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By S. L. Crouch, C. Fairhurst

The general term "coal mine bump" refers to the sudden and violent failure of in-situ coal. Coal bumps occur in most countries where coal is worked by underground methods. They are related to geological factors and mining techniques. Coal bumps can be characterized as unstable releases of energy associated with yielding that occurs with progressive mining. Unstable releases of energy occur when the coal is able to absorb less energy than is released by the surrounding rock mass during the yielding process. At any stage of mining, the amount of excess energy so released is governed by the mining geometry, the overburden stress, the elastic properties of the rock mass, and the stress-strain characteristics of the seam material. If the coal in the vicinity of the working face is crushed, the peak abutment pressure occurs at some distance into the intact portions of the seam, and mining takes place in essentially destressed coal. With subsequent mining, additional yielding occurs, excess energy may be released, and the peak stress is again shifted into the solid. This process continues until the mining geometry is such that the zone of peak stress is effectively surrounded by yielding coal, at which point it can be anticipated that further mining will produce dramatic redistributions of stress and be accom¬panied by large releases of energy. On this basis, the differences between several alternatives for mining a given block of coal may be pronounced.

Jan 1, 1975

By Hugh J. Leach, J. C. Van de Water

In open pit mining, as in other industries, it has I become necessary to improve operating efficiency in order to combat higher labor and supply costs. Moreover, orebodies are becoming leaner, pits are getting deeper, stripping ratios are increasing, and hauls are getting longer. There has been a steady increase in size, speed of operation, and reliability of the various machines involved in breaking, loading, and hauling ore. Changes have seldom been radical but are rather the result of steady improvement. Drilling: Notable advances have been made in the use of rotary drills and air powered percussion drills for blasthole drilling. Several hundred of these machines are now in use as replacements for churn drills in softer rocks such as limestone and shale. Their application to hard rocks such as iron ore and taconite is under current investigation, but in the Lake Superior iron mining district, open pit blast-hole drilling in ore has been accomplished almost exclusively by standard churn drilling. The only recent advance has been the use of larger machines drilling 9-in. holes. This has increased drilling speed somewhat and allowed wider hole spacing, with consequent cost reduction.

Feb 1, 1956

By R. E. Head

UNDER existing economic conditions, the treatment of gold ores occupies an outstanding position in metallurgical activity. The increased price of gold has automatically brought about a reclassification of old dumps and low-grade orebodies, and many that formerly were considered valueless are now being vigorously investigated and worked. This situation has developed problems that have taxed the ingenuity and ability of metallurgists to the utmost. Some gold ores give a high extraction of gold by standardized methods of treatment; other ores of apparently similar character yield but a relatively small percentage of their gold when treated by the same processes.

Jan 1, 1936

By John G. Cazort

In August 1957, a cutter suction dredge started the removal of overburden from a bauxite deposit near Paranam, Surinam (formerly Dutch Guiana), South America. This event marked the climax of a program of investigation, design and construction which lasted almost five years. Cutter-suction dredges are used predominantly for harbor and river work, and land reclamation. While they have been utilized to remove overburden from ore bodies, notably at Steep Rock, Ontario, and Black Lake, Quebec, the conditions under which one is being used for this purpose in Surinam are unusual. Paranam is a mining town built by Suriname Aluminum Company, a subsidiary of Aluminum Company of America. It is located on the Surinam River, about 30 miles from the Atlantic Ocean. The bauxite mining, drying and shiploading facilities have been in operation since 1941.

Jan 10, 1960

By Leason Adams

THE thermocouple as a device for the measurement of temperature is rivaled only by the platinum-resistance thermometer. Both instruments are capable of the highest precision, but the thermocouple, on account of its cheapness, ease of construction, and small cross-section, is finding a continually widening field of usefulness for industrial control as well as for laboratory measurements. Formerly, the thermocouple was subject to two disadvantages: errors due to lack of homogeneity of the metal and the labor involved in the interpolation between fixed points on the temperature scale. Former publications from the Geo-physical Laboratory have described the methods' for the selection and testing of thermocouple wire and have presented standard calibration curves2 for platinum-platinrhodiun and copper-constantan couples, so that the most important objections to the thermocouple as a precision thermometer have been removed. The calibration tables published in 1914 covered the range 0-1755° for the platinum-platinrhodium couple and 0-350° for copper-constantan. It has seemed desirable to extend the table for copper-constantan to -200 and also to include a table for the Hoskins thermocouple. Accordingly, in this paper, the new tables are presented, together with a brief explanation of their use; and, finally, certain diagrams and a paragraph on "cold-junction corrections" are given. Standard Calibration Tables.-In Fig. 1, which illustrates how the electromotive force (e.m.f.) of each of the three couples varies with the temperature, the temperatures of one junction are plotted as abscissas and the corresponding thermo-e.m.f.'s as ordinates. The second junction of the couple is supposed to be at 0°; the curves, therefore, pass through

Jan 9, 1919

By S. C. Lindsay, D. J. I. Evans

With each year that passes hydrometallurgical processes are being more widely used to recover base metals from ores and concentrates. Generally these processes involve liquid-solid separation of metal-bearing liquors from barren residues. This may be done by countercurrent decantation, thickening and filtration, or filtration or centrifuging only. Choice of method is governed by chemical and physical characteristics of the pulps; cost of labor, power, materials, and waste disposal; and even by the amount of capital available when building plans are under way. Since all these controlling factors change with time and location and with technological advances, the separation method must be re-evaluated when new plants or expansion programs are contemplated. At the Sherritt Gordon refinery in Fort Saskatchewan, Alberta, an ammonia pressure leaching process recovers nickel, copper, and cobalt from the nickel concentrate produced at Lynn Lake, Manitoba.' Pregnant liquors are separated from the barren leach residues in a thickener-filter liquid-solids circuit. The decision to use this type of separation was based on a summation of economic factors during the pilot plant and design stages. Although countercurrent decantation was not incorporated in the refinery flowsheet, the problems solved in thickening the leach residues and the experience gained in operating the commercial plant are pertinent to countercurrent decantation, particularly where it is applied to slow-settling leach slurries or slurries having a relatively high vapor pressure of a valuable, obnoxious, or poisonous vapor.

Jan 1, 1960

By A. Aly Selim, Bruce D. Hanson

A computer model capable of simulating the basic production system in a variety of underground mining methods has been developed at the U.S. Bureau of Mines Twin Cities Mining Research Center. The simulation of the basic production system at the working face, which includes drilling, blasting, mucking, and roof bolting, is described in this paper. The model is event-oriented; that is, the status of the system is updated at the occurrence of an event. All event or activity times, including failure and repair of equipment, are treated as stochastic variables. A location dimension, in addition to the time dimension, is used, allowing the simulation of systems with a number of stopes or faces. To aid the user in determining the efficiency of his system, the model provides several reports. An event or activity report gives the frequency of occurrence, total active time, and cumulative delay statistics for each event. An equipment report delineates the availability and utilization of all equipment. A production report provides information on various performance measures such as tons produced and holes drilled. The cost report gives the cost of various elements in the system. Operating data from an actual mining situation were used in validating the model. In addition to the description of the model, examples of simulation experiments which were performed on a room-and-pillar mine system are given. Use of the model to determine methods for improving the efficiency of the system is discussed.

Jan 1, 1976

By Glenn B. Southward

The V system of mining used at the Norton mine of West Virginia Coal & Coke Co. was designed as a modified long wall with face conveyors, for use under roof conditions that would not permit regular long-wall methods. This mine is in the Lower Kittanning seam, which averages about 6 ft. in height. There is from 20 to 30 ft. of slate and shale immediately over the coal and above this is a bed of sandstone 40 ft. or more thick; the total cover will vary from 50 to 250 ft. In the room-and-pillar workings, the top in the rooms and headings is generally good but it is

Jan 1, 1924

By Albert Roberts

Summary In response to a growing intolerance towards ground vibrations and noise as environmental pollutants the engineer must consider the effects of his operations as they are likely to be judged subjectively by the public at large. Much work has been done on the study of vibration damage to structures, but the damage criteria normally applied do not take into account any resonance effects, nor do they embody any subjective criterion. Mu1tiple criterion techniques of subjective appraisal have proven to be of value .in the assessment of environmental comfort in relation to ventilation, air conditioning, and lighting. One such scale, the Reiher-Meister Scale, has also been applied to ground vibrations and noise, and an attempt has been made to correlate this scale with objective criteria, using the parameters of frequency and displacement. This paper quotes examples and compares ground vibrations resulting from blasting, the operation of, vibrating and impact-hamner pi1e drivers, forge hammers, and railway and road traffic. The Reiher- Meister Scale was applied to a subjective-objective correlation in relation to vibrations from railway traffic and gave results which did not conflict with experience.

Jan 1, 1971

By Paul D. Merica, W. A. Mudge

ONE of the most prominent features of our present-day industrial development is the ever-increasing demand put upon materials of construction Engineering ingenuity, within the past 25 years, has been unusually active, and in some fields at least engineers frankly say that engineering design has progressed as far as the limitations imposed by the properties of the present materials of construction will permit. Consequently, they are today demanding improvement in their working materials and seeking new ones, through the aid of which the present limitations of design may be overcome The activity of this search is evident in all fields, but it is particularly so in that of structural materials required to be resistant to corrosion The corrosion resistance of metals and alloys is never absolute and all-inclusive, a particular alloy will withstand some corrosive conditions well and fall utterly under others Furthermore, other properties, physical and mechanical, required in conjunction with corrosion resistance vary considerably for different commercial applications One wants a soft, ductile sheet metal resistant to atmospheric corrosion, another, a high-strength alloy resistant to sulfuric acid The last decade has witnessed active and definite progress in the development of high-strength, corrosion-resisting alloys In June, 1924, a symposium by the American Society for Testing Materials, on Corrosion-Resistant, Heat-resistant and Electrical-resistance Alloys, disclosed no less. than 60 commercial alloys the properties of which were described as being suitable for industrial service where corrosion resistance

Jan 1, 1935

By H. A. Davies

DURING a current program of research on the structure and properties of liquid sodium alloys, the need arose for information on the solubilities as a function of temperature of several B subgroup metals in liquid sodium. In the absence of reliable information in the literature for several of these systems, par- ticularly at temperatures in the range 100° to 300°C, an apparatus was constructed to determine solubilities by a direct melt-sampling technique, followed by wet-chemical analysis for both sodium and the solute metal. The details of the technique have been described previously.' The solubility of indium in liquid sodium was determined at eight temperatures in the range 100° to 270°C. The solubility as a function of temperature is shown on Fig. 1; this represents the liquidus line over this composition range. A cooling curve was plotted after the completion of the sampling and an arrest was observed at 94.9°C which must be interpreted as being the result of a eutectic reaction. By extrapolation of the liquidus to this temperature, the eutectic composition was estimated to be about 0.25 at. pct In. The present estimate of the eutectic temperature and composition are in good agreement with the values of 96.0° to 96.2°C and between 0.28 and 0.45 at. pct In, respectively, which were reported by Heycock and Neville.2 However, no further information on the liquidus of this system at the sodium-rich end could be found in the literature for comparison. One compound: NaIn, has been reported in this sys-

Jan 1, 1968

By John Birkinbine

Since the presentation of the paper upon " The Concentration of Iron-Ore," which the writer, associated with Mr. Thomas A. Edison, read before the Institute in February, 1889 (Transactions, vol. xvii., 728-744), much time and money have been devoted to applications of various forms of concentrating apparatus, particularly in treating magnetic iron-ores. An indication of the interest which has been developed is shown in the four payers presented at and printed in advance for this meeting." The question, does magnetic concentration pay? is now being discussed by many owners of magnetite deposits, and affirmative answers can be readily obtained from patentees or agents of special machinery, while ultra-conservatism may give a prompt negative reply, based mainly upon the apparent impracticability of handling, crushing, sizing and separating large quantities of ore, and upon the generally

Jan 1, 1891

By A. J. Bowie

The discovery of the auriferous cement gravel deposits in and near Deadwood Gulch, Lawrence County, Dakota Territory, in 1876, created a mining excitement, and rush to the Black Hills. Numerous ten and twenty-stamp mills were built on Deadwood Gulch; Central City and the town of Deadwood sprang into existence, and became the centres of the mining industry of the Hills. Gold quartz deposits were subsequently discovered and located on a so-called mineral belt, extending from Whitewood Creek on the south, to Deadwood Gulch on the north. A northerly group of these quartz locations was purchased in December, 1877, by parties in San Francisco, who formed a company, incorporated under the name of the Father de Smet Consolidated Gold Mining Company. This company immediately commenced the work of exploration The deposits were proved to be extensive, and easily mined, but it was found that the ore, on an average, would not yield more than $10.00 per ton* of 2000 pounds. • At this trine the cost of supplies and materials in the Hills was high. Miners' wages were $3.50 per diem, and custom mills charged $6.00 per ton. The successful working of mines on "the belt" necessitated cheap milling. The ores being of so low grade,f this could be accomplished only with large and economically running mills. To insure the greatest possible economy, the Father de Smet mill

Jan 1, 1882

By L. M. Cathles, L. E. Murr

Results of two years of leaching of 160 metric tons of low grade industrial copper sulfide waste in a large (40` high 10` diameter) thermally insulated tank at the New Mexico Institute of Mining and Technology are analyzed in the light of a previously developed model of the waste leaching process. It is shown that the model is verified in all major aspects and that the parameters in the model that characterize the leaching of a particular sulfide waste are usefully constrained by the results of the tank leaching experiment. The similarity between waste leaching parameters determined from the tank experiment and from interpretation of the leach behavior of test dumps constructed of similar waste encourages optimism it may be possible to predict the leach behavior of field dumps from suitably interpreted column experiments using the computer model developed.

Jan 1, 1980

By Robert W. Bartlett

A computer model for predicting the rate of oxidative leaching of copper from fragmented low grade sulfide ores is presented. The model involves the kinetics of the dissolution of chalcopyrite grains and solution diffusion of oxygen within rock pores. Adjustable curve fitting parameters are not used. The model was tested by comparing computed extraction curves with experimental results for a -11 inch ore obtained by block caving and leached at 90°C and 400 psi oxygen for one year at the Lawrence Livermore Laboratories.

Jan 1, 1973

By R. S. Archer

THE name molybdena was employed by Pliny to denote various substances resembling lead. Later this name was applied to galena-the naturally occurring sulfide of lead-or substances of similar appearance. By the middle of the eighteenth century, it was applied to graphite and to the mineral sulfide of molybdenum (MoS2) now called molybdenite. This confusion is quite understand- able inasmuch as these substances look and feel very much alike. In 1778, the Swedish chemist Scheele published a treatise in which he pointed out essential differences between graphite and molybdenite. On treatment with nitric acid, molybdenite, unlike graphite, produced a peculiar white earth with acidic properties which he called molybdic acid. Since the same mineral gave off sulfurous fumes on heating, he concluded that it was a sulfide of molybdenum. In 1790, there appeared an account of the isolation by P. J. Hjelm of the new element molybdenum, as a metallic powder, by heating the oxide with carbon. It was not until Bertelius conducted the necessary experiments, about 1818 to 1825, that the foundation of the chemistry of molybdenum was laid. The only recorded use of molybdenum during the first century after its isolation was as a chemical reagent, primarily for the determination of phosphorus. It was not until the last decade of the nineteenth century that the use of molybdenum in steel appears to have been investigated. A

Jan 1, 1953

By William G. Pariseau

Advances in numerical methods of analysis and computer technology during the past decade have brought many formerly intractable ground control problems within easy reach of present day graduate mining engineers. However, the new technology brings with it new problems. The identity of these problems are largely those arising from a lack of familiarity with the capabilities and limitations of the new technology. In this regard, the central problem in ground control planning is the calculation of ground motion associated with mining. The fundamentals of this problem leading to a form suitable for computer programming are therefore reviewed. Solution procedures in the broad sense including the gathering of input data and the interpretation of output are described. Computer program capabilities necessary for ground control analysis are discussed and the steps necessary to implement an analysis are outlined.

Jan 1, 1983

In the history of American mining, so far as I know, there is no cleaner, brighter, or more completely successful mining adventure than that of the United Verde Extension.* It deserves to be placed on record here. The mine is at Jerome, 25 miles northeast of Prescott, in Yavapai county, Arizona. For 30 years before the U.V.X., as it is known to mining men, achieved celebrity, the Jerome district was identified with a copper mine, the United Verde, one of the great mines of the world. The success of this mine, of course, stimulated the search for similar orebodies, or for an extension of those already known, in adjacent ground; but, despite vigorous prospecting, the United Verde remained for many years alone in its glory. The reason for this solitariness was geologic: a fault with a big throw frustrated the effort to trace the ore-zone, thereby causing exploratory work to be both uncertain and costly. Despite these failures to develop other mines in the vicinity, the belief persisted that all the ore was not localized in the United Verde mine, but before we consider the reasons for such a belief we must look at the geologic conditions. The basal rock of the Jerome district is a schist, which has been correlated with the Yavapai formation of the Bradshaw quadrangle. This schist is geologically ancient, for it is of pre-Cambrian age. It is composed of volcanic tuffs, together with sediments, both argillaceous and siliceous, all of which

Jan 1, 1932

By R. H. Thorpe

Longwall working in Britain developed to overcome problems arising from depth of seams causing roof and ventilation difficulties. This system became very widespread particularly in the thicker seams, where faces of up to one mile in length were not uncommon. In the thinner sections, in order to remain competitive, the longwall undercutting machine was developed. Following the development of the coal cutter, every other aspect of the face operation was examined and mechanized as it became a bottleneck to output and efficiency. The face system itself was modified and workings concentrated with the same objectives.

Jan 1, 1977

By E. H. Rose

It must be evident to almost everyone by now that a massive transformation is occurring in our iron ore economy. Its equal has been seen only once before in the entire history of the North American steel industry, and not even once before within the personal memory of anyone now engaged in it. The lone precedent was the beginning of ore shipments from the Mesabi Range in October, 1892, which was before anyone still short of normal retirement age had been born. No younger observer, in the steel industry or in any other, has ever known anything else than that the Lake Superior region-in which the Mesabi is the giant-has supplied all but a small fraction of total North American blast furnace ore for the use of three generations of steelmakers. Directly or indirectly, it was the discovery of the Mesabi which created most of the prime and satellite companies that have since come to prominence in the various ore-consuming phases, and it was the same discovery that had broader effects on the entire spectrum of their technologies than any other single event that has ever happened since, although the advent of byproduct coke is a close runnerup. It affected every sector of the national economy and was a keystone in making our standard of living what it is today.

Jan 9, 1961