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By Harry Asche

The last 12 months has seen the construction of the first Earth Pressure Balance (EPB) TBM excavated tunnel in New Zealand on the Project Hobson sewer storage tunnel for Watercare Services Limited, with the concurrent excavation of the second EPB tunnel on the Rosedale Outfall project for North Shore City Council. Together these tunnels involve a total length of 6km and follow an 8 year pause in TBM activity in Auckland. TBM performance on these two projects is thus of significant interest as there are four major tunneling projects totaling over NZ$8B being planned for Auckland, in similar ground conditions. Auckland?s bedrock is a weak sandstone/siltstone (East Coast Bays Formation), subject to infilled paleovalleys. The geology in the region has been significantly influenced by volcanic activity; 49 volcanoes are present within 20km of the city centre. The paper describes the design and construction challenges for the projects, including TBM performance, ?sticky spoil? management, and risks associated with basalt lava flows and two paleovalleys. Watercare?s Project Hobson also saw the successful implementation of a Geotechnical Baseline Report?one of the first uses of this type of document in Australasia. Rosedale Outfall is designed for high internal water pressures with varying hydraulic flows, with the risk of exfiltration explicitly addressed.

By J. M. Dempsey, R. A. Litle

Asarco Incorporated’s Omaha, Nebraska refinery site and the City of Omaha’s downtown redevelopment projects are the perfect example of the marriage of the Brownfield and Sustainable Development strategies. Nebraska’s largest voluntary site remediation project created a focus point for redevelopment and has spurred over $1 billion in economic investment within a 1-mile radius of the site. Asarco was faced with options of very expensive and uncertain facility upgrades or a shutdown. Local leaders, Asarco, and regulators worked together to convert a controversial and complex site to a park-like redevelopment area with numerous long-term benefits to the City and the environment.

Jan 1, 2004

By S. J. Stokowski

Abstract An extensive drilling and laboratory testing program indicates that a construction aggregate resource is present within the Oligocene Sombrerito Formation limestone, southwestern Dominican Republic. The first part of the testing program included the collection, photographing and geologic logging of diamond drill cores to allow lithologic subdivision of the strata into potential quarry layers. The primary lithostratigraphic units are: I- (youngest) approximately 10 m of white, dense marine limestone II-approximately 5 m of white, interbedded dense and chalky marine limestone III-more than 2 m of tan, chalky, calcitic dolomite. Unit I is often altered by lateritic weathering and/or dolomitization. Unit II is often altered by dolomitization. The cores were individually crushed by quarry layer into coarse and fine aggregate sizes for chemical and physical analyses: specific gravity and absorption, MgSO4 soundness, sand equivalent, Atterberg limits of the minus #40 mesh fraction, and LA degradation. The unaltered portion of Unit I is suitable for all construction aggregate uses. Unit II is best suited for crushed stone base. Each of the non-weathered units decreases in coarse-aggregate yield and quality with depth and diagenetic dolomitization. Dolomitization typically causes about 5% lower yield of coarse aggregate, a sand equivalent of about 20 units below the original value an increase in absorption of about 3%, an increase in the LA of up to 13%, and a decrease in the average five-cycle MgSO4 soundness of about 17%.

Jan 1, 1991

By F. Habashi

Asbestos, an extremely useful natural resource, has been studied extensively mineralogically and for industrial application. Its extraction from ores has been greatly improved with respect to safety in the work place. In spite of that, there is a decisive effort in many countries to ban its use on the grounds that it is a toxic substance. This action resulting in drastic decrease in production and the possibility of destroying the industry. The chelation of asbestos with organic dyes seems to be a promising way to abate its toxicity. Dyeing can be done when the fibers are slurred in water at ambient conditions in the same way as textile fibers.

Jan 1, 2009

By R. Owen, T. Canty, C. Marks

The industrial vision system provides on-line 2D particle size analysis for aggregate slurries in both the overflow and underflow of hydrocyclones. This paper covers required vision system features allowing CCD cameras to function in the harsh environment of a mine milling area. The study conducted demonstrates the system’s capacity to obtain particle size distributions for controlling hydrocyclonic separators. The particle size distribution is obtained within seconds and immediately updated to allow for process adjustments. Results are then provided as a graphical computer generated display or output as a 4-20mA current loop for process control. The primary use of the vision system is in classifying particles in cyclone overflows which are often a few microns in size. Typical size information for actual mine slurry samples are presented and possible control schemes discussed.

Jan 1, 2002

By M. Akser, M. Tomas

Six Sigma is a methodology that uses a structured and disciplined approach to improve process performance (higher throughput, better recovery, lower cost, shorter cycle time, etc.). Specially trained people called “black belts” lead and manage Six Sigma projects. Black belts, with assistance from their team, ensure that projects follow the DMAIC (define, measure, analyze, implement and control) process phases. Timely completion of each project, with measurable deliverables, is key to Six Sigma’s significant financial success. Implementation of Six Sigma has been growing in recent years in a wide range of industries. The heavy mineral industry, like many other industries, could benefit from what Six Sigma has to offer. Specific Six Sigma project examples are included from DuPont’s Heavy Mineral Production Plant in Florida.

Jan 1, 2005

By G. Danko

MULTIFLUX, a new thermal, hydrologic, and airflow model and software is being developed to solve the flow of heat, moisture, and air in and around an underground opening. MULTIFLUX couples two distinct domains that are solved separately first and re-coupled as an iterative task: (1) the rockmass, and (2) the airway. The airway is solved with a lumped-parameter Computational Fluid Dynamic (CFD) module which is an embedded part of the MULTIFLUX code. The CFD model includes convection, conduction, and radiation for heat, as well as convection and diffusion for moisture transport in an air-filled opening. The CFD model also solves for the airflow field. The surrounding rockmass model may be from any analytical solution, or from a complex thermal-hydrologic numerical model such as NUFT or TOUGH2. The rockmass model is interfaced to MULTIFLUX using a novel technique called Numerical Transport Code Functionalization (NTCF). The method provides fast convergence on a personal computer platform. The paper reports the results of MULTIFLUX simulations for a mine drift, comparing calculations with a known mine climate software, CLIMSIM, and with measured data. Through this validation example, the performance of MULTIFLUX is demonstrated. The results show excellent agreement due to the use of realistic modeling assumptions and boundary conditions.

Jan 1, 2009

By E. C. Westman, F. J. Shreve

This paper presents the design and construction of a multi-channel geophone array that improves tomographic imaging capabilities in both surface and underground mines. Especially important in the design of the array is sensor placement. Three issues related to sensor placement are addressed in this paper: 1) sensor placement in long, horizontal boreholes, 2) development of simple, robust, MSHA-acceptable clamping unit, and 3) orientation of the geophones within the borehole. Improved imaging capabilities will produce energy, environmental, and economic benefits by increasing exploration accuracy and reducing operating costs.

Jan 1, 2002

By P. Rostami

It is important to study the ventilation system in order to better design and control of the working environment in deep underground mines. With increasing depth, heat, and humidity performance may be reduced and impair the attention of workers. The purpose of this paper is to apply a complex; development-end model configured in the MULTIFLUX program, developed at the University of Nevada, Reno, USA. The MULTIFLUX development-end model template has been benchmarked against measurement results from two UK coal mines in previous studies. The present study is a test of MULTIFLUX application in a metal mine. The model incorporates the simulation of the air flow field in the drift and the auxiliary air duct; simultaneous heat and humidity transport from the drift wall; heat and mass exchange between the air in the drift and the ducts; and the evaporation of process water and/or condensation of vapor as governed by the psychometric conditions. The results are compared with field data, measured at the Lucky Friday Mine (LF) in Idaho, USA, an underground mine and also shown between the results from the MULTIFLUX-based model, and those from another program, Kduct, developed at the Kyushu University in Japan.. Gao, K. Uchino & M. Inoue Fukuoka, Japan (2002)?

Jan 1, 2011

By J. L. Carr

Continuous mining machines are extensively used in the underground coal mining industry. These machines are typically remote-controlled, and severe injuries and fatalities occur every year when a miner is struck or pinned by the machine. Proximity detection systems offer a means to prevent these types of injuries and fatalities by sensing the presence of a miner and disabling machine motion. Researchers at the National Institute for Occupational Safety and Health (NIOSH)have developed the Intelligent Proximity Detection (iPD) system to provide enhanced protection while minimizing false alarms. The iPD system uses a set of pre-defined rules to determine which machine motions are safe and which would present a potential hazard, and automatically disables only the potentially hazardous motions. This system has been installed and tested on a Joy 14CM continuous mining machine at the NIOSH Office of Mine Safety and Health Research in Pittsburgh. Under laboratory conditions, the achievable accuracy and performance of the iPD system has been quantified with respect to a number of variables including position of the conveyor boom, presence of the machine?s trailing cable, and orientation of the miner-wearable component. Disclaimer: The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Reference to specific brand names does not imply endorsement by the National Institute for Occupational Safety and Health.

Feb 27, 2013

By A. Mayton, W. Porter, A. O’Brien

In 2004, management at Unimin’s Gleason, TN operation began implementing ergonomic interventions specifically targeted to reduce risk of musculoskeletal injuries (MSIs). Together with corporate and site management, Unimin identified work site hazards and began to modify work practices/equipment. Some interventions were relatively simple and were implemented immediately. Others, like improvements to a mobile shredder, were more complex but were eventually resolved through a participatory approach with employees, management, manufacturers and NIOSH. This paper discusses ergonomic interventions that were successfully implemented using a bottom-up approach to reducing the risk of injury.

Jan 1, 2007

By R. Adsero

The analysis of equipment trends in AUSIMM?s Revision of Monograph 19; Australasian Mining and Metallurgy Operating Practices (AMMOP) in the paper by Dight et al (in press) raised some interesting and in parts disturbing trends in the Open Cut Mining Industry. According to the US Bureau of Labour Statistics the US mining and petroleum industries? productivity is down by 12% since 2004 while the Australian Bureau of Statistics shows the productivity of the Australian mining industry is down by 34% since 2001. In terms of open cut equipment median output for draglines is down by 15% since 2003; electric rope shovels are down by 41% since 2003; hydraulic excavators are down by 39% since 2008; front end loaders are down by 39% since 2007 and trucks are down by 41% since 2006. Clearly the boom has not been good for the efficiency of the mines. During this same time, best practice (defined as the average of the top 10% by annual output per unit of input) has declined but not by as much as the median (eg. shovels down by 8%, excavators down by 19% and FEL?s down by 5%). This paper will build on the analysis of AMMOP to understand the differences occurring between median and best practice and identify the factors contributing to the decline in performance. As the industry enters a period of potentially lower prices for commodities and reduced margins pressure will be brought to bear on mine sites to start moving more with the equipment they have. An understanding of where efficiency has been lost will be a key component in that. The information contained in AMMOP, and the subsequent analysis of that information in papers such as this one will be crucial to reversing the decline in open cut equipment performance.

Feb 27, 2013

By E. Carvajal I

Large diesel engines provide the mining industry the substantial power and torque needed to move large amounts of material efficiently. But the stresses generated by such power and torque necessitate complex maintenance programs to ensure the utmost operating capabilities are not compromised. Of all its available sensors, the Exhaust Temperature differential between the right and left banks can provide the most valuable indicator of the overall operating condition and potential degradation of a large diesel engine. BHP Billiton Escondida Mining has implemented real-time remote monitoring, diagnostics, reporting, and tracking of Exhaust Temperature differential using Modular® technology. As a result of the processes and procedures put into place surrounding their MineCare maintenance management system, Escondida has proactively replaced over 300 injectors, resulting in an increase of 4% in Engine availability.

Jan 1, 2011

By Steve Kral

The timing was right for SME to celebrate its 50th anniversary in February as a member society of AIME. The mining industry is in the midst of a commodities boom that appears to have legs. Not only is the demand for metals, construction materials and the like increasing in developing nations, but developed nations have also seen the demand for those materials increase at impressive rates. So, in addition to networking and seeing old friends, attendees at the SME Annual Meeting and Exhibit in Denver, CO. Feb. 25-28, had several reasons to enjoy the week — a healthy industry and their society’s landmark anniversary. This annual meeting was held jointly with the Colorado Mining Association’s (CMA) 109th National Western Mining Conference.

Jan 1, 2007

Column flotation has been successfully implemented on a production scale in the Athabasca oil sands. In this application, bitumen is recovered and mineral matter is simultaneously rejected from a middling stream originating from a primary separation vessel. Exploiting the natural hydrophobicity of bitumen, the middlings streams have traditionally been processed utilizing conventional, mechanical flotation cells. Although these cells offer adequate bitumen recovery and mineral rejection rates, operating costs are high due to the required maintenance of the wetted mechanical components. In comparison, column flotation provides superior metallurgical performance while offering a lower maintenance demand. Both metallurgical and mechanical characteristics of column flotation are discussed to demonstrate the benefits of this technology for the recovery of bitumen from oil sands.

Jan 1, 2012

By S. K. Gilman

Zircon (ZrSiO4) sand production of about 1.1 Mt/a(1.2 million stpy) predominates the global supply of zirconium minerals. Baddeleyite (ZrO2) contributes less than 1 percent of supply. Zircon is almost exclusively produced as a co-product from the mining of titanium minerals, mainly from mineralized beach sands. In 2004, there were a number of new projects under consideration that were more dependent on zircon revenue than for titanium minerals. This reflected sustained higher zircon prices and forecast ongoing supply shortages in the absence of major new discoveries.

Jan 1, 2005

By P. D. Chamberlain, R. M. Nadkarni, D. J. Kinneberg

Introduction The relationship between precious metal miners and gold refiners has been uneasy over the years. Reasons for this uneasiness and lack of trust include technical factors, economics of scale, and cultural differences. Technical factors take two forms. First, concentrates, precipitates, and sponge produced at the mine site are notoriously difficult to sample. A nonrepresentative sample can be the cause of misunderstanding and distrust. Dote, however, is relatively homogeneous and can be correctly sampled and analyzed with greater reliability. Second, the technology and chemistry of fine gold and silver production is complex and quite different from dote production. Most mining companies are content not to be involved with additional processing steps. From the standpoint of process economies, it is easy to see why miners and refiners are separate groups. Mine location is dictated by the natural occurrence of ore bodies. Heavy capital investment requirements for infrastructure in remote locations usually limits companies to produce the first marketable product from a mine. Beyond that point, the economies of scale and large capital investments for refineries generally dictate that the outputs of several mines be combined to feed a single refinery. The refin¬ing process is so complex that refineries are generally built in larger cities with a skilled labor pool. Therefore, only the largest mines can afford to refine their own output. Lastly, there are cultural differences between the miner and the refiner. The miner, particularly the small gold miner, is by definition a risk taker in a risky business. Refineries, on the other hand, have historically been operated under legal or implied monopolies approved by the government. The government is interested in owning gold, either for currency reasons or because many national mints are major users of gold coins. It is not surprising, then, to find that miners may regard refiners as part of an unresponsive government bureaucracy or, worse, as "city slickers." It is easy for the two groups to distrust each other with these different backgrounds. The interface between miner and refiner does exist and affects nearly all precious metal mining companies and most refineries. This paper discusses the technical and economic aspects of the interface. It points out how both parties can improve the relationship. Technical interface Precious metals selectively dissolve to produce a pregnant solution. They are then recovered from solution by zinc precipitation (Merrill-Crowe process) or by absorption onto activated carbon. This is followed by stripping and electrowinning. At this point, the mining company must decide whether to ship precipitates (or sponge) to refiners or to produce a dote. Some factors the company must consider are the ability to sample precipitates, concentrates or sponge, security of storage, and production rates. An important factor is the incremental cost (capital and operating) of converting precipitates or sponge into dote at the mine. Generally, mines prefer to melt precipitates or sponge to dote to avoid prob¬lems associated with sampling them. There are three types of fur¬naces used by mining operators to melt precipitates to dote. The first and most widely used is a sil¬icon carbide crucible heated ex¬ternally with a gaseous liquid fuel. The crucible is easy to use and slag can be skimmed before pouring dote. This simple system is capable of handling 1 t/a (32,000 oz per year) gold. It could cost as little as $20,000. More complex systems could cost up to $200,000. The second type of furnace is the gas- or propane-fired rever¬beratory furnace. This is usually used only by large-scale opera¬tors in the silver business. Precip¬itates in reverberatory furnaces come in direct contact with the flame. The large volumes of flue gas can carry significant amounts of dust and fume that must be re¬moved from the gas before dis¬charging it to the atmosphere. In the days when the Rand re¬finery in South Africa used reverberatory furnaces, the silver leaving the furnace in the form of vapor and fume was estimated at 2.2% of the total silver charged to the furnace. The gold in the gases was about 0.03% of the gold charged. Most of this silver and gold was recovered in the exhaust gas scrubber system. These scrub¬ber systems can be more costly than the furnace itself.

Jan 10, 1986

By G. T. Adel, J. D. Miller, C. L. Lin

Washability analysis determines the maximum separation efficiency that can be achieved in the operation of coal preparation plants. Unfortunately, there are no on-line techniques for determining this most fundamental information. It now appears possible to determine coal washability on-line through the use of x-ray computed tomography (CT) analysis. This paper presents the results for the development of a CT-based, on-line coal washability analyzer. The development of appropriate hardware and software necessary to adapt a CT analyzer for use in determining coal washability is discussed. Testing of the analyzer using well-characterized coal samples is presented.

Jan 1, 2000

?Classification System Efficiency (CSE)? is a simple, powerful concept which can be used to measure and improve ball mill circuit efficiency. This paper describes six plant case studies which demonstrate the use of CSE to diagnose and/or improve grinding circuit performance, with related improvements in circuit efficiency ranging from 3 to 30 percent. The increased effective mill grinding energy is recaptured from energy that was going into over grinding, which can greatly benefit downstream mineral separation. The achievable CSE for given circuit design/operating variables is described, providing every plant metallurgist with the means to determine the potential for increasing their particular grinding circuit?s efficiency through increased CSE.

Jan 1, 2012

By R. B. Pedersen, A. Filipa, A. Marques

"Shallow-depth (<200m) high temperature submarine hydrothermal systems are not commonly observed on mid-ocean ridge settings, as most known systems are located within arc - island-arc volcanic settings, often proximal to coastal areas (meteoric waters added). In 2013, during the Centre for Geobiology’s 2013 oceanographic cruise (R/V G.O. Sars), a dredge successfully sampled massive sulfides and hydrothermally altered rocks from the top of a volcanic edifice (~144-284 m depth) located on the northern sector of the Kolbeinsey Ridge. Dredged samples include vesicular altered basalts, and matrix supported anhydrite, barite and barite-pyrite-anhydrite volcaniclastic breccias. Sulfidesulfate breccias depict complex zoning where numerous small vent orifices are distributed with large blades of marcasite that appear intergrown with barite. Native sulfur was observed in one of these small vent orifices. On a microscopic scale, numerous spherical silica-rich structures appear associated to these breccias. These rocks are evidence for the presence of a relatively high temperature (minimum 150ºC) shallow-water seafloor hydrothermal system in the Arctic mid-ocean ridge, far from mainland influence. This new discovery presents a unique opportunity to study the dynamics of fluid chemistry, metal mobility and precipitation in shallow hydrothermal systems. The remote location of this system dictates that fluid recharge will be influenced solely by seawater and magmatic fluids, In July-August 2014 we expect to survey this new field and acquire new and comprehensive data."

Sep 1, 2014