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By T. Federighi, S. Ceresara, C. Panseri

The results of an exploratory investigation by means of resistivity measurements at -195ºC, on the aging characteristics of a set of Al-Mg alloys with a maximum content of 7 pct Mg, are reported. Whereas for dilute alloys (Mg < 1.5 pct) only a decrease in resistivity is observed at about 100°C (due to the elimination of quenched-in vacancies), for more concentrated alloys such a decrease is preceded by an increase in resistivity in the range between -60ºand +40°C. Following some previous suggestions, this increase is considered as good evidence for clustering of solute atoms @reprecipi-tation process). From the analysis of the results it appears that, although the process is substantially similar to that observed in other Al-rich alloys, it is characterized by a strong interaction between vacancies and zones. THE process of formation of Guinier-Preston zones, i.e., preprecipitation,1&apos;2 which occurs during the aging at about room temperature in many supersaturated aluminum-rich alloys, has been extensively investigated in the past few years by several workers.2,3 owever, a very interesting question arises when the case of Al-Mg alloys is considered: although it is very easy to supersaturate Al-Mg alloys, just in the same way as for many other aluminum alloys showing preprecipitation, only very little experimental evidence was available until a short time ago in the literature supporting the existence of "natural" aging in supersaturated Al-Mg alloys (see, for example, Refs. 4 to 6). On the other hand, as is well known, the X-ray method is not useful in this case because the X-ray scattering factors of magnesium and aluminum atoms are about the same. Recently, however, Cordier and Detert7 have stressed that during the aging at about room temperature of a supersaturated Al-Mg 10 pct alloy it is possible to detect an increase in resistivity; since, as is well known, such an increase is observed also in most alloys showing preprecipitation, the above authors have interpreted their results as evidence for the formation of magnesium-rich clusters (or Guinier-Preston zones) during the aging. In the course of or ientative investigations on preprecipitation in several aluminum-rich alloys, we also could detect a similar phenomenon in more dilute Al-Mg alloys, see Instituto Sperimentale Metalli Leggeri, Annual Report, 1959, and also Ref. 8. Since the details of our observations, although of a preliminary nature, differ from those of Cordier and Detert and allow one to draw a more advanced picture of the preprecipitation process in Al-Mg alloys, we have thought it useful to report our results in this paper and to comment on them briefly.

Jan 1, 1963

Discussion of the paper of C. W. WASHBURNE, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 93,. September, 1914, pp. 2365 to 2378. ROSWELL H. JOHNSON, Pittsburgh, Pa.-It seems to me rather important to bear in mind one thing which is sometimes lost sight of, that the marine sedimentary rocks are laid down in water. We have to start with an initial charge of water. That being so, and the surface tension between the water and the -oil being as slight as it is, as referred to by Mr. Washburne,. the phenomena of capillarity are bound to be most important as between the liquid surface and the gas surface. So far as the liquid-gas surface is concerned, capillarity, in my opinion, is of the utmost importance, and it seems to me this paper of Mr. Washburne&apos;s is of great value to us for that reason. Starting out as we have, with our attention concentrated upon gravitational sorting, we have had to wait for the discussion of movement furnished by Munn, and this discussion of capillarity by Washburne, for a more balanced view of the situation. It seems to me that in the accumulation of oil and gas we have a problem of the interworking of gravitational sorting, capillarity, viscosity, immiscibility, and movement. All five things seem to me to be important. I would have expected Mr. Washburne to have given a fuller treatment of the relation of movement to capillarity. In my own experiments I find that gravitation and capillarity alone seem remarkably impotent when everything is at rest, but if I furnish a little movement, gravitation and capillarity step in and accomplish a great many results that one would not expect. Take a horizontal tube and fill a portion at the middle with an ordinary sand saturated with oil, and then put water and sand in each end, and the tube may remain at rest a very long time without that oil distributing itself along the top of the tube. But with a little motion that oil will gradually work up to the upper side. So gravitation and capillarity alone are rather impotent unless they get this element of movement. It would not be necessary to have very extensive movement, but some degree of movement is essential. Now if natural gas, in addition to the method of origin by the action of bacteria on organic matter in mud, may also arise by pressure at great depth, as the overburden is added, a great deal of motion may result. I think more motion is produced in this way than by the descent of meteoric waters.

Jan 4, 1915

By Paul T. Allsman

Passage of the Mining Act of 1866, superseded by the Act of 1872, was the first major entry of the Federal Government into the problems of mining. Such a law was necessary simply to help re- solve a number of disputes in mining. Now, however, a hundred years later, the extent of government involvement in the mineral industry often comes as a shock to the mining engineer who has reached management level. In fact, he has been poorly prepared for an understanding of the role of government in the industry and he becomes frustrated, even hostile. In our political system, private industry is responsible for producing minerals and the Government sees to it that production will be adequate for a peace-time economy and for any emergency. There have been great social and political changes since World War I1 with the result that the Government&apos;s participation in our society has steadily increased. A new dimension in business and government relations has been introduced which should be examined more closely.

Jan 5, 1966

By HERBERT G. MOULTON

FROM prehistoric times to our own day man has struggled against extremes of climate. Human life, originating in semi-tropical or temperate areas, was unable to progress into the northern latitudes until fire was discovered and some form of clothing provided. It was found possible to maintain life even in the hottest parts of the tropics, but only at a great sacrifice of comfort and efficiency compared with the more temperate zones, or in cooler areas with the protection of clothing and artificial heat. It was no accident, but the natural result of climatic conditions, that efficiency became the greatest and civilization the most advanced in areas where the natural climate was favorable, or in cooler zones where protection against severe cold could be se-cured by relatively simple methods of conserving or producing heat.

Jan 1, 1933

By D. H. Gray, G. Bergamini, I. Fatt

A method developed by soil scientists for measuring permeability anisotropy of soils has been adapted for use in studies of sandstone permeability aniso-tmpy. Studies on Berea and Bandera sandstone show that permeability of these materials decreases upon application of simulated overburden pressure. Permeability reduction of Berea and Grubb sandstone cores subjected to simulated overburden pressure is shown to be a function of the ratio of radial to axial stress. INTRODUCTION The effects of mechanical stress on reservoir rock parameters are now generally accepted as being important in reservoir engineering calculations. In several oil fields the unique behavior of the reservoir has been attributed to the influence of overburden pressure or internal fluid pressure on rock permeability or fluid content. l Although the gross effects of overburden pressure on permeability, porosity, waterflood efficiency, electrical resistance and sonic velocity have now been established,3-9 there are some very interesting, and perhaps important, details of rock behavior under stress that have not heretofore been studied. In this paper we will show that permeability anistropy of several sandstones is a function of overburden pressure. We will also show that permeability reduction of cylindrical samples of two sandstones, when subjected to mechanical stress, is a function of the ratio of radial to axial stress. Most studies of overburden pressure effects made in the past have attempted to duplicate reservoir conditions by applying hydrostatic external pressure on all surfaces of the sample. Assuming perfect elasticity, that is, no viscoelastic flow during geological time, reservoir rock in situ cannot be under hydrostatic stress as is apparent from the value of 0.25 for Poisson&apos;s ratio for most rock. In the absence of tectonic forces the horizontal stress component If there are directional permeability effects, as has been reported from field and laboratory studies, l0,11 then one would expect hydrostatic stress as used in the laboratory to give a different permeability reduction from that occurring under reservoir stress conditions. The influence of stress on directional permeability was measured by a modification of the method first described by Maasland and Kirkham for use on soil samples.12 Their method permits calculation of the permeabilities along each of the three mutually perpendicular axes of a cubic sample. The modification reported in this paper extends the method to observing these permeabilities when the sample is under hydrostatic stress. The Hassler sleeve type of core holder is satisfactory for studying overburden pressure effects on permeability if a known force is applied to the end plugs. Wyble6 used a sleeve core holder but did not load the end plugs. In this paper we combine sleeve pressure and axial force to give permeability changes which we believe are close to those occurring in reservoirs when reservoir pressure changes. The combination of sleeve pressure and axial force assumes, however, that the sleeve pressure simulates both vertical stress and horizontal stress in one direction. METHOD PERMEABILITY ANISOTROPY The Maasland and Kirkhaml2 method of measuring permeability anisotropy uses a cube of porous material which is Open On three faces and has discs with a Center hole for an air inlet cemented to the other three mutually perpendicular faces (Fig. 1). The rate at which air pressure falls in a bottle of known volume, and pressure slightly above atmospheric, when the bottle discharges through each disc, is

By Elmer R. Kaiser

G. A. Vissac (Consulting Engineer, Vancouver, B. C.) —Some of the data presented in this paper, in connection with cost studies of washed coals, should be clarified and qualified. Washing a raw coal down to a low ash content may mean higher losses in refuse, but the cost of the operation may be more than compensated by the increased value of the resultant product. However, careful engineering and accurate machinery are required to insure maximum profits. Washing at a low gravity separation demands a very accurate automatic process, chiefly when the small sizes of coal are being handled. Coal consumers today are buying mostly on a Btu basis, cognizant of the fact that low ash contents result in lower installation costs and in savings in handling and transportation charges. The attached Table X gives the actual balance sheets of the various cleaning operations corresponding to various ash contents for the two coals presented in the paper, using the old technique of a two-products separation. or the new technique, now commonly used in Europe, of a three-way separation made possible by new methods and new equipment. Savings in capital costs, handling, and transportation have been calculated on the basis of a delivered cost f.O.b. plant of $10.00 per ton of coal at 16.5 pct ash (actual 1953 average price reported by Consolidated Edison, N. Y.), and of $3.50 at the mine also for 16.5 pct ash coal. In both cases this corresponds to values of 126 and 4.26 per 1 pct of combustible and per ton, respectively, on delivered and on at the mine prices. As an example, the middle western coal at 16.5 pct ash, raw, washed down to 4 pct ash in a two-way process will give 53.75 pct of clean coal at 4 pct ash and 46.25 pct of refuse at 31 pct ash. The value of the losses will be 0.4625x(100—31)x0.042 = $1.34. Add the cost of washing, capital, and operation, which is $0.35. The total cost will then be $1.69. But with a three-ways separation we will have 53.75 pct of first-grade coal at 4 pct ash, 37.25 pct second-

Jan 1, 1955

By K. Hodgson, N. C. Joughin

The detailed mechanism of rockbursts and other forms of damage due to rock failure in underground mining is as yet unknown. Studies of the energy changes which necessarily occur when an excavation is made underground seem to provide the best understanding of the phenomena leading to rock failure and damage (see Cook 1). It is common knowledge that the damage and rockburst hazard increases with depth and is greatest at remnants and in regions mined in an irregular manner. The rate at which energy is released as an excavation is enlarged provides an objective parameter to describe mining geometry in terms which are significant to studies of rock failure. In this paper, it is shown empirically that the rate of energy release per unit area increase in the size of an excavation is closely related to seismicity and incidence of damage in the mine. Consequently, it is suggested that the energy release rate is an important parameter in the design of underground mine layouts. Observations were made at two mines: the East Rand Proprietary Mines, Ltd. (E.R.P.M.), at a depth of about 9000 ft, and at Harmony Gold Mining Co., Ltd., at a depth of about 5000 ft. At both of these mines continuous recording seismic networks were in operation. (See Cook and Joughin.3) DESCRIPTION At E.R.P.M. the gold-bearing reef dips at approximately 35 degrees and is presently being mined at depths from 8000 ft to 11,000 ft below surface. The rock surrounding the excavation consists of a very homogeneous quartzite extending far into the hangingwall and footwall. The stoping width is approximately 40 in.

Jan 1, 1967

By A. Perry Thompson

I- GeneRal Distribution, AppeaRance, and Relations ........ 563 11. Data fRom MicRoscopic Examination............... 568 1. Criteria for Distinguishing Primary from Secondary Minerals...... 568 2. The Leonard Vein Filling..................... 574 Quartz............................ 575 Pyrite............................ 575 Enargite............................ 576 Covellite............................ 578 Bornite............................ 581 Chalcocite........................... 583 Chalcopyrite.......................... 586 3. The Fault-Vein Covellite..................... 587 The Speculator Ore........................ 587 The East Gray Rock Ore.....,.............. 589 4. Other Occurrences of Covellite.................. 591 111. Conclusions........................... 592 1. The Replacement of Minerals..................592 2. The Character of Mineralizing Solutions .............. 594 I. General Distribution, Appearance, and Relations Mining in Butte has seldom encountered covellite in commercial quantities. The notable occurrences, extending vertically and laterally perhaps several hundred feet, presented scattered, bladed lenses of this mineral in a matrix of quartz, pyrite, enargite, bornite, and chalcocite. But under the microscope covellite is seen to be widespread in the Butte ores, though in such small quantity that megascopic examination will not discover it. In early mining operations covellite was found in the Gray Rock vein, a member of the Blue vein system. As described by Sales,&apos; it persisted as an occasional ore mineral, associated with quartz, pyrite, tetrahedrite, bornite, chalcocite, and minor amounts of sphalerite, from the 700-ft. to the 1,200-ft. level of the East Gray Rock and Diamond mines. Crushed quartz-monzonite and later quartz completed the vein filling between

Jan 1, 1916

By R. L. Blackwood

The solid inclusion cell for absolute in situ stress measurement has been found to give reliable results in coal. The cell is described briefly, along with the methods of installing, overcoring and taking readings in underground coal mines. The validity of the cell performance is demonstrated by reference to the stress-relief curves obtained during overcoring and a three-dimensional B.I.E.M. analysis of the installation to test for stress anomalies deriving from the geometry of the overcoring groove-borehole-cell arrangement. Case studies of two stress measurement projects using the cell are presented for coal mines in New South Wales, Australia.

Jan 1, 1982

By John Birkinbine

Through the partiality of my fellow-members I have been able, during seven years&apos; service on the Council of the American Institute of Mining Engineers, to note the development of technical societies, a subject which commends itself as an appropriate theme for me, in retiring from the office of President, at a time when we meet in convention with Canadian technical societies. Our next assembly, called at Chicago at the time fixed for an International Engineering Congress, offers additional reason for the selection of this topic. If subsequent statements appear to give to the American Institute of Mining Engineers greater prominence than to kindred organizations, they may be excused upon the ground of long association with and loyalty to its members, and to a personal knowledge of their work. Besides, data as to its growth and development are more accessible; and at a meeting of the Institute features connected with it may be considered as of greater immediate interest than those affecting other organizations. The purpose of this address is, however, to use the record of the Institute as indicating a similar development of other technical societies, rather than to claim preeminence for any organization; the work of each must speak for it. There is a general tendency to form associations at the present time. Organizations have been created and are active in every profession and in all branches of labor, trade, industry, commerce, manufactures, science and art. A record of such associations and their aggregate membership would be startling, and would show how large a percentage of the population of North America is connected with one or more of them; but the figures cannot be even approximately estimated. The class of associations representing national, state, or local trade interests, such as boards of trade, chambers of commerce, etc., may be used as an illustration. A late report shows that in the

Jan 1, 1893

RAYMOND M. Howe (author&apos;s reply to discussion*).-Dr. Unger states that magnesite will hardly supersede dolomite in fettling after a heat; that it is hard to believe a slag composed of oxide of iron containing about 6 per cent. of phosphorus is the active corroding, agent in a boil in a furnace; and that boiling cannot be said to be the result of the chemical action of a high-phosphorus slag on a basic bottom. These are well-established facts that no one would venture to question. The authors were misinterpreted in the statement that "in the summary, it is claimed that magnesite low in lime, or of greatest purity, ranks first in resistance to slaking," etc. On the contrary, the position has been taken throughout that while a low lime content is advantageous, the presence of several per cent. of iron oxide (an impurity), is necessary in order to confer the proper bonding and sintering properties in dead-burned grain magnesite to be used for furnace hearths. We cannot subscribe to the view that pure magnesia is no better fitted for a refractory than pure lime,&apos; nor that the pure natural varieties of magnesite; such as Grecian or Washington, must necessarily be burned with silica and oxide of iron to produce a satisfactory material. On a small scale, pure magnesia has been satisfactorily used as a refractory in the form of crucibles. In the production of dead-burned grain magnesite from the Grecian or Washington mineral, iron oxide is added but the addition of silica is neither customary nor desirable. It is possible to manufacture brick of good quality from both the Grecian and the Washington material without adding either silica or iron oxide, providing they are burned at a sufficiently high temperature. This is regularly done on a commercial scale both in America and abroad when brick of. exceptionally high refractoriness or special purity are desired. The following analysis is of an English brick of Grecian magnesite which is extremely low in all impurities.1

Jan 6, 1919

By H. W. Rogers

The first steam shovels used in this country were built by the Otis Company, of Boston, about 50 years ago, but as they were of very crude construction and rather unsuccessful only a few were built. For possibly 10 years prior to 1884 successful steam shovels were made and used on certain classes of work, but it was not until that time that they were manufactured in quantities and began to play an important part in all classes of excavation. From that time up to the present day there have been gradual but continuous improvements on the original shovel, not only in the mechanical construction, but also in the design of boilers and engines which are best adapted to this class of service. In proposing a change from steam to electric operation we have to deal with a steam equipment which has not only proved its worth but has probably reached its highest stage of development and efficiency. That the electric shovel is a possibility cannot be denied, as at present from 12 to 18 shovels are in operation in this country. These shovels may be divided into three classes: the friction electric, which is operated by a single constant-speed motor with friction clutches; the three or four motor direct-current equipment, and the three or four motor alternating-current equipment. It is the second and third classes that I wish to deal with, as the first class does not compare favorably with the steam shovel so far as speed is concerned, although it may be operated as cheaply. There is probably no other class of machinery that presents a duty cycle as severe as that of the shovel, which is very short, varying from 7 to 12 sec. on the hoist, from 7 to 12 sec. on the thrust, and from 10 to 18 sec. on the swing, making a complete cycle in from 17 to 30 sec., and the motor to meet these requirements must have a sufficiently low armature inertia to permit of rapid acceleration and quick reversals under small power. It should also be a motor of rugged design, as it must be subjected to severe overloads and shocks and frequent reversals. This is especially true of the hoist motors and, to a lesser degree, of the swing motor; the thrust motor being practically stalled during the digging operation, although it may revolve or overhaul, according to conditions, and is operated at full speed only after the hoisting operation is completed.

Jan 1, 1915

By Karl Eilers

This process, invented by Messrs. Hanisch and Schroder, of Rosdzin, was patented in 1883. It has attracted considerable attention in Germany, as a very neat and simple method of extracting sulphurous acid from the gases produced by roasting, and of condensing this acid so as to obtain it in the very compact anhydrous liquid form. The special importance which such a process may have at this time in the United States is suggested by the growing inconvenience, amounting to distress, experienced in such localities as Butte, Mont., where the sulphurous gases from large roast-plants have proved not only fatal to vegetation but injurious to human health. It is reported that the authorities of Butte are earnestly considering the enterprise of removing, if practicable, the dense and suffocating cloud which now hangs over that city, and of which sulphurous acid undoubtedly forms the greater and most oppressive, if not the most poisonous, part. May it not be that the solution of this problem is furnished by a

Jan 1, 1892

By F. A. Loving

This paper describes experiments which represent an effort to measure preciscly the pressure-time history in detonating condensed commercial explosives. The performance of explosives in mining has been a favorite subject for experimentalists and theorists for many decades. Much useful empirical information has been developed; but it has not yet been possible to predict, or even to account for, the behavior of explosives in mining on the basis of fundamental physical principals. A basic piece of information that would appear necessary for any rigorous analysis is the pressure-time history in the detonating condensed explosive. The experiments described here represent an effort to measure this relationship precisely in commercial explosives. THE EXPERIMENTAL METHOD The experimental method, first described by Cowan and Jacksonl has been extensively evaluated by Cowan and Balchan for relatively simple explosives. The experimental procedure involves the detonation of a layer of explosive between metal plates whose external surfaces are polished to a mirror finish (Fig. 1). Precise measurements of the deflection of

Jan 1, 1967

By E. L. Jr. Spain

THE deposits described in this paper occur over much of Wayne County and in the southeast portion of Hardin County, Tennessee, and in the northeast and northwest portions of Mississippi and Alabama respec-tively. The presence of tripoli in this region has been known for some time and descriptions of various occurrences in Tennessee have been made by Jewell1 and Miser2, while Hilgard3, Lowe4 and Logan5 have treated the deposits that occur in the adjacent portions of Alabama and Mississippi, but there has not been a general survey of the entire field summarizing completely the geology of the deposits with respect to their origin and stratigraphic relationships. During 1934, while engaged in surveys of mineral resources through this region for the Tennessee Valley Authority, the writer collected data with this in mind, and has assembled them in this report. He is indebted to H. S. Rankin and N. A. Rose, of the Tennessee Valley Authority Geology Division, for field assistance.

Jan 1, 1936

By D. Gignac, P. A. Studemeister, H. Koza

Two epiclastic horizons in an Archean volcanic sequence host the gold occurrences on the Dunraine property near Wawa, Ontario, Canada. The Grace horizon of cherty and pelitic tuff strikes northnorthwest and dips east. Native gold occurs with arsenopyrite in bedlike and podlike bodies of quartz lenses and stringers set in a pelitic matrix. The Parkhill horizon of lithic graywacke with associated flow-breccia strikes southwest and dips south, Native gold occurs with minor sulfides in similar bodies of quartz erratic within the Parkhill horizon. The auriferous bodies occupy paleotopographic channels and troughs within the two horizons. The former producers are the Parkhill mine with 1689 kg (54,300 oz) Au, Darwin mine with 473 kg (15,200 oz) Au, and Van Sickle mine with 48 kg (1536 oz) Au between 1902 and 1944. The gold occurrences are syndepositional with the host volcanic sediments laid during a pause in explosive volcanism. Fumaroles along steep gullies on the flank of a subaqueous volcanic center precipitated aprons of auriferous silica-sulfide mud. Downslope slumping resulted in exhalative debris flows; gold concentrated in flexures and depressions along slumpage channels. Renewed explosive volcanism covered the auriferous sediments with pyroclastic tuffs, arresting the slumping of in situ fumarolic deposits.

Jan 1, 1986

By L. A. Weakly

The Viburnum ore trend is the largest, single known ore body of lead in the world. Four well-known mining companies operate in the trend, which is approximately 64 km (40 miles) long and up to 610 m (2,000 ft) wide, located some 121 km (75 miles) southwest of St. Louis, MO. Total production from the mines for 1979 was 33 kt/d (36,000 tons) of ore or 472 kt/a (520,350 tons) of lead and coproduct metal. The district is the number one producer of lead, providing 90% of the United States&apos; output with its coproducts, zinc ranking second, and copper and silver both ranking sixth in total US output. Mining is done in a stratiform deposit approximately 305 m (1,000 ft) in depth with the host rock principally dolomite. Ore is mined in large open stopes by the method commonly referred to as room-and-pillar mining. Mining methods and equipment are fairly similar, with the mines classified as trackless, all mining equipment operates on rubber tires. This paper will present a description of the different methods and equipment used to move ore from the active heading underground to the ore shaft for hoisting to the surface. Basically, three methods are incorporated: front-end loader and truck haulage combination; front-end loader and truck, with main line track haulage combination; and front-end loader and truck, with conveyor haulage combination. The logistics of each system, such as method of use, equipment specifications, ore handling rate, and those cost figures that could be made public, will be included.

Jan 1, 1983

By A. F. Crawley

THIS paper describes part of a series of density measurements on low melting point metals being undertaken at the Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada. This program has received support from the Canadian Zinc and Lead Research Committee and the International Lead and Zinc Research Organization. Examples of the type of work being done have already been given in earlier papers&apos; , which deal with the densities of lead, tin, and some of their alloys. Densities were measured using a graphite pyc-nometer by a technique which has already been described." The cadmium and indium, supplied by the Consolidated Mining and Smelting Co. of Canada were of 99.999 pct purity. Density determinations on indium, as for lead and tin,1,2 were made under a vacuum of about 5 x 10-6 torr because the oxidation and vaporization characteristics of the metal do not create experimental difficulties. This contrasts markedly with cadmium which, even at the relatively low temperatures of our experiments, has a high vapor pressure and a strong oxidation potential. To suppress the harmful effects of these properties, determinations on cadmium were made with success under an atmosphere of argon, the technique having been previously established in this laboratory for measurements on zinc.3 The densities of cadmium and indium are listed in Table I and plotted in Figs. 1 and 2. From the graphs, it is readily observed that the densities of both metals vary linearly with temperature. This relationship expressed mathematically is of the form:

Jan 1, 1969

By H. Reginald Hardy, Y. P. Chugh, Robert Stefanko

Many materials including rocks, ice, metals and their alloys, wood, etc., emit transient vibrations in the audible and subaudible range when stressed. In rocks, this phenomenon is referred to as "microseismic activity, " "rock noise, " or " seismo-acoustical activity. " In metals this phenomenon is often termed "acoustic emission." Each individual microseismic disturbance is generally referred to as a "microseismim" or an "elastic shock." The terms "microseismic activity" and "microseismim" will be employed exclusively in this chapter. Microseismic activity has been observed in many rocks loaded experimentally in the laboratory.1 The form of a group of typical microseismims is shown in Fig. 1. Quantitatively, the microseismic activity in rock under stress is most commonly described by the number of microseismims observed per unit time. This is commonly known as the "noise rate." The noise rate in general increases with increasing stress level and rises sharply just prior to failure of the material.2 The origin of microseismims is not well understood, but it appears to be related to processes of deformation and failure which are accompanied by a sudden release of strain energy. In a polycrystalline material, microseismims may originate at the micro-level as a result of dislocations or at the macro-level by twinning, grain boundary movement, or initiation and propagation of fractures through and between the grains. It is assumed that the sudden release of stored elastic strain energy accompanying these processes generates a stress wave which travels from the point of origin, within the material, to a boundary where it is observed as a

Jan 1, 1972

By C. F. Cockrell, K. K. Humphreys, H. E. Shajer

It is quite conceivable that the question of using coal or an alternate fuel in the future by large industrial consumers may be decided on the basis of possible profitable utilization of flyash. Accordingly, the Coal Research Bureau at West Virginia University has been attempting to develop new uses for this waste material. This effort has resulted in the development of a process for producing flyash-based face brick and other structural materials which generally exceed published specifications for competitive clay-based materials. These structural materials, containing up to 97% waste coal ash, can be produced from flyash derived from most coals without regard to the physical or chemical properties of the coal ash. Preliminary production cost estimates indicate that face brick can be manufactured at a rate of 9000 brick per hr or more with a resultant gross profit of over $24.00 per thousand brick. Plant payout time for a plant of this size would be only about 1.2 years assuming a market price of approximately $55.00 per thousand, a well established figure for comparable clay brick. With flyash production expected to more than double in the next 15 years, there is an increasing need for a practical and Profitable method for the utilization of large tonnages of this material (see Table I listing total flyash production of utilities in each state of the U.S.). Present industrial and governmental physical and chemical restrictions, particularly for use as a lightweight filler or pozzolanic material, have limited the use of flyash considerably. For those ashes which have met the required standards, utilization is not always assured because of lack of promotion and poor public acceptance. Less than 6% of the total flyash production in the U.S. was sold in 1962. The remainder was dumped in disposal areas at costs as high as $2.42 per ton.&apos; It is quite conceivable that in the near future the question of using coal or an alternate fuel by large industrial consumers may be decided on the basis of the possible utilization of flyash. To help insure future coal demands, the Coal Research Bureau at

Jan 1, 1968