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By AIME AIME

TECHNICAL achievement in mining will be rewarded at the forthcoming Annual Meeting of the Institute when the William Lawrence Saunders Gold Medal will be presented to Herman C. Bellinger. Mr, Bellinger was unanimously selected on the first ballot of the Medal Committee. Mr. Bellinger has had notable technical success as vice-president in charge of operations for the Chile Exploration Co., a position he has held since 1920.

Jan 1, 1941

By P. Bartel

Coal cleaning can be effected by the bacterium Sulfolobus acidocaldarius, which in oxidizing sulfur and dissolving mineral matter requires carbon dioxide and oxygen; carbon dioxide as a carbon source and oxygen as an electron acceptor. The desulfurization of coal by thermophilic bacteria under elevated partial pressures of carbon dioxide and oxygen was studied at a total pressure of 1 atm. The partial pressure of carbon dioxide was varied over the range 0.00032 to 0.33 atm (0.00032, 0.007, 0.10, 0.33 atm), and the partial pressure of oxygen was varied over the range 0.14 to 0.40 atm (0.14, 0.21, 0.30, 0.40 atm). The maximum rate of coal desulfurization increased by 32%, from 9.0 to 11.9 mg S/1 hr, as air was enriched in carbon dioxide from its atmospheric level of 0.00032 atm to 0.10 atm. Enrichment with carbon dioxide up to 0.10 atm, at constant oxygen partial pressures, increased the desulfurization rate, but enrichment to 0.33 atm caused the rate to decrease. At constant carbon dioxide partial pressures, the desulfurization rate was maximum at oxygen partial pressures of 0.21 and 0.30 atm. At higher (0.40 atm) and lower (0.14 atm) oxygen partial pressures the rate decreaed by 9 to 20%. The desulfurization rate decreased by 58X, from 9.0 to 3.8 mg S/1 hr, when the air pressure was increased from 1 atm to 3 atm. The effects justify an economic analysis during design and operation of a commercial air feed in a process to desulfurize coal by microbial action.

Jan 1, 1986

By Georgy Cherkashov, Livia Ermakova

Active development of the exploration and further exploitation of deep-sea minerals requires special emphasis on the protection of the marine environment. The complexity of this subject lies in the fact that potential impact and effects of future mining activity are not completely known. One of the main sources of potential impact near the seafloor, as it expected, would be a generation of sediment plumes, their dispersion and redeposition of sediment. Meanwhile, their dimensions, rates of dispersion and redeposition are a big issue. Other plumes are expected in the surface layer as a result of discharges of processing waters and particles after sorting on board of mining vessel, and their features are also not clear. At the same time, understanding of these aspects would be crucial for definition of environment impact area, delineation and designation of different types of protected areas (Areas of Particular Environmental Interest, Impact and Preservation Reference Zones) and future assessment of environmental impacts. Attempts to address these issues demonstrated wide variations between the data of field experiments on the one hand and the results of analytical and numerical models on the other. According to in situ measurements, plumes were detected at a distance vary from one to less than 20 km [e.g., Burns et al., 1980; Sharma et al., 2001; Nautilus Minerals, 2008 etc.], whilst some models show results up to 100 km [Rolinski S. et al., 2001] and more. It seemed that results of in-situ experiments are preferable, but they were not many indeed. However, these data were used in different investigations rather widely, but their focus, as far as we know, was not on the matters related directly with plumes.

Jan 1, 2018

By Larry J. Hughes

Ground-based electrical geophysical techniques have be valuable for three indirect exploration strategies: "tracer" sulfide mineralization, 2) mapping structure with or controlling mineralization, and 3) mapping proven to 1) mapping? associated alteration zones. When sulfide mineralization is associated with gold, it often can be mapped using induced polarization (IP). This technique can detect pyrite in amounts as small as 0.2% by volume, and in some cases can distinguish pyrite from anomalies due to graphite and clays. A case history illustrates mapping sulfides in a shear zone. Structure and alteration mapping are often the domain of controlled source audio-frequency magnetotellurics (CSAMT) due to the superior lateral resolution and depth penetration of this technique. Typical CSAMT targets include silicified sediments and volcanics, faults, brecciated zones, argillic alteration, clay and graphite horizons, and certain lithologies. Examples of mapping silicification and mapping epithermal alteration are presented in CSAMT case histories over Cannon mine in Washington and Hishikari mine in southern Japan. In our experience, four things are needed to use geophysics effectively in precious metals exploration. First, the explorationist must correctly identify the exploration stage at which the geophysics is most useful. Second, the explorationist must clearly define the types of "tracer" mineralization, host geology, or alteration which need to be defined by the geophysics. Third, the right electrical technique needs to be applied to the problem to provide the best chance of success. Fourth, the explorationist must be willing to commit adequate finances to do the geophysics properly. With careful adherence to these principles, geophysics can greatly enhance exploration success while reducing the total cost of exploration.

Jan 1, 1989

By J. D. Miller

X-ray computed tomography (CT) techniques have been developed for the medical services field in order to provide accurate internal images of the human body.(l-7) Now, a decade later, CT techniques are starting to be used in non-medical applications such as, non-destructive testing(8), flow pattern analysis(9), drill core examination (10,11), and coal characterization(12,13). In these fields of application, CT techniques offer the potential to extend our knowledge and understanding beyond that provided by more traditional methods of analysis. Although, CT systems involve very specialized and expensive equipment, the advantage of x-ray CT in revealing the detailed internal structure of an opaque material non-destructively should make it an important tool to provide a more complete analysis of mineral processing phenomena. X-ray CT systems generally consist of an x-ray source/collimation unit and a detector/data acquisition unit. The object to be examined is placed between the two functional units as shown in Figure 1. With this system the density array of selected cross sections of a chosen opaque object can be obtained in two dimensions. There are numerous areas in mineral processing to which x-ray CT technology can be applied and it is the aim of this article to identify these potential areas noting the advantages and limitations of the technology. Particular emphasis is placed on particle composition distribution and multiphase fluid flow measurements. In the case of particle composition distribution, liberation analysis and coal washability are considered. While in the case of multiphase fluid flow, swirl flow in the air-sparged hydrocyclone is given by way of example.

Jan 1, 1989

By Fred W. Brackebusch

"The use of paste technology for surface tailings disposal may offer economic, technical, safety, and environmental advantages for both underground and surface mining operations. Paste is a non-Newtonian fluid having some shear strength during transport and placement. The strength is augmented after placement by consolidation, water loss, and by addition of chemicals. Economical dewatering systems are necessary to the success of surface paste tailings disposal. In an underground mine, the paste backfill plant can produce paste for surface disposal about 50% of the time because only about 1/2 of the tailings are needed for backfill. The distribution of paste to the surface stack involves expensive pumping equipment and thus a nearby location of the stack is desirable. The viscosity of paste can often be manipulated by modifying pH. Placement of the paste in a designed stack configuration depends on topographic and climatic factors as well as paste properties.INTRODUCTIONThe use of paste technology for mine backfill is becoming accepted for underground mines mainly because of ground control and economic reasons. Paste technology is just starting to be applied for tailings disposal with only a few hardrock metal mines worldwide using the technology; however, it has been used extensively for red mud disposal in the aluminum industry. The disposal of dry tailings is very attractive from environmental and safety points of view because of limited water which might potentially escape and pollute river systems. Dry stacking systems, however, are expensive because of filtration and truck transportation costs. Paste can be produced from most tailings streams by special types of thickeners. Furthermore, it can be transported in pipelines, therefore paste technology may be more economic than dry stacking but still have some of the major advantages. Understanding of paste technology has improved through experience with operating underground backfill systems in recent years and because of testwork and research programs by mining companies, consultants and equipment vendors. Thus we may be on the verge of taking a new look at tailings management using paste technology."

Jan 1, 2002

By Marko Lampi, Marc Nicolle, Janne Karonen, Kari Valkama

"In the ten years from 2003 to 2013 global mine production of copper has increased by over 23% to meet demand while the weighted average head grade has dropped from 0.9 to 0.7% Cu. These divergent trends of increasing demand and declining economic grades will extend the life of many existing mines and improve the viability of marginal and/or complex copper deposits. Against that context this paper outlines hydrometallurgical copper sulphide leaching options as alternatives to the more conventional pyrometallurgical processing route of copper sulphides. Three copper sulphide leaching and refining processes are discussed: total pressure oxidation, ferric sulphate leaching and copper chloride leaching. The effect of mineralogy on the choice of processing technology is discussed as well as some of the unit processes used. Additionally, possible benefits that a hydrometallurgical process may offer over an existing pyrometallurgical route are discussed. Subsequently, two very important aspects to the development of projects involving the leaching of copper sulphides are discussed. Finally, a number of conclusions are presented that will be useful to keep in mind when considering projects involving the leaching of copper sulphides. INTRODUCTION In the ten years from 2003 to 2013 global mine production of copper has increased by over 23% to meet demand while the weighted average head grade has dropped from 0.9 to 0.73% Cu (Murphy, 2014). If these divergent trends of increasing demand and declining economic grades continue, they will contribute to the extension in life of many existing mines and improve the viability of marginal and/or complex copper deposits. Against that context, this paper outlines hydrometallurgical copper sulphide leaching options as alternatives to the more conventional pyrometallurgical processing route for copper sulphides. Three copper sulphide leaching and refining processes are discussed: total pressure oxidation, ferric sulphate leaching and copper chloride leaching. Ferric sulphate leaching and copper chloride leaching are carried out at atmospheric pressure while total pressure oxidation takes place at elevated pressures."

Jan 1, 2015

By R. H. Smith

The total energy demand in the United States increased about 4 per cent annually during the 1960's 1 and is expected to increase at the same rate during this decade. Z Fuel oil growth in the 1960's was only Z per cent per year until 1968, but it increased to 8 per cent in 1969 and 11 per cent in 1970. Fuel oil demand is expected to grow at a 6 per cent rate through the 1970's. Part of this rapid increase in demand has been caused by restrictions placed on the sulfur content of fuels. High sulfur coal can no longer be burned in many parts of the country and has been replaced by low sulfur fuel oil. An insufficient supply of natural gas has also contributed to fuel oil demand. Air pollution regulations have not only caused an increase in fuel oil consumption, but they have also caused a reduction of sulfur content in residual fuel oils. Current regulations call for 1 per cent maximum sulfur content fuels over much of the country. Sulfur contents of fuels are limited to 0. 3 per cent in certain areas on the east and west coasts. Sulfur in residual fuel oils from high sulfur imported crude oil is reduced to 1 per cent currently. However, sulfur reduction to 0. 3 per cent is difficult and expensive.4 As a result, refiners may be hard pressed to supply the market for low sulfur fuel oil. The oil shale deposits in Colorado and Wyoming potentially are a huge source of low sulfur fuel oil. It will be shown that the low sulfur content and more importantly the sulfur

Jan 1, 1972

By Dominic Fragomeni, Tony DiFeo, Martyn P. Hay

"As part of an investigation into flotation modelling of industrial scale operations, Falconbridge Ltd organised a “blind” test of the SUPASIM flotation model developed by Eurus Mineral Consultants (EMC). Two sets of rougher rate data, a flowsheet and the number and size of cells in the rougher bank were supplied from a plant that had been previously surveyed in November 2003. The name of the plant, cleaner circuit details and circuit mass balance were, at the time, unknown to EMC. With only these data, flotation performance was simulated and the cleaner circuit sizedFalconbridge then compared predicted and actual float performance and mass balance and found that final concentrate recovery and mass and circuit cell volume matched closely. Simulated recoveries relative to actual were +0.4% Cu, +0.1% Ni and -0.7% Co. However, prediction of metal distribution in the internal streams making up the various circulating loads showed some sizeable errors. On this initial success, the trial was extended and additional float test data for rougher feed, cleaner feed and cleaner scavenger feed was generated on site in April 2005. Further simulations significantly improved prediction accuracy for metal distribution in the internal streams. The average difference between predicted and actual recovery for all streams was reduced from 10.5% to 0.4%. This updated simulation was then used to ascertain the impact on final recovery, grade and plant circulating loads of increasing feed tonnage from 114 to 150t/hr. A number of scenarios were simulated in order to understand the contribution that (a) the fast and slow floating fractions and (b) regrinding of cleaner tailings are making to overall plant recovery.Simulation was then used to determine how much the flotation kinetics of both rougher feed and cleaner scavenger feed have to increase in order to deliver a 1.5% improvement in overall plant recovery. These improved kinetic values provide a target for laboratory testwork and operating conditions can be varied to determine how best to achieve these new values of fraction and rate."

Jan 1, 2006

By Frank Cappuccitti, James A. Finch, Stéphanie Gélinas

"A colorimetric technique, originally developed for methyl iso butyl carbinol (MIBC) based on the Komarowsky reaction, has been extended to a wide range of common mineral flotation frothers. The procedure, which is briefly described, is shown suited to on-site determinations in a campaign at Kennecott Utah Copper Copperton Concentrator (Rio Tinto). Some observations are described, including: frother (MIBC) concentration evolution down a bank, frother distribution between pulp and froth phases, and loss of frother over time due to adsorption on certain minerals. A possible interference with a fuel oil addition was overcome. MIBC in recycle water was also measured.The ability to monitor frother easily will help interpret gas dispersion behaviour and should permit further optimization of flotation cell hydrodynamics and chemistry. The capability to directly measure should help optimize the type, amount and location of frother addition, and to assess frother recycled with reclaim process water.INTRODUCTIONOwing to the lack of analytical methods, the task of determining frother concentration in plant flotation circuits is not routinely performed. Industrial sites seldom outsource analyses that are both costly and inconvenient, due to the necessity of shipping freeze-dried samples to remote testing facilities. A more direct colorimetric method has recently been demonstrated for the laboratory characterization of common industrial frothers (Gélinas and Finch, 2004). The approach, based on the Komarowsky reaction (Penniman et al., 1936; Coles et al., 1942; Duke, 1947), was previously described by Parkhomovski et al. (1976) for methyl iso butyl carbinol (MIBC). The reaction involves the interaction of the OH group of a higher alcohol, concentrated sulphuric acid, and salicylaldehyde, to yield coloured solutions with intensities that can be analyzed by UV-visible spectrophotometry."

Jan 1, 2005

By Barbara Fotta, Lynn Rethi

Within the Mine Safety and Health Administration's (MSHA's) classification of metallnonmetal (MAM) mining, the number of independent contractor' employees has increased significantly in recent years. In 1985 independent contractor employee hours reported to MSHA accounted for 4.5% of all M/NM mining employee hours (excluding office workers); by 1994 that proportion had doubled to 9.0%. As a result, these workers now account for an increasingly significant proportion of fatal and nonfatal mining accidents. According to MSHA's statistics, annually computed fatality incidence rates (the number of fatalities per 200,000 employee hours) for independent contractors working in M/NM mining are consistently higher than those for operator employees. Over the five-year period from 1990 through 1994, 53 independent contractor employees were fatally injured while working on M/NM mine property (See Table 1). More than one third of these fatalities (36%) were due to accidents involving powered haulage; 21% were machinery accidents; and 11% percent were falling material accidents. Combined, these three accident classifications accounted for 68% of all independent contractor fatalities occurring on M/NM mine property during these years. Clearly, current efforts to increase the safety of the mining workforce must also address the safety of the independent contractor employee. This report is a preliminary attempt to identify trends in the employment and safety of independent contractor workers by identifying which segments of M/NM mining are experiencing the greatest increases in the number of independent contractor employees and by examining changes in the rates and types of accidents in which these employees are involved. The employment and accident data used in this report were obtained from the MSHA database. [ ]

By Hal McVey

Introduction The role of marketing in the minerals and mining industry takes on different degrees of importance depending on the commodity, but nowhere are sales and marketing more important than in industrial minerals. This article compares industrial minerals marketing with the marketing of other mining and mineral products. Marketing in Mining Some broad generalizations on the marketing of industrial minerals in relation to other mineral products can be made without getting bogged down with exceptions to generalizations. Two totally different areas of mineral production are crude oil and natural gas, and metals, including ores and concentrates. Although these commodities are the basis for two completely different industries, they share two things in common from a marketing standpoint: • Their value per unit volume is usually high enough so that they can be transported great distances. • Their specifications are readily definable and, therefore, the quality of a standard product from a production run can be communicated by stating certain chemical and physical features. This permits sales to be consummated by telephone, telex, and letter, without the need to pretest the products under use conditions. In regard to the first item, industrial minerals, as opposed to oil, gas, and metals, are in most instances site specific. Location of the point of production in relation to the point of use is of paramount importance based on a generally lower unit to volume value. This means that transportation is a major factor, with the cost of getting the mineral to market commonly exceeding its f.o.b. value. Coal marketing has many characteristics in common with industrial minerals. Coal sales can es-

Jan 11, 1983

By O. C. Irwin

For several years the C. F. & I. Co. men have been working on a fan signal and many different schemes have been tried. I will describe a few of them. A make-and-break attachment was placed on the fan shaft which caused a light to flicker. A hinged door was placed on air course and counter balanced so that it would have a slight travel when the air pressure was reduced an appreciable amount. This motion was used to open the power circuit, blow a whistle, or ring a bell. Series transformers were placed in motor leads of fan drive motor and the variation in amount of power to motor was used to control the fan signal through a magnet or relay. A governor was placed on the fan shaft which opened a signal circuit when speed of fan was reduced. We tried to produce a machine actuated by the volume of air, (that is on the principle of the anemometer) but had to discard this due to its being too delicate. None of the above schemes seemed to fill the conditions which the State and our Mine Inspector wanted covered. They gave us the following demands for a signal: 1. Must open mine circuit and sound alarm when air pressure was reduced below a certain amount. 2. Must be fool proof. 3. Must work on any kind of fan drive (steam or motor). 4. Must be safe to ' install- in any mine or fan house. 5. Must not depend upon mechanical device which could become inactive due to friction or other causes. 6. Must be as simple and easy to adjust as possible.

Jan 1, 1925

I TOLD you before that four things are necessary in addition to good judgment for one who wishes to practice the art of casting well. The first is to make the moulds and to have the furnace well made, the wood of a good kind, dry and seasoned, and the material disposed to melt. I have given you enlightenment on all these in detail, and on the last point as well, as you can see in the discussion on the alloys of metals where, among other things, I told you a good deal about those of copper. Therefore I wish to say but little about them in this chapter, but in order to follow the order promised you, I tell you that when you can, and if the labor or expense does not displease you, you should always alloy the whole quantity of the metals that you wish to put into one work and should make them into cakes of one kind. For, in addition to being more conveniently arranged in the furnace and mire easily handled, they all melt at one time and with much less work than they would if they were in pieces of different kinds. It is necessary to give corruption to copper, for if you decided to melt fine copper by itself in a reverberatory furnace your soul would burst before you had any honor therefrom. Then, if you wished to cast a fine thing from it, it would not succeed because it is dot fluid, on account of its viscosity; and if it should succeed, it would be all full of holes, like a

Jan 1, 1942

Book review Burkin, A. R. (ed.) . Leaching and reduction in hydrometallurgy. London, Institution of Mining and Metallurgy, 1975. £10. hydroxide pyritearsenopyrite NIM reports Report no. 845 A n electron-microprobe study of the nickel distribution in a serpentinite from Volspruit, Potgietersrus. (22nd Oct., 1969; re-issued Dec. 1975). Report no. 1546 Pilot-plant smelting campaign on iron ores from Tete. (22nd May, 1973; re-issued Jun. 1976). Report no. 1557 Cost estimates for the production of pig iron in the Tete district of Mocambique. (18th Jun., 1973; re-issued Jun. 1976). Report no. 1600 Dilute-acid leaching of slag from Tete ore. (20th Nov., 1973; re-issued Jun. 1976). Report no. 1602 The roasting of Tete slag for the extraction of vanadium. (20th Nov., 1973; re-issued Jun. 1976). Report no. 1635 Magnetic separation tests on Tete slag and ore. (30th Apr., 1974; re-issued Jun. 1976). Report no. 1671 Pyrometallurgical retreatment of a slag for the recovery of vanadium. (11th Oct., 1974; re-issued Jun. 1976). Report no. 1785 Some thermodynamic aspects of systems relevant to the flotation of sphalerite. Report no. 1808 Spectrophotometric determination (with pyrocatechol violet as chromogenic agent) of aluminium in zirconium metal and in the residue from anodesludges. Report no. 1813 The economic potential of some pegmatites from the Kenhardt area in relation to the trace-element content of their border zones. Report no. 1817 The rapid determination by X -ray-fluorescence spectrometry of tungsten in tungsten ores and concentrates. Report no. 1820 The thermodynamics of the formation of chlorocomplexes of iron (III), cobalt (II), iron (II), manganese (II), and copper (II) in erchlorate medium.

Jan 8, 1976

By L. F. Reinartz

The furnace in which rimming steel is made has an important bearing on the quality of the steel produced. Furnace.—Particularly in the manufacture of low-carbon rimming steels, it is necessary to have an efficient, easily regulated furnace, because of the relatively high finishing temperature requirements. In recent years, the most important development in design of open-hearth furnaces has been the sealing and insulation of the greater part of the furnace to prevent air infiltration and loss of heat. Efficient, straight-line valves insure proper draft. Combustion controls guarantee correct gas-air ratios. Furnaces of all sizes ranging from 20 to 200 tons have been used successfully in the manufacture of rimming steels. Metal bath is varied from 20 to 40 in. in depth without appreciable variation in quality. Charging.—A normal open-hearth charge consists of pig iron (hot or cold), scrap of miscellaneous nature, and slag-making additions, such as limestone and burnt lime. Because of local conditions, some plants find it necessary to discard the use of pig iron and use some carbonaceolis substances with varying percentages of cast iron to replace the pig iron. It is questionable whether such practice will consistently produce the quality of rimming steel required for auto stampings and other severe drawing requirements. Pig Iron.—An open-hearth furnace under proper control should melt 150 tons of low-carbon rimming steel on about 35 to 38 per cent pig-iron charge basis. In some practices, best results are obtained when the total charge contains from 0.40 to' 0.50 per cent silicon. If reasonably low-

Jan 1, 1935

By Renato P. Cunha

The paper presents the results of a comparative and parametric analysis in which a numerical program developed exclusively for groups of deep foundations under general loading (vertical, horizontal and moment loads) was used. This program, developed in the doctoral thesis work of Zhang (2000), extends the finite layer method to accommodate a simultaneous general loading on top of piled raft foundations, allowing the establishment of a coupled relationship between displacements (in all three directions), rotations (in two directions), and external loads. Zhang (2000) has extensively tested and validated this program against well known case histories, but has not applied it to piled rafts overlying unsaturated tropical soil materials. Hence, this paper further explores the applicability of this program by using it to simulate the behavior of experimental field loading tests carried out at the University of Brasilia (UnB) experimental site. At this site, Cunha and Sales (1998) and Sales (2000) carried out several loading tests on small scale isolated rafts (1 x 1m) and piles (L=5m, dia=0.15m), group of piles (4 piles, raft clear off the ground) and piled rafts (1 and 4 piles underneath a raft in contact with the soil). The authors adopt Zhang's program to backcalculate, hence simulate, this series of experimental field loading tests under vertical loading. They also use this set of results to "calibrate" the program for further parametric analyses. The parametric analyses were carried out with different piled raft configurations in this same soil type, trying to evaluate their field behavior under the effect of distinct (geometric) configurations of pile distribution.

Jan 1, 2002

By T. Gibson

It is generally accepted that South African coal mines have gone through the mechanization of most of its underground mines, and while there certainly were a lot of productivity improvements, the lack of visibility on these machines operating underground still leave vast areas for improvement. The average actual cutting time still remains very low, in the 30 per cent area, which leaves significant improvement possible. Currently all analysis is carried out using hand-written reports. Unfortunately this is subjective and often inaccurate because of human interpretation. In addition in order to avoid costly component failure, a monitoring system is required to warn of eminent failures and condition monitoring. The challenge faced was to supply and install a system that was ‘Open’ and could be retrofitted to existing machines in operation because of the current standard of communication links to the underground sections. In addition it was intended to use, existing ‘off the shelf’ software and hardware and adapting this for the harsh underground mining conditions wherever possible in order to reduce costs. As development occurred, as with all technology, doors opened to other opportunities such as, remote access data logging and Internet based reporting. We focused on the Voest Alpine Bergtechnik (VA) range of continuous miners, as need arose to achieve the desired cost improvements because of the strategy of service contracts the subsidiary company, Voest Alpine Mining & Tunnelling (VAMT) offer the mining industry in South Africa. This paper describes a data logging system that has been installed on various continuous miners that provides data in real time, on line, and that could be expanded to any electrically supplied underground mobile or stationary mining machine.

Sep 1, 2001

By William R. Groseclose, Cecil E. Tackett

Since 1965 when the first mole was used on Bureau work, the Bureau of Reclamation has completed 17 tunnels of over 5,000 feet in length. The longest was 12.8 miles. Total length of the 17 tunnels was 376,207 feet, or over 71 miles. The finished diameter varied from 7 feet 0 inch to 18 feet 0 inch with 82 percent (58 miles) being less than 12 feet 0 inch in diameter when lined. All of these tunnels except one are gravity flow, water conveyance tunnels with relatively flat gradient. One is a low-head pressure tunnel. All were constructed by contracts resulting from fixed-price bids. Starting in 1964 the Bureau of Reclamation initiated the practice of giving several options in the specifications on methods of tunnel excavation. Since that time, construction work has been completed on 17 tunnels. Of this number, 11 were mole excavated and 6 were excavated by conventional drill and blast methods. In general, there has been 2 feet of mole excavation for every 1 foot of drill and blast. Cost comparisons are based on only 13 tunnels because the Bureau has 4 recently completed tunnels that have pending claims; therefore, final cost data are not available. Some definite trends show from the data available; however, the number of completed tunnels in some categories is so small the results cannot really be considered a trend. As more data become available, the indications will become more reliable. The information is presented to indicate general trends and comparisons and cannot be meaningfully used for a one-on-one comparison because of individual tunnel differences not considered.

Jan 1, 1974

At a time when Congressional stiffening of health and safety regulations in the nation's coal mines seems all but an afterthought, when the problems confronting both mine operator and worker are being tossed about like a pigskin in an Australian- rules football match, what could be more appropriate to the times than to incorporate a discussion on these matters into the proceedings of an annual coal meeting. Integration of both technical and topical discussion provided the strength for this 28th Annual Meeting of the Central Appalachian Section of the AIME, convened at the The Greenbrier, White. Sulphur Springs. W. Va., Oct. 31-Nov. 1. Three technical sessions prepared for the occasion were served to those in attendance. First of these was held on Friday morning. Rendered excellent coverage, topics included Roof Structure Analysis at Blacksville No. I, presented by David Eyer, Christopher Coal Co.; Methane Monitors (evolution and evaluation of present day detection equipment); and Instantaneous Control Reaction to Mine Fires and Explosions, in which Elmer A. Fike illustrated the point quite vividly by showing a film on the potential of such control equipment. Indeed, the ability to snuff out a mine fire before it is allowed to spread even beyond its own igniting sparks speaks very well for itself. However, Fike hastened to point out that certain difficulties had to be overcome before these "fire watchers" could be implemented successfully in mines. These "bugs," inherent in virtually all coal mining environments, include ignition of sulfur pockets on mine facings and delivery of sparks on trolley rails, both of which may impede the accuracy of such control monitors.

Jan 12, 1969