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By James D. Reilly

The time-worn adage "an ounce of prevention is worth a pound of cure" was never more applicable than when used in reference to coal mine safety. Many individuals have dedicated many hours to developing effective accident prevention programs, and much has been accomplished. Each production escalation, however, creates new hazards and safety problems which need special study and research. It is a never ending cyle. To study the progress of coal-mine safety is to raise memories of many individuals who have been dedicated to removing the hazards that have developed with increased productivity and deeper penetration into the earth for coal. Some vivid examples of this dedication are the works of the men who pioneered the use of the safety lamp and the use of rock dust in mining.

Jan 1, 1968

By E. A. Metz

Work related pulmonary diseases are in the top TEN causes of occupational disability and death in the United States. Likewise, it also ranks high inmost of the other industrial countries. It is difficult to know the true occurrence of occupational lung disease because of poor documentation. This is especially true when one examines workers’ compensation claims. Most frequently, silica and asbestos are paramount in our discussion of work related pulmonary disease. Little consideration is given to other “dust-related” diseases, irritant reactions, reactive airway responses, and hypersensitivity reactions. The major classification of occupational lung diseases will be discussed. This includes both acute and chronic disease that arises in the work place, especially, the mining industry. It’s more important to make an accurate evaluation and diagnosis for the prevention of disease among other workers.

Jan 1, 2000

By T. E. Bernard

Occupying a refuge alternative (RA) is an accepted practice in mine fires and explosions when escape is not feasible. MSHA has promulgated a final rule on refuge alternatives that includes a recognition that thermal environment is an important consideration. To this end, an environmental index was specified. The question remains about how to test a refuge shelter to demonstrate that it meets the final rule. The analysis followed five activities: A. Provide an estimate of heat generated by an individual refuge alternative occupant; B. Evaluate the Steadman Apparent Temperature criterion of 95°F; C. Discuss simulations based on body temperature or skin temperature limits; D. Suggest method of simulating human heat generation during refuge occupancy; and E. Suggest alternative methodologies/criteria for evaluating heat and humidity survivability inside a refuge alternative.

Feb 27, 2013

By Jochen Belz, Allan Henneker, Nod Clarke-Hackston

For the construction of tunnels and other underground structures, extraction of the exact amount of material is of paramount importance both economically and for engineering purposes. In the Sequential Support Method (NATM) immediate (sequential)and smooth support by means of shotcrete, steel arches, lattice girders and rockbolts, either singly or in combination are used; cutting of the precise (albeit sometimes of complex geometry) profile is an integral part of the method. In order to save unnecessary excavation and provide better information to the machine operator, VMT GmbH has developed a system to support precise excavation of the tunnel profile when using road headers or other partial face cutting machines. This paper outlines the principles of this system with examples from Australia, Ger-many, Sweden and Spain and will cite examples of typical savings achieved.

Jan 1, 2007

By F. Block, K. Kohli

Outcrop barrier pillars serve to keep mine personnel and the public safe from sudden uncontrolled flows of water accumulated in active and abandoned underground mine workings. When an outcrop barrier fails, the result is an outbreak of water to the surface and is termed as blowout. Mine blowouts are associated with above-drainage mines and can occur through the coal outcrop and sealed portals. A blowout is often catastrophic, a threat to the people on the surface living or working in the path of a potentially large flood. In addition, blowouts can destroy homes, cause landslides and severe erosion and release pollution and acid mine drainage. This paper provides guidance on the planning, design, evaluation and inspection of barriers to address the problem of mine blowouts associated with above-drainage coal mines.

Jan 1, 2007

By Adam Shang Robert Fu

The Yung-Chung-Tunnel in Taiwan, constructed for the Taiwan-East Railway Bureau, collapsed during construction when a water bearing, fractured marble zone was intersected. The inflow was approximately 4,000 liters/second. In spite of 30 relief holes the total inflow into the tunnel remained constant. The pre-excavation grouting through the re-aligned tunnel had to be conducted under extreme flow-conditions. A hot bitumen grouting program was selected for technical and economical reasons out of 13 international proposals. The technical challenges were: grouting under severe flow conditions high formation water pressures to be injected with hot bitumen at high temperatures and pressures The hot bitumen grouting program resulted in a dramatic reduction in the hydraulic conductivity and stabilization of the formation and facilitated a problem-free excavation.

Jan 1, 2007

By Christopher Snee

??care has to be taken that the design is driven by sound geological reasoning and rigorous engineering logic rather than by the very attractive images that appear on the computer screen.??Hoek 1999 Design of a cavern is inextricably linked to the engineering geology of the site. The importance of sound geological reasoning will be illustrated by transportation projects in New York City where there are proposals for at least 11 caverns. These caverns have been the subject of advanced exploration techniques and geological interpretation but even so the raw data falls short of the sophistication of modern numerical methods. This paper will give geological explanations for the engineering characteristics of the rock in New York City which will provide guidance for practitioners when approaching cavern design in New York and elsewhere.

Jan 1, 2008

By A. Kevin Beaton, Robert W. Laakso

The desire for dry passageways promotes the NATM as it provides a final support system most suitable for the installation of a waterproofing membrane. Waterproofing during construction is a cost effective way to enhance safety and function as well as increasing the life of an underground structure. The NATM approach utilizes the surrounding mass as an integral element of the "ringlike" support system. At the Pennsylvania Turnpike Commission Lehigh Tunnel No. 2 various rock classifications were determined to require support measures ranging from 2 to 12 inches of shotcrete along with spiling, wire mesh, deformed bar, lattice girders and rock bolts as needed. Field instrumentation and monitoring programmes are a key factor for the success of the NATM. When the support "shell" stabilizes smoothing shotcrete, waterproofing and a final liner can be placed.

Jan 1, 1991

By D. M. Lane, J. M. Berkoe

Engineers and Owners share a common desire to build reliable, efficient plants on schedule at reasonable costs. This paper describes one tool that Bechtel finds can integrate these objectives by “putting innovation into practice”. Examples of such innovative engineering practice include the use of computational fluid dynamics (CFD) to determine efficient designs. This paper outlines several examples of CFD applications on actual Mining and Metals Projects from around the world. The focus here is to highlight the modeling objectives, analysis strategy, actual benefit obtained from the work, lessons learned to improve future efforts and the common mistakes that can obscure the correct or best results, despite impressive graphics. The tools are powerful, and the results are more powerful when applied with skilled and well-directed human effort and ingenuity.

Jan 1, 2000

By Steve Kral

When the price of gold cracked the US$9.60/g(US$300/oz) mark last year, the gold-mining industry began to crank up again. This followed several years of gold prices that had languished in the mid-200s. Existing mines increased production and mines that had lain dormant for many years were getting second looks. The United States still produces a large amount of gold. But not much of the new production is coming from that country. Instead, strict environmental regulations still have companies wary of trying to invest the millions needed to start a new mine or expand existing ones. And after years of studies and negotiations between legislators, environmental interests and the mining industry, the United States still has not crafted a new mining law.

Jan 1, 2003

By M. Karmis, S. K. Weisiger

The traditional method for training personnel in the mining and other heavy industries has been face-to-face, either via a lecturer in a classroom or through an apprenticeship. With the advent of applications tools such as video, computers, and the Internet, however, a much broader range of training delivery methods is available. Especially exciting are the broad capabilities of multimedia packages that combine the best features of numerous delivery methods. Applying multimedia environments in training holds great potential, especially when there is considerable difficulty in reconstructing real training environments. The authors discuss various delivery methods currently used in training employees, including perceived advantages and disadvantages of those methods. The authors then discuss and evaluate current computer-based training efforts of the mining industry and present an example of a multimedia training tool.

Jan 1, 2001

Characterization of ore and waste-rock material using automated quantitative micro-mineralogical techniques (e.g., QEMSCAN® and MLA) has the potential to complement traditional acid-base accounting and humidity cell techniques when predicting acid generation and metal release. These characterization techniques, which most commonly are used for metallurgical, mineral-processing, and geometallurgical applications, can be broadly applied throughout the mine-life cycle to include numerous environmental applications. Critical insights into mineral liberation, mineral associations, particle size, particle texture, and mineralogical residence phase(s) of environmentally important elements can be used to anticipate potential environmental challenges. Resources spent on initial characterization result in lower uncertainties of potential environmental impacts and possible cost savings associated with remediation and closure. Examples illustrate mineralogical and textural characterization of fluvial tailings material from the upper Arkansas River in Colorado.

Feb 27, 2013

By J. Brent Hiskey

Thiourea is a reagent capable of complexing gold and silver. With the proper oxidant, thiourea can effectively dissolve metallic gold and silver. A thiourea leaching system possesses potential advantages over conventional cyanidation including acidic solutions instead of alkaline, cationic complexes in contrast to metal-cyanide anoionic complexes, and faster leaching rates with acidic solutions of thiourea. Generally, the rate of metal dissolution in thiourea solution is fastest when ferric ion is employed as an oxidant. Acidic thiourea solutions for certain applications could offer a nontoxic and noncorrosive option for processing gold and silver. This paper provides information regarding the fundamental chemistry of the acidic thiourea system, and reviews the dissolution of both silver and gold in acidic solutions of thiourea. The recovery of gold and silver from acidic thiourea solution is discussed.

Jan 1, 1981

By O. Ogunsola, M. Downing

This paper gives a brief overview of impacts of coal blending on coal-fired power plants performance and discuses the preliminary results of an on-going study aimed at evaluating the effect of coal properties on the effectiveness, compatibility and thermal reactivity of coal blends. Plant survey studies reported no significant impacts on an existing plant designed for a high rank coal when switched to a blend of low- and high- rank coal. However, slight modification of some aspects (handling, fuel storage/stockpile, transportation, preparation, and general housekeeping) of plant design and operation may be necessary. The preliminary results of an on-going study at the Mineral Industry Research Laboratory shows that more compatible and better blends could be made from coals where ranks are closer than from those where ranks are far apart.

Feb 24, 1997

By Fredrick Fränding

In mining and quarrying operations, electric motors can fail for a variety of reasons. Some failures are directly linked to demanding production requirements and contaminant-laden environments and, consequently, are difficult to prevent. A sizeable number, however, are caused by ?offline? factors that have nothing to do with production. These include inadequate or substandard motor repair practices and improper motor shipping, storage and installation. The fact that failures are at times attributable to repair- or rebuild-related errors and problems raises the stakes when selecting an electric motor repair provider. Teaming with high-quality electric motor shops can help a company reduce failures due to offline factors, improving motor reliability and cutting downtime costs. Regardless of location or annual revenues, the best motor shops have similar business cultures and share many of the same characteristics.

Jan 1, 2009

By Thomas J. DeMull

Development of the Batu Hijau copper project was completed in the fourth quarter of 1999 with the formal handover and start-up of ore processing facilities. The project began in August 1996 when the owner, PT Newmont Nusa Tenggara (PTNNT), awarded an engineering, procurement and construction (EPC)contract to Fluor Daniel (FD) for the development of the project. This included a copper concentrator, port, power plant, town site and infrastructure. PTNNT managed the development of the mine and the procurement of the mine equipment. In 1996, Batu Hijau was the largest mining project ever undertaken. Developing the Batu Hijau Mine was complex. It involved the work of thousands of people in all parts of the world to plan, engineer, procure, fabricate and manufacture equipment, supply and deliver materials and equipment, and build the plant.

Jan 1, 2002

By Johan Bosch, Wout Broere, Minh Ngan Vu

"INTRODUCTION Shield tunnelling is often used in constructing underground infrastructure in cities due to the ability to limit settlements and damage to existing buildings. However, in an urban environment with soft overburden and buildings on pile foundations such as the North-South Line project in Amsterdam, there is a tendency to design the tunnel well below the surface and below the pile tip level in order to reduce interaction between tunnelling process and piles. This results in deep tunnels and deep station boxes. When the tunnels are located close to the surface and above the pile tip level, this would reduce the required depth of the station boxes and the construction cost. Moreover, other benefits of shallow tunnels are the low operational cost in the long-term and shorter traveling time from the surface to the platforms. Still, the tunnels should be constructed in such a manner that existing buildings are not structurally damaged, which results in a minimum required distance between tunnelling process and existing buildings. In this paper, the extent of the area that is influenced by tunnelling will be investigated in order to determine the limit distance from tunnelling to existing foundations without inducing too large building deformation. From analysing empirical data of many shield tunnels, Peck (1969) firstly presented the settlement trough on the surface induced by tunnelling in soft soil as a Gaussian distribution. This is also confirmed by other authors (Cording and Hansmire, 1975; Mair et al., 1993; Ahmed and Iskander, 2010). In this study, the Gaussian curve is used to investigate the ground movement when tunnelling in order to find the effects on existing structures. Based on the results from centrifuge test and empirical data, Mair et al. (1993) showed that the subsurface settlement profile distributes as the Gaussian curve also. The width of settlement trough at the depth z depends on the depth of the tunnel z0 and a coefficient K depending on depth. Other studies by Moh et al. (1996), Grant and Taylor (2000) and Jacobsz (2003) based on Mair et al. (1993) proposed a limited change of K in various kinds of soil."

Jan 1, 2016

By Rick Bearce, Minsu Cha, Mike Mooney, Yuanli Wu, Lisa Mori

"Proper soil conditioning is critical for effective earth pressure balance (EPB) TBM tunneling. Chamber pressures can reach 3-5 bar yet the vast majority of testing is performed under atmospheric conditions. This paper illustrates how pressure influences foam stability and conditioned soil behavior, and how atmospheric test results must be viewed in the context of expected chamber pressures. Torsional shear strength, compressibility and abrasivity of foam conditioned sand were found to be ideal when the void ratio was above the ASTM-determined maximum void ratio, achieved by sufficiently expanding the soil grain structure with foam, herein when the foam injection ratio at pressure exceeded 45%. Otherwise, the engineering properties of foam conditioned sand were not ideal, i.e., appreciable torque and abrasivity, low compressibility. INTRODUCTION Proper soil conditioning is critical for effective earth pressure balance (EPB) TBM tunneling. The formation soil at the cutterhead must be transformed into a highly compressible, low shear strength and low permeability medium within the excavation chamber to allow effective EPB performance. This behavior must be maintained for a certain residency time while the soil is in the chamber and screw conveyor. The vast majority of published studies on conditioned soil behavior have been performed under atmospheric conditions (Quebaud et al., 1998; Bezuijen et al., 1999; Psomas and Houlsby, 2002; Vinai et al. 2008; Thewes et al., 2012; Peila, 2014); however, the desired soil behavior must occur under chamber pressures that can reach 5-7 bar. The influence of pressure on conditioned soil is significant and is dramatically different than behavior under atmospheric pressure (Williamson et al., 1999; Mori et al., 2015). This paper illustrates how pressure influences conditioned soil behavior and how atmospheric test results must be viewed in the context of expected chamber pressures. The influence of pressure on foam bubble size (including with time) is shown through digital image analysis. The influence of pressure on foam half-life is also investigated. The compressibility, shear strength, and abrasivity of conditioned soil under pressure is presented and explained in terms of density, soil and air compressibility and porosity."

Jan 1, 2016

By Ewan Alexander

"As human beings, we have managed risk since the dawn of the ages and have been adept at doing so. In order to survive, we hunted or gathered. If we did not take enough risk, we died. If we took much risk, we died (Fig. 1). As individuals and tribes, risk had to be optimized to maximize our chances to thrive, as individuals and as tribes.In today’s world, the risks are vastly different, but in order to thrive, these must be managed. And no industry knows this as much as mining. In fact, the International Council of Mining & Metals (ICMM) has proposed the Critical Risk Model (Fig. 2) as a means of identifying critical risk, critical controls and associated performance standards. The ICMM focuses on sustainable development performance in the mining and metals industry. It has 23 members, representing some of the largest mining companies in the world.This approach is going to help the mining industry. But it must be applied effectively, with the acknowledgment that the system alone cannot be effective. We can say this confidently, as even companies known for the strength of their risk and safety management systems continue to experience significant incidents, and, in some cases, catastrophes. Why does that happen when all safety metrics, including injury rate, are pointing in the right direction? In the view of the author, it is only when leadership, culture and systems work in complete harmony that the resilience of an organization to manage its significant risk is at an optimal level. It remains an ongoing leadership challenge to maintain that balance and the optimal mindset in the organization. So how do you maintain that special balance?Let’s start with a basic premise. Leadership, supported by simple effective systems, creates culture which creates outcomes. Everyone going home safely is an outcome, as is cost effective operations, and to achieve those outcomes efficiently, the organization must focus on the inputs. And those inputs include effective leadership, effective systems (for the purposes of this article, risk and health, safety and environment (HSE) systems), good planning, stable operations and competent workers. This article will focus on gaining maximum performance from your risk management system."

Oct 1, 2016

By H. Yen, D. E. Walsh, H. K. Lin

"Comminution circuits are widely used in nonferrous and precious metals milling. Steel crushers, grinding mills and grinding media are typically used in comminution circuits. Comminution circuit wear products, in the form of metallic iron (steel) fines, are unavoidably produced and report to undersize products in the classification circuit, i.e., flotation or leach feed, while tramp grinding steel (TGS) reports to classification oversize products and returns to the grinding mill, building up in the circulating load. In laboratory studies, TGS reduced grinding efficiency significantly, the impact being dependent upon the size of the TGS present in the mill. Because iron fines adsorb flotation reagents effectively, iron fines increase reagent consumption and reduce flotation recovery. Iron fines are also capable of reducing gold recovery in cyanidation circuits via a cementation reaction. When using filtered gold solution from the cyanidation circuit of an Alaskan gold mine, the gold concentration in solution was reduced by 0.2 to 2.6% over various reaction periods when iron fines were present in the solution.IntroductionComminution circuits are widely used in copper, lead, zinc, nickel, cobalt, molybdenum and precious metal mills. Flotation and leaching processes are usually preceded by comminution (crushing and grinding) circuits in order to liberate valuable minerals for effective separation, concentration or dissolution by the subsequent flotation or leaching processes.Steel crushers, grinding mills and grinding media are typically used in comminution circuits. Comminution circuit wear products, in the form of metallic iron (steel) powder, are unavoidably produced and report to undersize products in the classification circuit (flotation or leach feed), while tramp grinding steel (TGS) reports to oversize productions during classification and returns to the grinding mill, building up in the circulating load. Variables affecting the amount of metallic iron powder and TGS produced in a comminution circuit include ore hardness, grinding mill operating conditions, comminution circuit design and the metallurgy of the steel used for manufacturing crusher liners, mill liners and grinding media. As one example, a comminution circuit product of 80% passing 200 mesh at the Pogo Mine, AK is estimated to contain approximately 2 kg/t of metallic iron. A finer grind will generally produce a comminution circuit product with higher metallic iron fines content."

Jan 1, 2015