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By David R. Ray, Arthur J. Pyron, William F. Thomann

"Proterozoic plutonic and volcanic rocks in the Franklin Mountains, west Texas, exhibit similar values in average concentrations of equivalent uranium (eU), equivalent thorium (eTh) and equivalent potassium (eK) when compared to Proterozoic igneous rocks of the southwestern United States. Variations of radioelement concentrations for all Proterozoic igneous rocks of the Franklin Mountains range from 1.1 to 357.1 ppm U, 2.1to 259.1 ppm Th and 2.5 to 10.2% K.Recent geologic mapping of the Proterozoic rocks in the Franklin Mountains revealed several types of granites previously unrecognized, and these warrant further exploration for U and Th resources. Fluorite-bearing granites and riebeckite pegmatites are likely targets for further investigation, as these have the highest U and Th concentrations compared to all other granites.IntroductionThis is a summary of the paper presented at the CIM Geology Division Uranium Symposium held in Saskatoon, Saskatchewan, September 8-13, 1981. The purpose of this study was to evaluate the distribution of uranium (U), thorium (Th) and potassium (K) in Proterozoic igneous rocks in the Franklin Mountains, and compare radioelement concentrations to Proterozoic igneous rocks elsewhere in the southwestern United States.General GeologyThe Franklin Mountains are located in west Texas and southcentral New Mexico, within the southeastern part of the Basin and Range Province o f the southwestern United States. The Franklins are a complex fault-block range trending northsouth with strata dipping toward the west. Ages of the rocks range from Proterozoic to Cretaceous. Harbour (1972, 1960) provides the most recent account of the general geology of the Franklin Mountains. Most recent accounts of the detailed Pro Proterozoic geology o f the Franklins are provided by Hoffer (1976), Thomann (1980, 1981), Pyron (1980), Ray (1982) and McCutcheon (1982)."

Jan 1, 1983

By L. Adler

A fairly complex analysis is required to select, or evaluate a piece of excavating and bulk handling equipment and obtain its performance. At present there is little agreement as to what specific points should be considered, and even less on what procedure to follow. This paper provides both of these in a consistent and direct form. The analysis applies to all types and sizes of equipment from the bulldozer and the continuous miner, to the B.W.E. The importance of the equipment characteristics, job activities, and work conditions are stressed and separate analytical stems are established in a flow chart for these. They are combined using suitability tests in the following steps: 1) problem statement, 2) natural conditions, 3) suitability guidelines, 4) appropriate equipment types, 5) operational activities, 6) encumbered space, 7) geometric design, 8) equipment sizing, 9) failure and limits, 10) performance and consumption, 11) public policy checks, and 12) costs and profitability. Public policy and economics while considered throughout receive emphasis towards the end. The procedure is iterative, containing distinct feedback loops. Specifying the steps and sequence provides a necessary structure which has long been overdue.

Jan 1, 1983

By Francois E. Heuze

INTRODUCTION Rock slope stability typically is governed by the geological discontinuities. This stability can be improved by drainage, unloading, adjustment in slope orientation, adjustment in slope angle, and also by reinforcement such as bolts or tendons. This paper addresses the modeling of bolt reinforcement in rock slopes. Most geological discontinuities such as joints have rough surfaces; they dilate during shear displacement. Their shear strength is characterized by two envelopes (Fig. 1); the peak envelope is distinct from the residual envelope when the joints can dilate. If the dilation is restrained transversely, such as with bolts, the normal stress will increase and the joint strength also will increase. It has been demonstrated that this increase may be considerable (Obert et al., 1976). The new normal stress at peak strength is a com- posite function of the properties of the rock mass and of the steel (Heuze, 1979). Hence, the dilation and its resultant effects on joint shear strength must be included in the analysis and design of the reinforcement. We present a model which can be used to perform such an analysis. Early studies of rock reinforcement in mining and civil applications (Lang, 1957 - Panek, 1962 - Osen and Parsons, 1966 - Lang, 19721, did not consider the specific effects of bolts on joint shear strength. In 1973, Heuze and Goodman reported direct shear tests on rough sandstone joints with bolts perpendicular to the joint plane (Fig. 2). The peak shear strength of such joints was greatly in excess of the shear strength of the unbolted joints. The excess

Jan 1, 1983

By R. J. Lipp, I. Iwasaki, R. H. Heerema

The presence of calcium ion in iron ore pulps that are upgraded by selective desliming can result in indiscriminate flocculation of both iron oxide and siliceous gangue slimes. In order to overcome this adverse effect, deflocculation by three complexing agents, namely ethylenediaminetetzaacetate (EDTA), sodium tripolyphosphate (STPP), and sodium hexametaphosphate (SHMP), was investigated. The precipitates and complexes of these agents with calcium ion were characterized by potentiometric and conductometric titrations, and the surface properties of quartz and goethite were studied in the presence of calcium ion and of the complexing agents by means of streaming potential measurements and flotation tests. The results were then correlated with selective flocculation tests on an artificial mixture of quartz and goethite. EDTA markedly improved the selectivity of flocculation when added in near stoichiometric amounts, whereas STPP was less effective and SHMP was totally ineffective due to strong, indiscriminate dispersion. Remanent calcium polyphosphates on the goethite surface interfered with the adsorption of starch flocculant.

Jan 1, 1983

By Greg Border

Many unique ventilation problems have been faced as Avery Island Mine's large openings have been mined. High humidity of outside air combines with the hygroscopic salt to create a corrosive atmosphere. Massive rooms preclude routine use of brattices to direct air flow to the working faces. Large amounts of explosives are consumed in single blasts. Resulting concussion pounds air control structures and ANFO ignition creates large amounts of nitrogen dioxide in single rooms. Geologic constraints confine new shafts and slopes to areas thought to be free of potential ground water hazards. Dust control techniques are limited by dry product demanded by customers. The Avery Island Mine's ventilation system has evolved to deal practically with the conditions and to dependably provide fresh air to the miners. International Salt Company's Avery Island Salt Mine, a multiple level room and pillar operation, has been mined steadily since about 1900. It is known as one of the "Five Island" salt dome mines of South Louisiana's Gulf Coast. Production from the area places Louisiana first in United States rock salt mined tonnage, according to the United States Bureau of Nines, 1982 (1). International Salt Company is a major force in U.S. salt production, as it also operates mines in Detroit, Michigan; Cleveland, Ohio; and Retsof, New York; a solar salt facility in Bonaire, Netherlands Antilles; and a solution mining plant at Watkins Glen, New York.

Jan 1, 1983

By Richard H. Olson, Lawrence A. Roe

Talc, when it can be isolated as a pure mineral, has a composition of 63.36% Si02, 31.89% MgO, and 4.75% H20. However, as an industrial commodity, talc rarely approaches theoretical purity. Nevertheless, the impure talc products of commerce find a multitude of uses and few substitutes in many industrial applications. Minerals commonly associated with and sold together in talcose mixtures are tremolite, chlorite, dolomite, mica, and magnesite. Steatite was originally a mineralogical name applied to pure talc. In today's commerce steatite generally refers to the massive variety of talc suitable for electrical insulator manufacture. Block steatite ore can be machined into various shapes. Impure varieties of massive or block talc are still commonly referred to as soapstone. Soft massive talc, suitable for crayon manufacture, has been referred to as French chalk. It has been common practice to discuss talc, soapstone, and pyrophyllite under the same general heading. In the case of soapstone and talc, this is a natural thing since many different types of platy, soft minerals exhibiting a high degree of lubricity (commonly referred to as "slip") have been grouped together and called soapstone or talc. Further, there is a mineralogical relationship of pyrophyllite to montmorillonite and talc to hectorite. Thus, talc and pyrophyllite are sometimes referred to as clay minerals. When finely divided talc or pyrophyllite are combined with water in proportions to make a slurry, the end product does have the appearance of a clay-water mixture. Soapstone for utensils and ornaments was mined by prehistoric Indians on Santa Catalina Island, CA. In the mid-1800s, soapstone from deposits along the western foothills of the Sierra Nevada mountains was used by white settlers for building and ornamental stone and in the linings and foundations of furnaces (Anon. 1956). Previous to 1916, the annual recorded production in California did not exceed 2000 tons. In the period 1912 to 1918, output rose sharply when the Talc City, Western, and Silver Lake mines were put into operation. From 1916 to 1935, the state's annual output of talc was in the range of 9,000 to 20,000 tons. In the mid-1930s, the use of talc in wall tile grew rapidly. In California, the production of talc grew to 63,000 stpy in 1943. The post-war building boom helped California production to grow to 120,000 tons in 1951. In 1968, production was 165,000 tons, 1969 was 145,000 tons, 1970 was 185,000 tons, and 1972 was 155,000 tons. Talc mining in New York state dates to about 1878 when a Colonel Palmer and associates opened the first commercial talc mine on the Nelson Freeman farm near Talcville, New York. In 1893, this operation was sold to the International Pulp Co. which changed its name to the International Talc Co. in 1944. The company was acquired by R.T. Vanderbilt Co., Inc. in 1974. A new talc operation, the Gouverneur Talc Co. owned by the R.T. Vanderbilt Co., began operations near Balmat, NY, in 1948. The initial capacity of the processing plant was 200 stpd (Gillingham, 1950). Subsequent expansions have increased capacity to over 600 stpd. The Vermont talc industry began just after the start of the 20th century. Talc was discovered in the area of the present Johnson, VT, talc mine in 1902. The American Minerals Co. initiated plant operations at Johnson in 1904. The Magnesia Talc Co. opened a plant at Waterbury, VT, in 1913 (Burmeister, 1963; Trauffer, 1964) and acquired American Minerals Co. in 1923. The Waterbury mine has a long history as a producer of talc crayons. The Eastern Magnesia Talc Co. was formed in 1924 by a merger of the Eastern Talc, Co.

Jan 1, 1983

By R. H. McCorkell

"Sample drops were evaporated on Lexan disks on which fission tracks were etched and counted after neutron irradiation. [U] = 0.01 ppb could be measured. This method is rapid, cheap, simple and accurate when sufficient control and checking is possible, but several types of error were encountered in its use, the natures and sources of which were investigated but not always determined. The most troublesome were ""annealing"" processes which sometimes altered the fission tracks so that they were not fully revealed, or acquired varying appearances, after etching. Several different annealing processes seemed to exist and seemed to be produced by alteration of the Lexan surface by dissolved components in the solutions and, perhaps, by radiation and local heating during neutron irradiation. The appearances of the etched tracks varied with the natures of the droplet solutions even when annealing appeared to be absent, and for this reason, standards are best prepared by additions of known amounts of U to sample solutions. Contamination of sample droplets by U-containing dust from the air is best avoided by preparing the disks away from areas where other U-analysis is being carried out.IntroductionFission tracks are regions of radiation dam age produced in solids by the fission of atoms such as 235U. They can be enlarged to sizes visible through optical microscopes by etching surfaces through which they pass with solvents in which the solids are slightly soluble. A sample to be analyzed for U may be placed against a film of a solid of negligible uranium concentration (the track detector) and irradiated with thermal neutrons in a nuclear reactor to fission 235U. The track detector is then etched and the number of tracks per unit area, ?, which is proportional to the uranium concentration of the sample, c, and the neutron do se, n, is found by counting through a microscope. Uranium in solutions ha s been measured by evaporating drops on track detectors, irradiating, etching and determining the number of tracks per drop, T(2,3,4,5). Extensive test s of this method are reported here."

Jan 1, 1983

By H. E. Wilborg, G. V. Henderson

This chapter deals with those sands employed by foundries for the manufacture of cores and molds used in the casting of such common metals as steel, gray iron, ductile iron, aluminum-based alloys, and copper-based alloys. Most metal is cast in "green sand" molds in which the sand mixture, consisting primarily of silica, clay, and water, forms a plastic material. This plastic material is rammed around a pattern in a split box called a flask, then the box is separated, the pattern is withdrawn, and the metal is poured. These green sand molds are broken apart when the metal has solidified. The sand is then remixed and a new mold made for the next casting. To a lesser extent silica sand is mixed with resins or oils and, after forming, the mixture is hardened by either heat or chemical reaction. In any case, the foundry mold or core is used just once before being broken up and remixed for manufacturing another core or mold. By far the greatest consumption in the foundry is of those types of sand high in silica, low in clay (under 0.5%), and occurring in numerous locations thoughout the United States. Consumption End Uses Foundry sands fall into four distinct categories: silica sand, lake sand, bank sand, and natural molding sand. Silica sand is a general term used to describe washed, graded, dried, and cooled clay-free sands which are found in many parts of the United States. They generally contain 90 to 100% silica but vary greatly in chemical analysis and grain structure. Lake sand is the sand dredged from Lake Michigan or dug from the dunes bordering that lake. Bank sand is composed primarily of silica grain but containing up to 5% clay. It is shipped in both the damp and dry state but the normal processing of bank sand consists only of drying and scalping. Occasionally two different grades of bank sand are blended prior to or during loading. Natural molding sand is a term used to describe a sand containing sufficient clay as mined to be suitable for molding purposes. Clay content may vary from 10 to 24% with the balance of the material consisting primarily of silica sand. These sands range in fineness from one peaked on the 20 mesh to one which contains more than 50% of the particles passing the 270 mesh. Lake sands are relatively coarse and are used in great quantities for the production of automotive castings. Bank sands and natural molding sands are gradually phasing out as the production of castings becomes more a science and less an art. The vast majority of foundry sands used today are those known as the silica sands and lake sands. Foundry sands are used in two basic ways. The majority are used in the green or uncured state with the balance used in the cured or set state. Green sand is grain bonded with clay and contains varying amounts of water to plasticize the clay in order to bond the grains together. Green sand is either naturally bonded or "synthetic" sand. The naturally bonded molding sands are generally found in the Hudson River Valley of New York State, Cumberland County in New Jersey, and in Tennessee and Mississippi. Synthetic sand is molding sand compounded in the individual foundry. It is made up primarily of graded silica sand, western or southern bentonite, water, and carbonaceous and/or cellulosic materials. Green sand is used primarily in making molds. The use of naturally bonded green sand has been declining for many years, primarily because naturally bonded sands are more difficult for the foundryman to find and control. Synthetic green sand, on the other hand, can be

Jan 1, 1983

By G. T. Lineberry

Reduced clearance is one of the most important characteristics of encumbered space in underground coal mining. Another key variable is the maximum velocity at which a piece of mobile mining equipment can operate in this limited space. Typical velocity- clearance curves for different mine transportation systems are developed and characterized. Applications of the relationships are examined, emphasizing their significance in the design and control of mine materials handling systems.

Jan 1, 1983

By Martin B. Treuhaft

Expectations for coal in the early to mid-1970's prompted the government and industry to pursue research and development programs to increase underground and surface mining coal productivity and net coal recovery. Several programs concerned advanced surface mining methods for thin seam coal recovery. Three such programs, along with related areas of interest, are presented in this paper, namely: (1) extended depth augering for trench-strip applications; (2) high recovery auger heads for enhanced recovery; and (3) variable wall mining in low cover longwalls. Conceptual development is examined, prototype testing is discussed, and potential operations are considered.

Jan 1, 1983

By Brian J. Gorva

The key objective of forming a cartel is to increase profits to members of the cartel by taking the following action: a) control output; and b) control price. However, while attempting to obtain monopoly profits the cartel members have to contend with costs associated with cartelization and such costs include the following: political costs; the cost of coordinating output and price; organizational costs (such as cheating); and administrative costs (such as the cost of attending cartel meetings). The objective of commodity exchanges is to provide an open, free market where buyers and sellers may openly complete transactions and pricing information can be immediately disseminated. These transactions include the following: a) to provide facilities for "hedging", or transferring price risk from buyers and sellers of physical commodities to "speculators" through the medium of buying and selling futures contracts, and b) taking physical delivery of metal on due dates.

Jan 1, 1983

By C. Dale Elifrits

Observations made from laboratory analysis of samples of fine-grained argillaceous materials (shales) subjected to various changes in moisture content have been correlated to loss of strength in the rock material. This reaction to a change in in-situ conditions (subsequent to mining) at a mine site combined with the observed relationships of surface-disturbing subsidence features at locations where the predominant overburden material is fine-grained, provides a predictive tool for the subsidence engineer.

Jan 1, 1983

By David J. Boron

The United States has the largest total (364 billion metric tons) and recoverable (182 billion metric tons) coal reserves in the world.1 However, progressive coal utilization in this country has been hampered by environmental constraints, such as restrictions on sulfur dioxide, nitrogen oxides, and particulate emissions. New technologies are being pursued both to appease these environmental concerns and improve economic performance and process efficiency. These technologies, however, have not reached the level of effectiveness required for optimum operation. If more stringent emission standards are imposed, it is likely that the coal industry, and the industrial and utility sectors will look increasingly toward the successful development of new and advanced coal cleaning technologies in order to continue and promote the use of coal in this country. The EPA New Source Performance Standards In 1979, the Environmental Protection Agency in response to the amendments to the Clean Air Act of 1977 issued new source performance standards (NSPS) for utility and industrial boilers. The NSPS set emission standards for sulfur dioxide, nitrogen oxides, and particulates affecting boilers of 250 MM Btu per hour heat input or 'greater that started construction after September 1978. Plants starting construction or in operation before September 1978 remained subject to the provisions of the regulations promulgated in 1971, i.e., SO2 emissions of 1.2 15/MM Btu. The NSPS for SO2 emissions provides a sliding scale for SO2 reduction depending on the sulfur content of the run-of-mine coal, with an upper limit of 1.2 lb of SO2 per million Btu and a minimum emission level based on 70% SO2 removal. Table 1 summarizes the EPA NSPS for SO2 emission standards.

Jan 1, 1983

By T. P. McNulty

During the last decade, many exhaustive studies have been made of process energy requirements for the production of various metals and materials. Some excellent technical papers and text books have resulted, and some of these are included in the bibliography of this paper. These studies were, of course, prompted by the economic pressures which resulted from the beginning of the "Energy Crisis" in 1973. Our intensified consciousness of the cost of energy led, then, to a greatly improved understanding of the energy consumption attributable to individual mining, processing, and refining steps. It is worth noting, however, that an awareness of the cost of energy is not new and that efforts to minimize this cost were an important part of sound mine and plant management practice throughout the earlier days of our industry. One only has to read a few accounts of mining operations around the beginning of this century to develop an appreciation for the cost of supplying wood, coal, fuel oil, or electric power to remote locations.

Jan 1, 1983

By William K. Brown

Are the results of an exploration program worth the cost? This is a question I suspect many of you are familiar with and, theoretically at least, it is an easy question to answer. The answer, of course, lies in comparing the future earnings stream the program is expected to generate, to the present value of the cost of carrying it out. While historical costs can be determined without much difficulty, estimating the value of a future earnings stream involves all sorts of assumptions regarding future costs, metal prices, inflation rates and an appropriate discount factor; and in the context in which the question arises, requires additional assumptions about mineral deposits which have yet to be discovered. As a practical matter, this kind of approach isn't likely to produce a very convincing answer; certainly not one convincing enough to satisfy a skeptical audience; nor one likely to temper the illusions of recent converts to mineral exploration, who are convinced that if enough money is spent, profitable discoveries will inevitably follow. Within broad limits, however, I believe it is possible to analyze the costs and results of gold exploration in the U.S.A. over the past 20 odd years in a useful manner. And while such an analysis is imperfect, it will provide some insight into this fascinating subject.

Jan 1, 1983

By André Bérubé

"IntroductionSince the disappearance of Les Forges du Saint-Maurice at the end of the last century, many historians have taken an interest in the lengthy past of this enterprise. They considered the political, socio-economic, administrative and anecdotal aspects of the industry, but barely dealt with the elements of technology. The purpose of this article is to try to fill this gapru.Les Forges du Saint-Maurice was an integrated industrial concern, specializing in the production of semi-finished wrought iron and finished cast iron, that operated almost without interruption between 1734 and 1883. Les Forges first came into being in 1729, when Montreal merchant Francois Poulin de Francheville submitted to the king of France a request for the right to exploit the bog iron ore deposits on his seigneury of Saint-Maurice. This request, agreed to in 1730, was one of a long series of attempts, previously unsuccessful, to establish a local iron industry in the colony. Several such proposals were held up by a lack of capital from promoters or a too rigid application of the mercantilist policy by the metropolis. In 1730, however, the French minister Maurepas favoured a more liberal policy which would encourage private enterprise. The benefits of an iron industry to the naval construction industry was a factor that caught the attention of administrators. The choice of the site for Les Forges was based on the following factors:• the abundance of surface deposits of bog iron ore in the Saint-Maurice region;• the presence of a vast supply of hardwood and conifers needed in large quantities by this industry;• the proximity of sandstone and limestone deposits, indispensable materials for the construction and operation of the blast furnace;• the presence of a water stream, with sufficient flow to provide the hydraulic power needed for the operation of the machinery."

Jan 1, 1983

By Deborah A. Kramer

An economic and technical evaluation of a proposed process to recover alumina by leaching calcined kaolinitic clay with sulfurous acid is presented in this Bureau of Mines report. After the insoluble portion of the clay has been removed by leaching, monobasic aluminum sulfite is precipitated from the pregnant leach solution by partial hydrothermal decomposition. Further heating completes the decomposition to an impure alumina hydrate. This intermediate is purified in a modified Bayer process, which includes dissolving the alumina hydrate in a caustic solution at high temperature and pressure, then decreasing the temperature and pressure to precipitate alumina trihydrate. Calcining the trihydrate produces the alumina product. A cost estimate was prepared for a plant producing 1,000 tons of alumina per day, 350 d/yr. The estimated operating cost is approximately $475 per ton of alumina. This is substantially higher than a comparable estimated operating cost for the Bayer process of $250 per ton of alumina. The proposed process does not appear economically attractive, even as a method to modify a current Bayer processing plant to use a kaolinitic clay feed. High capital costs and high energy requirements make the process prohibitively expensive.

Jan 1, 1983

By K. F. Unrug

An overview of the history of mining technology, both past and present, shows that some of the new concepts being successfully applied have changed the reserve categorization and are having an overall impact on production. Past coal mining operations in the eastern coal fields, and especially in Appalachia, extensively utilized stripping with the predominately applied contour method. As a result, vast mountainous areas have abandoned benches left behind by past mining operations. While thicker seams previously stripped were usually mined by underground or mountain top removal methods, thin seams beyond technical or economical limits were left intact after contour mining had reached the ultimate height of the wall. These thin seams quite often contain high BTU, low ash and sulfur coal that makes them attractive for a secondary recovery due to the market requirements. Secondary highwall recovery has obvious potential and is economically attractive; however, with the present state of industrial experience and lack of analysis of site data, a trial and error approach is used by operators.

Jan 1, 1983

By Eivind B. Jensen

Introduction Though temporarily shutdown due to the depressed economy, the Henderson mine is a large underground molybdenite producer, using a continuous panel-caving mining system. The location of the ore body requires access from the surface through three shafts, the collars of which are located about 3.15 km (10,350 ft) above sea level. At this altitude, normal temperatures are such that heat must be added to intake-ventilation air for about half of each year. This prevents ice from building up in the intake shafts, waterlines from freezing underground, employee discomfort, and equipment-related problems such as pneumatic rock drill icing and cold starting of diesel engines. Because of topographic and environmental constraints, the Henderson mill and concentrator are located 24 km (15 miles) from the mine, on the west side of the Continental Divide. All ore from the mine is transported to the mill by an electrified rail haulage system, with 15.4 km (9.6 miles) of the trip being underground through a double-track tunnel. A shaft at the midpoint of the tunnel exhausts air drawn from the mine and from the portal that is at an elevation of 2.7 km (8,950 ft). Intake air at the portal must be heated for part of the year to prevent ice buildup. Mine Ventilation System The mine ventilation system uses three sources of fresh air and two exhausts. The primary freshair intake is No. 3 shaft. It is concrete lined to a diameter of 7 m (23 ft) for a total depth of 698 m (2,291 ft). An airflow of 755 m3/s (1.6 mil¬lion cfm) is supplied to this shaft by two vane-axial 932-kW (1,250-hp) fans on the surface. The air is distributed within the mine by means of fresh-air distribution levels connected to production and development levels by raises. A secondary source of fresh air to the mine is provided by No. 2 shaft, the primary man and material access. This shaft is concrete lined to a diameter of 8.5 m (28 ft) for a total depth of 946 m (3,105 ft). Downcast airflow is induced by a pressure differential produced by the fans in the system such that net intake and exhaust volumes are equal. The No. 2 shaft flow of 165 m3/s (350,000 cfm) enters the mine network from the production and haulage levels. Exhaust air is moved from the various working levels through connecting raises to exhaust col¬lection levels that return it to No. 1 shaft. No. 1 shaft is the primary mine exhaust. It is concrete lined to a diameter of 7 m (23 ft) for a total depth of 788 m (2,584 ft). Three vane-axial 932-kW (1,250-hp) exhaust fans are located at the collar of No. 1 shaft, producing a flow of 850 m3/s (1.8 million cfm). In addition, an airflow of 71 m3/s (150,000 cfm) from the intake distribution level is exhausted via the haulage tunnel, by means of No. 4 shaft located midway in the tunnel. The main features of the mine ventilation network are summarized in Fig. 1. Ventilation Air-Heat Plants No. 3 Shaft In the early design phase of No. 3 shaft, it was recognized that air heating would be required to maintain underground temperatures above 0°C (32°F) during cold winters in the Colorado mountains. When the air reaches the mining

Jan 1, 1983

By Roy Bartholomae

Noise generated by continuous mining machines in underground coal production is an important health hazard. Bureau of Mines Contract J0387229 covers investigation of this noise through laboratory tests of simulated cutting operations and through in-mine noise measurements. The results of these investigations indicate that coal cutting noise and conveyor noise are dominant sources of mining machine operational noise. Typical noise levels for both cutting and conveying operations are approximately 97 dBA (decibels A-weighted). For full operation of all machine systems, the overall sound pressure level is approximately 101 dBA. In-mine and laboratory test results show excellent agreement in both A-weighted overall levels as well as in A-weighted one-third-octave band spectra.

Jan 1, 1983