to provide a theoretical and practically researched foundation, which may be used to assist Zambian Mining Companies in making informed decisions on the issue of Strategic Outsourcing and the degree to which this may support the successful and sustainable growth of the Zambian Copper Mining Industry. If judiciously implemented, Strategic Outsourcing has the potential to generate a practical business valuation and process to assist Mine Management in the achievement of their business goals and consequently the return on investment to their Shareholders.

Jan 1, 2005

By N. C. Clarke, T. Wu, M. le Page, K. J. Henley

In 1994, Gold Mines of Australia acquired the rights to the historic Mt. Lyell copper mine, and commenced a feasibility study into expanding production. The ore was shown in laboratory tests to be amenable to single-stage, fully autogenous grinding (FAG) of underground primary crushed ore, and this route offered the maximum cost savings. Flotation performance was expected to be enhanced. However, batch flotation tests done on pilot-scale autogenously ground ore showed an unexplainable recovery loss of between 1% and 3% Cu. A second pilot plant trial was set up, with the ground product feeding banks of continuous flotation cells. Single-stage FAG, FAG/pebble and FAG/ball circuits were tested. Results confirmed a loss of about 3% recovery with single-stage FAG milling. The FAG/ball circuit eliminated the loss. Analyses showed that autogenous milling probably produced more chalcopyrite/pyrite composites and that recovery of these composites was lower than with ball milling. In size fractions below about 53 microns, where chalcopyrite is well liberated, copper recovery was less affected by milling method and flotation selectivity. It was concluded that for the Mt. Lyell situation, a FAG/ball circuit was preferable to single-stage FAG.

Jan 1, 2002

By A. Haldar

The major problem encountered in the casting of hypereutectic Al-Si alloys is the stoppage of flow below the rigidity level of solid fraction. In this study, the flow stoppage mechanism was studied using three Al-Si alloys with 14%, 18% and 22% silicon. The horizontal foam patterns used were 12.50 mm (0.50 inch) wide with two section thicknesses 12.50 mm (0.50 inch) and 6.25 mm (0.25 inch) with a common sprue. The primary silicon distribution along the length of the casting was studied to determine the mechanism of flow stoppage. It was found that the surface of the flow tip of Al-14%Si alloy was smooth with a few undulations. As the silicon level increased, undulations at the flow tip increased. The number and size of undulations were maximum for the Al-22%Si alloy. Microstructural analysis using optical image analyzer revealed that the flow tip consisted mainly of eutectic silicon in the aluminum matrix and a few primary silicon crystals (PSC). The PSC were in the interlocked condition few centimeters behind the flow tip. It was also found that the gap between the flow tip and the PSC concentrated area increased with an increase in silicon level. Phase characterization was done with SEM-EDX to identify the precipitating phases.

Jan 1, 2007

By François Tremblay

It is well known that removal of organic material such ,as Jacquer, paint, plastic prior to melting improves aluminum recovery. In addition to being an important economically, decoating of aluminum scrap has a positive impact on the environment, through better control of gaseous emissions. Most of the existing thermal decoaters for aluminum have been designed to operate with scrap containing a level of organic material lower than 10%. The main field of their present application is for recycling of used aluminum can, where levels of organic material are lower than 4%. Alcan has recently developed a new thermal decoating system in order to extend applications of this process to a much wider variety of aluminum scrap. The new decoater efficiently processes aluminum scrap with a level of organic material up to 50%. This new technology features the use of fluidized bed technology to thermally control the process. This innovative feature improves both performance and control over conventional delacquering systems based on hot air convection. This paper describes the basic principles of the technology and the design of the? first industrial unit commissioned by the Alcan Recycling plant in Shelbyville (TN) at the beginning of 1994. Typical applications and operating advantages are discussed.

Jan 1, 1995

By C. C. Merrill

Studies were made to determine the amenability of yttrium to fused-salt electrorefining in a controlled atmosphere. Tests were conducted in a LiCl- YCl3 electrolyte system at 710° C. The major variables studied were the YCl3 content of the electrolyte, from l.7 to 13.4 mol percent, and the initial cathode current density, from 410 to 1,630 amperes per square foot. Vacuum distillation was employed to remove salt from the deposited metal. Metallic impurities, except for lithium, could be reduced to near or below their lower analytical limits, ranging from 10 ppm for Cu to 300 ppm for Ta; reduction of oxygen content, however, was accomplished only in metal produced from electrolytes with 5.4 mol percent YCl3 or less. Initial cathode current density had little effect on the purity of the product.

Jan 1, 1967

To improve the reliability of the Bureau developed bore-hole gage now widely used to determine the absolute state of stress in rock. Approach Use the knowledge gained by extensive field tests to design a more rugged and reliable Instrument using lighter and stronger materials. How It Works The original gage consisted of a stainless steel cylinder 1-3/8 Inches In diameter and 10-1/2 inches long. The new gage is made from titanium. This lighter material reduces the weight of the gage by 43 percent, which enhances the gage placement and depth of overcoring in vertical up? holes. For added strength, the titanium case and placement end are now threaded to the gage body instead of using screw fasteners. Three pairs of strain gaged transducers are positioned to measure the diametral deformation of a 1-1/2 diameter borehole at 60-degree intervals around the Inner surface of the borehole. Each transducer consists of a beryllium copper cantilever with a strain gage cemented on each side. These transducers are secured Into the gage body by a tapered shank for minimal creep. The transducers opposite each other are wired together to form a 4-arm external bridge circuit. A pair of transducers is referred to as a component. Any deformation of the borehole, which occurs during overcoring, is detected by pistons which translate the motion to the components. Each

Jan 1, 1982

By J. R. Shultz, R. J. Lambert

One of the present trends in the mining industry is the increased use of mining contractors. In the past, many project owners have utilized mining contractors for topsoil stripping or overburden removal, usually on a short-term or periodic basis. In recent years, mining contractors have not only removed the overburden, but mined the product as well. Why is this change occurring? A prevalent trend in the mining industry appears to be the outsourcing of non-core and non-strategic functions, allowing producers to focus more on areas of technical expertise where higher incremental value is added—that is the processing, refining, and marketing of the product. As capital allocation becomes more critical, this trend is likely to continue.

Jan 1, 2002

By C. -K. Fang

"Aging effect on the wear resistance of alumina particulate-reinforced 6061 aluminum matrix composites with a block-on-ring wear tester has been investigated. Specimens with various Al2O3 volume fractions of 0%, 10% and 20% were employed in this work. Experimental results indicated that over-aged monolithic 6061 Al had the best wear resistance, as compared with under-aged and peak-aged conditions. For the composite containing 10% Al2O3, over-aging and peak-aging resulted in similar wear resistance, which was higher than that for underaging conditions. For the composite containing a high volume fraction (20%) of Al2O3, the wear resistance reduced with the increase in aging time. Although longer aging time was favourable to the wear resistance of monolithic 6061 Al, it was detrimental to that for the Al2O3/6061 Al composite with high volume fraction of particles. IntroductionMetal-matrix composites (MMCs) have received attention in many engineering applications because of the demands for high specific strength (strength-to-weight ratio) and specific stiffness, good high temperature capabilities and wear resistance. The manufacturing processes of fiber-, whisker-, and particulate-reinforced MMCs have been well developed (Hosking et al., 1982). Because of the reduction in fabrication cost, the applications of MMCs have been widely extended to light weight-bearing sleeves, calipers, automobile parts (brake rotors, drive shafts, connecting rods, piston rings, and cylinder liners), sporting goods, aerospace components, tanks (wheels, speed brakes, and track shoes) and other industrial applications. Among the three types of metal matrix composites, particulate-reinforced MMCs are promising because of their homogeneous and isotropic material properties and low cost. Additionally, they can be formed using conventional metal processing techniques."

Jan 1, 2003

By Peter Shuttleworth, Chris Fesq, Eddie Woods

Precast concrete segmental linings for tunnels have traditionally been designed with conventional steel bar reinforcement. In many cases, this has been satisfactory in service, but in others, major problems have occurred with the durability of the linings. Commonly this has resulted from corrosion of the reinforcement, mainly from chloridesin ground water, causing spalling of the concrete and leading to very expensive and disruptive repair programs. This paper discusses the relative merits of designing tunnel linings with steel fiber reinforcement to provide long-term durability, improved impact resistance and toughness for greater load capacity across joints, enhanced robustness during transportation and erection, plus improved fire resistance with the addition of polypropylene fibers. Guidance is also given in the selection of the correct fiber type, mix design and testing methods to establish the optimum dosage required and production techniques to ensure even distribution and compaction.

Jan 1, 2005

By Zvonimir Ester

The course of motorway tunnel under construction was set only 2 m away from the main motorway. The thickness of the tunnel overburden rock was 9 m. During the tunnel construction the traffic on the motorway was not supposed to be interrupted. The tunneling was carried out by NATM with classical drilling of blastholes and by blasting.

Jan 1, 1998

By M C. Goode

The use of electrical or electronic safety systems to protect personnel, and the engineering tasks associated with the design, manufacture and maintenance of these systems are referred to using the term ‘functional safety’. In the past ten years, the use of such systems has transitioned from its traditional base, in oil and gas major hazard facilities, to being a part of most large mining and materials handling projects. In particular, functional safety is rapidly becoming a significant component of Australian iron ore projects, typically in the form of emergency stops, remote isolation, drive through interlock, robot cell entry or mobile machine anti-collision systems. While these types of systems have been in use in iron ore for a long time, functional safety standards (eg AS61508, AS62061, AS4024.1503) require more rigourous demonstration of the level of risk reduction provided by the systems.The early engineering project development phases require a number of key decisions to be made around functional safety implementation. The decisions made at this point in a project will go on to dictate the required types of risk assessment and analysis, equipment selection, sizing of substations, and training and maintenance requirements for owners. For project teams that are unfamiliar with functional safety, or inexperienced in its application, an incorrect decision or failure to understand the requirements of the chosen standard can lead to a failure to meet contract requirements, as well as major cost and schedule overruns.This paper examines the implications of functional safety on early engineering studies, focusing on the following questions: How does a designer or company determine what standard is best suited to their project? What key aspects of functional safety design need to be considered during project development? And finally, how can the impact of functional safety to the project be minimised?CITATION:Goode, M C, 2017. Functional safety impacts on study stages of major projects, in Proceedings Iron Ore 2017, pp 347–352 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Martin B. Hudson, Andrew K. Cho, Rolff B. Knobel, Les R. Chernauskas, Jonathan L. Ernst

ABSTRACT The Bruce Museum, located in Greenwich, Connecticut, is home to an extensive display of art and natural history exhibitions. A large addition was designed to be constructed adjacent to the museum requiring new spread footings to be installed up to 16.5 feet below the existing foundations. The soil conditions at the site consist of highly variable sand and gravel overlying weathered rock and sound bedrock. The Contract Documents called for traditional foundation underpinning. Traditional underpinning techniques, however, presented two major challenges on this Project; (1) deep underpinning pits would be required involving multiple levels and staging with tieback support and (2) the highly variable soil and bedrock composition and elevations presented uncertainty in the design and construction of the pits. In lieu of traditional underpinning, Geosciences Testing and Research, Inc. (GTR) proposed an “active” soil nail underpinning system. A major reason that the soil nail underpinning option was feasible, related to the fact that the soil nails and facing could be installed slightly in front of the existing footings rather than directly underneath the existing footings. The soil nail wall design involved one to four rows of soil nails with nail positions and wall depth able to be adjusted “on the fly” as excavation progressed depending on the field conditions encountered. To create the “active system,” the soil nails were pre-loaded to mitigate wall deformations that would be associated with a standard passive soil nail wall design. To evaluate the performance of the active soil nail wall and confirm design assumptions, an extensive automated monitoring, on-site testing and inspection program was proposed and executed by GTR to monitor deformations of the wall and the museum in real-time, evaluate and confirm bedrock and soil bond stresses and ensure that each soil nail was pre-loaded and locked off. Careful analysis, planning, and use of the observational method illustrates the importance of collaboration between design and construction personnel and applying engineering judgement throughout construction. The use of the observational method includes the potential for modifying design based on conditions observed. This paper presents a unique case study of the “active” soil nail underpinning system to support and protect sensitive structures, close collaboration between design and construction facilitated by real-time deformation monitoring, and its successful application as a safe and cost-effective alternative to traditional underpinning.

Oct 1, 2022