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By Kenneth E. Mathews, Ross D. Hammett, S. Byron Stewart

Theoretical models have been important throughout the history of engineering as a means of understanding past experiences and predicting future performance. Most modelling involves assumptions and a degree of idealization, and it is shown that it is important that the effects of these be recognized when making use of models. One of the principal concerns in underground mining is the effect of the excavations on the states of stress in the rock adjacent to these excavations. As mining proceeds to depth, stress concentrations may be sufficiently high to cause inelastic behaviour of the rock and yielding along joint surfaces. At this stage, attention must be given to the sequencing of the mining process to ensure that the ground control techniques applied are optimized. Increasing use is being made of computer modelling techniques to assist with design. Three case studies are presented to illustrate the application of computer models in mine planning and ground control. In all cases, the data available for design was limited, but the mines were fully developed and openings could be inspected. The mining methods studied are cut and fill stoping, room and pillar stoping, and longhole stoping.

Jan 1, 1983

A BLAST can be "full of sound and fury," signifying nothing but a poorly confined charge, or it can be a muffled, well controlled explosion which moves the rock efficiently and places it in the desired location with the least amount of fuss and bother. Why one method will do the job and another proves to be almost useless is shown by the machine-gun camera studies of quarry blasting made by the Atlas Powder Co. staff. The sequence, or machine-gun, camera is the latest scientific device for the study of cause and effect factors in blasting. Movie cameras, previously used, although of some use, were limited because slow shutter speeds and small negatives failed to give clear, sharp prints. During World War II, the AAF developed the sequence camera, which figuratively stops the blast at regular intervals, making study and evaluation feasible. The camera is simple and inexpensive and offers material for accurate examination of blasting techniques. The machine-gun camera takes three 5x5 in. exposures per sec at a 1/450 sec shutter speed, four times faster than a movie camera. Negatives are 30 times larger than those of movie cameras, giving large, sharp prints. The rock movement is frozen on the picture as the sequence of the blast takes place. Pictures on this page show the advantage of individual machine gun photographs. But the sequences made possible by this camera give graphic, dramatic and conclusive support to recently developed detonation theories.

Jan 1, 1952

By George A. Lamb

AMONG the main interesting developments in the coal market have been the changes that have taken place between the consumer groups. Important signs of these changes began to appear many years ago, but in a modest way, and were apparent only to the few fuel experts making broad statistical determinations. It is doubtful, however, that any of these experts appreciated the significance of their early findings, and perhaps none had the imagination to consider how extensive these changes might be eventually with respect to solid fuels sales and distribution. (Reference here will be principally to bituminous coal.) Railroad Fuel Major changes in coal use did become pronounced after World War II, and it did not take an expert to see what was taking place and how serious the impact was likely to be. First, was the case of the steam and diesel locomotives. The railroads had been considered the best coal customers; they were steady and large purchasers and usually paid a better price than most others. Railroad fuel provided the basic mine realization and it often was the source for operating cash during general market slumps. It was the outlet for 20 pct of the bituminous coal production, as much as 110 million tons in 1946.

Jan 2, 1957

Jan 1, 1943

Jan 1, 1943

By J. A. Herbst, A. L. Mular

Digital simulation is defined and simulation techniques are re- viewed. Typical methodology involves the selection of models, the adjustment of raw data, the selection of a fitting strategy, the assessment of model accuracy in a statistical sense, and the development of an executive simulation structure. Simulations serve as aids for process engineers in evaluating the feasibility of a proposed flowsheet and the effect of a modification to an existing flowsheet. In addition, simulation plays an important role in off-line optimization and in the evaluation of alternative circuit control strategies. Several examples are presented to illustrate these uses for simulation including applications in crushing circuits, grinding circuits, and flotation circuits. It is the opinion of the authors that, within the next decade, mineral processing plants will be studied routinely via digital simulation during the preliminary design stage. Simulation will constitute an important component of the design decision making process.

Jan 1, 1978

By Om P. Pande, Larry S. Diaz

Modern mineral processing plants could not operate efficiently, or even exist, without instruments which indicate, record, control, and in some cases anticipate the many changes that occur in a process. Even in plants which are operated manually, instruments are used to tell the operator when he should turn a valve or press a handswitch. Accordingly, all mineral processing plant engineering and construction projects must give careful consideration to this area of design activity.

Jan 1, 1978

By Norman A. Jull, A. L. Mular

Fundamentals of cyclones are reviewed briefly, where a typical cyclone is considered. Graphical cyclone data available in the literature have been converted to mathematical equations for convenience. Preliminary selection and design procedures for both cyclones and pumps are provided, and a sample calculation for a hypothetical grinding circuit is covered in some detail. In general, cyclone and pump suppliers should be consulted for definitive design purposes. Some cyclone suppliers currently employ digital computers for definitive design to ensure greater accuracy.

Jan 1, 1978

SEC. 1. The membership of the 'Institute shall comprise six classes, namely: 1. Members; 2. Honorary Members; 3. Senior Members; 4. Associates; 5. Junior Members; 6, Rocky Mountain Members. All shall be equally entitled to the privileges of membership, excepting that no member of any class whose residence shall be outside of the United States of America, except those residing in Mexico and Canada, shall be entitled to vote. SEC. 2. Members: A person to be eligible for election or transfer into the class of Member must be at least 27 years of age and must have had at least six years' employment in the practice of engineering, mining, geology, metallurgy, or chemistry, during at least three years of which he must have held positions of responsibility in one or more of these fields. This shall not apply to Rocky Mountain members.

Jan 1, 1932

Sec. 1. The membership of the Institute shall comprise six classes, namely: 1. Members; 2. Honorary Members; 3. Senior Members; 4. Associates; 5. Junior Members; 6. Rocky Mountain Members. All shall be equally entitled to the privileges of membership, excepting that no member of any class whom residence shall be outside of the United States of America, except those residing in Mexico and Canada, shall be entitled to vote. SEC. 2. Members: A person to be eligible for election or transfer into the claw of Member must be at least 27 years of age and must have had at least six years' employment in the practice of engineering, mining, geology, metallurgy, or chemistry, during at least three years of which he must have held positions of responsibility in one or more of these fields. This shall not apply to Rocky Mountain members.

Jan 1, 1941

By W. Rall, A. J. Birkle

The effect of fast-neutron irradiation on the micvo strcture of a common reactor pressure-vessel steel, A212 Grade B, was studied using thin-foil transmission electron microscopy. The dislocation density of the irradiated material is considerably greater than that of the nonirradiated control material. Annealing studies indicated that dislocations and hardness ill the irradiated material annealed out—as docs the radiation-induced embrittlement according to other- investigators— at temperatures STEELS in nuclear reactors are affected by neutron irradiation. In the American Society for Testing Materials (ASTM) A302B and A212B steels commonly specified by designers for reactor vessels, between 650° and 800°F. However, the dislocations and hardness in control samples cold-worked to 9 and 70 pct did not anneal out readily, and a high dis -location density was observed, even after a 1-hr anneal at 850°F. Based on the hypothesis that cllrster defects, rather than the increased dislocation density, are primarily responsible for mdicltiotz-iudziced e)nbriftlen7ent, reconzmendations are made for reducing the susceptibility to such ernbrittlement. exposures at a temperature of 550°F or lower to neutron dosages encountered during a 20- to 30-year life (-3 X 10'' nvt, >1 mev) may increase the nil-ductility transition temperature (NDT) as much as 300" or 400".'9 Therefore, to prevent brittle failures in reactor structures, extreme caution is required to reduce thermally induced stresses during all reactor shutdowns and startups when the temperature is below the NDT of the pressure vessel.

Jan 1, 1964

By Henry Carlisle

Henry Carlisle: This is November, 1960, and my good friend John Gustafson is sitting on the other side of a tape recorder. I, Henry Carlisle, am going to ask him some questions on the highlights of his life, and he has been good enough to say that he will play this question and answer game with me. Now, John, let's pick out a very interesting period when you went to North Labrador and made a preliminary investigation of the big iron deposits there. You were working for either Timmins or Hollinger, which was it? John K. Gustafson: I was in charge at that time of a Hollinger Exploration Co. office in Toronto. We had acquired options on enough shares to control Labrador Mining and Explorations Co., and through Hollinger North Shore Ltd., another company, we had a 3000 square mile concession in Ungava, Quebec, on the direct extension of the iron ore fields.

Jan 7, 1972

By J. F. Abel, F. T. Lee

Subsidence is controlled by a complex com¬bination of mining and geologic factors. For example, a compilation of worldwide data shows that, as the percentage of shale in the overlying rock mass decreases and the amount of sandstone increases, the angle of draw (and the area affected by subsidence) decreases. Limestone in the over¬burden appears to cause a more than twofold decrease in the angle of draw compared to a like amount of sandstone. Increased amounts of sandstone were accompanied by a greater surface subsidence relative to the mining height. The total thickness of overburden did not appear to influence the subsidence magnitude above super-critical panels. The greater the thickness extracted, the smaller percentage of that thickness shows up at the surface as subsidence. The greater the percent of the seam extracted, the greater the subsidence reaching the surface. The maximum subsidence above room-and-pillar panels de¬pends on the pillar height and minimum width as well as the other factors listed.

Jan 1, 1984

By Volker Weiss, George Sachs, AE. P. Klier

PHYSICAL chemistry contributes to the understanding and efficient operation of hydrometal-lurgical processes in many ways, among them by providing quantitative answers to the following questions. 1) Can a given chemical reaction or process be made to operate and. if so, under what conditions? 2) what are the' factors which determine the rate of the reaction and how can this rate be regulated in practice? Thermodynamics attempts to answer the first of these questions and kinetics the second. The answer

Jan 1, 1958

By T. F. Witherbee

The subject of an article in the Engineering and Mining Journal for October 13th, 1877, namely, Blast Furnace Treatment of Silicious Iron Ores,, is of great interest to myself, and doubtless to many others who hare been troubled with a seemingly unaccountable percentage of silicon in their pig iron. It is to be regretted that the author of the article did not give us complete details of his charges, and thus prevent a possibly fatal error in the very beginning of the discussion of the points raised in his communication. As it now stands, I think we will have to fall back upon the statement that, " every conceivable mixture of fluxes and ores (A and B) has been used." Let us first, in order to simplify the calculations, do with she

Jan 1, 1879

By William Barrett

IN order properly to evaluate the data related to geomagnetic surveys, it is highly desirable to have all the available information concerning the magnetic properties of the, involved media. This is true of surface as well as subsurface formations and becomes of increasing importance as advancement in instrumental and interpretative technique permits the analysis of relatively slight magnetic reflections of buried masses. Since the magnitude and areal distribution of the usually complex resultant magnetic field at the surface of the earth is a function of the susceptibility1 of the involved matter, it necessarily follows that susceptibility determinations will afford valuable data for geophysical correlation. The present method was developed to meet the need for routine analysis of specimens in the geomagnetic laboratory where it was felt that general utility, ruggedness, ease of manipulation and reproducibility of results was of greater importance than extreme sensitivity.

Jan 1, 1931

By Milan Matula

One of the main characteristics of the development of rock mechanics in some countries is a close cooperation between experts in rock mechanics and workers in related fields, including soil mechanics and engineering geology. The purpose of this chapter is to outline the contribution that engineering geology can make to rock mechanics and to present a few examples of engineering geology studies that have been used in solving some practical rock mechanics problems. Engineering geology investigations dealing with the influence of geological factors on the physical properties of rock materials and rock masses fall into three main categories : 1) Systematic study and correlation of the physical properties of the main rock types with the petrogenetic evolution that caused the differences in the properties of these various rock types. 2) Study of the heterogeneity and anisotropy of both rock materials and rock masses. 3) Delimitation of rock masses which are approximately uniform in physical properties (quasihomogeneous units). Delimiting of the quasihomogeneous rock masses is the main contribution that the engineering geologist can make to rock mechanics. This delimiting is based on the evaluation of many complex geologic factors, not on test results alone, and therefore is most effectively done by trained engineering geologists. The foregoing types of studies are being used in Czechoslovakia for several purposes, including : 1) the compilation of regional engineering petrologic data-that is, the systematic definition of the main rock types of the country in terms of their representative physical characteristics;

Jan 1, 1970

By C. J. Barber

This paper Donald describes how New Jersey Zinc Co. made surveys for a connection between the Ivanhoe and Van Mater shafts at Austinville, Va. Except to say that the two faces had to meet "accurately" on line and grade, Donald does not indicate the required precision. Assuming that there were 24 angles in the 1 ½ -mile traverse and 15 in the one-mile traverse, it can be shown that if the average error in plumbing each shaft was ±30" and the average error in measuring each traverse angle was ±10", then the average error at the point of connection would have been about ±1.9 ft normal to the line between the shafts. This calculation assumes that any errors in the triangulation would be negligible compared with the errors in the plumbings and traverses, and it also neglects taping errors. With no constant errors or blunders, the latter would be important only in lines normal to the line between the shafts.

Jan 7, 1959

By Luke L. Y. Chang, Bert Phillips

ThE tendency toward further oxidation of the intermediate oxides and the high volatilization rates of the higher oxides have prevented direct attainment of equilibrium data for the system tungsten-oxygen. As a result, St. Pierre et al.1 have proposed a phase diagram (to 800°C) based on thermody-namic data to 1200°C for the known tungsten oxides (WO2z, W18O49, W20O58, and WO3) and a report on a tungsten suboxide W3O.2 Recent modification of a technique previously described3 5 now permits adequate preservation of compositions of mixtures of metallic tungsten and metal oxides (e.g., of tungsten, cobalt, calcium, samarium, titanium) in order that condensed phase relations may be established to 1700 This method has been applied to study the high-temperature stability of tungsten oxides. In the method used, the desired compositions were sealed in nonreactive containers such that only a small gas volume remained. Each sample then established its own equilibrium atmosphere at temperature. This method has advantages in the study of systems of the W-0 type where knowledge of the condensed phases is desirable but for which composition and pressure of the gas phase are not readily attainable because of oxide volatility. Mixtures of 99.99 pct tungsten metal powder and purified tungsten anhydride (WO3) or in some cases W18O49* were equilibrated in pellet form in sealed

Jan 1, 1964

By John Dilworth

THIS paper treats primarily of the valuation of developed coal properties by the method of capitalizing their estimated average future earnings. However, in it reference is also made to valuations of undeveloped coal lands and to various methods of appraisal other than by future earnings. FUNDAMENTAL VALUATION PRINCIPLES Before discussing in detail coal property valuations, a few statements bearing on the general subject will be made to present certain of the writer's views on the question as a whole. 1. A certain property at a given time has but, one true value. This is not universally admitted. The appraiser rather frequently finds that a coal owner has in mind three valuations for his holdings; one, the figure at which he feels they should be appraised for taxation purposes; another, the much higher one that should be used if a loan is to he negotiated on the property; and a third, intermediate between the other two, the price for which he would be willing to dispose of his holdings were they for sale. The last is usually nearest to the true value, and because this is so the statement is generally accepted that the fair value of such a property is the price arrived at by negotiation between a willing seller and a willing buyer who are otherwise disinterested. 2. Notwithstanding the foregoing, it is only very generally and approximately true that the proper measure of the value of a given developed1 coal acreage is the unit or per-acre price for which one or more bodies of similar coal in the salve district have been sold recently. To give a few reasons why such a measure of value can not be strictly applied, it may be noted:

Jan 1, 1927