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By Dr. O’Neil Thomas J., Donald W. Gentry

"There are two characters to the value of mining properties-one mine may have a value, owing to its real intrinsic worth; an- other (having no intrinsic value) may have a value by being so situated as to harass the working of the really valuable mine-in mining camps one is looked upon as much of ligitimate enterprise as the other.'' -Victor Clement to Simeon Reed, Wardner, Jan. 11, 1890, Reed Mss. APPROACHES TO VALUATION Value and costs are two terms basic to financial analysis which cause, perhaps, the greatest amount of misunderstanding in mine valuation studies. When discussing the value of an asset or the costs of producing a product, it is absolutely essential that the speaker define the terms being used. There are many types of value and many categories of costs. Without specific accompanying definitions, value and cost data are not very meaningful. Value refers to a measure of the desirability of ownership of property. Some of the types of value which might be encountered in a mine valuation study are: 1) Market value 2) Full cash value 3) Salvage value 4) Replacement value 5) Capitalized value 6) Book value 7) Assessed value 8) Insured value Each of these has a specific meaning which can be applied to determine a monetary amount in a specific situation. The major item of interest here is the broader question of "what is the value of the mine?" or "what is the mine worth?" In this case, we are speaking of market value. Market value is the value (price) established in a public market by ex- changes between a willing buyer and a willing seller when neither is under duress to complete the transaction. Market value fluctuates with the degree of willingness of the buyer and seller and with the conditions of the sale. The use of the term market suggests the idea of barter. When numerous sales occur on a market, the

Jan 1, 1984

By Philip D. Wilson

IT has been my privilege to read the article prepared by R. S. Dean entitled "Production of Alumina from Low-Grade Domestic Materials" which appears on another page of this issue. Dr. Dean should be congratulated on the preparation of such an erudite and scholarly dissertation on bauxite and on the work which the Bureau of Mines has been doing in connection with the development of processes to use low-grade domestic materials.

Jan 1, 1943

Commonwealth of Pennsylvania, Department of Internal Affairs, Topographic and Geologic Survey, Harrisburg, Pa George H. Ashley, State Geologist All available printed Bulletins may be obtained through the Commonwealth of Pennsylvania, Division of Documents. Where a price has been set on the publication, checks should be made out to the Commonwealth of Pennsylvania. A Syllabus of Pennsylvania Geology and Mineral Resources has recently been published by the Survey as Bulletin G1, and consists of a general survey of the state An appendix of this bulletin also gives a complete bibliography of Survey publications It will be sent upon request. The State Geological Survey has gone through several phases and reorganizations, publications of three of them being numerous and important A fire, in 1927, destroyed supplies of many of the papers of the present Survey. Available bulletins of the present Survey are: Bulletin M6: Bituminous coal fields of Pennsylvania, in 4 parts available as follows: pt 1, General description of coal, 50 cents; 3, Bituminous coal resources, 25 cents, 4, Analyses of bituminous coals, 25 cents Bulletin M10, Fire clays of Pennsylvania; Mll, Molding sands of Pennsylvania; M12, Anthracite culm and silt (1928); M13, Feldspar in Pennsylvania; M14, Magnetite deposits of French Creek (1931); County Report C1, Adams County, pt 1, Geology and geography (in press), County Report C2, Geology and mineral resources of Greene County (in press); Topographic and Geologic Atlas A5, New Castle Quadrangle (1929), $1; Topographic and Geologic Atlas A27, Pittsburgh Quadrangle (1929), $1; Topographic and Geologic Atlas A168, Lancaster Quadrangle (1930), $1. The present Survey has also issued a number of short mimeo¬graphed bulletins any of which will be sent upon request Briefly they are: No. 15, Mineral resources of Pennsylvania; 20, Iron ores; 28, Magnesite; 40, White clay deposits, Monroe County; 45, White clay deposits, central Pennsylvania; 47, Manganese, Eastern Pennsylvania, 48, Pyrite from bituminous coal mines; 59, Bog

Jan 1, 1933

By W. N. Best

Crude oil attracted attention because of its excellence as a fuel for openhearth furnaoes; for making crucible steel and brass; for melting copper, lead, tin, zinc, nickel, silver, malleable iron, gray iron; and for the production of steam in all sizes and types of boilers. For heating furnaces, mold-drying ovens, core ovens, ore roasters, calciners, hotair furnaces, sand drying, asphalt road work, etc., its superiority over other fuels is due to the fact that the heat is at all times under perfect control, so that a constant temperature may be attained and maintained at the will of the operator. This mcans a maximum amount and uniform quality of work. Crude oil is of two kinds, paraffine base and asphaltum base, and varies from 11 to 46 gravity BaumB. The light-gravity oil does not require heating before use; but oil of less than 20 gravity Baumé should be heated to just below its vaporizing point, in order to reduce its viscosity and to obtain the highest efficiency of combustion. Heavy California oil vaporizes at 230". F., Mexican crude oil at from 175" to 210" F., and Beaumont, Texas, oil at 142" F. Fuel oil vaporizes at 130" F. Scientific Installation Essential The burning of oil is an art based on science, and the "rule of thumb" should never be employed, especially in heating heavy crude oil. Thermometers should be used on both suction and supply pipes so that the fireman or smith will at all times know the temperature of the fuel. The indicators on such thermometers should be large enough to be readily seen by the operator, night or day. It is necessary to have an unvarying pressure of steam or air through the burner, to atomize the fuel. Also, the air used to support combustion should be delivered through a nozzle under the burner at a constant pressure. The oil pressure must not fluctuate; under no eircumstances should it vary more than 1 1b. The oil pump, which should be brass-lined, with the aid of the pulsometer and superheater, will insure a constant

Jan 1, 1916

By Henry Faul

Measurement of radioactivity of rocks and ores has developed into a complete method of geophysical exploration. The problem falls into three natural categories: (1) surface radiation measurement in the field and underground; (2) radioactivity logging of drillholes; and (3) laboratory analysis of samples. Portable counters are used in the field for tracing radioactive formations and for quanti tative estimates of radioactive content of surface rock. Wartime advances in battery design make it possible to construct small precision counters that can be carried easily. Even the smallest conventional diamond drillholes can be logged, and actual content of the radioactive element can be measured. The exact grade of very thin active layers or veins can be estimated only approximately. Samples may be analyzed for their alpha, beta or gamma activity, and beta assaying is the best suited to rapid routine operation. Simple calibration with standard samples is sufficient for rough work, but a density correction is necessary when greater precision is required. Samples with high emanating power should be fixed and stored for three weeks to reestablish the radium-radon equilibrium prior to precision assaying. Carno-tite can be fixed by sintering or molding with plastics. Among the important new developments, a low-voltage Geiger tube has been 'designed recently, and crystal scintillation counters hold great promise for high-efficiency gamma-ray measurement. Introduction During the last few years we have witnessed an unprecedented rise in the demand for radioactive minerals, coming as a direct consequence of the discovery of nuclear fission and subsequent developments, the full impact of which is by no means in sight even now. It remains certain, however, that radioactive minerals, and especially those which can be used as ores of uranium and thorium, will continue to be of great interest not only to the prospector and mine operator but also to the various inspection parties envisioned by most of the schemes advanced for the control of nuclear energy on a world-wide basis. It is clear, therefore, that the measurement of radioactivity in rocks in the field as well as in samples in the laboratory has become a method of geophysical exploration of some importance. If we consider the recent technological advances in the general fields of nuclear physics and electronics it seems proper to review the present status of the methods and procedures of radiological exploration. General Considerations Equilibrium If we take a fixed amount of uranium that has just been purified, some of it will immediately start decaying into its first daughter element which in turn decays into its own daughter and so on down the line until the last daughter is reached—a stable isotope of lead. The rate at which a radioactive element decays is frequently expressed as the half-life, which is the length of time required for the decay of half the atoms in a given amount. The half-life is inversely proportional to the decay constanl X which is defined as the number of atoms which decay in one unit of time divided by

Jan 1, 1949

By Henry Faul

Measurement of radioactivity of rocks and ores has developed into a complete method of geophysical exploration. The problem falls into three natural categories: (1) surface radiation measurement in the field and underground; (2) radioactivity logging of drillholes; and (3) laboratory analysis of samples. Portable counters are used in the field for tracing radioactive formations and for quanti tative estimates of radioactive content of surface rock. Wartime advances in battery design make it possible to construct small precision counters that can be carried easily. Even the smallest conventional diamond drillholes can be logged, and actual content of the radioactive element can be measured. The exact grade of very thin active layers or veins can be estimated only approximately. Samples may be analyzed for their alpha, beta or gamma activity, and beta assaying is the best suited to rapid routine operation. Simple calibration with standard samples is sufficient for rough work, but a density correction is necessary when greater precision is required. Samples with high emanating power should be fixed and stored for three weeks to reestablish the radium-radon equilibrium prior to precision assaying. Carno-tite can be fixed by sintering or molding with plastics. Among the important new developments, a low-voltage Geiger tube has been 'designed recently, and crystal scintillation counters hold great promise for high-efficiency gamma-ray measurement. Introduction During the last few years we have witnessed an unprecedented rise in the demand for radioactive minerals, coming as a direct consequence of the discovery of nuclear fission and subsequent developments, the full impact of which is by no means in sight even now. It remains certain, however, that radioactive minerals, and especially those which can be used as ores of uranium and thorium, will continue to be of great interest not only to the prospector and mine operator but also to the various inspection parties envisioned by most of the schemes advanced for the control of nuclear energy on a world-wide basis. It is clear, therefore, that the measurement of radioactivity in rocks in the field as well as in samples in the laboratory has become a method of geophysical exploration of some importance. If we consider the recent technological advances in the general fields of nuclear physics and electronics it seems proper to review the present status of the methods and procedures of radiological exploration. General Considerations Equilibrium If we take a fixed amount of uranium that has just been purified, some of it will immediately start decaying into its first daughter element which in turn decays into its own daughter and so on down the line until the last daughter is reached—a stable isotope of lead. The rate at which a radioactive element decays is frequently expressed as the half-life, which is the length of time required for the decay of half the atoms in a given amount. The half-life is inversely proportional to the decay constanl X which is defined as the number of atoms which decay in one unit of time divided by

Jan 1, 1949

By Lloyd Jones

THE strip industry made rapid strides in regard to both width and gage until about 1922, when the maximum width was about 20 in. In the hot mills, strips of thin gages in wide widths could be pro-duced, but only at a sacrifice of length of coil, con-siderable increase in power, and decreased tonnage out-put on the min. Hot mills, like the Bray sheet mill and the modern strip and skelp mills, demonstrated that . wider strip could readily be rolled, if such a product was desired. The strip manufacturers were really limited in width, not by the hot strip, but by the cold rolling of wide strip. This factor was roll pressure. The diameter of rolls increased as the width of strip increased. For cold rolling strip 20 in. wide, cold rolls were approximately 20 in. diameter. As the rolls became larger, the arc of contact between the rolls and the strip increased approximately, according to the formula, b=\/Rd where b = the width of contact R = roll radius d = total reduction Now the crushing strength of cold steel of low carbon varies from 70,000 to 100,000 lb. per sq. in. With each succeeding pass the crushing strength increases and may approach 250,000 lb., according to the total reduction. The total reduction in cold rolling of low-carbon steel will range from 40 to 70 per cent of the original thickness, usually in about three or four passes. On this basis, assuming a reduction of 20 per cent in one pass, the crushing strength of steel assumed at 120,000 lb., we have a total pressure between rolls, which (assuming that the rolls do not deform) equals: Roll Strip Strip Diameter, Width, Thickness, In. In. In. Pounds 10 10 0.100 380,000 20 20 0.100 1,080,000 30 36 0.100 2,375,000 42 50 0.100 3,900,000 These figures are approximate, but you will note that in increasing the width five times, or 50 in., the total pressure between the rolls increased approximately ten times. In other words, the pressure per inch of width increased from 38,000 to 78,000 lb. for the same per-centage of reduction.

Jan 3, 1928

By K. P. Chong

Introduction One of the requirements of processing oil shale or other energy bearing rocks is to optimize particle sizes and permeability distributions in fragmentations as indicated by Hommert (1984). Basic to the understanding and planning of in situ fragmentation and ex situ mining of oil shale are the mechanical properties. During the past six years, an innovative and unique program was established by Chong et al. (1979, 1980a, 1980b, 1982a, 1982b) that developed an efficient methodology for standardized and simplified mechanical testing of the western oil shale. The experiments include precise, representative, and duplicable sample preparation; uniaxial static compression testing; "modified" split cylinder testing; uniaxial creep and relaxation testing under extended periods of time; dynamic testing with varying strain rates; and 3-D constitutive relationships. However, as far as the fracture mechanics is concerned, as Edl (1980) pointed out, there is still a lack of understanding "of the fundamental explosive rock breakage mechanisms," which "has necessitated extensive reliance on very costly empirical approaches." Fracture mechanics of rocks and oil shale (Costin, 1981; Schmidt, 1977; Abou-Sayed, 1977; and Barker, 1977) has been based on conventional fracture mechanics using regular notched samples with limited variations of oil yields and assuming the material to be isotropic and elastic (Kobayashi, 1975; Caddell, 1980). A cylindrical double cantilever beam (DCB) specimen with a "V" slot, known as a short rod specimen, has been used by Barker (1977) to determine fracture toughness of rock materials. The inherent geometric stability of the reinforced DCB specimen makes it suitable to be used with all brittle materials. Due to its remarkable stability for the initial crack growth, the DCB specimen can be used for dynamic fracture toughness testing as well. This specimen is more suitable for the evaluation of fracture toughness at high strain rates than most other fracture specimens. However, Barker's DCB specimen is not very well adaptable for short cores or layered rocks since the specimen contains numerous layers (say in a 100-mm (4-in.) long specimen), and the rock properties change from layer to layer. Schmidt (1977) studied the fracture mechanics of oil shale with two oil yields, using notched beams. Using several independent established testing methods, Costin (1981) pioneered the investigation of the static

Jan 1, 1986

THE 143d* meeting of the American Institute of Mining and Metallurgical Engineers was held in New York, Feb. 19-22, 1934. It consisted of the annual business meeting, 45 technical sessions at which 217 papers were presented (more than ever before), two sessions of the Board of Directors, two meetings of Section delegates, three formal lectures, luncheon Monday, Tuesday and Wednesday for members and guests, three group dinners and five group luncheons, eight committee meetings, the annual reception and dinner dance, an informal dance, a smoke-dinner and the annual meeting of the Woman's Auxiliary. Attendance showed an improvement over the previous year, as follows: Total, 1534 in 1934, and 1475 in 1933; dinner dance, 543 and 426; smoker-dinner, 425 and 394; informal dance, 295 and 250; women's registration, 160 and 133; luncheons, 1034 and 734. The Coal Division held a general session and three sessions on Coal classification. It also met jointly with the Committee on Ground Movement and Subsidence. At the general session, John B. Dilworth presented a report of the Committtee on Methods of Valuing Coal Proper- ties and R. H. Sweetser a report of the Committee on Evaluation of Coal for Blast-furnace Coke. C. B Huntress, Executive Secretary of the National Coal Association, was the principal speaker at a luncheon on Monday, at which Eli T. Conner, Chairman of the Division, presided H. N. Eavenson, newly elected President of the Institute, and Edward W Parker, Secretary-Treasurer, of the Anthracite Institute, also spoke. The Executive Committee of the Division met Tuesday afternoon. The Sectional Committee on Classification of Coal met on Thursday morning and the Technical Committees on Scientific and Use Classification of Coal on Thursday afternoon. The Committee on Mining Methods held two general sessions, one for presentation of a half-dozen interesting papers on strictly mining subjects, the other on Aerial Transportation. It also participated jointly in a session on ground movement and subsidence with the committee of that name and the Coal Division The Institute's Standing Committee on Aviation had its inception at the session on Aerial Transportation

Jan 1, 1935

By G. S. Cole, G. F. Bolling

Recent experitnents on crystal growth have indicated that thermal convection in the liquid influences the conditions of solidification and subsequent crystal characteristics. However, the important columnar-equiaxed transition in castings has not been examined as a function of this free convection. An experiment is presented here to demonstrate a change in the transition as convection is suppressed. Lead- and tin-based alloys were cast in stainless-steel molds either without special procedures or with thin grids placed horizontally across the tnold diameter in portions of the castings. While the grids allowed some diffusion of heat and mass transport to occur during solidification, massive fluid flow was hindered in the vegiotz of the grids. A larger percentage of columnar grains appeared in the grid region than in other parts of the special castings or than in all regions of normal castings. This structural difference can be explained in terms of thermal convection. THERE is little information about the possible effects of natural convection which may occur during the solidification of a casting. Ruddlel-3 has stated that the movement of liquid metal produced by convection might assist in the transfer of heat, but in the absence of confirmatory evidence he suggested that this idea be treated with caution. chalmers4 considers, but does not assess, the importance of fluid motion in casting, while Tiller5 suggests that, in liquid metals which have extremely high thermal diffusivities, the effects of thermal convection may be negligible. In addition, throughout the literature, there are statements indicating the possible presence of thermal convection but without proofs or evaluations of its influence. Natural convection may be divided into two categories: thermal convection, where liquid flow is due to density differences caused by temperature gradients in the liquid (e.g., liquid near a cold wall falling with respect to hotter liquid further away from the wall); and solute convection, where flow is due to density differences as a result of concentration gradients, see Wagner.6 In most instances thermal convection predominates over solute convection. Nevertheless, even thermal convection has not been studied in any detail and is difficult to handle, since it can vary quantitatively from one experiment to another depending upon the exact positions of heat sources and sinks or the attitude of the container with respect to gravity. In spite of these difficulties it is possible to realize that a higher rate of heat transfer must result with convection than in any situation where conduction acts alone. Thus, the degree of increased heat transfer is the important undecided question in considerations of casting. It will be demonstrated here that a reduction in convective flow leads to a suppression of the columnar-equiaxed transition in a casting and that this suppression is related to a decrease in the degree of heat transfer. Fortunately it is possible to do this by comparative rather than quantitative measures. The insertion of horizontal plates or grids into a simple mold does not appreciably influence heat transfer per se, but in reducing the allowable height through which colder liquid may fall freely it reduces natural thermal convection. This leads to a reduced fluid velocity, a different flow pattern, and an altered heat transfer which can be measured. EXPERIMENTS The alloys were prepared from elements of 99.9 pct nominal purity and cast into an uncoated 2-in.-diameter stainless-steel mold insulated at the bottom with a suitable refractory so as to ensure predominantly radial heat flow during freezing. Casting was performed either in empty molds or in molds containing grids or plates in various configurations . The grids were constructed of aluminum screen (1/32 in. thick) which was cut to the desired shape, cleaned in aqua regia, and coated with a mixture of 2 parts aqua dag graphite -1 part Sauereisen cement mixture, thus supplying a hard, protective, and insulating layer approximately 0.006 in. thick. The

Jan 1, 1965

By Euclid P. Worden

In 1977, an article in World Mining1 reported a total of 2726 rotary blasthole drills in service. This figure included only those machines produced by three of the manufacturers building drills of this type. The total, therefore, is much higher. Rotary drilling in the mining industry is big business to the manufacturers and suppliers involved, and a significant cost item to mine operators. The time has come to take a hard look at rotary drilling technology with an eye to reducing costs by increasing drilling efficiency. The efficiency of any rotary drilling operation is best measured in terms of the rate of penetration achieved by the bit. In blast hole drilling, there are five factors which affect the rate of penetration. They are: (1) bit selection, (2) weight on the bit, (3) rotary speed, (4) hole cleaning, and (5) formation properties. Of these factors, all but one may be controlled by the operator. Looking at any one in detail may reveal possible improvements in the system. One of these factors -- proper hole cleaning - will be discussed in this paper. In order for a bit to perform at its maximum capability, each tooth or insert should strike fresh clean rock as it falls into its drilling position. If the tooth or insert lands on previously drilled cuttings, a major portion of the energy delivered to the bit is absorbed in redrilling this broken material. A major portion of the interest, therefore, should be directed to the proper cleaning of the bottom of the hole. In an in-depth study of the cleaning of large diameter holes, Allen2 reports that horizontal air velocities of 38.10 m/s are necessary to prevent the saltation of drilled cuttings on the bottom of the hole. The exact flow pattern on the bottom of the hole, however, is not generally known. The air leaves the bit through the jet nozzles and the mouths of the cones, but where it goes from there is uncertain. This problem should be investigated by the bit manufacturers because they can best utilize the results of such an investigation to provide a more effective product. Some work has been initiated in this area and competition will probably increase its intensity. Bailing velocity is the best criteria to measure the cleaning of the hole, including the bottom, and is the factor on which efforts toward improvement must be concentrated. The first consideration is "What should the bailing velocity really be?" In drilling deep holes for oil and gas, 15.24 m/s is the generally accepted figure. In blasthole drilling, the figures of 25.40 m/s for average rock to 35.56 m/s for iron ore were first mentioned by Capp3 in 1962. The recommendations are the same to this day. A number of questions could be asked in regard to the apparent disparity between these two sets of figures. Various investigators have derived formulas which support one or another of these criteria. A thesis on the subject was written by Alexander4 who derived a formula based on research which resulted in velocities in the lower end of the ranges quoted previously. He set out to compare this figure to laboratory tests and his tests indicated that the velocities given by the derived formula appeared to be high.1 Perhaps the best reason that the 25.40 to 35.56 m/s range has been used, is that these velocities seem to work. Below the accepted figures, low bit life and slow penetration rates occur. Above these figures, increasing amounts of abrasive wear on the drill pipe and stabilizers seem to appear. There is a fallacy to this entire approach, however. The entire velocity calculation is made using nominal bit and pipe sizes and compressor deliveries with no compensation made for losses in the system. Perhaps an examination of some of the things that are not presently considered could lead to some practical improvements in the operation.

Jan 1, 1980

By Leonard Larson

BEFORE direct or wet smelting of copper concentrate was adopted at the McGill smelter, in November 1932, actual furnace smelting tests had indicated the possibility of smelting between 400 and 500 dry tons of wet concentrate per furnace day. Under calcine smelting practice, solid charge up to 1165 tons per furnace day had been smelted. It was realized that in order to smelt wet tonnage in equivalent amount per furnace day, a higher combustion rate and higher temperatures would be neces-sary within the furnace. The reverberatory furnace considered in the following history of wet-smelting de-velopments is a unit 127 ft. long and 28 ft. 8 in. wide, inside dimensions (Fig. r). This furnace was in operation through all the years from 1934 to date. During 1933, the first complete year of direct or wet smelting, the plant was on a curtailed copper-production basis and the available concentrate tonnage to be smelted was limited. The average coal-firing rate in the reverberatory for that year was 124 tons per furnace day. This rate was lower than the average for years immediately preced-ing under calcine smelting practice. With this coal-firing rate, an average of 391 tons of new metal-bearing material (N.M.B.M.) was smelted per furnace day. The following year, 1934, the coal-firing rate was in-creased to 139 tons and the smelting rate increased to 448 tons N.M.B.M. per fur-nace day. In succeeding years production required that either more tonnage be smelted in the one furnace or an additional furnace be placed in operation. With this situation confronting the smelting depart-ment, it was determined to continue the program of increasing the coal-firing rate and also to intensify the temperature in the smelting zone of the furnace. In order to accomplish this, various improvements were made to aid combustion within the furnace. The burners were enlarged, in-creased primary air was supplied to the burners, and changes were made in the furnace to enlarge and streamline the out-let, thus increasing the furnace draft.

Jan 1, 1940

By M. J. Taylor

A common method of classifying non-water- impounding mine waste structures is necessary to facilitate professional comnunications within the industry and between representatives of industry and government. Camnon classifications can a1 so he1 p quickly create and maintain a mental picture of the structures being discussed. Three categories for classification presented in this paper include: (1) configuration and location with respect to existing topography. (2) material characteristics of waste, and (3) environmental sensitivity or characteristic; of the disposal area. Configuration and location classification involve terminologies typically utilized for waste dumps over the past several years. General classification categories for non-impounding structures include: (a) valley-fill, (b) cross-valley, (c) side-hill, (d) ridge, and (e) heaped. Material characteristics can govern the location, engineering details, and environmental sensitivity of the waste structure. Material classification includes: (a) hazardous, (b) non-hazardous, (c) inert, (d) fugitive dust susceptible and (e) leachate susceptible. A1 though many characteristics are potentially applicable, this paper will focus on the categories mentioned above. Environmental sensitivity of a waste structure encompasses many objective and subjective evaluations plus many multi-disciplinary considerations. Environmental sensitivity incorporates numerous factors in addition to those highlighted in configuration and location, and material characteristic classifications. A few examples of how this categorization can govern the engineering design and location of waste dumps are provided in this paper. In addition to the verbal descriptions of classifications, a simplified version of the combined classifications with an alphanumeric format and its methodology is discussed in this paper. Surface water controls often govern the classification or vice versa. In order to maintain a non- impounding status, water must be prevented from collecting behind the structures. Depending on material characteristics, water inflow to or over the site can cause significant environmental or human consequences. Finally, the access of water to the waste dumps can play a large role in the degree of environmental sensitivity to the site. This paper provides a framework in which to discuss the other aspects of this conference and also provides insights as to how the framework is based on actual practice.

Jan 1, 1985

By Howard I. Epstein, John R. Buzek

Thickeners are simply large tanks, usually circular in shape, which are designed to allow settling of solids and to operate with continuous overflow of clear water and underflow of thick pulp. The dimensions of the thickener are usually such that dewatering of very fine pulps may be accomplished while still overflowing clear water. Some thickeners such as the Center, Hardinge and Hydrotator types combine thickening with filtering2 while others such as the Dorr type are pure thickeners. l .2 , 3 A schematic diagram of the traction type Dorr thickener is shown in [Fig 1]. This type is appropriate for tanks over 15 m (50 ft) in diameter. This tank employs a rotating raking mechanism which moves the settled material toward the central discharge. For this and other thickeners, it is common to have a shallow conical tank bottom in order to conform to the geometry of the raking mechanism, and it is often desirable to elevate the tank for ease of access to the product. When the tank does not rest on the ground, the forces resisted by the cone are large, and thick plates must be employed. The fabrication of these tanks requires temporary supports in order to erect the cone. A flat-bottomed tank could also be used because the settled material would soon form a hardened conical surface. However, because of the presence of large bending forces, even larger plate thicknesses are required than for the conical bottom. Significant cost savings often can be realized by the use of a scalloped-bottomed tank such as the one partially shown in [Fig. 2]. The particular scalloped bottom discussed in this paper employs radial beams forming the outline of the cone-shaped bottom. These beams are supported directly by columns. Cone segments are hung between adjacent beams. The exact geometry of these segments depends upon the cone angle and radius, the number of radial beams, and their inclination. The geometry is chosen to satisfy certain clearance restraints and to utilize the material as efficiently as possible. The resulting thickness of these segments is significantly less than that of the equivalent plate for the tank with a conical bottom. This result, along with the simpler fabrication procedures required, accounts for the cost savings associated with this design. The raking mechanism employed may be the same as for the conventional conical bottom since the settled material soon forms a conical surface. Determination of the internal force mechanism for the scalloped bottom leads to designs that utilized material efficiently and thus maximize the cost savings. The complicated geometry of these bottoms along with the difficulty in analyzing the structure are factors which may have limited the use of scalloped-bottomed tanks to date. When such tanks have been built, the uncertainties associated with the internal forces have led to designs that are somewhat inefficient. In this paper, equations relating the geometric parameters are presented along with simplified closed-form solutions for the internal forces in the cone segments, from which the loads applied to the beams and the loads carried to the cylindrical tank shell can be deduced. An example is presented to show the magnitude of the savings which may be realized with this configuration.

Jan 1, 1979

By Douglas Bunting

IN THE anthracite fields of Pennsylvania, mine fires occur with more or less regularity and their existence is an ever-present hazard in coal mining. In all probability 90 per cent. of the mine fires can be ascribed directly or indirectly to the ordinary miner's open lamp. Other causes may be smoking, electrical installations, gas explosions, gas feeders, and the communication of fire to the outcrops from ash dumps, culm banks, timber and brush fires. Fires in pump rooms, engine rooms, and barns have been largely eliminated as a result of the Act of .Assembly, approved June 15, 1911, which provides that all inside buildings, including engine rooms, pump rooms, barns etc. shall be constructed of incombustible materials. Smoking of pipes, cigars, and cigarettes should be prohibited in the mines and too much care cannot be exercised in preventing fires by enforcing all rules designed for that purpose. Mine fires that involve underground fighting are invariably dangerous, and all fires, irrespective of the method pursued in extinguishing them, involve property loss and expense. Each fire generally presents a more or less original problem, dependent on the particular conditions. Generally mine fires may be divided into two classes: Those occurring in inaccessible workings and those occurring in accessible workings. The methods pursued in extinguishing or controlling mine fires are as follows: (1) direct attack, (2) smothering by sealing, (3) flushing with silt or other solids, (4) flooding with water, (5) cutting off, (6) surrounding with incombustible materials, (7) digging out by stripping from the surface. Most fires are extinguished in their incipiency by direct attack and failure to extinguish by this method is due to late discovery, lack of water, and facilities for fighting, or improper procedure in the initial attack. Should the method first pursued be unsuccessful, careful consideration should be given in determining next the method to be adopted; then the work should be carried on as rapidly as possible and under the supervision f the most competent persons. Materials and supplies should be fur-

Jan 9, 1921

By Russell Franks, W. O. Binder

In recent years a considerable tonnage of the 18 per cent chromium and 8 per cent nickel steels has been used in lightweight high-strength structures that must be resistant to deterioration under atmospheric conditions. These steels are austenitic in character and their strength can best be increased by cold-working. Although a marked increase in tensile strength is obtained, claims have been made that the cold-worked steels do not possess fully satisfactory elastic propertics. Under certain conditions, however, this has caused no great concern, because, as explained by Ragsdale,1,2 he cold-rolled steels have been widely applied for construction of lightweight, high-strength trains using spot welding for joining purposes. Ffield3 agrees that the ease with which thin sections of the cold-rolled 18-8 steels can be joined by spot welding is greatly in their favor, but that they would be more satisfactory if higher elastic properties and a higher modulus of elasticity could be obtained. He states that, as far as the mechanical properties are concerned, the straight chromium stainless steel is superior to the cold-worked 18-8 steel, and in order to illustrate, he prcsented the data of Fig. 1, which also give a stress-strain curve for a low-carbon 13 per cent Cr steel. Ffield† proposed that columbium-bearing or titanium-bearing cold-rolled 18-8 steels be given a heat-treatment (preferably for 1 hr.) in the range 400" to 600°C. to precipitate carbides in order to obtain better mechanical properties. Discussions by Sutton,4,5 de Ganahl,6,7,8 Krivobok and Lincoln,' Knerr,l0 and Thaden11 have given further information on the properties of the cold-rolled 18-8 steels compared with other materials used in lightweight, high-strength structures. These investigators and others point out that the ultimate tensile strength of the cold-rolled 18-8 steel can be increased to 200,000 lb. per sq. in. or higher; Krivobok et al. indicate that

Jan 1, 1940

By Russell Franks, W. O. Binder

In recent years a considerable tonnage of the 18 per cent chromium and 8 per cent nickel steels has been used in lightweight high-strength structures that must be resistant to deterioration under atmospheric conditions. These steels are austenitic in character and their strength can best be increased by cold-working. Although a marked increase in tensile strength is obtained, claims have been made that the cold-worked steels do not possess fully satisfactory elastic propertics. Under certain conditions, however, this has caused no great concern, because, as explained by Ragsdale,1,2 he cold-rolled steels have been widely applied for construction of lightweight, high-strength trains using spot welding for joining purposes. Ffield3 agrees that the ease with which thin sections of the cold-rolled 18-8 steels can be joined by spot welding is greatly in their favor, but that they would be more satisfactory if higher elastic properties and a higher modulus of elasticity could be obtained. He states that, as far as the mechanical properties are concerned, the straight chromium stainless steel is superior to the cold-worked 18-8 steel, and in order to illustrate, he prcsented the data of Fig. 1, which also give a stress-strain curve for a low-carbon 13 per cent Cr steel. Ffield† proposed that columbium-bearing or titanium-bearing cold-rolled 18-8 steels be given a heat-treatment (preferably for 1 hr.) in the range 400" to 600°C. to precipitate carbides in order to obtain better mechanical properties. Discussions by Sutton,4,5 de Ganahl,6,7,8 Krivobok and Lincoln,' Knerr,l0 and Thaden11 have given further information on the properties of the cold-rolled 18-8 steels compared with other materials used in lightweight, high-strength structures. These investigators and others point out that the ultimate tensile strength of the cold-rolled 18-8 steel can be increased to 200,000 lb. per sq. in. or higher; Krivobok et al. indicate that

Jan 1, 1940

By Blamey Stevens

(San Francisco Meeting, October, 1911.) My previous paper is entitled, The Laws of Igneous Emanation Pressure. The present paper lays no claim to the exactitude and completeness of a law, since it is of a provisional nature and may be disregarded when experiments have established a basis for more exact reasoning. The general physical states in which aqueous emanations may occur are first considered. The possible physical conditions under which the mineral elements may occur in emanations are then discussed, and a classification of deposits, dependent on emanation, is proposed. A system of scientific experimental investigation is outlined, and it is shown that the physical and chemical properties of emanation may be exactly determined thereby. The investigation is urged as feasible and simple, and not necessarily requiring large and costly apparatus. It is the only step necessary to make possible the formulation of a complete set of laws of igneous emanation. Process of Emanation. In a rising column, magma ranges in temperature from 900° to 1,200°C. Exhalation must begin at some fairly great depth. What this depth may be we can only surmise, since no experimental evidence is available. Exhalation, however, continues as the magma flows upward, until at another level the occluded gases have all escaped. This depth is probably upward of 5,000 ft. (See Fig. 1.) All exhalations must come from between these two levels. As the whole emanation is the sum of the exhalations and residues, the residues must come from below the uppermost level. They will be most abundant when coming, from those parts of the intrusion which have solidified below the lower level.

Apr 1, 1912

By Henry A. Wentworth

(New York Meeting, February, 1912.) ELECTROSTATIC separation of ores in its present form is generally known as the Huff' process from the name of Charley H. Huff, of Boston, Mass., through whose constant and persistent labors (with the invention of Clinton E. Dolbear as a basis) the successful commercial process embracing separative machinery and the various electrifying devices has been developed step by step, and the finances for the long period of development provided, and the method finally established and recognized throughout the world as an important and successful addition to the ore-dressing department of metallurgy. The permanent field-success of electrostatic separation began in 1908 with a 20-ton Huff experimental mill built specially for the purpose by the American Zinc, Lead.& Smelting Co., in Platteville, Wis., a plant which was a success from the start and was gradually increased in capacity as the market-conditions warranted to 100 tons of concentrates per day. Much credit is due to the above-mentioned company for its initial venture, and for its assistance in applying the process to field use. Prior to 1908 electrostatic separators had been installed and operated (but for a comparatively short time, however) in a number of places; some under the patents of Mr. Dolbear by himself and associates, and some under the patents of Lucien I. Blake and Lawrence N. Morscher, by W. G. Swart, mining engineer, of Denver, who has always been a courageous advocate of electrostatic separation. Due to the difficulties experienced in the generation of the electrical charges, the primitiveness of the separators, the wooden construction instead of iron as at present, the lack of control of the electrical fields and other difficulties overcome by the later inventions of the Huff Electrostatic Separator Co.,

Jun 1, 1912

By John Birkinbine

Among the notable deposits of iron-ore, the Iron Mountain at Durango, Mexico, is prominent. But, although it has been noticed in records of travel and official reports for three centuries, the statements made concerning it have been so largely alloyed with improbabilities that general credence has not been given to data relating to the Cerro & Mercado, that being the name by which this remarkable mountain of ore is known. Location. Geographically, the mountain is centrally located, being situated immediately at the City of Durango, which is distant in direct lines (as the crow flies) as follows: From the Rio Grande River at El Paso, Texas, in the north, 510 miles; from the same stream at Laredo, Texas, in the northeast, 410 miles; from Tampico, in the east, 475 miles; from the City of Mexico in the southeast, 520 miles; from Mazatlan in the west, 110 miles. At El Paso, the standard-gauge Mexican Central Railroad, and at Laredo, the narrow-gauge Mexican National Railroad, enter Mexico. Tampico is a prominent Mexican port on the Gulf of Mexico, and Mazatlan occupies a similar position on the Gulf of California. To reach Durango from Laredo or Tampico, spurs of the Sierra Madre Mountains must be crossed, and between Mazatlan

Jan 1, 1885