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By Paul H. Johnson

Resource Engineering and Development, Inc. is desigining and building a portable 150 to 225 tpd, flotation-cyanide leach plant with unitized, skid-mounted components. This plant design, with its portability, low capital investment, and high recovery of silver and gold from many partially oxidized ores, is well suited to treat many small, highgrade deposits, old waste dumps, and old mill tailing piles. A description is given of flotation and/or cyanide leach tests run on 18 partially oxidized, newly mined ores; waste dump materials; placer slimes; and old mill tailings.

Jan 1, 1981

By F. F. von Glehn

There is no doubt that simulated ventilation networks must be adequately verified before they can be extrapolated and used for predictive purposes. There are two general approaches as to how the verification can be established and these are summarised as follows; The first approach is to measure all individual branches with trailing hoses or barometers to get individual pressure drop and flow per branch and then calculate individual resistance factors for input into the software. The simulator is run, checking that the output makes general sense (check some sensitivities if possible). The network is now considered as verified. The pressure drop to be measured is relatively small and thus it is inherent that the measured set of individual K factors will be imprecise no matter how much care is taken in the measurements and the resultant simulations will inherit the same problem. In the second approach, the network is assembled using estimated (Atkinson) K factors (based on physical features of airway, past experience and catalogued typical K factors). Only the main primary flow rates are measured and hence the relative distribution of the primary ventilation in the main airways is determined (probably about 10 off primary air flow measurements). Main critical pressure differentials at main and booster fans and across critical doors are measured (probably about 6 off primary pressure differential measurements need to be made). The simulator is run and the computer model is used to iterate and select an updated suite of K factors so that the flow balances and pressure differentials are correctly simulated (typically only 2 or 3 iterations are all that is needed). The network is now considered as verified. The pressure differences to be measured will be substantial in absolute terms and can be measured with high precision. Also, because only primary flows are measured, these will generally be measured at higher air speed points and hence improved relative accuracy. This leads to more accurate simulation results. This paper examines the advantages and disadvantages of the two approaches. 1 Background

Jan 1, 2009

By D. S. Saxena, Jack K. Tuttle

Lack of understanding of useful applications of explosives on construction work stem primarily from the fact that explosion is commonly associated with destruction. On rock excavation and other construction works a certain quantity of explosive is harnessed to perform useful work at the source e.g. blasts to disintegrate rock. Development in rock blasting techniques, including the use of multiple-row blasting with short delay ignition, have made it impossible to excavate rocks close to or below buildings even in closely built-up areas. To permit the use of explosives on construction projects, in ways that will not damage existing structures, guidelines have been developed from careful measurements of intensity of ground vibrations. Accurate electronic instruments are now available for doing this. PLANNING AND CONTROL Blasting operations must be carefully planned and carried out to avoid discomfort to persons or damage to property. This increase in the use of rock blasting in city areas alone has led to a number of problems due to ground vibrations, air shock waves, and the psychological effect of noise. While the latter seldom if ever causes damage, it does create irritation and discomfort to persons living or working near the blasting sites. A result of this is a steady increase in the number of complaints in respect of damage to houses and other premises. Many such complaints are genuine and damage may undoubtedly be caused when incorrect blasting techniques are used.

Jan 1, 1997

By D. Bogh

Wound rotor motors are used in difficult mining applications where there is a need to start high inertia, hard starting loads while limiting inrush current They are recognized as robust and simple to control. This paper will cover the performance, specification, and important issues to be considered when applying medium voltage wound rotor motors in mining applications. Medium voltage grinding, crusher, and conveyor applications will be discussed. Specifically covered are motor efficiency, speed range, and rotor control. Crane motors often have wound rotor construction, but their load cycle and ratings are outside the scope of this paper.

Jan 1, 2011

By M. E. Kuchta

Research is currently being conducted at the Colorado School of Mines in the use of high-pressure water for scaling down loose rocks in underground mine openings. In addition to improved miner safety, the adhesion strength of shotcrete applied to rock surfaces treated with high-pressure water is also increased significantly resulting in improved overall support capabilities of the shotcrete layer. Test results show an increase in adhesion strength by a factor of four on a concrete test wall cleaned with water at 21 Mpa (3000 psi) as compared to a surface cleaned at 0.7 Mpa (100 psi).

Jan 1, 2002

Phelps Dodge Mining’s Bagdad, AZ copper facility uses a large series of cone crushers and ball mills to reduce copper ore to very fine particles. The solids are mixed with water to create a slurry. Milk of lime is added to this slurry to raise the pH. Small amounts of reagents are also added, including a frother to make bubbles, as well as a collector chemical that causes the copper minerals to stick to those bubbles. This material is pumped to a series of froth flotation cells to concentrate the copper. Air is blown into the flotation cell tank and the pulp mixture is vigorously agitated. Rising bubbles carry the copper particles over the edge of the flotation tank. The bubbles break after they flow over the edge.

Jan 1, 2005

By Greg Wieland

Deep sewer tunnels are required to meet future growth demands of the City of Austin?s down-town redevelopment. The tunnel is 18,000 ft long and varies in finished diameter from 54 inches to 96 inches. The tunnel crosses under Austin?s Town Lake three times and there are four main work shaft sites. Geology, groundwater, foundations, downtown redevelopment, and an active, healthy community put significant constraints on the design. This paper discusses a major underground project for downtown Austin and discusses the risk considerations and the opportunities the design team took toward optimizing the project design for the construction phase.

Jan 1, 2008

By A. Korchevskiy

While Russia continues to be a worldwide leader in asbestos production, the environmental and health status around Russian asbestos mines is not well known and understood, internationally. A literature review was performed to evaluate the potential impact of Russian mining operations on mesothelioma incidence rates in the Ural region where the majority of the asbestos deposits are located. Asbestos that has been mined in this region includes chrysotile, crocidolite, and anthophyllite forms. The Nicholson-Peto (1986) model was applied to published exposure data and mesothelioma mortality statistics in different cities and villages of the Ural region to estimate mesothelioma potency factors (KM) for the various associated fiber types. It was demonstrated that mesothelioma potency factors, as determined by Berman and Crump (2008), could be used to predict mesothelioma risks of non-occupationally exposed individuals in locations where either pure chrysotile, or both crocidolite and chrysotile, are mined and milled. A mesothelioma potency factor was calculated for anthophyllite that appeared to be higher than expected based on previously published studies. The highest incidence of mesothelioma was identified in a community close to a crocidolite mine. The study confirms the validity of utilizing current risk models for non-occupationally exposed populations near asbestos mining activities where asbestos exposures are relatively low and provides methods of characterizing mesothelioma risk in the former Soviet republics (FSRs).

Feb 27, 2013

By Todd Wanless

This paper addresses the challenges experienced by the designer and three government agencies during implementation of major improvements for the Turkey Creek Tunnel in Kansas City, Kansas. The tunnel serves as a vital stormwater conveyance system for upstream flood control. Major structural deficiencies were identified within the tunnel including complete loss of sidewall and invert. Without immediate attention, complete loss of the tunnel arch could lead to blockage and extensive remedial repairs under difficult conditions. Considering that tunnel flows must be maintained during construction, a phased design and construction process has been implemented to expedite stabilization of the erosion cavities followed by tunnel liner repairs.

Jan 1, 2008

The only significant iron ore deposit in Hungary could be found in Rudabánya. The mine was closed in 1986. The area of Rudabánya was always the home of heavy mining activity. In former times, mainly silver and other non -ferrous metals were excavated.

Jan 1, 2011

By N. Ahmed

The collection of hydrophobic particles in the froth phase in flotation has been studied. A continuous flotation cell was developed, in which the froth phase could be isolated from the pulp zone. Hematite particles, d80 = 87 µm, were floated in the pulp, using a conventional oleate collector, while glass spheres of similar diameter, d80 = 82 µm, were introduced in wash water added to the froth. Four samples of glass spheres, with contact angles between 0 and 82 degrees, were used. The results indicate that the efficiency of collection of the hydrophobic particles in the froth can be very high. The process is strongly influenced by the hydrophobicity of the particles and the surface area available for attachment in the froth. Recommendations for the flotation of particles in the froth phase are made, especially regarding the desirable hydrophobicity as reflected in the contact angle, the froth depth, the solids concentration in the feed to the froth, the air rate and the wash water rate.

Jan 1, 2001

By J. B. Gwiazda

S. Budirsky J.B. Gwiazda's article deals with an interesting problem that has not been studied thoroughly up to now. Gwiazda has proposed a technical solution that eliminates horizontal load imposed by the supports on the roof. That load is due to a discrepancy between the trajectories of the canopy and the overlying strata. It is true that the improved lemniscate guidance system proposed by Gwiazda could eliminate the horizontal load but, on the other hand, it would represent a higher cost of the supports, and it would complicate the already complicated mechanism of powered supports. That is why we must be convinced that the proposed improvement is actually needed. From that point of view, the following questions should be elucidated. As shown in Fig. 1, the point 0 travels along the curve a, which produces horizontal load on the roof in the direction of the coal face. As stated by Gwiazda, "such a high load is capable of destroying the roof above the support, causing rock debris to be scattered around the face." The results of our measurements carried out in coal mines of the Czechoslovak part of the Upper Silesian Coal Basin show that the convergence in the modern type of powered supports does not exceed several millimeters (not more than 10) per hour. Similar conclusions were drawn from field measurements performed in the Polish part of the Upper Silesian Coal Basin (see S. Romanowicz and H. Szopka in Proceedings, Scientific and Technical Symposium Simmex'85, Katowice, Poland, pp. 73-83). The small vertical closure of the supports also induces a small horizontal displacement of the canopy. In addition to this, the transmission of forces between the roof and the canopy is influenced by the layer of debris on it, i.e., the canopy slides without imposing a greater horizontal load on the roof. This was deduced from field measurements of Voest-Alpine F 4/4500 powered supports equipped with rams instead of the common front lemniscate links (denoted as 1 in Fig. 5). In these supports, the pressurizing of the space of piston rod (1a in Fig. 5) causes the rams to close, which induces horizontal load on the roof in a direction toward the coal face. After the setting of a support unit, the pressure in the piston rod space was found to drop, frequently to zero, because the small horizontal sliding between the canopy and the debris or inside the debris caused the horizontal reaction from the roof to fall to zero, although the debris were pressurized by vertical setting load. As a consequence, there was no horizontal load imposed by the canopy on the roof. A rise of the horizontal load was recorded only after the passage of the shearer and during lowering of the adjacent units. Thorough information on the results of the aforementioned field measurement is given in the paper, "Analysis of the performance of shield powered supports installed in a thick seam," published in Mechanizacja i automatyzacja gornictwa, 1982, No. 12, pp. 38-46. An English translation of the paper is available from the author. We have deduced from our observations that horizontal load imposed by the canopy on the roof in the direction toward the coal face is useful for roof control because it limits the displacement of the immediate roof toward the gob particularly during the rise working. We came to the conclusion that horizontal load on the roof toward the coal face should be induced on purpose. Could Mr. Gwiazda prove with the results of field measurements his contrary opinion? Has the small horizontal displacement of the canopy toward the face actually had an adverse effect on the roof? As shown in Fig. 2, during the setting of a support unit, the canopy imposes a horizontal load on the roof in the direction of the gob. In this case, I share Gwiazda's opinion that the horizontal load could have an adverse effect on the roof. Nevertheless, two important circumstances were neglected - the horizontal compliance of the supports and the interaction of adjacent units. The question of the compliance was analyzed precisely by I. Krumnacker in Gluckauf-Forschungshefte, 1984, No. 5, pp. 219-223. He found that due to the clearance between the hinge pins and the eyes of the sheild and due to the elasticity of the steel structure,

Jan 1, 1987

The trend for using larger equipment in open pit mining to achieve cost effectiveness raises the question about the optimum economic point of scale in the current world of globalization. The present paper treats this question through the prism of a new methodology of assessing the impact of the size of production equipment on the economic outcomes of coal mining ventures. The methodology incorporates a production scheduling optimization model that implements both principles of mine planning, coal quality optimization and waste deferment. The implementation of the waste deferment principle dealing with the spatial and time aspects of the mine sequence arrangement allows the adequate modeling of the optimality of production equipment scale through the use of mine investment parameters, such as, purchase and ownership costs and discounted cash flows analysis. A case study is provided to illustrate the applicability of the new methodology.

Jan 1, 2004

By J. W. Langford

A more effective method of fracturing and chipping the formation is necessary to significantly increase the productivity of blasthole drilling with a roller cone bit. The conventional rotary blasthole bit engages the formation and initiates spalls, chipping and fractures in the formation at a rate dependent on the amount of pull down force applied by the drill. The rotary speed of the drill increases the number of fractures and creates drilled chips that are removed from the hole by the air circulation. An engineering project was motivated to develop a low pressure, low impact downhole percussion hammer to provide an overstrike force to a blasthole bit, in addition to the conventional pull down force and rotary speed. The objective of the project was to utilize existing rig air packages in the range of 50-110 psig and provide an overstrike force to the bit in the range of 1100-1500 impacts per minute. Laboratory testing performed on Barre granite achieved, on average, a 40% improvement in rate of penetration. This performance has been confirmed in actual blasthole drilling in copper and iron ores mines. During the testing phase, additional unexpected benefits have also been realized.

Jan 1, 2011

By J. Davies

This paper describes the successful management and construction of the 5.18 m (17 ft) diameter, segmentally lined, North Dorchester Bay CSO storage tunnel in Boston, MA. This 3,300 m (10,830 ft) long tunnel was mined through variable soft ground with only 6 m (20 ft) of cover, using an earth pressure balance tunnel boring machine. These extensive data collected from the projects unique automated and internet accessible geotechnical and TBM monitoring system, will be examined and used to explore the relationships between geological conditions, TBM operating parameters and measured settlements. The paper will also discuss the use of screw revolutions as an indicator of muck volume.

By A. W. Popp

After forty years of exploration and development, the heavy mineral sand deposits of the Murray Basin are on the eve of substantial exploitation by Iluka Resources Limited, Southern Titanium NL and RZM/Cable/Bemax, whom plan to initiate mining and processing operations in 2005. A trial mining and processing operation was undertaken on the Wemen North strandline deposit in 2001-2003 by Murray Basin Titanium, a joint venture of Sons of Gwalia and RZM/Cable, which brought to light a number of mining and processing problems which have since been the subject of extensive studies and process development work. The mineralogy of these weathered strandline deposits is complex by industry standards due to the variety of the heavy minerals present, coatings on the mineral grains and the extensive weathering and alteration which has taken place during the past 50 million years. This paper provides an overview of the complex mineralogy that, in turn, dictates the processes that can be used to recover the valuable heavy minerals. The Murray Basin encompasses some 300,000 km2 and has been a depositional basin, often land locked, since the start of the Cenezoic Era. The economic heavy minerals include ilmenite, altered ilmenite, leucoxene of highly variable composition, rutile, and zircon. There are also other heavy minerals present such as cassiterite, chromite, and monazite in quantities that pose both problems and opportunities. The clay content and overburden thickness also play a major role in the selection of the deposits to be mined. Project Services Consultants (PSC) has undertaken the preparation of this paper as part of its ongoing participation in the mineral sands industry and in particular the project development activities in the Murray Basin region currently being undertaken by Iluka Resources. PSC has been involved with the mineral sands business for several years with senior staff having in excess of 30 years global industry experience. The company is well placed to provide a range of services to clients like Iluka Resources in the areas of project development, execution and strategic development and industry advice.

Jan 1, 2005

By M. M. Rajkovich

Just prior to the close of the century, the Federal Mine Safety and Health Review Commission issued its long-awaited decision in Berwind Natural Resources, et al v. Secretary of Labor, to usher in the new millennium. The case arose as a result of a mine explosion in Eastern Kentucky resulting in MSHA’s issuance of 225 citations, not only to the contractor, but to four affiliated entities of Berwind Corporation. While an Administrative Law Judge dismissed those citations as to three of the Berwind entities, both MSHA and the remaining Berwind entity appealed the case to the Commission. Although the Commission effectively left intact the Administrative Law Judge’s decision, it announced a new theory of liability that would apparently be applied in the future, namely the Unitary Operator Theory. This presentation will provide an in-depth look into the Berwind decision and explore the means under which MSHA might impose liability for contractor violations upon other entities in the future.

Jan 1, 2001

By Susan L. Bednarz

Recent advances in digital cameras and image processing allow photographers to produce excellent high-resolution action shots in low light and high contrast conditions commonly encountered underground. Digital photography is often used for construction and inspection documentation for underground structures. Designers, owners, and contractors benefit from quality photographs that document incremental progress and project milestones. Documentation photos serve as a lasting record of as-built conditions, are an important marketing tool, and help the owner build public support for expensive public works projects. When the project is complete, the only mementos that the participants will hold onto are the photographs.

Jan 1, 2008

To build an effective entry roof beam, a roof bolting or supporting system must be of the ability of providing a clamping force to the bolted roof strata. Currently, two roof bolting systems are widely used to serve the purpose of providing such a clamping force. They are resin and mechanical anchorage bolting systems. Both numerical modeling and double shear testing results indicate that a greater pre-installed load or pretension of a roof bolting system is very critical for effective beam building. Although it?s generally accepted that a mechanical anchorage bolting system can provide a greater pretension than a resin anchorage bolting system does (Su and Poland, 2007 and Peng, 2008), no published field data are available to support such a conclusion. This paper analyzes the results of our field tests on both roof bolting systems, explains why one roof bolting system is better than the other under a typical roof condition, and finally discusses the effective means for coal mine operators to determine the best roof bolting system for their roof conditions.

Jan 1, 2011

Syncrude Canada produces a large part of Canada’s crude oil supply. The company processes about 225,000 bbl/day. The oil produced is used for jet and automobile fuel, home heating oil, plastics and other consumer synthetics. Crude oil is produced through a process of mining, extracting and upgrading bitumen. A rich supply of bitumen is contained in the Athabasca oil sands deposit in northern Alberta. Tailings from the bitumen processing are sent to a settling basin.

Jan 1, 2000