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By Andrzej M. Wala

A knowledge of the friction factor (K-factor) is necessary in planning and designing mine ventilation systems for least cost and highest effectiveness. The friction factor used must be accurate and reliable for correct estimation of airway resistances. At present, the friction factors are determined by using tables of published values. These values were established principally for metal-mine openings having small effective areas. This presents a problem to the ventilation design engineer whose responsibilities center around the design of effective ventilation systems for large room-and- pillar mechanized underground coal mines. Friction factors selected from these tables could be excessively conservative for large scale room-and- pillar operations. With only limited data on the K-factor (which are considerably site dependent) for Kentucky's coal mines and for all the above mentioned reasons, it was concluded that there is a need for field investigations to determine these values in-situ for existing mining conditions in Kentucky. The author describe the study carried out in ten coal mines located in eastern and western Kentucky and present the results of the investigation in both tabular and graphical form.

Jan 1, 1991

By Ronald J. Riberich

The Mineral Economics and Management Society (MEMS) held its fifth annual conference in Montreal, Quebec, Canada earlier this year. “The Minerals Industry: Responding to the Global Challenge” was the first MEMS conference to be held outside of the United States. About 125 mining- and minerals-related professionals attended. The MEMS program included six sessions and three distinguished speaker addresses. The session topics included: “Minerals in the Macro economy: Development in Demand,” “Trends in Global Metals Supply: The Producers’ Challenge,” “Global Environmental Issues: Policy Perspectives,” “Global Environmental Issues: Quantitative Analysis” and “Minerals in the CIS: Phoenix or Albatross?” A student session was also offered. It provided a competition for monetary awards for outstanding papers.

Jan 1, 1996

By Rudolf E. Greuer

Introduction The Institution of Mining and Metallurgy and the Institution of Mining Engineers organized the Third International Mine Ventilation Congress held in Harrogate, England. Sixty-one papers were presented and about 300 participants registered. About 30% of the participants came from Great Britain, 20% from South Africa, and about 5% each came from Australia, Canada, China, France, US, and West Germany. The remainder of the participants came from 18 other countries. Eleven of the papers presented dealt with methane, three with diesel exhausts, four with dust, four with radioactivity, 18 with heat, and 15 dealt with main and auxiliary ventilation. Six of the papers dealt with mine fires, which is a boundary region between main ventilation and gas concerns. Ventilation Congress proceedings are available. See ME, December 1984, page 1687, New Books page. With CH4 and radioactivity topics, the Australians dominated since they are becoming large coal and uranium producers. With diesel exhausts, the most important problem in highly mechanized mines, the North Americans were prominent. The South Africans, working in 90% SiO2 in their gold deposits, were preeminent in presentations on dust. They also led in topics related to heat, joined by the West Germans whose mines are getting deeper. In main and auxiliary ventilation, Great Britain and West Germany provided the majority of contributions. Methane The large number of methods for the precalculation of CH4 liberation in longwall mining all contain three elements: gas content of the coal, gas emitting zone (or influence zone of face), and degree of gas emission. Determination of the gas content, commonly accomplished by taking coal samples, does not pose much difficulty. But this is not the case with the other two factors. Most existing approaches rely on rock mechanics observations. Some only rely on intuition or speculation. The West German coal mines conducted a large research project between 1977 and 1982, in which gas pressures around longwall faces were measured. Gas pressures and gas contents can be related. Therefore, influence zone and degree of gas emission can be determined simultaneously. The precalculation of CH4 liberation in room-and-pillar mining is simpler. Since foot and hanging walls remain essentially intact, gas pressure distribution and gas flow can be calculated using hydraulics equations. A key to these calculations is permeability. A group of Australian researchers reported that the permeabilities of rock under three dimensional stress differs from rock under destressed conditions. This fact was known, but no systematic observations existed. These were provided. Methane drainage has been practiced for more than 40 years. It is used with great success in longwall operations. Some of the West Germans think that methane drainage from the footwall is neglected. Under certain geological conditions, they claim this is as important as drainage from the hanging wall. A research project was presented in support of this claim. Considerable efforts have existed for more than 10 years to use methane drainage in room-and-pillar mining. A paper described the accomplishments of Consolidation Coal Co. Since coal and rock are not fractured as much as in longwall mining, gas transport takes place by the slow diffusion from micropores into the cleats. Then, it is transported by laminar flow along the cleats until a drainage borehole or the mine workings are reached. Boreholes about 300 m (1000 ft) long can reduce the gas content of a band of coal 100-m (330-ft) wide by 50% in one year. A paper from India described methane drainage from gob areas. A French paper reported that especially high methane concentrations can be drained from gob areas if the face ventilation is descensional. Methane buoyancy and ventilating pressures compensate each other, and little air dilution by leakage takes place. Another French paper described a newly developed gas and air velocity monitoring system making use of a microcomputer. Four papers on methane dealt with gas outbursts. Two Australian contributions described the problems encountered with CH,-CO2 mixtures and the attempts to solve them with drainage boreholes having 10 to 20-kPa (1.5 to 3-psi) suction pressures. A Hungarian paper described problems and attempts to reduce the risks of gas outbursts in Hungary. Prediction of gas outbursts in coal seams was the focus of an English paper. Observations show that they are frequent when coal, through its geological past, has become soft and brittle with a resulting increased desorption rate. An instrument for gravimetric de-

Jan 1, 1985

By R. Benemelis

The existence of resins in some coal deposits in various parts of the world has been known for many years. These resins vary considerably in chemical structure and properties. The resin that is found in Utah coal, however, is rather unique, and has properties particularly attractive for the manufacture of printing ink mastics and adhesives. This resin is a rather dark, very high melting point, low molecular weight hydrocarbon resin. Its typical properties are shown in Table I. Its largest use by far, has been in the printing ink industry. The history of Utah coal resin is interesting, but unfortunately one of disappointment and failure.

Jan 1, 1990

By K. Mohamed, G. Rashed

A conventional mechanical anchor bolt consists of a smooth bar threaded at the anchor end, with a conical wedge, and a mechanical shell anchor. When the smooth bar is torqued, the conical wedge pushes the shell anchor against the borehole wall. Coal mines use mechanical bolts in addition to other types of bolts to control the deformation and stabilize the yielded coal ribs. Limited research has been conducted to understand how a mechanical anchor performs in a coal rib. Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted the study described in this paper to define the loading characteristics of mechanical bolts (stiffness and capacity) installed in coal ribs at five underground coal mines. Standard pull-out tests were performed in this study to define the loading characteristics of a mechanical rib bolt. Based on the strength of the coal seam and the conditions of the coal mines, the bolts were installed at different amounts of torque. A typical tri-linear load-deformation response was obtained from these tests. It was found that the anchorage capacity depends on the coal strength, and the anchorage stiffness depends on the installation torque. The outcome of this research provides essential data for rib support design. INTRODUCTION Rib falls are a serious hazard in underground coal mines. In the last 10 years, rib failures have resulted in 17 fatalities, representing 52% of the ground-fall fatalities in underground coal mines in the United States (MSHA, 2018). Although resin bolts has been used increasingly in the last few years to control coal ribs, mechanical bolting (mainly expansion-shell bolts) is still used in many underground coal mines. Recently, NIOSH researchers surveyed 90 sites in 14 underground coal mines in the Eastern United States and found that 79% of the mines determine their rib support requirement based on the depth, mining height, and the loading conditions, of which 35% use the conventional mechanical bolts. Conventional mechanical bolts are preferable for rib support because they do not require the miners to be too close to the rib during rib bolting. Hence, using the conventional mechanical rib bolts can reduce the risk of injuries and fatalities during the installation process. The mechanical bolt or the point-anchored bolt is the oldest type of rock bolt that is still in use today. The point-anchored bolt is a tensioned bolt anchored down the hole with a mechanical expansion shell or a grouted medium (Peng and Tang, 1984). Figure 1 shows the components of the mechanical anchor bolt. The mechanical anchor bolt consists of a plug, a shell anchor, a headed smooth bar with the top end threaded, a bearing plate, a hardened washer, and sometimes a friction-reducing washer. The shell anchor can be either standard or bail type. The shell of the standard type is held in place by a nut, while the bail anchor uses a strap to hold the shell in place (Peng, 2008). The diameter of the smooth bar is generally 5/8 in for the #5 bolt or 6/8 in for the #6 bolt. The diameter of the hole that the bolt is inserted into must be carefully controlled since an oversized hole can result in poor anchorage (Moss, 1971). The anchorage is obtained by applying torque to the bolt head, which in turn pulls the wedge down in the shell and expands the serrated leaves against the sides of the hole-wall. In the resin-grouted anchor, the resin replaces the mechanical expansion shell at the end of the hole. The anchorage is achieved by bonding between the resin, bolt, and the hole-wall.

Jan 1, 2019

By John Hillman

The reconstruction of the British mining industry which began shortly after nationalisation in 1947 continued until well into the 1950s with the support of the Government. This support diminished as plentiful supplies of cheap oil from the middle East made many coalmines un¬economic. The planned rundown which followed was foreshadowed in the 1965 White Paper which outlined the financial measures to speed the closure of uneconomic collieries. The decline appeared likely to continue into the 21st century as the role of coal in UK energy requirements became less and less significant. This policy was well on course in 1973 when the oil crisis led to a complete reappraisal of the position. A Government examination in 1974 of the coal industry then supported the National Coal Board's general strategy of major capital investment as set out in its 'Plan for Coal' (1). Plan for Coal aimed at halting the intended decline in the industry's capacity and restoring it to 120 million tons of deep mined output in 1985. The Plan proposed action along the following lines (a) increase output by major Investment in construction at existing collieries with sufficient reserves to give 13 million tons per annum extra output (b) invest in extending the life of existing collieries by gaining access to additional reserves, to give 12 million tons per annum extra output © by sinking new mines, produce an extra 20 million tons per annum. Figure 1 shows the contribution (2) expected from each of the three sources up to 1990/1. The measures taken were expected to offset the inevitable exhaustion of existing pits and provide the additional 40-42 million tons capacity needed to restore annual output in 1985 to 120 million tons. Parallel to this programme for expansion of deep mined output, opencast mining was to produce 10-15 million tons per annum. A recent review however, indicates that new mines are likely to yield only 10 million tons per annum by 1985, mainly owing to the need for public inquiries into proposals for new mining and the resultant fact that planning approval takes 'much longer than originally expected. Nevertheless the objective of 120 million tons deep mined output by 1985 is still considered achievable of means of a greater contribution from existing mines. This programme was originally estimated to cost 2,-56 million dollars at March 1974 prices, out revised estimates of the cost of Plan for Coal indicate that it may now exceed 6,960 million dollars at mid-1977 prices. Plan for Coal includes a substantial investment in new and reconstructed coal preparation plaints. At mid-1977 prices more than 322 million dollars Ls so be invested in coal preparation projects in the UK, at the rate of, about 70 million dollars a year. This rate 3f capital expenditure has been maintained over the past three years and covers investment in a wide range of coal preparation coals for the power station, coking and domestic markets.

Jan 1, 1978

By C. G. Snavely

Martin County Coal Corporation produces coal from seven continuous miner sections in two coal seams which are often interlaced with rock partings. Because of high clay content and coal oxidation, all minus 100 mesh material is discarded in the preparation process. We began experimenting with various drum lacings on continuous miners in 1983 to improve product size consist and increase machine cutting rates. To date, + 6.35 mm material has increased from 61 to 73% of mined product, minus 0.15 mm material has decreased from 6% to 4% of product, and machine cutting rates have increased by 50 percent.

Jan 1, 1985

By Sandro Moro, Giuseppe Tiberti, Giovanni Plizzari, Antonio Conforti

"During TBM operations, thrust jacks apply high-concentrated forces to the last installed precast segment. These loads generate a disturbed region in the precast segment under the thrust jacks, in which significant tensile stresses (defined as splitting or bursting stresses) occur perpendicular to the load direction. In addition, due to the demand of compatibility, the combined effect of TBM high-concentrated loads determines tensile spalling stresses in the area far from the loads. Therefore, local rebars or fiber reinforcement are required in these areas. This paper focuses on the study of the effects generated by high-concentrated loads exerted by TBM hydraulic jacks, mainly in terms of both spalling and splitting phenomena. Experimental tests on small-scale specimens showed that polypropylene fiber reinforcement significantly enhances both the bearing capacity and the ductility. Moreover, polypropylene fibers resulted in very effective control of compatibility cracks.INTRODUCTIONTunnel segments are generally reinforced by conventional rebars (RC segments) in order to resist the tensile stresses both at Serviceability (SLS) and Ultimate Limit States (ULS).In the two last decades, Fiber Reinforced Concrete (FRC) has been used in many precast tunnel segments (sometimes also in combination with conventional rebars). Steel Fiber Reinforced Concrete (SFRC) is generally used for these applications even though there is a growing industry interest on macro-synthetic fibers for structural applications. Conforti et al. (2015) showed that polypropylene (PP) macro fibers can be used as shear reinforcement in both wide shallow and deep beams. Referring to precast tunnel linings, very few early experiences are reported in literature. Bonalumi et al. (2015) developed full-scale tests on tunnel elements reinforced by PP fiber reinforcement and conventional rebars (hybrid solution). The design process of segmental concrete tunnel linings generally models the standard load cases of demolding, storage, transportation, positioning and embedded ground condition. In all these stages the ring can be modelled as simple curved beam elements (having a height equal to the lining thickness and a width equal to the segment length). During these loading conditions, flexural demand is generally limited; thus, in case of conventional RC elements, a rather low ratio of longitudinal curved rebars is usually adopted (?s of about 0.2-0.3%)."

Jan 1, 2016

By John Hickey

Management teams at mining companies begin to ask themselves whether to take a company public and, if so, how to do it as they approach the normal threshold for going public in terms of revenue and operating performance. Today, the expense of going public generally suggests the company has at least $20 million in annual revenue and at least $2 million in cash. The revenue number can be lower for mining companies with large reserves. In order to properly attract the investing public, the company must also be operationally strong with robust prospects. The company should have a strong management team and a consistent history of double-digit growth that will continue into the foreseeable future. Assuming the thresholds are met, a company?s management needs to weigh the pros and cons of going public.

Jan 1, 2012

By D. E. Traut

A fluidized countercurrent ion-exchange system was developed, operated, and evaluated by the Bureau of Mines. The system consisted of integrated multiple-compartment absorption and elution columns in which the solution flows are continuous except for short periods when resin increments are withdrawn. The exchange of uranyl sulfate between a simulated acid leach uranium solution and a strong-base, ion-exchange resin together with the subsequent elution with an acidified sodium chloride solution was studied. The effects of the number of sections, section heights, amount of resin withdrawal, and solution flow rates were investigated. Also examined were the kinetic and equilibrium relationships for the absorption step. The experimental data indicate a strong interdependence between variables. Solution retention time appears to be a major limiting variable. The column was efficient over a range of conditions, but close control was needed for optimum operation.

Jan 1, 1975

By Kevin Lundberg, Philip Sander, Daniel Weinberger, John Reilly

Since the early days of risk management, developments in technology and guidelines (ITA, ITIG, OGG, UCA) have advanced risk management and probable cost estimating, which are now widely recognized. WSDOT’s CEVP risk-based cost validation process is now established after 20 years. This paper traces these developments, summarizes advanced techniques, and presents examples of US and international projects with results. A particular case of using advanced risk evaluation to allow enhanced-capability TBMs to be considered in a competitive bid process is presented. Further advances, including the use of digital twin risk-based representation of complex projects, are described.

Jun 13, 2023

By C. D. Keith

Erie Mining Company, a pioneer in the iron ore pelletizing industry, has continued to develop methods and equipment to improve cost and quality. Under the management of Pickands Mather & Co., this property, owned by Bethlehem Steel Corporation, Youngstown Sheet and Tube Company, Steel Company of Canada, Ltd., and Interlake, Inc., has initiated a number of operating improvements for the taconite industry. One of the most noteworthy of these, which is applicable to the entire mineral industry, is the principle of fine screening with rappers (FSR). Erie's original efforts in the field of fine screening, which date back to 1961, were described in the April 1967 issue of the MINING ENGINEERING magazine. In that same month, Erie placed into operation a full scale PSR and regrind plant addition, capable of processing 10.3 million long tons of iron ore concentrates, produced by conventional taconite grinding, classification, and magnetic separation methods. Since this first successful commercial operation of the PSR principle et Erie, it has been applied in eight other iron ore beneficiation plants end is being tested by other U.S. and foreign companies. In addition to the use of PSR units at Erie Mining Company, Pickands Mather has applied PSR to other of its managed properties end to projects under development. This paper covers these applications as well as a now application at Erie Mining Company.

Jan 1, 1971

By V. Aghazadeh, E. Bidari, M. Aazami

In this study, mineralogical and microanalysis characterization, as well as diagnostic leaching and cyanidation tests, were performed to gain a better understanding of the refractory nature of the arsenical zone of a Carlin-type gold deposit and also to evaluate possible treatment routes to maximize gold recovery. The results obtained showed that only 56% of the ore’s gold content is amenable to direct cyanidation. The majority of the remaining gold was found as submicroscopic gold and in association with sulfide minerals, such as orpiment, pyrite, and sphalerite. It was also found that despite the abundance of silicate and carbonate minerals in the arsenical zone, they do not play a key role in the refractory nature of the ore, and gold can be liberated from such minerals by appropriate grinding. The analyses further revealed that orpiment dissolves readily during cyanidation, and this dissolution retards the kinetics of gold extraction. Pyrite and sphalerite were generally found to occur in fine network texture and in association with quartz. Flotation of such auriferous sulfides may be difficult due to their oxidized surface. Fine grinding (−20 μm) was found to be partially effective in improving gold extraction.

May 28, 2020

By Yoginder P. Chugh

Physical mine modeling and computer simulation techniques were used to conduct technical feasibility and economic analyses of selected pit configurations for surface mining a single coal seam dipping at about 15 percent to a maximum depth of 150 feet. The pit orientations along the dip (dipline), strike (strikeline) and along an apparent dip were studied. Physical models of each pit configuration were prepared first to delineate potential operational problem areas, and also to furnish a data base-for the computer simulation models. A dragline micro- simulation model (Fluor), a shovel/truck simulation model and a cost analysis model were used to conduct the study. Sensitivity analyses were conducted on variables such as the pit width, block length, and angle of dip. The productivity (Cu.yds/hour) of the mining equipment (dragline or stripping shovel) under each set of conditions was used to optimize the pit configuration. Both block length and panel width were found to significantly affect the dragline productivity larger size trucks were preferable to smaller size trucks in the pit configuration along an apparent dip. The cost analysis results showed that the pit configuration along the seam dip was more economical than the pit along the strike or along an apparent dip.

Jan 1, 1984

By B. M. Flohr

Railroads are cost competitive with trucks for hauls greater than 500 miles - WRONG. Today I will tell you about many rail movements of less than 100 miles throughout the country. Rail is a short haul transportation alternative you must consider. Transportation today is the largest controllable cost in the total cost of production of goods. In fact it is the one cost area where aggressive management, using new tools, can achieve significant reductions. You can't control the price of metals in the world market, you can't control labor rates since they are tied to industry norms, and the price of raw materials are relatively insensitive to specific price reductions to your firm. Transportation is the one area where major savings are now being realized. Sample Movements First, I will give you several examples of short haul rail moves to make you a believer that they do exist. Then I will show you the reasons why railroads suddenly "like" short hauls.

Jan 1, 1986

By Robert L. Runkel, D. Kirk Nordstrom, James W. Ball

Low-flow reactive-transport processes in Wightman Fork downstream of the Summitville Mine, south-central Colorado were simulated using the OTIS and OTEQ solute-transport models. The simulation was calibrated using data from a synoptic study conducted during October, 1998. Discharge over the 8-km reach from just below the mine site to the Alamosa River confluence ranged from 0.077 to 0.17 m3/s; travel time was 10.7 hours; pH ranged from 4.6 to 5.7. Simulations revealed that mass balance for SO4 was maintained, and that pH, Fe, and Al were non-conservative. Simulations allowing hydrous ferric and aluminum oxide or hydroxysulfate precipitation matched observed water quality conditions more closely than simulations without precipitation.

Jan 1, 2000

By J. J. Gusek

Several final pits in the Seneca No. 1 Surface Coal Mine were abandoned in the 1960's without being reclaimed. In addition, a progressive landslide aggravated by the abandoned mine land conditions was threatening a county road and private property. An AML-funded project to stabilize the landslide and reclaim the final pits was completed in 1986 for the Colorado Division of Mines and Geology (formerly Colorado Mine Land Reclamation Division). The site was visited after ten growing seasons. The land is stable and the vegetation re-establishment is strong. Volunteer native plant species are now invading the reclaimed sites.

Jan 1, 1997

The United States is being invaded... by foreign capital: marks, francs, pounds, yen, lire, riyals, you name it: On almost any given day the Wall Street Journal will contain a new report on a department store, newspaper, bank, hotel, agricultural land, supermarket chain, et a1 being bought into by overseas investment. Xenophobic reaction to this revised national condition has begun to set in. Several farming states have and are introducing legislation to monitor foreign land buying. In Congress a mandatory reporting requirement for foreign purchasing is currently under study. In a relatively short period the country has reverted from world leader- ship in overseas acquisition and involvement to become itself one of the prime investment opportunities in existence. Interestingly enough, one of the industries where this changed status has become most apparent and pronounced is within that small/regional/segmented/low value-to-weight bulk commodity enterprise ranked as the backbone of the nation's construction activity. U.S. cement making is not only undergoing internationalization in its ownership, but also in its product, equipment, and engineering expertise.

Jan 1, 1979

By B. F. Westfall

Throughout the 1960's and 1970's world trade grew rapidly, reaching a peak of USS1.8 trillion in 1980. Since then the world recession of the early 1980's shrunk trade to about US$1.6 trillion. The reduced cash flow to developing economies made it difficult to service their huge international debts, Nowadays lenders are reluctant to grant Third World countries additional credit. The shortage of export financing, plus trade barriers set up by developed countries, is further inhibiting international trade. Therefore, countries are turning to new and creative alternatives to financing imports of consumer as well as of investment goods. Non-cash transactions, including different forms of countertrade, are rapidly growing alternatives to traditional trade financing patterns. In 1983 about 30% of international trade, or close to US$600 bill ion, were presumably done by non-cash transactions, up from barely 2% in 1976. By year 2000, half the world trade is likely to be conducted on basis of barter. As of mid-1984 some 88 nations used countertrade regularly and Governments of at least 15 Latin American countries had arranged or mandated commercial countertrade.

Jan 1, 1986

By E. E. Krist

El desmuestre de un criadero tiene un buen número de finalidades. En la fase inicial es necesario definir los límites del yacimiento y el contenido o ley del mineral hasta el punto de que pueda ser establecido si es, de hecho, un yacimiento económico. Igualmente, las muestras tienen que ser generadas de forma tal que las evaluaciones geológicas y metalúrgicas puedan ser Ilevadas a cabo. Finalmente, cuando se conoce la suficiente información concerniente a la geología, mineralogía y metalurgia, puede ser desarrollado un método minero y su plan, y construidas las oportunas plantas metalúrgicas para procesar los minerales a medida que se encuentran disponibles1. Con las minas actuales grandes y complejas a cielo abierto los métodos de desmuestre único deberían de ser inadecuados. La perforación por diamante, la perforación por percusión, pozos subterráneos y galerías, juegan todos conjuntamente un papel parcial en la definición total del yacimiento. En la mina Twin Buttes, de la Anamax Mining Company, el desmuestre y la definición del yacimiento conducirán eventualmente a la existencia de tres plantas metalúrgicas de proceso y, quizá a, una operación de minería subterránea. Fue puesto en marcha un concentrador de sulfuros de 30.000 tons. por día en Septiembre de 1969 y una planta de 10.000 toneladas diarias de lixiviación de óxido fue puesta en servicio en Mayo de 1975. La finalidad de esta presentación es la de exponer históricamente el desmuestre del yacimiento que ha sido Ilevado a cabo en Twin Buttes, describir brevemente el criadero, y exponer los métodos analíticos corrientemente utilizados para ayudar al geólogo, al metalúrgico y al diseñador de la mina en sus respectivas evaluaciones.

Jan 1, 1982