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By H. -J. Langhoff

"The paper describes not a result, but a starting point to implement sustainable development to a region characterized by a typical down river landscape, agriculture, and extractive industry. The NaturFreizeitNiederrhein GmbH (NFN) is a private company with associates from administrative bodies, the local mining companies and multiple representatives of environmental protection groups (local and national), tourism organizations, cultural societies and also aquatic sport and fishing clubs. Center of the concept is the "NFN Lake District." The development concept aims to provide the agricultural industry with alternative means of income, while protecting wildlife and the ecological balance as well as preserving the social und cultural system and enhance the safety against flooding from the river Rhine. The mining industry contributes their coordination of obligation concerning reclamation and recultivation of the already existing individual projects. While designing the landscape components and establishing the infrastructure for the different tasks, the production of gravel and sand is yield as a by product. The result is a long term perspective for region and industry."

Jan 1, 2005

By K. Donahue

Clay minerals play an important role in the gravitational stability of man-made rock piles by affecting geotechnical and hydrological characteristics of the material. The Goathill North rock pile at the Questa Mine in northern New Mexico has been the focus of a multi-disciplinary study to determine the effect of weathering on rock pile stability and in particular to determine if clay minerals are forming in the rock pile due to surface weathering. The results of x-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicate the clay minerals found within the fine-grained soil matrix of the rock pile are of hydrothermal origins and did not detect any neoformation of clay minerals. The foremost mechanism for an increase in clay minerals within the rock pile is the physical break down of hydrothermally altered rock fragments to release hydrothermal clay minerals. The hydrothermal clay minerals within the rock pile show evidence of weathering by the dehydration of smectite from 2-water to 1-water interlayers within the clay mineral structure. This dehydration is most likely due to higher temperatures and low relative humidities in the Goathill north rock pile during surface exposure.

Jan 1, 2009

The National Institute for Occupational Safety and Health (NIOSH) conducted a study to determine the effectiveness of a filtered air delivery system to reduce respirable dust exposure to roof bolter operators in underground coal mines. When performing roof bolting operations, roof bolter operators may experience exposure to high levels of respirable dust during a working shift, especially when working downwind of the continuous mining machine. While drilling and installing roof bolts, this filtered air system supplies a clean curtain of air over the roof bolter operator by means of a plenum mounted beneath the canopy. This experimentally designed air curtain, adapted for roof bolting machines used in this study, is based upon previous design prototypes, computational fluid dynamics (CFD) simulations, and trial-and-error testing. Both prototype and final designs were tested in the full-scale mining galleries at the Office of Mine Safety and Health Research (OMSHR) in Pittsburgh before being taken underground for field testing. Test results of the system in both laboratory and field studies show reductions in operator exposure to respirable dust when the operator is positioned directly under the protected zone of the canopy.

Jan 1, 2012

With the dawning of a new century came the beginning of a new era in the coal industry. Instead of the traditional practice of only buying and selling produced coal in the United States, a coal futures market was established. The New York Mercantile Exchange began trading coal futures in July 2001. But, even in this new era, many of the old is-sues that have beset the coal industry still remain, as was evident in2001. Coal production increased to are cord level during 2001, according to preliminary data from the US Energy Information Administration(EIA). Production in 2001 rose by4% to 1.01 Gt (1.12 billion st), compared with 2000 (Table 1). This barely surpassed the previous record level of 1 Gt (1.11 billion st)set in 1998. Coal consumption remained unchanged. The additional production was used to replenish the depleted stockpiles that had resulted after two years of declining coal production and increasing coal consumption.

Jan 1, 2002

By D. Kruse

Top down constructed large diameter (up to 90 m [300 ft]) shaft design and constructability issues present an interesting suite of challenges and opportunities highlighted in this paper. The study covers 2D and 3D finite element models used to: analyze various failure modes, evaluate the shaft liner and internal structures? response to seismic loading, assist in segment design, and assess final structural design tradeoffs. Efforts to achieve economic advantage over conventional heavy civil practices have prompted innovative solutions for ring and segment design, ring build assembly, and annulus backfill grouting. Intended for soft ground conditions, relationships between soil parameters and structure design are also explored.

Jan 1, 2011

By S. Rupprecht

"This article addresses the prevalence of poor public reporting practices of coal exploration results, coal resources and coal reserves in southern Africa. Currently, the reporting of coal tonnage without supporting coal qualities or saleable tonnes and quality is a poor reporting practice that occurs far too often. Not all coal is equal — therefore it is extremely important that investors or potential investors are provided with the full details of both run-of-mine (ROM) and saleable coal tonnage, their associated qualities and other material and relevant information.Competent or qualified persons should note that publicly reported information should be sufficient to enable an informed reader to make a reasonable and balanced assessment of the significance of the information provided. “Companies are encouraged to provide information in their public reports, which is as comprehensive as possible (CRIRSCO, 2013).” However, too often this isn’t the case, and material matters are either not reported or inadequately disclosed.According to the South African National Standard (SANS) 10320:2014 draft document, “tonnage and coal quality that will be available for sale, either in the raw ROM state (raw saleable) at a specified moisture content, or after beneficiation of the ROM coal by processing operations to produce materials at specified qualities, size ranges and moisture contents. The assessments must demonstrate that at the time of reporting, the marketing of the products is reasonably justified. The basis of the predicted practical product yield to achieve the saleable coal reserve must be stated. The moisture basis of reporting shall be stated.” An example as to why coal qualities are so important to the public, the requirements of South Africa’s electric public utility (Eskom) power stations are detailed in the followint paragraphs. The Kendal power station, commissioned in 1988, operates at a calorific value (CV) range of 19 to 20 MJ/ kg, an ash content between 29 and 34 percent and volatiles between 20 to 21 percent. Other power stations, such as Kriel or Hendrina, may require different qualities, such as a CV range of 22 to 23 MJ/kg, an ash content between 20 and 28 percent and volatiles between 22 to 23 percent. Thus, in terms of domestic saleable coal, it is not just about reporting the coal qualities but also informing the investor as to which power station the coal is intended to be sold as “boilers are designed to burn particular qualities of coal” and “it is not always possible to transfer coal between stations because of different quality requirements at each station (Chetty, 2010).” Sulfur content is another important quality with the ideal coal content having a quality of less than 1 percent sulfur."

Jul 1, 2019

By Yousef Ghorbani, Jafar Abdolahi Sharif, Fatemeh Kazemi, Ataallah Bahrami

Kinetic models are the most important tool for predicting and evaluating the performance of flotation circuits. Gilsonite is a natural fossil resource similar to an oil asphalt, high in asphaltenes. Here, in order to determine the kinetic order and flotation rate of a gilsonite sample, flotation experiments were carried out in both rougher and cleaner stages. Experiments were conducted using the combinations of oil–MIBC and gas oil–pine oil, with one test without collector and frother. Five kinetic models were applied to the data obtained from the flotation tests using MATLAB software. Statistical analysis showed that the results of the experiment with oil–MIBC were highly in compliance with all models. Kinetic constants (k) were calculated as 0.1548 (s−1 ) and 0.0450 (s−1 ) for rougher and cleaner stages, respectively. Rougher and cleaner tests without collector and frother also matched all models well (R2 > 0.98), with k values of 0.2163 (s−1 ) and 0.284 (s−1 ), respectively. The relationship between flotation rate constant, maximum combustible recovery, and particle size showed that the maximum flotation combustible recovery and flotation rate were obtained in the size range of −250 + 106 μm in the rougher and cleaner stages. The combustible recovery and flotation rate were higher in the rougher flotation process than in the cleaner stage.

By Yousef Ghorbani, Jafar Abdolahi Sharif, Fatemeh Kazemi, Ataallah Bahrami

Kinetic models are the most important tool for predicting and evaluating the performance of flotation circuits. Gilsonite is a natural fossil resource similar to an oil asphalt, high in asphaltenes. Here, in order to determine the kinetic order and flotation rate of a gilsonite sample, flotation experiments were carried out in both rougher and cleaner stages. Experiments were conducted using the combinations of oil–MIBC and gas oil–pine oil, with one test without collector and frother. Five kinetic models were applied to the data obtained from the flotation tests using MATLAB software. Statistical analysis showed that the results of the experiment with oil–MIBC were highly in compliance with all models. Kinetic constants (k) were calculated as 0.1548 (s−1 ) and 0.0450 (s−1 ) for rougher and cleaner stages, respectively. Rougher and cleaner tests without collector and frother also matched all models well (R2 > 0.98), with k values of 0.2163 (s−1 ) and 0.284 (s−1 ), respectively. The relationship between flotation rate constant, maximum combustible recovery, and particle size showed that the maximum flotation combustible recovery and flotation rate were obtained in the size range of −250 + 106 μm in the rougher and cleaner stages. The combustible recovery and flotation rate were higher in the rougher flotation process than in the cleaner stage.

By H. Maleki

As mining continues toward deeper reserves in thick western US coal fields, the control of mining induced-seismicity has become a priority in many operations in Utah, Colorado, and Wyoming. Gradual floor heave, common in many coal mines, has historically not been a safety issue. However recent occurrences of sudden floor heave accompanied with seismicity in a few deep mines have fueled this investigation. The focus is to identify and study the mechanisms resulting in sudden heaving of the mine floor in western U.S. deep coal mines through analytical calculations and back analyses of an actual event in a cooperative mine. Based on review of available data in three mines, underground observations and back analyses of an actual event, the authors have identified the following contributing factors (1) presence of stiff stratigraphic units and thick seams mined at depths exceeding 1000-ft (2) presence of geological discontinuities reducing the in-situ strength of the coal with calculated factor of safety near 1 for the mine floor (3) mining approaching areas of higher than normal stress gradient associated with previous mining or structural anomalies or surface topographic highs and (4) an additional source of energy triggering sudden failure such as periodic caving or slip along geological discontinuities. Preliminary examination of seismic data for the actual event in the cooperative mine and underground observations excluded fault slip at the mining horizon as the triggering mechanism but highlighted the significance of weak, anisotropic strata conditions near the intersection of two faults.

Jan 1, 2009

Collaboration between education providers is the key to long-term sustainability and improved quality in mining education. The mining industry is now, more than ever, an industry doing business on a global basis. Staff are recruited by global mining companies in many different countries and can find themselves deployed anywhere in the world. The mining engineer of tomorrow must be willing to take on this international challenge, and must be educated to a level where he or she has a comprehensive grounding in technical aspects of mining engineering, but also a well-founded appreciation of management, social, environmental and cultural issues that may be encountered around the world. In order to deliver such an education, academic providers must collaborate at both a national and international level. This paper provides an overview of progress that has been made in Australia through the national joint venture ? Min¬ing Education Australia (MEA). Supported by the mining industry in Australia, through the Minerals Council of Australia (MCA), MEA has been operational since 2007 and is seeing the development of a range of innovative courses and delivery methods, together with a high level of staff cooperation across the country. MEA has also commenced some international teaching initiatives that are seen as a catalyst for a far greater degree of international collaboration in the future. Such activity is not only to the benefit of the students who are taught by experts from around the world, but it also ensures that individual univer¬sity programs remain viable in terms of staffing numbers and financial performance. The paper also presents some statistics on recent upward trends in mining engineering student numbers from around the world, in response to the global shortage of mining engineers.

Jan 2, 2010

By David C. Yang

A packed column (or static tube) flotation system is an innovative technology which utilizes a controlled dispersion reagent scheme and a new machine. The unique aspect of the machine is its packed-bed design permitting an unlimited froth bed height with countercurrent water washing for effective processing of fine particles. In operation, the conditioned ore slurry is fed into the middle section of the column where separation processes begin. Air, introduced at the bottom of the packed column, contacts the hydrophobic particles and floats them off continuously as the feed is added, while the gangue sinks to the base of the column. The system functions efficiently because intimate particle-bubble contact is achieved by the packing design which has no moving parts and requires no ancillary air-bubble generator. Other attractive features of the packed column flotation include high throughput, low power requirements, and simple control. Results from laboratory and pilot plant tests of this system show remarkable improvements over current industrial practices on a wide variety of ores and coals.

Jan 1, 1988

By Robert E. Murray

The title of my paper, "A Company's Response to Federal Coal Leasing," brings to mind a picture of a dog chasing its tail. This is what the coal industry, has been doing since the Federal coal leasing moratorium went into effect in 1971. We've gone around in many circles, but we are only very slowly, if at all, getting closer to catching our tails, i.e., efficient, economical, and rational Federal coal leasing. My companies, The North American Coal Corporation and its four Subsidiaries, The Falkirk and Western Plains Mining Companies and The Coteau and Missouri Valley Properties Companies, together hold in excess of 4.5 billion tons of lignite reserves in North Dakota. Some of our North Dakota properties are substantially interspersed with Federal coal, with the government holding title to the minerals in every other section. This checkerboard pattern of Federal ownership has made it difficult to develop and market some of our reserves, and, as a result, it has become imperative that we be familiar with and active in the Federal Coal Leasing Program.

Jan 1, 1982

By A. D. Davis, J. L. Sorensen, C. J. Webb

Environmental impacts from acidic mine drainage are growing national concerns that are particularly acute in the headwaters of the Rocky Mountain region. In the Black Hills of South Dakota, approximately one thousand mines are inactive or abandoned, most of them in the headwaters of major drainages. This paper examines the Bear Butte Creek basin, a heavily mineralized watershed with significant historical mining impacts and a surface gold mine permitted in 1997. The watershed loses its surface discharge to swallow holes in the karstic Madison Limestone. The integrity of the aquatic ecosystem was monitored with a suite of sitespecific bio-indicators. Stream surveys covered the entire reach of Bear Butte Creek from near its headwaters to the swallow holes in the Madison aquifer. Data from the stream surveys, water-quality sampling, and bio-indicator surveys clearly showed that water-quality impacts are limited mainly to Strawberry Creek and to the area of Bear Butte Creek near and downstream of the town of Galena.

Jan 1, 1999

By Shemek Oginski

The 5 km (16,194 lf) of 6.1m (20 ft) diameter TBM driven tunnel built by the J.F.Shea Co. will serve as sewage overflow storage. The TBM tunnel and four connecting tunnels excavated by drill and blast methods in hard granite will remain unlined. Based on the Geotechnical Baseline Report (GBR), the Contract documents provided a design with no required pattern of rock bolts, no probing, no pre-excavation or consolidation grouting, and lastly, no final lining of the tunnels was deemed necessary. This paper will provide a general overview of these topics with the emphasis on the actual ground conditions encountered versus the projected conditions provided in the GBR and how the GBR reflected the design of the project. Proposed modifications to the temporary and permanent ground support will be presented and the necessity of probing and pre-excavation grouting will be evaluated.

Jan 1, 2005

By Tyler Acorn, Brandon Wilson, Jeff Boisvert

Scenario-level uncertainty is a representation of large-scale differences encountered when considering ultimate mining pits optimized over various subsets of stochastic realizations. Accounting for scenario-level uncertainty allows mine plans to be assessed against several probabilistic subsurface interpretations. Scenario-level uncertainty is found through clustering stochastic geostatistical realizations and optimizing final pits across the realizations in each cluster. Where these pits are geometrically different, plans for each scenario differ. Knowing these differences allows the value of each planning alternative to be assessed based on the value and relative probability of each scenario. These results also facilitate the use of formal decision-making frameworks for planning, leading to optimization that better represents the full statistical characterization of the deposit. An example utilizing this approach evaluates both infrastructure placement and drilling program requirements. In both cases, scenario-level uncertainty improves initial plans by limiting opportunity costs and identifying additional potential.

By Tyler Acorn, Brandon Wilson, Jeff Boisvert

Scenario-level uncertainty is a representation of large-scale differences encountered when considering ultimate mining pits optimized over various subsets of stochastic realizations. Accounting for scenario-level uncertainty allows mine plans to be assessed against several probabilistic subsurface interpretations. Scenario-level uncertainty is found through clustering stochastic geostatistical realizations and optimizing final pits across the realizations in each cluster. Where these pits are geometrically different, plans for each scenario differ. Knowing these differences allows the value of each planning alternative to be assessed based on the value and relative probability of each scenario. These results also facilitate the use of formal decision-making frameworks for planning, leading to optimization that better represents the full statistical characterization of the deposit. An example utilizing this approach evaluates both infrastructure placement and drilling program requirements. In both cases, scenario-level uncertainty improves initial plans by limiting opportunity costs and identifying additional potential.

By Yousef Ghorbani, Abolfazl Danesh, Fatemeh Kazemi, Ataallah Bahrami, Morteza Abdollahi, Mohammad Raouf Hosseini

This study aims to investigate the effects of operational variables on concentrate grade, recovery, separation efficiency, and kinetic parameters of the copper flotation process. For this purpose, the effects of the pulp solids content, collector and frother dosage, and preparation and concentrate collection time were studied using a Taguchi experimental design. The results of statistical analyses indicated that the concentrate collection time and pulp density were the most influential parameters on concentrate grade. Considering copper recovery, concentrate collection time, collector dosage, and pulp density were the most significant variables, in decreasing order of importance. Also, the separation efficiency was mostly influenced by the concentrate collection time. Furthermore, kinetic studies showed that the second-order rectangular distribution model perfectly matched the experimental flotation data. The highest kinetic constant of 0.0756 s−1 was obtained from the test, which was performed with 35% solids content and 40 and 20 g/t collector and frother, respectively. The highest predicted copper recovery of 99.57% was obtained from the test at 30% solids content, and the collector and frother dosages of 40 and 15 g/t, respectively

By J. O. Marsden

Part I in this series of papers considered the chemistry of medium-temperature pressure leaching of copper sulfide concentrates and reviewed the metallurgical testing and initial process development for this technology. This initial work resulted in the development of a process flowsheet utilizing superfine grinding (to a P98 of 12 to 15 µm and P80 of 6 to 7 µm), pressure leaching at 160° to 170ºC, followed by conventional solution extraction (SX) and electrowinning (EW) for the recovery of copper. However, this process required a significant amount of concentrated acid to be fed to the pressure leach vessel to meet the reaction requirements, representing a cost of between $0.03 and 0.05/lb copper (2006 basis) produced by the process. It was immediately recognized that the development of a process that did not require such a large acid addition would be advantageous. This paper, which is Part II in the series, describes the development of a process that incorporates medium-temperature pressure leaching and direct electrowinning (DEW) in a novel and innovative process flowsheet. Phelps Dodge (a subsidiary of Freeport-McMoRan Copper & Gold Inc.) refers to this as the ?MT-DEW-SX? process. Part III in this series covers the large-scale demonstration of the MT-DEW-SX process at Bagdad, Arizona; and Part IV addresses the development and design of a full-scale commercial application at Morenci, Arizona.

Jan 1, 2007

By Klaus Rieker

Over the last 30 years Wayss & Freytag Ingenieurbau AG has gained a lot of experience in mechanized tunnelling on various major projects. During this period most important developments concerning the machine technology for EPB- and Slurry-Shields have taken place. Since the first application of a hydro shield for the Wilhelmsburg Collector project in Hamburg in the early seventies, several stages of development have led to the current state-of-the-art in mechanized tunnelling. The continuous improvement of TBM techniques allows the execution of high quality tunnelling, particularly with regard to maximum safety and efficiency. The practical experience of the construction companies is of essential importance in order to continue further development and improvement.

Jan 1, 2005

Even though the economy of the United States remains in recession ? or not, depending on which economist you listen to ? muicipalities still need improved transportation, water and wastewater transit systems. And they are willing to spend the necessary funds on those systems, provided they are affordable, environ-mentally friendly and sustainable. From June 20-23, professionals in the tunneling and underground construction industry from around the world gathered in Portland, OR to learn new ways of providing those systems using the latest technology available. The North American Tunneling (NAT) conference attracted 803 attendees and 108 exhibiting suppliers of equipment and services.

Jan 1, 2010