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By J. R. Koehler

Yield pillar-based gate road designs oftentimes fail to provide mine operators with adequate ground control because of the unknowing misemployment of "critically" sized pillars. A "critical" pillar is one that is too large to either yield nonviolently or yield before the roof and floor sustain permanent damage, but is too small to support full abutment loads. To demonstrate the critical pillar concept, a field study of a tapering gate road was conducted by the U.S. Bureau of Mines at the Sunnyside Coal Mines, Sunnyside, UT. Extreme pillar stresses and associated coal bumps characterize the response to first panel mining of a 16.8-m wide critical design. Significantly lower pillar stresses, early yielding of the pillar and adjacent panel rib, and an absence of coal bumps suggest that a narrower 12.2-m-wide design more closely approaches proper yield pillar dimensions. Probehole drilling of several 1 O.6-m-wide pillars revealed low stress levels and substantial pillar and panel rib yielding prior to abutment onset, indicating a properly functioning yield pillar design.

Jan 1, 1995

By K. A. Grace, D. E. Ranta

The application of geology does not cease with the discovery and delineation of a mineral resource, but continues in the calculation of the economic parameters that determine reserves. Reserve determination, reduced to essentials, is the determination of the cost of production of a mineral commodity from a resource. This cost comprises mining, processing, waste disposal, reclamation and marketing costs. Geological input is vital in the calculation of the individual cost parameters from mining to reclamation, and even has same impact on marketing. Geology thus has a critical role in the determination of reserves.

Jan 1, 1992

By K. A. Grace

"An ore is a rock regardless of its rarity or value."* The application of geology does not cease with the discovery and delineation of a mineral resource, but continues in the calculation of the economic parameters that determine reserves. Reserve determination, reduced to essentials, is the determination of the cost of production of a mineral commodity from a resource. This cost comprises mining, processing, waste disposal, reclamation and marketing costs. Geological input is vital in the calculation of the individual cost parameters from mining to reclamation, and even has some impact on marketing. Geology thus has a critical role in the determination of reserves.

Jan 1, 1985

By P. Tsakiris

The increasing social interest for the environmental issues, forces the authorities to enact more rigorous regulations. The mining industry is one of the sectors that concentrate vigorous remonstrance. It is an absolutely justified reaction, as a result of the numerous contaminated and polluted sites that have been inherited by previous operations and they remain unremedied. The lack of a consolidated global legislation, transfers the burden of decisions to the national level. This paper consists of two parts. At the first part, it discusses the critical role of the state to form an effective environmental policy, feasible for the context of the national economy. Afterwards it analyses two of the main points, which must be considered by the regulator for the excavation activity, the abandoned sites and the duration of the mining investment. The aims are to defuse, in the short-term, the public pressure, protecting the economic growth and, at the same time, to form a basic structure for the development of the corporate social responsibility. The second part presents an alternative financial instrument for the Greek regulatory framework, conformed to the characteristics of the Greek Economy, and analyses the expected benefits both for the business and the social welfare.

Jan 1, 2002

By B. Yarar

The critical surface tension of wetting (?c) of Cu2S, FeS2, PbS, and MoS2 were determined by plotting flotation recovery versus YLV which was arranged by methanol, and Extra-polating to % R = 0. ?c values ranged from 26 dyne cm-1 for MoS2 to 49 dyne cm-1 for PbS and elemental sulfur gave a value of 31.5 dyne cm-1. Minerals exhibiting natural flotability of different extents, could be separated from their mixtures in the absence of conventional flotation reagents, but controlled ?LV. Correlations between non-stoichiometry and degree of natural hydrophobicity for MOS2 are also reported in this paper.

Jan 1, 1983

By Bill Tucker, Mike Black

"PROJECT OVERVIEW Crossrail, Europe’s largest construction project, will increase London’s transportation capacity by 10% when it opens in 2018. The Crossrail scheme is a combination of surface and underground railway that stretches 118km east-west through central London from Reading, Berkshire and Heathrow airport in the west to Shenfield, Essex and Abbey Wood in the London Boroughs of Greenwich and Bexley in the east. Crossrail will serve 40 stations, ten of which are new, and bring 1.5 million people within 45 minutes commuting distance of London’s key central business districts. 21km of the Crossrail route comprises twin-tunnels beneath the heart of central London. It is the central section of the route, and the challenges that had to be overcome to construct its tunnels under the historic capital that forms the subject of this paper. The route of the Crossrail tunnels can be seen in Figure 1. These tunnels weave their way through the city’s underground landscape, linking eight new underground stations which connect to the existing London Underground network, providing interchanges with nine existing lines as well as the National Rail and Docklands Light Railway networks.Crossrail began construction of enabling works in May 2009 and launched the first of eight tunnel boring machines (TBMs) in May 2012. 42km of major tunneling work was completed in May 2015, and included 11km of sprayed concrete lined tunnels at the five mined stations (Bond Street, Tottenham Court Road, Farringdon, Liverpool Street and Whitechapel) in addition to the bored tunnel sections. The remaining three sub-surface stations at Paddington, Canary Wharf and Woolwich were constructed as large open boxes prior to the TBMs passing through. Crossrail, Ltd. is a special purpose company formed by the project’s joint sponsors, Transport for London and the Department for Transport, to manage design, construction and commissioning of the project. In 2009, Crossrail engaged Bechtel Ltd. as its delivery partner and a joint venture, Transcend (comprised of CH2M, AECOM and the Nichols Group), as its programme partner. The project is being managed by an integrated programme management team which is staffed by Crossrail and its partners. The railway, when opened, will be operated by Rail for London. With tunneling completed in accordance with the project’s master control schedule, the new railway is scheduled to commence dynamic testing in late 2017, with a phased opening of the tunneled sections and stations through Central London in 2018."

Jan 1, 2016

By E. J. Hammer

In the crushing and grinding of metallics for beneficiation, the sizing is normally done to liberate the metals or sulphides for further processing to improve recoveries of the basic metals or minerals. The objective is to reduce the ore in size through various closely controlled stages to that degree of fineness which gives an economic liberation of valuable mineral, but which avoids as much as possible the production of sliming fractions. A different philosophy applies to the crushing and grinding of Gypsum. Our requirements normally demand controlled grinding and/or crushing of the material not only to a fineness suitable for further processing of the mineral into end products, but to produce various sizes of material which are them- selves saleable products. The majority of our tonnage ultimately ends up in stucco for Wallboard. Therefore, our mineral reduction is normally designed toward this end, but it is done in a manner that permits drawing off inter- mediate products to meet various Customer requirements. This forces us into compromises at times in our equipment installations, and our equipment must sometimes be more versatile and complex than we would like it to be. We try to process our basic rock, Gypsum, for the most efficient size reduction. We market 5 to 6 different sizes intermediate to the end product, which generally is the fineness of material to be used for stucco for Wallboard, and we do this with controlled crushing, grinding and sizing cycles of the material. To summarize, we use a different philosophy of crushing and grinding than the metallic field which uses comminution or crushing and grinding to improve recovery, whereas we choose our equipment to crush and grind primarily for product performance.

Jan 1, 1969

By D. Küster, G. Franken, P. Schütte, J. Vasters

The CTC (Certified Trading Chains) mineral certification system has been piloted in Rwanda since late 2008. CTC project implementation is jointly driven by the Federal Institute for Geosciences and Natural Resources (BGR) and the Rwanda Geology and Mines Authority (OGMR), in cooperation with other national stakeholders. Five Rwandan mineral producers participate in the CTC project with their flagship mining concessions. Based on independent third-party audits, CTC certifies supply chain due diligence measures of these companies engaged in the artisanal mining sector through on-the-ground assessments of mining conditions, transparency, as well as mineral origin and traceability. The CTC system thus allows responsible mineral producers and their clients to verifiably demonstrate supply chain due diligence and good governance in conflict-affected and high-risk areas.

Jan 1, 2011

Many states rely upon the Pennsylvania 1957 “Gas Well Pillar Study” to evaluate the coal barrier surrounding gas wells (Commonwealth of Pennsylvania, 1957). The study included 77 gas well failure cases that occurred in the Pittsburgh and Freeport coal seams over a 25-year span. At the time, coal was mined using the room-and-pillar mining method with full or partial pillar recovery, and square or rectangle pillars surrounding the gas wells were left to protect the wells. The study provided guidelines for pillar sizes under different overburden depths up to 700 ft. The 1957 study has also been used to determine gas well pillar sizes in longwall mines since longwall mining began in the 1970s. The original study was developed for room-and-pillar mining and could be applied to gas wells in longwall chain pillars under shallow cover. However, under deep cover, severe deformations in gas wells have occurred in longwall chain pillars. Presently, with a better understanding of coal pillar mechanics, new insight into subsidence movements induced by retreat mining, and advances in numerical modeling, it has become both critically important and feasible to evaluate the adequacy of the 1957 study for longwall gas well pillars. In this paper, the data from the 1957 study is analyzed from a new perspective by considering various factors, including overburden depth, failure location, failure time, pillar safety factor (SF), and floor pressure. The pillar SF and floor pressure are calculated by considering abutment pressure induced by full pillar recovery. A statistical analysis is performed to find correlations between various factors and helps identify the most significant factors for the stability of gas wells influenced by retreat mining. Through analyzing the data from the 1957 study, the guidelines for gas well pillars in the 1957 study are evaluated for their adequacy for room-and-pillar mining and their applicability to longwall mining. Numerical modeling is used to model the stability of gas wells by quantifying the mining-induced stresses in gas well casings. Results of this study indicate that the guidelines in the 1957 study may be appropriate for pillars protecting conventional gas wells in both room-and-pillar mining and longwall mining under overburden depths up to 700 ft but may not be sufficient for protective pillars under deep cover. The current evaluation of the 1957 study provides not only insights about potential gas well failures caused by retreat mining but also implications for what critical considerations should be considered to protect gas wells in longwall mining.

Jul 28, 2020

By Joe Roby

Rolling disc cutters are the business end of hard rock and mixed face tunnel boring machines (TBMs). Since their first successful employment on a TBM over fifty years ago, disc cutter technology has constantly evolved, allowing modern TBMs to excavate very hard and abrasive rock efficiently. Disc cutters have also been employed successfully on earth pressure balance (EPB) and slurry machines, cutting rock under water and ground pressure. The range of materials excavated by machines today is broader, excavation rates higher and cutter costs lower than ever before, proving the value of investment in cutter development. This paper describes recent improvements in disc cutter components including cutter ring materials and processing, as well as improvements in lubricants, bearings, seals and cutter condition monitoring. These developments have resulted in more reliable cutters capable of operating in a wide range of geological conditions. Ultimately these improvements result in a better value for both contractors and project owners.

Jan 1, 2008

By Marcus M. Key

Silicosis among metal miners is an ancient disease, probably as old as mining itself.' However, the primitive forms of mining were not productive of much silica dust, and the short life span of slaves used in mining probably precluded the development of more than a few sporadic cases of silicosis. Early diagnostic terms of miners' asthma and miners' phthisis suggested an occupational relationship and a tubercular component, but little attention was given to silicbsis until the turn of this century when epidemics of silico-tuberculosis arose due to the great expansion of the mining industry in the United States, especially silver and gold mining. The expansion was accompanied by mechanization and the introduction of pneumatic tools, which generated increasing amounts of fine silica dust. Mining communities were crowded and hygiene was poor.' The tubercle bacillus would probably have flourished even without the predisposition of silicosis.' As is so often the case in occupational health, biostatistical analyses first called attention to the problem, and environmental-medical studies later confirmed its existence. The bio-statistical analyses were occupational mortality statistics compiled by the Prudential Life Insurance Company in 1907, showing evidence of excessive mortality from tuberculosis and relationship to dust exposure. I The

Jan 1, 1971

By Virgil R. Huff, Ihor Havryluk

P. T. Pacific Nikkel Indonesia (PTPNI) was incorporated in Jakarta, Indonesia in February, 1969 by a group of Dutch and North American companies. At the same time, a Contract of Work with the Government of the Republic of Indonesia was signed, granting Pacific Nikkel all the necessary licenses and permits to explore and develop all nonradioactive minerals in two separate areas in Irian Jaya, eastern Indonesia. Nickel mineralization occurrences were confirmed by Dutch geologists in the two areas in 1952 and 1955, however, detailed exploration began in June 1969 after the Contract of Work was signed. Since that time, numerous studies and investigations have been conducted to determine the feasibility of producing metallic nickel in Irian Jaya. Four engineering studies, two bulk sample tests, an oceanographic survey, and a preliminary site investigation indicated that construction and operation of a nominal 100 million pounds per year metallic nickel plant on Gag Island were technically feasible. The fourfold increase in the price of oil in late 1973 without a corresponding adjustment in the price of nickel necessitated a reevaluation of the project, the results of which showed that the project required other conditions to be viable. Subsequently, analysis of: the future projected nickel supply-demand and cost-price relationships, the economics of treating a higher grade feed, and participation by the Government of Indonesia, indicate that the project will be viable. Therefore, planning of the Gag Island Nickel Laterite Project is continuing with the objective of commencing production to supply the market in the 1983-1984 time period.

Jan 1, 1979

By John D. Morgan

The U.S. economy annually needs over 4 billion tons of new mineral supplies. The value of domestically produced energy and processed materials of mineral origin exceeds $175 billion annually, but domestic production of both raw and processed minerals is not keeping pace with demand.

Jan 1, 1974

By Alexander N. Winchell

"Location. The Cuyuna iron district extends from the region of Kimberly, near the Center of Aitkin County, Minnesota, south-westward through Deerwood, Ironton, and Brainerd, across Crow Wing and Todd counties, across the Mississippi River, and for an unknown distance farther southwest in the same direction. It is known that the Huronian rocks, in which the ores of the Cuyuna district are found, reappear near the western border f Minnesota, but no ores have been found in this region. The district has a length of more than sixty miles, but the more important portion as now known 'is confined to Crow Wing County in an area which is less than thirty miles in its longest dimension. The commercial headquarters for the district are in the city f Brainerd, on the Mississippi River.History. The discovery of iron ore in the Cuyuna district was accomplished with no aid from surface outcrops, but solely through the use of the dip needle. The mantle of glacial drift overlying the iron formation varies from twenty-five to 359 feet in thickness, and it was by means f the magnetic attraction of the iron bearing rocks that their presence was discovered with the dip needle by Cuyler Adams, about 1895. The general geologic map of Minnesota, published by the State Geological Survey in 1909, showed the extension of the Huronian rocks of the Mesabi district passing through this area. Two years later, Leith published a sketch showing the hypothetic extension of the iron bearing formation through the same area. The first drilling was done in 1903, near Deerwood, Minn., by Cuyler Adams, and exploration was continued to the present time in increasing amount. The Northern Pacific Railway extends throughout the length of the district and affords an easy outlet for the ores. The Soo Line Railway completed a spur into the district in 1910. Both roads carry the ore to the docks at Supe¬rior, Wis., the average haul being about ninety miles. Shipments began in 1911, the Kennedy mine being the first producer. By 1918, the number of shippers reached twenty-seven, with a total output of nearly two and one-half million tons for that year."

Jan 1, 1920

By R. C. Woodhead

During past years the most difficult problem presented to the coal preparation engineer has been the cleaning of fine coal, The problem of handling fine coals is more involved than the coarser sizes, because the higher surface moisture contents complicate screening, and the larger percentages of fine near size material complicate separating problems. Low gravity high capacity specific gravity separations were not possible with equipment available at that time. Coal preparation engineers did develop machines that would effect a separation of the fines, however, to maintain a high efficiency, the point of separation had to be a relatively easy one. The more difficult separations were made in the coarse coal sections of the washeries, and the fines were generally cleaned at higher specific gravities in equipment such as tables, feldspar jigs, rheolaveurs, etc. Clean products from both processes were mixed, resulting in overall lower ash contents, During the last several years, however, we have been confronted with increasing demands ZGP more precise separations of finer coals to still further reduce ash contents. A study was begun and a program instigated to improve the cleaning of fine coal, The result of this endeavor was the development of the new cycloidal heavy medium cyclone.

Jan 1, 1964

By Terry Ramsey, N. Finkelstein

INTRODUCTION The Cyprus Pima Mine is located 20 miles southwest of Tucson, Arizona and about fifty miles north of the Mexican border. The Cyprus Pima orebody was discovered in 1950. Feasibility studies were begun in 1952 employing underground development. Economic studies showed open pit operations to be feasible and stripping of overburden was begun in late 1955. The first ore was reached in October of 1956. A 3,000 tpd (tons per day) concentrator was completed and began operation January 1, 1957. From these beginnings, Cyprus Pima Mining Company has expanded into a plant processing approximately 54,000 to 56,000 tpd. Four expansions were required to bring the plant up to its present capacity. Each expansion incorporated what had been learned in previous operation of the plant. The first expansion was completed in August of 1963 doubling design capacity to 6,000 tpd. In reality, because of softer than average ore, capacity was closer to 8,000 tpd. Expansion I1 was completed in July 1966 bringing design capacity to 18,000 tpd. Expansion I11 followed immediately. Completed in the summer of 1967, this expansion increased the design capacity to 30,000 tpd. The actual dry tonnage of this portion of the operation in 1974 averaged 38,400 tpd, again, primarily as the result of treating softer than average ore. The latest expansion (Expansion IV), completed in December 1971 and utilizing a semi-autogenous grinding circuit, is located in a separate building (Mill 11) approximately 200 yards southeast of the original mill (Mill I). Expansion IV was designed for 14,000 tpd, but after circuit modifications, averaged 16,500 tpd in 1974.

Jan 1, 1976

By Dave Rogstad

The DART NC-1B Tunnel Project consists of two 5,100 m TBM excavated tunnels, a principal underground station, a partially completed future station, a surface station, and eight associated ventilation shafts and exit tunnels. This paper presents a case history of the project's construction, and will focus on six topics that give this project a unique and unusual history; the TBM excavation, two major differing site conditions, roadheader excavation, polyfiber reinforced shotcrete lining, the NATM design geometry, and a design/build type of contract.

Jan 1, 1995

By T. W. Camm

Some of the defining characteristics of narcissists include a grandiose sense of self-importance, preoccupation with success and power, a sense of infallibility, and a supreme confidence in their ability and intelligence. Ironically, many of these characteristics are rewarded in business organizations, which may explain why there seems to be so many narcissists in management positions. Assuming we will be dealing with narcissists throughout our career, it makes sense for us to understand what makes them tick, and more importantly what we can do to work with them in a constructive manner.

Feb 23, 2014

By Robert C. Bacon

The first commercial installation of the Dashaveyor has recently been completed at the White Pine Mine in Northern Michigan. After four years of development work, including prototype testing, and pilot plant operation, this new and unique system is being tested under operational conditions. Many of you may be familiar with the concept through numerous articles which have appeared in the technical press. But this discussion of the system will be simplified and less time consuming with the presentation of a portion of a film showing the Dashaveyor in actual operation. After the movie, I will show some slides which will supplement and clarify it and hopefully lay the basis for questions you will undoubtedly wish to ask.

Jan 1, 1968

By Ruston A. Ford

This paper reviews the development of the David Bell Mine, from early exploration, through discovery, construction, start-up, underground development, and production. Details are provided regarding the mine development, the mechanized cut and fill stope production, the proposed long-hole stoping with delayed backfilling mining method for the lower levels and the cyanide leach carbon-in- pulp concentrating process. The mine development remains on schedule and under budget with results very much as predicted in the feasibility study.

Jan 1, 1987