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By A. P. Boller

In the victories of peace as well as of war, the science of engineering has played a prominent, if, indeed, not the leading part. While it might be interesting, and food for profitable thought, to trace the development of engineering from early times in its bearings upon the social betterment of mankind, it will be sufficient on the present occasion to suggest a few thoughts that it is hoped will aid the unprofessional listener to an appreciative consideration of the subject-matter laid down for to-day's discussion, and possibly lead the professional brother to a higher conception of the profession to which he belongs. Since the advent of the railway era, it is difficult to grasp the sequence of historic events that have led to the wondrous derelopment of mechanical science, making possible the civilization that is our daily boast, and opening up a vista of future intellectual and moral advancement among the nations of the earth, 'before which the imagination becomes hopelessly lost. Even now, looking back over a period of only half a century, we often fail to realize the vast change in the relations of individuals and nations to each other., brought about by the results of those mechanical discoveries which, having made the whole world kin, exercise a resistless levelling influence that bears fruit politically in the spread of republican ideas, and morally in the elevation of the individual through the facilities given to the dissemination of Christian ideas and general intelligence. In this view, it seems almost like a work of supererogation for a body of representative men of one department of that science to which the whole world owe. so much, to meet here at the centre of our national life to plead not only for a practical recognition of the national importance of the work to which their lives are devoted, but also for national aid, on a scale beyond that of private effort, to the end that mechanical science may be carried to a higher plane than ever yet attained, each step on the way being of material benefit to every man, woman, and child in the community. Possibly this is strong language, but none too strong when we consider that the work for which we plead is one affecting not only vast scientific and commercial interests, but also human life, to a degree little ap

Jan 1, 1882

By W. J. Mcgaughey, R. G. McCreary, S. C. Maxwell, R. P. Young

"Seismic tomography is a process for obtaining images or maps of seismic velocity or other seismic properties of a rock mass. Seismic velocity images reveal variation in elastic moduli which, in tum, are related to several properties required in the geological or geomechanical assessment of a rock mass. Seismic velocity is sensitive to lithology, discontinuities, and in situ stress. Spatial or temporal variation of these properties may be indirectly assessed. Tomographic measurements are sensitive to volumes of ground, rather than determinations at points, or along lines or surfaces, as in conventional geological or geomechanical measurements or mappings.Tomography surveys are complementary to conventional measurements as they have the capability to interrogate a substantially larger volume of ground. They are thus useful in discerning trends or patterns in regions between or surrounding conventional ""point"" measurements of lithology, rock quality, stress, or other parameters of interest. Seismic velocity images give broad indications of trends in velocity; their spatial resolution of ground properties is typically on the order of five to ten per cent of the nominal survey dimension.Research in seismic tomography has been carried out for several years, and the capabilities and limitations of the technique in mining environments are beginning to be understood. This report reviews the present capabilities of seismic tomography surveys in mining, emphasizing rock mechanics applications. Six case studies are used as examples to demonstrate the capabilities of the method in assessing lithological variation, density and orientation of discontinuities, and the effects of stress."

Jan 1, 1994

By Arthur Tauber, Horst Kedesdy

FERRITES are sintered metallic oxides of the spinel structure type1 and belong to the class of soft ferromagnetic materials. Similar to a ceramic, they can be formed and fired to a dense body, exhibiting a high electrical volume resistivity ranging from 10 90 10' ohm-cm as compared with 10-6 hm-cm for some of the metallic magnetic materials. This high resistivity, with resulting low eddy current losses, finds special application at high frequencies. The dispersive susceptibility of ferrites at microwave frequencies has also led to many applications in this field. Where high resistivity with high permeability is desirable, ferrites are used in low frequency applications. During the last few years ferrites exhibiting rectangular hysteresis loops have been developed for computer and magnetic memory systems. The general formula for ferrites is MeFe2O4 where Me is a divalent metal ion such as Ni, Zn, Mg, Mn, Cu, Cd, and Fe. Only two of these ferrites are nonferromagnetic, namely, those with Zn and Cd. Solid solutions can be formed between different ferrites, and it is of interest to note that solid solutions of a ferromagnetic ferrite with a nonferromagnetic ferrite yield much better magnetic materials than the basic ferrite body. In general, it can be said that the solid solution formation between ferrites has widened the field of ferrite synthesis and has led to methods of preparing materials with a large variety of magnetic properties. During the last two decades the synthesis of ferromagnetic oxides has been the object of extensive research, but commercial production has been started only within the last ten years. Along with more fundamental studies, there remains the never- ending task of developing ways to realize the optimum characteristics of materials in large-scale production. Ordinarily, to produce a ferrite material it is necessary for the constituent oxides to be mixed intimately, pressed, and then fired at temperatures above 1000°C. Ferrite Synthesis: Formation of a basic ferrite by solid state reaction from Fe,O, and a monoxide such as NiO, under normal atmospheric conditions, is governed by a progressive diffusion of cations between adjacent particles of the constituents. Firing temperature, furnace atmosphere, and cooling can vary the magnetic properties, however. If, for example, a dioxide, a sesquioxide, or an oxide of the Me0 type is substituted for the monoxide, the reaction mechanism becomes more complex and extremely dependent on atmospheric conditions and firing cycles. For this reason reproduction often

Jan 1, 1958

By Arthur Tauber, Horst Kedesdy

FERRITES are sintered metallic oxides of the spinel structure type1 and belong to the class of soft ferromagnetic materials. Similar to a ceramic, they can be formed and fired to a dense body, exhibiting a high electrical volume resistivity ranging from 102to 107 ohm-cm as compared with 10-6 ohm-cm for some of the metallic magnetic materials. This high resistivity, with resulting low eddy current losses, finds special application at high frequencies. The dispersive susceptibility of ferrites at microwave frequencies has also led to many applications in this field. Ferrites are used in low frequency applications where high resistivity with high permeability is desirable. During the last few years ferrites exhibiting rectangular hysteresis loops have been developed for computer and magnetic memory systems. The general formula for ferrites is MeFe2O4 where Me is a divalent metal ion such as Ni, Zn, Mg, Mn, Cu, Cd, and Fe. Only two of these ferrites are nonferromagnetic, namely, those with Zn and Cd. Solid solutions can be formed between different ferrites, and it is of interest to note that solid solutions of a ferromagnetic ferrite with a nonferromagnetic ferrite yield much better magnetic materials than the basic ferrite body. In general, it can be said that the solid solution formation between ferrites has widened the field of ferrite synthesis and has led to methods of preparing materials with a large variety of magnetic properties. During the last two decades the synthesis of ferromagnetic oxides has been the object of extensive research, but commercial production has been started only within the last ten years. Along with more fundamental studies, there remains the never- ending task of developing ways to realize the optimum characteristics of materials in large-scale production. Ordinarily, to produce a ferrite material it is necessary for the constituent oxides to be mixed intimately, pressed, and then fired at temperatures above 1000°C. Ferrite Synthesis: Formation of a basic ferrite by solid state reaction from Fe2O3 and a monoxide such as NiO, under normal atmospheric conditions, is governed by a progressive diffusion of cations between adjacent particles of the constituents. Firing temperature, furnace atmosphere, and cooling can vary the magnetic properties, however. If, for example, a dioxide, a sesquioxide, or an oxide of the Me3O4 type is substituted for the monoxide, the reaction mechanism becomes more complex and extremely dependent on atmospheric conditions and firing cycles. For this reason reproduction often

Jan 1, 1958

By Richard Hogg, Erol Kaya, Jan M. Mutmansky

Characterization of the size, shape, chemical composition, and mineralogical content of mine airborne dusts generally requires a larger mass of dust particles than is typically collected using traditional sampling devices. In this paper, the general design of a passive dust collector is described and the field results are presented. The collector was constructed of galvanized sheet metal duct with a resin-coated honeycomb to provide an elutriation-type system for particle collection. Several versions of the collector were used in the field portions of the research. The dust samples collected from underground coal mines were found to possess angular particle shapes, relatively consistent size distributions, and elemental compositions that showed relatively little variation, at least for the more prevalent elements. In addition, the distributions of particles sizes obtained from the passive dust collector appear to be similar to those of samples collected at the same time in a conventional personal sampler except that the passive device seems to collect a larger quantity of coarse, non- respirable particles. Conclusions on the suitability of this dust collector for collecting characterization samples are presented. In addition, the potential for using such a dust collection system for supplying dusts for biomedical research is discussed.

Jan 1, 1993

By Willard L. Hunter

The Bureau of Mines smelted samples of chromite ore and concentrate from the General Services Administration (GSA) purchasing depot at Grants Pass, Oreg., in a submerged-arc furnace to establish smelting conditions and the energy requirement to produce high-carbon ferrochromium. Raw material, in the form of ore, flux, and reductant, and electrical energy are available on the Pacific coast to smelt the chromite. The concentrate can be smelted without prior agglomeration by employing hogged wood (wood chips) as a major portion of the reductant. The energy requirement is relatively low, about 3,960 kw.-hr. per ton of alloy. The ferrochromium produced will contain about 60 percent chromium. In addition to the smelting data, a statistical summary of the grade and amount of chromite purchased during the stockpile program and estimated chromite reserves and production volume are given. It is estimated that 632,000 tons of Cr203 contained in chromite of all grades is available in the western coastal States. Of this total there appears to be sufficient metallurgical-grade and beneficiable ore to sustain a smelting operation for 25 years at a consuming rate of 25,000 tons a year, utilizing material comparable to that delivered to the Government stockpile.

Jan 1, 1961

By Deutsch G. P

The output of an underground mine often depends entirely on the mine winding system. -Decisions made--at the design stage affect the economy and operation'of the mine'.througb -its entire life. A modern mine winding installation is an integrated system and its design requires a multidisciplinary approach including expertise in the-materials handling, mining, mechanical, civil, structural, electrical and control engineering fields. The paper-sets out the elements of typical mine wind- ing systems-and describes some of the more important decisions which must be made during the planning and design process, It is no longer.adequate to. base the choice of a system on the pre- ferences and experiences of individuals. Major Australian winding install- ations are usually designed on the basis of overseas experience and some of the detail design is often carried, out overseas. Differences in basic design criteria occur from country to

Jan 1, 1973

Joseph HartshoRnE, Pottstown, Pa.: I have read Professor Akerman's valuable paper with great interest. Few of the present generation of American steel metallurgists are aware of the very important part taken by Swedish engineers in the successful development of the Bessemer proeess, and I am afraid some of the older ones have forgotten it. Certainly, I think, most of us would have said that Terre Noire was the first to introduce the use of metal direct from the blast-furnace. It is very well, therefore, that honor should be given to whom honor is due. I can speak from personal experience upon one part only of Prof. Akerman's paper; namely, the effect of the temperature at which the molten metal is cast upon the quality of the finished steel. In a general way I have, of course, known for a long time that the

Jan 1, 1894

Joseph HartshoRnE, Pottstown, Pa.: I have read Professor Akerman's valuable paper with great interest. Few of the present generation of American steel metallurgists are aware of the very important part taken by Swedish engineers in the successful development of the Bessemer proeess, and I am afraid some of the older ones have forgotten it. Certainly, I think, most of us would have said that Terre Noire was the first to introduce the use of metal direct from the blast-furnace. It is very well, therefore, that honor should be given to whom honor is due. I can speak from personal experience upon one part only of Prof. Akerman's paper; namely, the effect of the temperature at which the molten metal is cast upon the quality of the finished steel. In a general way I have, of course, known for a long time that the

Jan 1, 1894

By Paul L. Russell

Numbers, arithmetic, mathematics. Where did it all come from? Who needs it? We all do, but many school children would not agree. Engineers, physicists, accountants, tax collectors, and most of the general public are well aware that modern society in large part is founded on mathematics and could not exist without it. Mathematics developed over thousands of years as part of the everyday life of man. No one area, tribe, or race can claim discovery. In fact, from the records that do exist, it is evident that many facets of mathematics were discovered independently of others who made similar discoveries. While proof may be lacking, the earliest concepts of mathematics may be some 250,000 to 300,000 years old. The first use of numbers as written records is unknown. However, a bone of a young wolf deeply cut with 55 notches-arranged in two rows, one of 25 notches, the other of 30-was found in Czechoslovakia. Dated to be about 30,000 years old, it is perhaps an early record of some kind of counting system. It is assumed that mathematics was developed as an answer to man's practical needs, but anthropological studies suggest that the art of counting may have developed in connection with the needs of primitive religious ceremonial rites. Fingers probably were first used to designate sets of from one to five objects. Using both hands, up to 10 items could be indicated. As civilization developed, so did the need for more flexible systems to record items of trade, measure land, and figure taxes. Aristotle noted that the development of the decimal system comes from the fact that most people are born with 10 fingers and 10 toes. In spite of this obvious fact many early civilizations used binary, ternary, and quinary systems while vigesimal systems (with 20 as a base) and even sexagesimal systems (with 60 as a base) were used by others. A form of writing was in use in both the Mesopotamian and Nile valleys as early as 3000 to 4500 B.C. In Mesopotamia, wedge-shaped marks were impressed upon soft clay tablets that were hardened in ovens or by the sun. Many thousands of such tablets have survived. When the tablets were finally deciphered, some were found to be records of items shipped in trade, inventories, tax accounts, and mathematics exercises for teaching. Mesopotamia is also the source of an interesting board game dating back to about 2500 B.C. Its buttonlike men and triangular dice were apparently used with squares of shell, inlaid with lapis lazuli and red sandstone. Unfortunately, rules of play were not found. In Egypt, record preservation was somewhat better. Discovery of the Rosetta Stone in 1799 eventually led to deciphering the Egyptian hieroglyphics that included a numbering system at least 5,000 years old. These records show a competence in counting and numbering. A calendar of good accuracy may have been in existence as early as 4,200 years ago. Mathematics, as practiced today, developed when the Greeks added logic and proof to arithme-

Jan 12, 1982

By Duk-Won Park

The excavation of a longwall panel causes a continuous stress redistribution in the surrounding strata for every face advancement. The understanding of the behavior of rock to high level of stresses is instrumental to the structural design of underground mines. In order to achieve a realistic analysis of the behavior of strata, the three-dimensional finite element method is frequently used. Also the model developed for the analysis has to be designed large enough to represent the influenced strata in the study area and a sufficient number of elements has to be used to provide detailed information on the stresses and displacements. Due to the size of the model and its numerical solution the CRAY X-MP/24 supercomputer has been used for this study. The mine site selected for the analysis is a coal mine located in the Black Warrior Basin in Alabama. The mine has two longwall sections at a depth of 2,000 feet with various dimensions of chain pillars, including yield pillars. Various research programs at this mine have been carried out by Park et. al. ( 1984 ). Therefore data were already available on the geology, and physical properties of rock and coal. In addition a rock testing program has been carried out to obtain rock mass classification parameters. The progressive failure technique has been utilized to simulate stress redistributions. The failure criterion after Hoek and Brown ( 1980 ) which is based on rock mass behavior was used for the iterative technique. Simulated stress redistributions are therefore very realistic. In order to automate the process involved in the application of progressive failure technique, a computer program has been developed. The combination of a large scale three-dimensional finite element model and the automation of progressive failure simulation provided a tool that can generate a large amount of information related to the behavior of rock and coal as a response to a longwall mining operation.

Jan 1, 1989

By Richard F. Down

The Tynagh mine of Irish Base Metals Ltd., a subsidiary of Northgate Exploration Ltd., of Toronto, Canada, is situated one mile from the village of Tynagh in County Galway, one of the western counties of the Republic of Ireland. Mining has been carried on in Ireland since the Bronze Ages, but, apart from a reference in the 1859 Geological Survey records to much earlier mining attempts, mining has not been a feature of the Tynagh area in recent times. The present ore body was discovered by geochemical techniques in 1961. Following a diamond drilling programme to delimit the orebody, a pilot plant was operated at the property in late 1963 and early 1964. Construction of the 2000 tons per day treatment plant began later in 1964 and production commenced in December, 1965. The orebody contains both sulphide and 'oxide' ores and these are treated to produce, by flotation, a variety of lead concentrates, a zinc concentrate, and a bulk lead-zinc concentrate, which are shipped to several European smelters. The term "oxide ores" is used here to mean all ores which contain economically important amounts of the oxidised minerals of lead, zinc or copper. THE ORE The ore body lies on the northern side of a major east west fault between sandstone and limestone; it is a boat shaped mass of residual or secondary ore lying over primary sulphide in limestone. (1) (2) The secondary ore consists of both residual sulphides and

Jan 1, 1970

One of the results of the work of the Committee on Precious and Base Metals is that the present Bulletin is as large as some of. the annual volumes of Transactions of the Institute, and we extend our. compliments and thanks to the Committee and express to the members thereof and to. the authors, who have so bounteously given of their time and information, the. sincere gratitude of the Institute. In order to get all these papers printed and distributed to the membership in advance of the meeting, it was necessary to divide the work between two printers. This accounts for the discrepancy in the pagination of the Bulletin; and we also ask the indulgence of our readers in case errors have crept into this preliminary edition during the period of unusual pressure. Program of the Butte Meeting.-The program of the Butte meeting will include six technical sessions for the presentation and discussion of papers and five half-clay visits to mines and metallurgical works. The following program is practically in final form, with slight additions which may be necessary later. Every effort will be made to have papers presented and discussed on scheduled time, so that members who are unable to attend the entire meeting may so plan their trip as to hear and discuss papers in which they are especially interested.

Jan 8, 1913

By E. W. Steele

In the copper-casting department of a modern electrolytic copper refinery there are two kinds of casting furnaces: the anode, for casting crude copper into anodes for electrolysis; the refined-copper, for casting the cathodes resulting from electrolysis into market shapes, such as ingots, wire bars, and cakes. Both furnaces are reverberatories of practically the same general design and are operated intermittently, putting through a charge normally in 24 hr. The treatment of the copper in the two furnaces is similar, in that oxidation followed by skimming and reduction (poling) is carried on in both; but in the refined-copper furnace, the work must be done with greater care and it is of extreme importance that not the slightest trace of impurity be introduced into the copper. The furnaces usually hold from 150 to 300 tons of molten copper, which constitutes the daily charge. Except in the case of furnaces in the Lake district, where the concentrates from native-copper ores are charged through the roof, the furnaces are charged through the side doors by charging machines similar to those used in open-hearth steel practice. In 1916, at the Perth Amboy plant, of the American Smelting & Refining Co., located at Maurer, N. J., a study was made of the possibility of firing the copper refinery furnaces with pulverized coal instead of by hand. The proposed method possessed obvious advantages over hand firing and coal was a much cheaper fuel than oil at that time. However, there were several objections to its use, the principal ones being the possibility of increasing the sulfur content of the refined copper and the additional slag that might be produced from the ash. The increase of the sulfur content of the refined copper was the more serious, as more than 0.002 per cent. sulfur is objectionable. Any increase of the slag would be expensive as the copper in this slag would have to pass again through the entire smelting and refining process. It was thought that certain modifications in operations and furnace conditions, which will be described later, would overcome these objections SO the proposition was discussed with a manufacturer of coal-pulverizing equipment. He was uncertain concerning the use of pulverized coal

Jan 1, 1925

By P. B. Marchant

"Based on laboratory and pilot scale continuous biooxidation of complex sulphide concentrates, commercial processing design and scaleup considerations are discussed. Capital and operating cost estimates for commercial biohydrometallurgical operations are summarized and potential applications of biotechnology are discussed. Biooxidation as an oxidative pretreatment alternative to enhance precious metals extraction from refractory sulphide concentrates in stirred tank reactors has received considerable attention recently due mainly to advances in the practical applicability of the process. Biooxidation of sulphides is certainly not a new process, however, application and control in large scale hydrometallurgical operations to treat refractory sulphides remains conceptual and the limited data available is restricted to relatively small laboratory and pilot scale operations. It is the intent of this paper to indicate scaleup and plant scale process design considerations for commercial bioleach circuits, based on recent operating experiences with laboratory and pilot scale continuous bioleach systems. An indication of the expected range of applications will be presented parameters for optimization will be discussed."

Jan 1, 1986

By Keith A. Heasley

Pillar recovery in deep coal mines with competent roof and floor can concentrate stresses and generate hazardous bumps. Actual calculation of the geologic strain energy released in association with these coal bumps has been rare, although energy release values have been utilized successfully for indicating burst potential in numerous hard- rock mines. This paper advances the current knowledge of energy release calculations as applied to coal bumps through an extensive analysis of an actual bump occurrence. The U.S.B.M, displacement- discontinuity code, MULSIM/NL, is used to produce a numerical model which generates stress, displacements and energy values associated with a pillar retreat section. This model is calibrated with actual field data, and then dissipated energy values from the model are examined as to their suit- ability for indicating bump potential. Ultimately, it is determined that prudent application of dissipated energy calculations can be used as a tool to investigate the coal bump potential of a mining plan or cut sequence.

Jan 1, 1990

By Arcy A., J. G. Davis, D&apos Shock

Results of a pilot operation in the Carlsbad Basin are discussed. After hydrafracing between wells, a block of potash was removed by solution techniques. The distance between frac wells was about 200 ft, the thickness of potash mineralization, 5 ft. By proper manipulation, a feed of concentrate brine was obtained. The ex-periment showed that the thin-bedded potash could be removed by the solution techniques. The details of well construction, method of operation, and removal rates are discussed. Continental Oil Co.'s laboratory research on the fundamentals of potash solution mining has been expanded by means of a series of field tests, and subjects such as well completion and hydraulic fracturing were added to the investigation. Both single-well and multi-well systems were studied in the field work. Discussion Background: The current paper discusses one field test in which potash was solution mined by a two-well system from a thin sylvinite zone. The potential economic value of solution mining evolves from (1) the use of drilled holes and solution techniques instead of excavated shafts and caverns and (2) the ability to mine both land and marine deposits through any type of overburden geology and below conventional mining depths. Recent interest has been focused on potash' and other soluble minerals, such as trona. Solution extraction minerals, such as copper and uranium, are also worthy of important consideration. In addition, many of the techniques are directly applicable to the construction of horizontal underground storage carverns in salt. There are two general approaches to potash solution mining. The first is to mine on a single-well basis, in which the same well bore is used for both injection and production. This method is slow, and the areal extent may be quite limited in other than very thick ore zones. The second, and the preferred approach, is to mine on a multi-well basis in which the solvent is circulated between wells. This technique, if applied in a manner which allows the ore zone to be mined from the bottom upward, results in nearly all the solution taking place from the cavern roof. Salt removal rates, therefore, are very much higher than from a single-well system.l Wells can be interconnected into a multi-well pattern by several means. One is to join single-well caverns in the lower part of an ore zone. Another is to use the hydraulic fracturing techniques developed in the oil fields.' We preferred the fracture approach because of its potential for creating the greatest area of salt exposure. Test Site Description: The field tests were conducted in New Mexico's Carlsbad Basin, where the potash deposits are flat and uniform over reasonable distances. Here, 12 potash zones are present in the massive Salado Salt section. The specific target was the Third Ore Zone which is about 4 ft thick at our location and about 1150 ft deep. The test pattern was designed in the shape of an equilateral triangle with a fourth well located in the center, 200 ft from each of the vertex wells. This configuration allowed the ore zone to be hydraulically fractured from the center well with good assurance that the fracture would intersect the bore of at least one outside well. Several multi-well test patterns would be available if the fracture connected all wells. Well Completion: Surface casing was set in the top of the Salado Salt at 600 ft to shut off water flows from the surface sands, and the salt section was drilled and diamond-cored to a point below the Third Ore Zone. A drilling fluid made of diesel oil with a small amount of emulsified water was used to drill and core the salt. This fluid was highly successful in preventing enlargement of the drilled hole and in promoting good core recovery. The three outside wells were completed by setting 51/2-in. casing at the base of a streak of anhydrite about 20 ft above the ore zone. Pipe was set high so that the intersection point of the fracture could be detected even if the fracture migrated above the ore zone as it progressed outward from the center well. The center well itself was completed by cementing 51/2-in. casing through the Third Ore Zone. Cement bond logs run on the center well have shown excellent bonding. Fracturing Practice: A mechanical tool was used to cut a notch through the casing and into the salt at a point about 1 ft below the ore zone in the center well. The purpose of this notch was to fix the point of fracture entry into the salt. The fracturing was done with water at injection rtaes as high as 30 bbl per min. The salt parted at 1450 psi; and it required only 5 min for the fracture to reach the well which was 200 ft to the south. It took about 5 min more to reach the other two wells. Caliper surveys were run to locate the point of fracture entry in the three outside wells. The fracture appears to have drifted downward slightly, entering the outside wells at the top of a streak of carnallite 8 or 9 ft below the ore zone. A cross section of the wells selected for the multi-well test is shown in Fig. 1. The figure includes KC1 values based on core analysis and the trace of the fracture plane between the wells.

Jan 1, 1971

By Thomas D. West

A short time ago, I had occasion to cast iron plates 1 in. thick, direct from metal containing Si, 0.51; 8, 0.045; Mn, 0.75; and P, 0.094 per cent. Much to my astonishment, I found that there was no trouble in planing them; whereas, if cupolaimetal of like composition had been used,*the planing would have been a difficult operation. I have often noticed a greater fluidity or " life " in furnace-metal, as compared with the cupola-product. Iron can be seen flowing down the furnace-runners from 50 to 100 ft., and reaching the last pig-bed in satisfactory condition, while cupola-metal might have solidified before it had flowed so far. I have seen Bessemer iron, which, on account of its low phosphorus-content, does not have the " life " of ordinary foundry-iron, held in a 30-ton ladle for nearly an hour and a half; and after skimming off the coke-dust, it still had to be cooled off' considerably before being cast. As a general proposition, it is known that the lower sulphur-content and the frequently higher temperature of direct-metal, compared with the same iron remelted in the cupola, has much to do with its greater life; yet some problems connected with this phenomenon seem to call for further study. For instance, furnace-metal containing more than 1 per cent. of silicon holds carbon, which is separated later as "kish." This separation does not take place to any great degree while the metal is very hot; but during its gradual cooling, at times, the kish is given off in such large quantities as to cover the ground from 20 to 30 ft. around the ladle. In making castings of direct-metal, especially with a high content of silicon, the separation of kish becomes an annoyance. Perhaps this throwing out of the excess of carbon makes the life of the metal shorter, after it has been remelted in a

Jan 1, 1905

By James J. Roettger, Robert J. Mitchell

"The results of a series of model stope pours designed to investigate working pressures on bulkheads during hydraulic pouring of classified tailings backfill are reported. Total bulkhead pressures and fill water pressures were monitored under the condition of a fully saturated backfill. Similitude of the model testing is discussed and equations are developed to estimate bulkhead pressures under prototype conditions. The model results show that good base drainage, combined with a bulkhead setback, can reduce the expected bulkhead pressures to values such that timber or concrete block structures should be capable of supporting a saturated backfill. Introduction Bulkheads are used in underground running operations to block drift openings in order that hydraulically placed sand backfill can be contained in stope pours. Whenever possible, the sand fill is designed to have sufficient percolation rate so that excess hydraulic transport water will gravity drain out through the bulk headed drifts. This avoids costly decanting systems. Early bulkhead design assumed that the bulkhead pressure could be as high as 0h = Hy where H is the fill height and ""y is the saturated unit weight of the fill (Thomas et al., 1979)(1). A typical design pressure for a 50 m fill height would be 1250 kPa giving a design force of 12,500 kN on a bulkhead located in a drift of 10m2 in area . Typical bulkheads were 1 m thick heavily reinforced concrete structures formed and poured into a notched drift. Not only were these expensive structures but the associated problems of inside drainage systems and curing time delays increased production costs. As experience with bulkheads for large bulk pours increased and fill pressure measurements became available [see, for examples, Libby et al., 1975(2), Askey et al., 1978(3)] , 'free drainage' timber and concrete block bulkheads were designed. Substantial savings have been realized using these types of bulkheads but greater engineering design and monitoring of backfill pours is necessary to ensure that backfill pressures do not exceed the bulkhead design pressures.The effective and total stress components of fill pressure, the engineering concepts associated with the 'free drainage' design and some detailed design considerations have been discussed by Smith and Mitchell (1982)(4) . It is important to the safe use of these designs, however, that the basic engineering concepts be demonstrated and communicated to those responsible for the day-to-day backfill operations. This paper describes and explains observations from a series of model studies designed to measure bulkhead pressures in a saturated fill."

Jan 1, 1984

By Deep Foundation

Whenever an organization launches an initiative, the question arises whether that initiative has staying power. Or is the initiative, as is quite often the case, merely a fad; that is, just an activity that suddenly becomes popular, but which does not stay popular for very long. When the Federal Highway Adminis- tration (FWHA) started its Advanced Geotechnical Methods in Exploration (A-GAME) initiative, that question was addressed, especially considering the fact that up to 50% of major infrastruc- ture projects suffer impacts to schedule or cost due to geotechnical issues. Many of these issues relate to risks identified directly or indirectly to the scope and quality of site character- ization work. Effective site charac- terization is critical for recognizing. potential problems that may affect design and construction and for ensuring safe, well-performing and cost-effective projects. Grounded on that, knowledge of all available site investigation methods should continue to be shared widely and the application of those methods should be encouraged on an ongoing basis throughout the project lifecycle. The A-GAME initiative covers five technologies: Cone penetration testing (CPT), monitoring while drilling (MWD), electrical geophysical methods, seismic geophysical methods, and optical and acoustic televiewers. Of these, three soil and rock investigation methods were highlighted that are underutilized not only here in the U.S., but also in many places around the world: CPT: a well proven and established method for soil characterization that turned 90 last year, in which continuous in-situ data are col- lected quickly and consistently. Geophysics: the science that assesses the physical properties of the soils and rock using seismic and electrical techniques, which con- tinues to advance in leaps and bounds as the application of well- understood technologies become more powerful.

May 1, 2023