Search Documents

Detailed observations were made for two existing continuous miner and shuttlecar systems. A simple model for the shift average cycle consisted of three time components - delays, mining and transport. Cycle improvement and productivity improvement factors are derived and used to predict the theoretical improvement which the observed cycles could achieve. Various strategies of action ranging from short-term optimisation through to long-term planning for continuous haulage systems are evaluated. High potential for improvement is shown for a wide range of operating conditions. An overview is presented for systems, currently available or under active development, which can accept coal directly from continuous miners and offer continuous haulage to the surface. Systems are broadly classified as mechanical-roof mounted, mechanical-floor mounted and hydraulic transportation.

Jan 1, 1982

By A. W. Cochardt

THERE are a number of effects that can cause material damping or internal friction. Some of these are frequency dependent, such as the thermo-elastic effect' and the stress-induced ordering.' Others depend on the amplitude of vibration, i.e., the damping related to the motion of dislocations3 and that due to magneto-mechanical hysteresis.' While many of these effects have been studied, only the magneto-mechanical effect has found extensive practical application. It is the principal source of damping in the current blade material in steam turbines.A magneto-mechanical hysteresis loop is seen in Fig. 1. If an unmagnetized, polycrystalline wire of a material exhibiting magneto-mechanical hysteresis, such as an Fe-14 pct A1 alloy, is twisted in torsion, a relation between shear stress and shear strain y is observed as indicated. The stress-strain curve does not follow Hooke's law -dashed line. Instead, the strain y increases nonlinearly and partly irreversibly, due to the motion of ferromagnetic domain walls,* until a critical stress is reached, which in this case is about 3,500 psi. If the applied stress is raised further, the strain appears to increase linearly and reversibly in accordance with Hooke's law, since all domains are now aligned in easy directions of magnetization nearest to the direction of the applied stress, and plastic flow has not yet started noticeably. On removing the applied stress, a remanent shear strain y, is observed, which is related to the irreversible magnetostriction of the material.' The energy dissipated in the material during a stress-strain cycle is proportional to the critical stress t, and the remanent magnetostrictive shear strain 7,. The purpose of this investigation was to make a survey of the magneto-mechanical damping of ferro-

Jan 1, 1957

By John C. Edwards

A computer code for laminar, steady-state, incompressible, two-dimensional flow developed by Gosman (2)3 was modified by the Bureau of Mines to calculate shock (minor) loss at the intersections of ventilation ducts. Turbulent flow was simulated using laminar flow equations and an appropriate wall shear stress. Results of the calculation showed good agreement with the experiment.

Jan 1, 1977

NATURE produces iron ore abundantly in many regions of the world, especially in Italy where not only is there a great abundance of it but also there are various kinds. In these our Tuscan parts it is a very familiar thing, since we are situated close to the island of Elba which is so overflowing and rich in this ore that it surpasses every other place where it is found. Thus not only do the regions of Tuscany share its great quantity because of their proximity, but more than two-thirds of Italy as well as Sicily and Corsica are supplied, and perhaps some more distant place. In addition, this ore is of such perfection that it

Jan 1, 1942

By Staff

GENERAL DESCRIPTION The Lucky Friday mine is located in Mullan, Sho-¬shone County, Idaho. The mining method is horizontal slice cut-and-fill (with timbering for support or un¬timbered) using hydraulic sand. Cemented sand fill at a 1:17 ratio is used in sill pours and at a 1:7 ratio for the final 152 mm (6 in.) capping in successive stope floor pours. Annual production with 100% cut-and-fill mining is 167 829 t (185,000 st). The average depth of mining is 1296 m (4250 ft) and the average travel time to the stope is 45 min. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size The ore body is 396 to 488 m (1300 to 1600 ft) long on strike, 1421 m (4660 ft) on dip, with an average width of 2.3 m (7.5 ft). Dip varies from vertical to1.2 rad (70°) Ground Conditions, Ore Value, and Production Requirements The ore body contains quite strong argentiferous galena and quartz. The hanging wall and footwall are strongly sheared and fractured. Ore value is $211/t ($192/st).

Jan 1, 1982

By A Gene Riggs

The Cerrejon Coal Project in Colombia, South America is one of the largest coal mines in the world. The mine is located in northeastern Colombia on the La Guajira penninsula. The area is in a remote valley 132 miles east of the city of Barranquilla.

Jan 1, 1984

C. M. GARLAND,§ Chicago, Ill. (written discussion 11).-7--In the development of Mr. Traer's method for the low-temperature coking of Illinois coals, after the principles laid clown by Prof. Parr, it was soon demon-strated that, in order to yield a product of uniform volatile content, the coal must be coked in thin layers, and consequently must be handled in comparatively small volumes. This means, in the first place, that great care must he observed in the design of the coking chambers to prevent the loss of the products of distillation, and, in the-second place, that labor-saving devices must be utilized to the greatest possible extent in order to reduce the cost of handling.

Jan 12, 1918

By Louis W. Cope

In the early 1900s, vat leaching was a common process for treating gold ores. It was, however, labor intensive and was abandoned in the 1930s. Technology advances in recent years, though, have caused vat leaching to once again become a viable alternative in precious metal processing. At least three plants have been built. Others are being considered as alternatives to agitation and heap leaching. What is vat leaching? Vat leaching is a process in which ore is crushed and screened to a size of between 6 to 12 mm ( 0.25 to 0.5 in.) This crushed ore is placed in a large, boxlike container where an alkaline-cyanide solution is added and later removed. The process might be likened to indoor, controlled heap leaching. The ore does not require fine grinding in a ball mill. Therefore, capital and operating costs are lower than agitation treatment. But the extra handling causes costs to be slightly higher than heap leaching. If any amount of fines is present, the ore should be agglomerated.

Jan 1, 1991

By R D. Morrison

This paper reviews the need for, and potential of, dry technologies in mineral processing, and considers the problems that will have to be solved for such technologies to be economic. The need for water in conventional mineral processing is reviewed, together with the advantages and disadvantages of operating wet and dry. A wide range of dry processing techniques have been developed in the past, some of which are in routine use either in mineral processing or in allied industries. However more information is needed to determine which of these is appropriate to replace conventional wet processing. It is concluded that a new paradigm is required for the design of processing flow sheets, which will need to extend to innovative ways of valuing particular process routes. Research is also required to develop current dry methods to increase throughput and overcome other disadvantages, and to develop new or refined dry separation methods, perhaps exploiting alternative mineral properties.

Jan 1, 2003

By David R. Maneval, Ralph A. Lambert, H. B. Charmbury

Subsidence, although it may or may not be apparent on the surface, is an inevitable consequence of deep coal mining and a frequent cause of damage to surface structures. Efforts to prevent subsidence go back many years, but there is still only one known antidote that is both technically feasible and predictable. This is the hydraulic or pneumatic stowing of solids-or flushing. In coal mines, however, flushing has been rarely used because it is considered the most expensive method of filling such mines, even though the reverse is true for ore mines. It is thus significant that the method has found favor in a comprehensive program the Commonwealth of Pennsylvania has undertaken to eliminate the hazards of abandoned coal mines within its jurisdiction. In "Operation Backfill," as the program is known, the Commonwealth has successfully used hydraulic flushing and fully justified the method economically.

Jan 4, 1967

By Thomas E. Marshall, Roy H. Grau

The U.S. Bureau of Mines has developed an acoustic test for determining if a rock salt sample is from a "normal" nongassy salt face or from a gassy face where an outburst has the potential to occur. The test is based on the observation that a salt sample taken near an outburst-prone zone produces an audible popping sound when it is dissolved in water. The sound is produced when pressurized gas that is trapped in salt samples is released. In the acoustic test, the sound is electronically measured, digitized, and transmitted to a microcomputer; the output is an average decibel value that classifies the sample as "normal" or "outburst." The acoustic test procedure and equipment are described, and raw test results and data analysis are shown. Results are also shown for several salt samples that were analyzed using a laser Raman microprobe.

Jan 1, 1990

By Charles H. Behre

This paper discusses education and training for economic geologists other than petroleum geologists. Candidates enter economic geology through liberal arts colleges, engineering schools and university graduate study. Whatever their backgrounds, rigorous courses are desirable-now conceded in theory, but not adequately recognized in practice. Besides basic sciences (each studied long enough to give a fair comprehension of its basic tenets), a functional command of English and two modern foreign languages is needed, as well as a broad understanding of mining, milling and metallurgy. A year of economics and finance is recommended. Surveying and drafting are essential skills. Yet geology should be represented in each term; otherwise the initial enthusiasm for the science, once contact is broken, may never be regained. A five-year curriculum is thus designed to take care of all major requirements and culminate in the M. S. degree. This curriculum reduces "cultural" courses below the average liberal arts requirements, but this is regarded as necessary. The pursuit of "culture" is assigned, as in most engineering and medical curricula, to extra college years or extracurricular time. To avoid the danger of over-crowding the schooling, the Doctorate in geology is preferred wherever possible. Its two added years should permit wider professional education; more browsing in "cultural" pastures; due attention to broader social implications; and some training in the research now increasingly required of the mineral industry. "In-course" training through cooperation between school and industry is especially advocated. The Institute should take the initiative in stimulating this practice.

Jan 1, 1947

To determine the characteristics of a mineral deposit, the usual practice is to take samples, analyse the properties of those samples and infer the characteristics of the deposit from these properties. This analysis can be done using statistical methods. In the present work we are concerned with two types of statistical approaches, classical statistics and spatial statistics. If one uses classical statistics to represent the properties of the sample values, the assumption is made that the values are realizations of a random variable. The relative positions of the samples are ignored, and it is assumed that all sample values in the mineral deposit have an equal probability of being selected. The likely presence of trends, zones of enrichment, or pay shoots in the mineralization, is ignored. The fact that two samples taken close to each other are more likely to have similar values than if taken far apart is also not taken into consideration. In contrast, spatial statistics will be used if one chooses to consider that the sample values are realizations of random functions. On this hypothesis, the value of a sample is a function of its position in the mineralization of the deposit, and the relative position of the samples is taken into consideration. The similarity between sample values is quantified as a function of the distance between samples and this relationship represents the foundation of spatial statistics. There are few situations where classical statistics can be used. The assumption that all sample values in the mineral deposit have an equal likelihood of being represented will be satisfied only if the sample values are randomly distributed, or if the sample positions are random. Sample values are in fact never randomly distributed within a mineral deposit. Further- more, geologists usually avoid taking samples at random (random sampling), as it is correctly accepted that samples located on a regular grid, or approximately on a regular grid, give more information than randomly located samples. In practice, classical statistics should be used only in the early stages of exploration, when the number of samples available is relatively small and the distances between samples are large. In these circumstances, and whenever the information available is not sufficient to permit the use of spatial statistics, application of the methods described in this chapter is justified.

Jan 1, 1978

By B. G. Meyburgh

SYNOPSIS As a result of a test programme over a period of approximately ten years and a decision to extend the uranium plant, it was decided to design and erect the first full-scale Purlex Plant in the Republic of South Africa. The plant at Buffelsfontein G.M. Co. Ltd. was commissioned in August, 1968, and to date has produced results superior to those predicted in the original estimates. The capital expenditure was R678 000 for a plant capable of treating 1 600 gallons per minute of pregnant solution. Compared with the conventional resin ion exchange process, it has been found that the saving in production costs is 21 cents per pound U3O8 produced. The amine loss is 10 parts per million, which is equivalent to a total organic loss of 250 parts per million. The uranium loss in the raffinate is less than 0.001 g/l U3O8. The final product is of a high quality and it is probable that it is pure enough to convert to the fluoride directly.

By D. E. Munson, P. R. Dawson

An empirical model is developed that predicts accurately the transient response of salt creep to incremental and decremental changes in stress and temperature. Even though the model is empirical, it is derived from a firm theoretical framework for the micromechanical deformation processes of both steady-state and transient creep. In the model, the transient creep functions modify the steady-state creep behavior, which in turn is based upon creep mechanisms and the def ormation-mechanism map. The model is applied successfully to experimental stress-drop results obtained for salt.

Jan 1, 1982

By R. C. Nascimento

It was investigated the effect of the addition of bentonite on the physical propertiesof pellets produced from fines of manganese ores. Cold-bonded pellets were produced. Pellets bearing up to 1 wt% of bentonite were submitted to strength compression resistance tests, fatigue of pellets to impact and maximum height of fall tests. A correlation of resistance of the pellets and time for curing were stablished. The produced pellets match the conditions for raw materials used in electric smelting hrnaces to produce manganese based ferro-alloys.

Jan 1, 1995

INDEX OF CONTENTSComposition of the Brown CoalsIntroductionComposition as minedComposition from drilling explorations:Latrobe Valley Area, East Gippsland, Welshpool-Alberton West Area, Altona-Bacchus Marsh Area, Lal Lal Area, Dean's Marsh Area. The Coal Constituents:Vitrain, fusain, detrital coal, resin, Sulphur, types, distribution, Ash, composition, sulphur, phosphorus, chlorine,,titanium, vanadium, distribution in seam, fusibility, source, mineral ash, chemical ash Bitumen, tar. Factors causing Variation in Composition:Pressure of overburden, moisture content, carbon, hydrogen, nitrogen, oxygen, calorific power, density, compression by warping, abnormal moisture, initial differences in vegetation, conditions of sedimentation, weathering before re-burial.Summary and AcknowledgmentsList of References

Jan 1, 1945

By Eugene Grace

IN THE careers of the men to whom I have referred we find typified the development of the chief prob-lems of engineering. The first is to shape and direct the forces of nature and thus to bring the world's resources to add to the comfort and welfare of man-kind. That, in a word, is the problem of production. Engineers have made a supreme contribution to the solution of that problem. But I feel that we have two somewhat newer branches of engineering which must command more and more of our attention. Those are what might be termed commercial and human engineering. Of what value is all our efficiency in pro-duction if we do not distribute efficiently, economically and effectively? And of what value is any of it unless we can add to the happiness and deeper satisfaction of those engaged in industry, as well as those who enjoy its -products? I predict that the outstanding advances in business over the next ten years will be in improved merchan-dising and distributing methods. Herein lies a wide field of opportunity for the engineer. We have briefly reviewed certain qualities of engi-neers who have become successful business executives. Is it possible for us to say that the material success of all these men was due to any one characteristic com-mon to each one of them? Indeed, I venture to assert that there is one quality which, in the last analysis, is determining as to whether any roan shall realize material success in this world of ours. That quality-so notable in the character of each one of the men I have named-is sound judgment. Moments arise in every life when it is necessary to say "yes" or to say "no" to a particular proposition or to a proposed line of action. It is the man who says "yes" at the proper time and "no" at the proper time who, in the final analysis, realizes business success. The ability to do this wisely is the mark of sound judg-ment, which is necessary in a business executive. I have known many business men seemingly slow in their mental processes, possessed apparently, of little imagination and of none of the flair which gives fasci-nation to so many characters, and yet who, when crises come-be they big or be they little-are able so to steer their business courses that they move in the right direction instead of into shallow waters or upon the rocks of trouble.

Jan 4, 1928

Report M48 Tracer tests on furnaces at M etalloys Limited. Report M52 A high-speed, multi-input serial-interfacing system for a computer with simultaneous back-1lP recording on magnetic tape. Report M53 The development of an automatic sample-changer and control instrumentation for isotope-source neutron-activation analysis. Report M69 The determination, by X-ray-fluorescence spectrometry,of tin and tungsten in ores, concentrates, and residues of scheelite, wolframite, and cassiterite. Report M77 Analysis of the results of a marked-ball test in relation to theories of ball wear in rotary mills.

Jan 1, 1983

By Calvin J. Konya

There have been many different brands of high precision caps introduced on the US market in the last five years. High precision timing definitely effects the performance of the blast. One should be able to optimize fragmentation and minimize environmental effects with the use of high precision caps and selection of the proper time period. The consumer who purchases the caps may not be fully aware of the tolerances in firing times of caps used in the field. This paper will discuss results of field tests of cap tolerances from an independent study conducted by Precision Blasting Services.

Jan 1, 1989