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By M. Misra, I. Anazia

The dispersion of oily collector has a significant effect on the flotation recovery of ultrafine coal. Generally, reagent dispersion is accomplished by mechanical mixing and/or ultrasonic agitation, followed by direct addition of dispersed collector into the flotation cell. Such dispersion and reagent addition techniques are invariably inadequate and nonselective. A new collector addition technique involving gas phase transport of atomized collector has shown improved results when compared to conventional reagent addition techniques. This technique involves atomization of the collector into the air stream. Under these circumstances, an aerosol is introduced into the flotation cell. Initially, the oil is dispersed within the air phase (continuous with respect to oil), and the air phase is dispersed within the pulp (continuous with respect to aerosol). In the flotation cell, the atomized oil droplets coalesce on the bubble's surface and create a de facto oil-encapsulated bubble. This approach provides excellent dispersion, increases selectivity, and, most significantly, increases the flotation rate of ultrafine coal. Atomization of collector/frother combinations yielded improved flotation recovery and maintained near uniform froth levels, which is a desirable feature in coal flotation. Microscopic examinations of the attachment of oil- coated bubbles at a coal surface were conducted by attachment time and contact angle measurements. Oil-coated bubbles attach at significantly faster rates and with a higher contact angle than oil-free bubbles.

Jan 1, 1988

By W. Belobraidich

Kennecott's Ray mine is located about 145 km (90 miles) north of Tucson in the Mineral Creek mining district of central Arizona. Mining in the district started in the late 1800's. The Ray mine itself was first mined by under- ground methods in 1911 and was changed to an open-pit operation in 1952. Mineralization is complex and includes sulfide, silicate, and native copper mineralization, as well as minor amounts of molybdenite. Sulfide ore, mined at Ray, is shipped by rail to Kennecott's concentrator and smelter at Hayden, 32 km (20 miies) away. Silicate ore, mostly chrysocolla, is processed near the mine in a vat leaching-electro- winning plant. The mine consists of two sulfide areas: (1) the West pit and the Central pit (the original Pearl Handle pit) and (2) a silicate area on the northeast perimeter of the Central pit. The pit now is over 304 m (1000 ft) deep and approximately 3048 m (10,000 ft) long. Roads within the ultimate pit are limited to a grade of 10%, while those outside the pit are limited to 8%. The mining equipment consists of 40 Wabco 1094 (120-st) haulage trucks [ranging from 109 to 227 t (120 to 250 st)], 12 electric shovels [ranging from 6 to 23 m (7 to 25 yd)], and 3 11-m (12-yd) Dart production loaders.

Jan 1, 1979

By A. J. Kroha, N. Wesis

Most copper mines produce both ore and low-grade "leach" rock or acid waters that contain recoverable copper. The sulfide ores pre¬dominate, and a portion that is too low grade for milling to produce concentrates for smelting, but has to be mined and trucked away anyhow, may be leached successfully with acid in dumps. Most of this leach material consists of sulfides and silicates or carbonates, and if the gangue is such that it consumes a high quantity of acid, this factor may rule out a leach operation. There are also valuable deposits that contain mostly acid-soluble copper, or occasional sulfide ores from which a sulfide concentrate can be roasted and acid-leached to produce a copper-bearing solution. Finally, there are milling ores in which the lesser part of the copper is acid-soluble and can be precipitated with iron or synthetic inorganic precipitants that produce metallic copper or copper sulfides that will float with the sulfides. Ordinarily, ores that contain copper associated with the sulfur ion, such as in the minerals chalcopyrite, chalcocite, bornite (and others), are milled to produce a 25-30% Cu concentrate for smelting, while a lesser amount of acid-soluble copper may be converted from solution to cement copper on iron scrap. A fast-growing percentage of such copper, however, is removed from solution with exchange resins or organic compounds in organic carriers such as kerosene (solvent extraction), then eluted with strong acid and subjected to electrolytic precipitation either in marketable form or as anodes that can be refined further. From the point of view of conventional copper smelting, copper flotation concentrates and cement copper are of chief interest in this chapter. Table I is a condensed open schedule for concentrates that generally run between 25 and 35% copper, and much less frequently as low as 12-15% or as high as 65-75% copper, the former being due to intimate relationship with pyrite (like the former United Verde Extension), and the latter representing such ores as the Bolivian Coro¬coro ore in which the copper is in the form of chalcocite in sandstone. These extremes are no longer common. When they occur, a special purchase schedule has to be negotiated. Included in Table 1, copper precipitates (cement copper) generally run from 70-85%a copper, and the same basic purchase schedule is used as with flotation concentrates. Sulfide Flotation Concentrates The sulfide copper concentrate produced in the mill as a flotation froth, with water then added for transportation of the heavy mineral particles from the flotation cells to thickeners, may run 60-80% water by weight, and the removal of water down to 25-50% by weight by means of thickeners, followed by further dewatering by continuous vacuum filters to 7-18% moisture by weight (depending on size of solids by screen analysis and also by content of clay) is a critical operation. Mill operators would like to produce a filter cake with 7-9% moisture content, but even with the help of steam on the filter this desirable condition is seldom realized when the concentrate is as fine as 80% -325 mesh. More commonly, the final concentrate is reground in pro- to produce best copper recovery and grade of concentrate (or molybdenite separation). In those cases, increasingly frequent, the filter product may not be a cake at all, but a mud that is hard to handle-even requiring a thermal dryer. Greater difficulty of form¬ing a manageable cake often comes from the copper-molybdenum separation by flotation, because the alkaline sulfides and hydrosulfides, or cyanide, or other similar reagents used for the separation, may leave the now relatively molybdenite-free copper concentrate even more difficult to filter. Handling a wet filter cake is difficult enough when its destination is only a short distance away-a matter of yards rather than miles. In those cases the filter cake may be thermally dried near the point of production, using rotary or multiple hearth, or fluidized-bed dryers. Alternatively, the concentrate may be pumped or carried in slurry form to the smelter and filtered there, or it may be spray-dried and compacted. For transportation to a smelter just a few miles to a few thousand miles away by ship or railroad other factors may be important, such as: in shipping by sea, avoidance of spontaneous combustion; in shipping by rail, losses by leakage if too wet or by wind and sun if too dry. It is the responsibility of the millman-usually the mill superinten¬dent-to make sure that his concentrates are in satisfactory condition when they leave the mill so that they meet these requirements: 1) They must have been accurately sampled and dry-weighed, the latter meaning that a moisture determination and gross weight must have been taken. 2) They must be dried sufficiently when necessary to prepare them for safe transportation. 3) They must arrive at the smelter with reasonable likelihood that they can be check-weighed and sampled fairly and equitably,

Jan 1, 1985

By M. G. Ayat, B. C. Scott

J. Dasher Having an interest in coal slurry pipelines from a decade of arguments with Ed Wasp and crew at Bechtel about pumping thicker slurries slower, I immediately read this article and found nothing in it pertinant to the title. Ayat and Scott pumped five unidentified coals at 9% solids (50%-60% is the area of interest) in a 25-mm (1-in.) pipe around two square elbows through a 76-mm (3-in.) cyclone for up to 60 minutes and sized a large number of samples of unstated size on an unidentified wet screening device. They did not measure power consumption, discharge pressure, flow rate, or give pump tip speed or impeller diameter. They siad the cyclone had a "high" pressure drop (unmeasured) and did much of the degradation (measured) but more or less per unit of energy expended? Hargrove was not measured, so there are no data as to whether it would correlate with degradation. The authors conclude, with no attempt, correlation is "hard to establish." Please experiment before concluding. I am at a loss to know what "increasingly smaller size" means, much less what theory says such particles take "exponentially larger quantities of energy," which the authors neglected to measure. If such experiments without pertinent data or justified conclusions must be published, please attach a pertinant title. reply by M. G. Ayat The first and the last criticism of this paper is that the work is not pertinent to the title. Anybody who reads this article will immediately realize that the work describes the breakage of coal particles to finer sizes in coal slurry pipes and pumps. If this is so, why not title the work "Degradation process in coal slurry pipelines"? What could be more pertinent to this title than the investigation concerning the degradation phenomenon of coal particles in a pipe carrying a coal slurry? Mr. Dasher complains that he does not understand the meaning of the term "increasingly smaller size." The first sentence of this article defines the degradation process as "the breakage of coal particles to increasingly finer sizes." The term "increasingly finer sizes" here means successive breakage of a fine particle to finer and finer sizes. According to Hukki (Hukki, 1975), the probability of breakage is high for large particles and rapidly diminished for fine sizes. We apologize for being brief about some of these definitions. The degradation process, breakage of particles to increasingly finer sizes, is so widespread in the mineral industry that we did not feel it necessary to bore the reader with lengthy definitions of some simple terms. Mr. Dasher states that the coals examined and their original size consist are unidentified. Please look at Table I and Table 2 in the paper again where you will find the original size consist of the coals examined and their full specifications. We only named the coals A, B, C, D, and E to avoid identifying the coal seams that were more susceptible to degradation. Not identifying the name of the wet screening device used in this work has also been criticized. In our opinion, wet screening operation is such a routine and standard procedure that naming the device by which the screening is performed would serve no purpose but to promote a sales approach. This was not our intention. We did not conclude that the correlation between the degradation process and Hardgrove Grindability Index is hard to establish as Mr. Dasher writes in his letter. We stated, not concluded, that "It is reasonable to assume that some relationship between the extent of degradation and its physical properties, such as Hardgrove Grindability Index, does exist. However, any definite correlation is difficult to establish." This statement is based on other researchers work, which are clearly referenced in the article. The conclusions of this paper were based solely on the findings of the experimental work. As for the theory of comminution that Mr. Dasher asks, we would like to refer him to some basic comminution books and articles where various theories are clearly described. For example, Hukki (Hukki, R.T.,"The Principles of Comminution; An Analytical Summary," Eng. Min. 176, 106, 1975) suggests that the relationship between energy and particle size is a composite form of three laws (Bond's law, Kick's law, and Rittinger's law). A comprehensive analysis of coal breakage processes is also performed by Broadbent and Callcott (S.R. Broadbent, and T.G. Callcott, "Coal Breakage Processes, I. - A New Analysis of Coal Breakage Processes;" and "Coal Breakage Processes, II. - A Matrix Representation of Breakage," Journal of the Institute of Fuel, pp. 524-539, December 1956). These and many other relevant publications explain the relationship between the particle size and energy much better that what can be said in this short reply. We will, however, agree with Mr. Dasher on one particular point. We, too, believe that if the investigation concerning the degradation process in coal slurry pipeline were to be pursued further, one could choose to determine one or more of the variables available in the process, such as discharge pressure, power consumption, percent solid, pipe diameter, etc.

Jan 1, 1989

By D. A. Newman

The accurate prediction of mine profitability is essential for success in the present minerals market as is the ability to quantify the influence/of variations in revenues and costs on cash flow. A menu based spreadsheet template has been developed to determine annual cash flow, maintain depreciation schedules, and estimate labor and operating expenses. Sensitivity analyses may be conducted to determine the effect of productivity upon mining costs and the effect of selling price escalation upon rate of return. The advantage of this approach is that it can be used by a wide variety of professionals without extensive computer experience.

Jan 1, 1988

By Oscar Auerbach, Marvin Kuschner, Rosemarie Mick, Geno Saccomanno, Stephen Wood, Victor E. Archer, Marlene Egger

INTRODUCTION Excess bronchogenic carcinoma has been demonstrated among underground uranium miners in the United States, Czechoslovakia, and Canada (Archer 1981). This excess cancer is attributed largely to radiation from the alpha particles delivered to the tracheobronchial epithelium by the decay of short-lived daughters of radon. Interaction between the radiation and cigarette smoking has been demonstrated in production of the excess cancer (Archer 1973). The distribution of histologic types of bronchogenic cancer among uranium miners was established as different from that in other men in 1964 when an analysis of the first 51 cases among United States uranium miners was published (Saccomanno 1964). It was confirmed five years later by Yugoslavian studies (Horacek 1969). A later analysis, using a relative frequency method, indicated that oat cell and other small cell undifferentiated carcinomas increased markedly with increasing exposure to radiation in uranium mines (Saccomanno 1971). A subsequent analysis used only cases from an epidemiological study so as to enable calculation of expected numbers. It showed that there was an elevation in incidence of epidermoid, adenocarcinomas, and possibly other types, as well as small cell undifferentiated carcinomas (Archer 1974). At that time, it was felt that the histological distribution of cancer among uranium miners was well established. However, one of the authors (GS) has noted that fewer oat cell carcinomas were appearing among uranium miners in recent years. In his material the fraction of oat cell carcinoma, in successive 5 year periods between 1960 and 1980 was 59, 46, 37, and 22 percent. The association with calendar years is almost certainly spurious, reflecting some other factor associated with time. From the standpoint of tumor biology such a change must be important. This is a preliminary report which attempts to determine the cause of that change. POSSIBLE REASONS FOR OBSERVED CHANGE IN CELL TYPES 1) It might reflect a decrease in radiationinduced carcinomas, so that most of the ones being seen now are cigarette-induced. This appears to be a possibility because radiation levels in mines had been markedly reduced in the early 1970s, and because most of the uranium miners now developing carcinoma had quit mining during the 1965-1975 period. 2) It might represent a change in interpretation by the pathologists involved. 3) It might represent a real change in distribution as a result of increased latency, an aging population, cessation of smoking, increasing pack years of cigarettes, or other factors which have changed with time. Each of these possibilities is being checked. Dr. Waxweiler, later in this conference, is presenting an updated mortality analysis of United States underground uranium miners. His data indicate that lung cancer incidence among the Study Group of uranium miners is still quite high, but the ratio of observed to expected is falling somewhat. It is apparent that decreasing exposures in uranium mines is not yet reflected in normal lung cancer mortality rates. Reason #1 is therefore very unlikely. Thirty-five percent of the histologic types of carcinomas in this study were classified by a panel of three pathologists, 45% were classified by one of the panel members, and 20% were classified by a number of

Jan 1, 1981

By Jerzy Iskra, Wlodzimierz Sikora

INTRODUCTION The effect of stress concentration in coal seams leads to a sudden release in the form of rock bursts. This effect is controlled along many lines, but the most efficient methods consist in preventing the accumulation of energy in the seam or in the roof. The over- burden weight resulting from mining is the main cause of excessive stresses in a seam. An additional weighting of roof takes place due to formation of abutment loads. The accumulation of energy in the roof takes place where thick sandstone beds occur in overburden strata. An essential problem is to watch, with appropriate measurements, the stress of coal and roof rocks, and to conclude, on this basis, the degree of rock burst hazard. The methods for determining the stresses in a coal seam are quite well developed at present. Let me mention here the seismoacoustic methods, or borehole overcoring measurement methods. On the other hand, an examination of the state of stress in the roof rocks is almost impossible at the actual stage of development of the measuring technique. Hence, the model of stresses in roof was analyzed and determined theoretically. Based on this model, a technology for roof fracturing was developed which aims at destressing rock masses in a planned way. The essentials of the fracturing method consist of a controlled breaking of sandstone roof beds in order to: - prevent the excessive weight on the pillar - prevent a spontaneous breaking of roof beds at a limiting state followed by sudden energy release. High pressure fluid infusion is used to release buildup of stresses. THEORETICAL AND RESEARCH BASES According to the tests carried out by A. Kidybinski by the method of finite elements, isobars of stresses occurring in the roof over the working face are shown in [Fig. 1]. The results indicate: - the highest values of compressive stresses occur in the roof directly over the seam, at a distance of about 5 m ahead of the working face - at a distance of about 22 m above the seam there is a line of transition of compressive stresses into tensile - within the tested roof area, the highest tensile stresses occur at a vertical distance of 35 m, and at a horizontal distance of 20 m from the line of the working face. H. Gil (1) determined the pres- sure initiating the fracture of roof rocks by the formula: [ ] On the basis of results of analysis of isobars, and of the initiation of failure stress formula (1), isobars may be designed for a given roof class. Assuming for sandstones the Poisson ratio equal 0.3, a field of failure stresses presented in [Fig. 2] is obtained. In this figure it can be seen in which areas the effects of sandstone breakage may be obtained with the operation of a determined hydraulic pressure. To use formula (I), the knowledge of Rr is still necessary. This value may be determined in two ways: - taking a sample and testing it in the laboratory, if there is access to roof rocks in the existing openings, - drilling boreholes in the roof from surface and examination of the rock mass by using hydraulic breaking, if there is no access to roof rocks.

Jan 1, 1982

By Kenneth A. Gutschick, Harry L. Francis

A large number of minerals and chemicals (Table 1), some mineral-derived, are used in the treatment of both potable water and domestic sewage waste water and solids (Anon., 1990). In water treatment there are ten principal process uses as shown in Table 2 (Anon., 1990), which also lists the major chemicals in each process. Since lime (calcium oxide, calcium hydroxide, and dolomitic lime) is the largest chemical (by tonnage) used in water treatment, this chapter will deal primarily with this product. Note that it is included in five of the process uses shown in Table 2, and that indirectly it is also used in at least one other category (taste and odor control, where lime is used with potassium permanganate to provide optimum pH condition). POTABLE WATER TREATMENT Water Softening The biggest use for lime in water treatment involves water softening, where it serves to reduce carbonate hardness caused by dissolved bicarbonate and carbonate compounds. Currently there are more than 1000 domestic water softening plants (Table 3) located in most sections of the country, but particularly in Ohio, other midwestern states, Florida, and Texas, where limestone bedrock abounds (Anon., 1990). Among the other uses for lime in water treatment are coagulation, disinfection, and removal of heavy metals due to high pH softening, removal of certain radioactive and organic compounds and fluorides, neutralization of acidic water, removal of silica, particularly with dolomitic lime, and removal of color. Most of the above advantages accompany water softening, although at some plants lime is used specifically for one purpose, such as silica removal with dolomitic lime, minimizing pipeline corrosion by addition of lime to correct an aggressive water, and others. Hardness in water comprises two types - carbonate hardness, caused by dissolved calcium and magnesium carbonates and bi- carbonates, and non-carbonate hardness caused by dissolved non- carbonate salts, particularly calcium sulfate, calcium chloride, magnesium sulfate, and magnesium chloride. Total hardness is the sum of the carbonate hardness and non-carbonate hardness. Waters are classified as soft (0 to 75 mg/L as CaCO,), moderate (75 to 150 mg/L), hard (150 to 300 mg/L), and very hard (above 300 mg/L). Most water plants strive to reduce total hardness to about 100 mg/L, although in recent years the tendency in some cities has been to allow a little higher value in order to reduce both chemical costs and the amount of water softening sludges produced. There are four basic types of softening plants: lime softening, primarily to reduce carbonate hardness; lime-soda softening, for reduction of both types of hardness (in some plants caustic soda is used in place of soda ash, but it is more costly); split lime-zeolite, where a base exchange mineral is employed in place of soda ash (this system also requires salt [sodium chloride] to regenerate the zeolite mineral); and finally zeolite softening, which is generally used in small systems for private houses and small municipalities. Principal disadvantages of the latter system are its relatively high cost and the salt requirement, which introduces considerable quantities of soluble salts into the waste water discharge system.

Jan 1, 1994

By Gonzalo Barrientos

Instrumentation and observation of real mine structures helped define the pressure arch at White Pine, a large copper mine in sedimentary rocks. The pressure arch, which is attributed to inherent horizontal stresses, is used in the design of mine openings.

Jan 1, 1969

By Daniel McConvey

Who is the Investor? -Mainly institutional, including resource funds, other mutual funds and pension funds. -Some hedge funds. -Retail investors. -How important is the reserve disclosure to these investors? -Do these investors know the difference between a reserve and a resource?

Jan 1, 2003

By David R. Baughman, Ray V. Huff, Paul D. Chamberlin

ISL Ventures, Inc. (ISLV) is developing a process for recovering gold and silver from ores using a chloride-hypochlorite lixiviant. The leach solution, composed of water, NaCl and NaOCl, is maintained at a pH of about 7. At this pH most base metals are not leached. This is important for deposits that contain cyanide-soluble copper. An inhibitor can be incorporated to slow the decomposition of the oxidant. This paper reviews the history of development, presents details of the chemistry and indicates the nature of deposits, which we believe to be amenable to production using the process.

Jan 1, 1999

By Gordon L. Steele

Candelaria, a century old mining camp in western Nevada, was famous for its high-grade silver veins. Continuing demand for precious metals resulted in renewed interest in the mining camp and it is now being mined with modern open-pit methods and heap leaching of disseminated silver ore between mined-out veins. The Candelaria operation, in Mineral County, NV, handles 32.7 kt/d of material and was designed, built, and functioning within a year of corporate approval. Occidental Minerals Corp., an Occidental Petroleum Corp. wholly owned subsidiary, is the project's general partner and Congdon and Carey is the only limited partner.

Jan 6, 1981

By Ronald S. Tanaka

In the planning stages for a dozen years, the 9.11 mile long Mount Macdonald Tunnel is the focal point of the $600 million dollar Rogers Pass Project. The paper will discuss the construction of the tunnel that is being carried out from both ends. The eastern portion contractor has used a tunnel boring machine to excavate the upper part of the tunnel and at the west end contractor selected the conventional drill and blast method. A ventilation shaft located near the mid point is the main part of a ventilation system unique in the Western Hemisphere.

Jan 1, 1987

By Jim Armbrust

JAMIE DAVIS: Our next speaker is Jim Armbrust, maintenance manager at Phelps Dodge, Morenci. Jim's presentation is titled "We Need More Training-How to Get the Biggest Bang for the Buck." We've talked a lot about preventative maintenance and we've heard several people talk about training. How do we train to use all these systems? How do we educate people? This will be a nice little wrap-up for us. JIM ARMBRUST: One common theme from this morning's talk is that we need more training. That's exactly what we'll be talking about for the next few minutes.

Jan 1, 1998

By V. I. Lakshmanan, P. D. Tackaberry

The use of activated carbon as an alternative to Merrill Crowe precipitation to recover gold from pregnant leach solutions is recognized. Recovery using activated carbon, however, suffers from the interference, due to organic fouling, clay content and increasingly from the presence of elements such as copper. Ion exchange separation technology is familiar to the mining industry (uranium) and its potential application to the gold mining industry is evaluated with considerable efforts by research workers in South Africa, Australia, and North America. The present paper reviews in detail the status of the research work that identifies potential opportunities.

Jan 1, 1990

By Thomas A. Gwynn

"A beautiful America will require the effort of government at every level, of business, and of private groups. Above all it will require the concern and action of individual citizens, alert to danger, determined to improve the quality of their surroundings, resisting blight, demanding and building beauty for themselves and their children." "Improvement of our environment" has become a cause much like "motherhood". The increased awareness of the public concerning this subject makes it most unpopular for anyone to be involved in anything that seemingly is detrimental to our environment. And this awarement goes far beyond our biggest pollution problem in America - the distribution of paper, abandoned automobiles, beer cans and other garbage by our enlightened society along every city, highway, trout stream, river and mountain in America. In fact, the greatest awarement comes because of the "sensational" reporting and writing in our various national communication media, wherein the same voting citizens who so generously distribute their refuse about the countryside are emotionally aroused and duped into transferring what is truly a national problem onto the shoulders of a few industries - notably and particularly the mineral extraction industry. Certainly mankind is more and more stumbling over his own garbage daily, a fact that is easier to sell a citizen of one of our large cities than a resident of the wide open spaces of the west. Yet even in the Rocky Mountain states, the "Land of Sky Blue Waters", the "Big Sky Country", and particularly in Salt Lake valley smog is not unknown. Pollution and littering have become problems that need to be faced squarely. In North Dakota alone it has been estimated that one section of farm land each year flows down the mighty Missouri and the greatest producer of sediment is now reported to be the highway department.

Jan 1, 1969

By José Luis Lee Moreno

This paper presents a preliminary phase of a study being conducted by the Department of Geochemistry of the Consejo de Recursos Naturales No Renovables in the vicinity of the Pachuca-Real del Monte Mining District. This district is located in central Mexico, about 100 km northeast of Mexico City. It has been in operation for the past 450 years and has produced about 38 million kg of silver and about 190 thousand kg of gold. At the present it is being worked by the state owned mining company of Real del Monte and Pachuca. The rocks of the area consist mainly of Tertiary volcanics, ranging in age from early Oligocene to late Pliocene. Ore bodies are recognized as epithermal, vein type fracture fillings. The main ore minerals are argentite and acanthite normally accompanied by base metal sulphides, Gold is present in small amounts as native gold and in other minerals. Orientation geochemical studies performed on soil and rocks over known veins in the district, showed zinc to be the best indicator. Lead and silver anomalies are restricted to the immediate vicinity of the veins, mercury shows the mineralized structures only when the "C" horizon is sampled, while antimony gave erratic values. The El Chico area is about 10 km north of the Pachuca-Real del Monte district and covers approximately 400 sq km. Geological evidence indicated the possibility of an extension of the Pachuca ore bodies in this area. Results obtained from soil and rock samples from El Chico, showed several anomalous area. Detailed investigations proved these anomalies to be related to faults and fractures which in several cases have been found to be mineralized. Drilling is planned with preliminary results expected by late 1974.

Jan 1, 1974

By Robert Stefanko

The widespread and increasing use of electrical power for mechanized power has made a tremendous impact on the coal mining industry. It is probably the single most important factor influencing the productivity of a coal mine. In fact, as a part of a study of 62 coal mines in Pennsylvania and northern West Virginia, plus information that was obtained from other sources, it was possible to show a direct correlation between the rise in the use of electrical power and mine productivity, Figure 1. This increased power demand has not always been achieved through proper planning and a careful evaluation of all design parameters, many of which are not even recognized. The result has been increasing problems in power distribution and utilization establishing the need for scientific studies including considerable underground measurements. Because the cost of power for ton of coal produced is generally a relatively low value, inadequate attention is paid its distribution and utilization. Furthermore, a poor system of records and a lack of adequate measurements add further to a paucity of statistical evidence that would permit a rational analysis of overall power costs. However, the direct cost figure alone is highly deceptive; of much greater value is the indirect costs associated with the use (or misuse) of electrical power underground. Success in highly mechanized mining correlates directly with equipment utilization. Today's machines have tremendous potential capacities but profits are measured in terms of performance and not potential. Thus the reliability of electric motors is an extremely important factor for consideration and the effects of all parameters should be carefully evaluated. Thus while studies are continuing on the evaluation of primary and secondary mine electrical systems with interesting results, this paper will be limited to reporting on the results of a study of a specific motor application.

Jan 1, 1972

By T. D. MacQueen

Thank you Mr. Stevens. It's a pleasure for me to be speaking to this meeting of the Society of Mining Engineers of AIME this afternoon, and the Gypsum, Association is grateful for the invitation. A brief word about who we are: the Gypsum Association is the trade association for the gypsum industry - the manufacturers of gypsum board and lath a-d plaster. We have a membership of eight companies. These eight companies produce about 90% of the gypsum products manufactured in the United States ... closer to 94% actually. Our headquarters is in Evanston, Illinois. We have an east coast office in Washington, D.C. where the eastern manager handles technical and building code matters and maintains liaison between all of the government agencies and departments and our industry. We also have a west coast office in Los Angeles where our west coast representatives is heavily involved with the Uniform Building Code and ICBO. And then in the Evanston office our manager of technical and building code services, Herb Carlsen, bites his nails and loses his hair over these problems and various other projects that come in, such as conversion to metric and various other things. We also have a research associate at the National Bureau of Standards in Washington who is currently concentrating his efforts on the combustibility of building materials. His studies involve current testing methods, definitions, data analysis, and proposed new testing methods,.' It is anticipated that this program will lead to a better understanding of non-combustibility of building materials and systems. I mentioned that our members represent over 90% of gypsum products,' manufactured in the United States; it might be well to point out a couple of statistics about what that really means. According to the Bureau of Mines,

Jan 1, 1977

By Robinson Leon-Diaz, Alberto Jaen-Toribio, Raymond Blanchard, Mike Deevy, Miguel Fuentes-Llanos

"Tunnels designed to NFPA 502 are required to withstand the RWS time-temperature curve, more specifically prevent progressive spalling and loss of strength of steel reinforcement. Fire boards or spray-on layers can be effective, however, these solutions have capital and whole-life cost implications. The use of “fire resistant” concrete based on a suitable aggregate with polypropylene fibers has also increased in recent years. This article presents a new methodology for thermal and structural analysis of segmentally lined tunnels, which permits the analysis of project specific fire curves and an assessment of different fire protection strategies. The effectiveness of fire boards is assessed along with whether “fire resistant” concrete alone is a viable means of achieving the required protection. Finally, since NFPA 502 recommends water-based fixed fire-fighting systems for Category C and D tunnels, we discuss the question of how a fixed fire-fighting system should be addressed within the structural design. INTRODUCTION Protecting road tunnels from structural damage and collapse is a key requirement for both life safety and business continuity. Where road tunnels are part of key highway corridors, protecting business continuity is a high priority for owners, operators and the Authority Having Jurisdiction. For existing tunnels, compliance with NFPA 502 may require upgrades with either passive fire protection and/or water-based fixed firefighting systems. For new tunnels, compliance with NFPA 502 requires a combination of good practice in design and fire testing. A water-based fixed firefighting system is a Conditionally Mandatory Requirement1 for Class C and D tunnels, i.e. all tunnels greater than 300m and 1000m long respectively. The basis for fire safety design of new tunnels and assessment of existing tunnels is the worst-case fire scenario. A number of factors, including but not limited to the following, influence this design fire scenario:"

Jan 1, 2016