Search Documents

By J. C. Jaeger

It frequently happens in engineering and mining situations that "bad" rock is encountered which consists of rock broken up into blocks a few inches or less in diameter by a network of intersecting joints. These joints may be open, or filled by veins of solid material, or covered with weathering products. Essentially, the material consists of an aggregate of small interlocking blocks. In such circumstances, major joint systems usually can be recognised and studied, but there are probably many minor planes of weakness which may cause the blocks to be of almost random shape. It is extremely difficult to determine the properties of such materials. Measurements on small specimens give the properties of the constituent rock and not the jointed material. At the other extreme, the material has occasionally been tested as loose aggregate in large triaxial pots, but this gives no information about the strengthening effect of the interlocking of the small blocks of rock. One simple approach, which has been much used, is to regard the rock as randomly jointed on a small scale and to apply soil mechanics theory to it. In this case, the normal and shear stress at failure are related by [ ] where the coefficient of friction p and the cohesion c will be those of the individual joints. Even in very bad rock, it is usually possible to drill core in small diameters of 1 to 2 in. which will contain a number of joints, both open and filled. The testing of such joints provides one simple method of determining some of the properties of closely jointed rock and will be discussed in detail in the next section. Calculations based on Eg. 1 with values of c and µ obtained in this way may be expected to give a lower limit for the strength of structures in rock.

Jan 1, 1970

By D. J. Varnes

Rocks in mines, quarries, and many outcrops commonly show evidence of being under high stress. Saw cuts and drillholes close in, partly mined coal bursts violently, and pillars crush and rock spalls in mines even at moderate depths. Similarly, strong and massive rocks such as granite and sandstone naturally divide themselves into sheets that lie more or less parallel to their outward topographic form. The sheets may be either convex or concave. Thin plates of bare rock surfaces bow up and buckle. Such effects often cannot be explained by the obvious loads now acting on the rock, that is, by loads resulting from overburden, topographic irregularities, or stress concentration around openings. The stresses exceed those that would result from such loads. Two interpretations of such excess stresses have been made. In one, the stresses are assigned in origin to now active tectonic forces. In the other, they are regarded as leftover and locked in from some previous state at which higher pressures prevailed. These two sources may both operate and they generally cannot be distinguished easily in the field. There are other complicating sources of stress such as temperature gradients and chemical alteration. Nevertheless, some bodies of rock, by exfoliating, show evidence of high internal stress even though they are practically unweathered and so isolated topographically that the presence in them of significant stress due to exterior loads or active tectonic forces seems unlikely (Fig. 1). Moreover, completely isolated rocks are known to change density, shape, or size 1,2 to expand under constant compressive stress;3 and even to disintegrate 4,5 without the intervention of weathering processes. The stresses involved here must be truly residual in the sense long used by metallurgists; that is, residual stresses in a body are those that remain.

Jan 1, 1970

By Ralph H. Sweetser

In these days of the almost exclusive use of byproduct coke as the blast-furnace fuel in this country, it may seem out of place, and smacking too much of reminiscing, to say anything about the use of anthracite coal for blast-furnace fuel. Viewed in the light of present day research and of developments in alloy steel, some observations seem appropriate regarding this raw material that played such an important part in the development of the iron and steel industry during 50 years of the past century. The research work of that period, in which the whole iron and steel industry was revolutionized, passing from wrought iron to steel and from charcoal to three new mineral fuels for blast furnaces, was done chiefly in the full-sized plants of that day; and it was done largely by the ironmasters themselves. The laboratory had not become a part of the ironworks, and scientific instruments were lacking around the blast furnaces; "rule o' thumb" and erroneous theories prevailed—and have not yet all been eliminated. The recent interest in meteoric iron in connection with nickel steels and other alloys proves that it is worth while to search for the reasons for excellence and the causes for failures in the metallurgy of bygone days. Turner1 gives the reasons why the blast furnace of Dr. F. W. Geissen-hainer on Silver Creek, Schuylkill County, Pennsylvania, about 10 miles northeast of Pottsville, was operated successfully with anthracite2 in August and September, 1836, and why several other attempts failed. It has taken a long time for us to find out that there are great differences in the behavior of anthracites from the several parts of the anthracite region, as well as differences in coking coals from the bituminous fields.

Jan 1, 1935

By William Fink

APPROXIMATELY two years ago the authors obtained data that indi-cated that initial precipitation could not be detected by change of lattice parameter in the aluminum-rich aluminum-magnesium alloys. Some of these data were first published in a brief note in MINING AND METAL-LURGY1. Cast specimens were used at that time and they showed initial precipitation relatively sooner than sheet material of the sane composi-tion. For this reason a more thorough investigation has been carried out using a homogenized aluminum-magnesium sheet containing approxi-mately 10 per cent magnesium. Materials.-The aluminum used in the preparation of the aluminum-magnesium alloy was of high purity, containing less than 0.01 per cent each of iron, silicon and copper. The magnesium was high-purity sub-limed magnesium. Preparation of Alloy.-Approximately 4 kg. of the aluminum was melted in a plumbago crucible in an electric furnace and the magnesium was added. The melt was thoroughly stirred with a graphite rod and fluxed with chlorine gas before casting. The alloy was cast in the form of a sheet ingot in a cold iron tilting mold (approximately 200 by 165 by 40 min.) and into small chill-cast, slabs for chemical analysis (75 by 40 by 5 mm.). The chemical analyses were made upon drillings from the analysis slabs. The analytical methods were those described in "Chemical Analysis of Aluminum," published by the Aluminum Company of Amer-ica. The composition of the alloy was found to be: magnesium 10.30, silicon 0.013, iron 0.008 and copper 0.005 per cent.

Jan 1, 1936

By C. R. McClure

The objective of this papef is to summarize briefly the practical use of rock mechanics in design and construction of various types of structures. These range from foundation for industrial facilities, nuclear power plants, bridges and dams to tunnels and underground caverns. The use of rock mechanics has varied from performing a few laboratory unconfined compressive tests on core samples to complete field and laboratory tests for underground power caverns. The primary difference between the rock mechanics studies we hare for construction projects and those most commonly found in the literature is that our tests must provide immediate answers to specific questions facing a design or construction engineer. For example, when we make a plate-bearing test we arrive at a load-deformation relationship. We realize that this is not a true modulus of elasticity. Yet, when considering the resistance the rock will provide against forces occurring in a pressure tunnel it is a far more useful value than the true modulus of elasticity of the rock. Another example of this difference in interest is in the use of flat jacks. Many people criticize the use of flat jacks because they measure the stresses in the disturbed zone very near the surface and do not represent the undisturbed stress condition in the rock. However, in actual construction it is frequently those near-surface stresses with which we must cope. We are interested in both the stress conditions present prior to excavation and those as modified by construction of an exploratory adit or drift. Fundamentally, we are interested in the practical application of rock mechanics in the solution of problems of design and construction of civil engineering works.

Jan 1, 1968

By Darrel W. Hansen

Morrow Point Dam and Power Plant are principal features of the Bureau of Reclamation's Curecanti Unit of the Colorado River Storage Project. They are under construction on the Gunnison River 20 miles east of Montrose, Colo. Johnson-MK is the prime contractor, and represents a joint venture of Al Johnson Construction Co., Minneapolis, Minn., and Morrison-Knudsen Co., Inc., Boise, Idaho. The power plant will be housed in an underground chamber in the left abutment, approximately 250 ft behind the original canyon wall. The chamber is 206 ft long and 57 ft wide. The distance from the foundation to the spring line of the roof arch varies from 51 ft in the service bay to 120 ft in the control bay. The roof arch has a rise of 16 ft. The longitudinal center line of the chamber is orientated east-west with the draft tubes discharging nearly due north. Access to the power plant chamber was possible through the cable tunnel, access tunnel, two draft tube tunnels, two penstock tunnels, exploratory tunnel, which became the ventilation tunnel, or the grouting and drainage tunnel leading to the dam. (See Fig. 1.) The shortest and fastest access was through the cable and access tunnels, and the contractor drove these two tunnels simultaneously. The cable tunnel and cable gallery excavation exposed a transverse section, at the west end of the chamber, that was 15 ft wide and extended from the crown to 5 ft below spring line. It was here that arch excavation began. The first 34 ft of advance along the arch was driven on three headings, and the muck was removed through the cable tunnel. Meanwhile, the access tunnel was completed, and a raise was driven from its crown to intersect the advancing arch excavation near the longitudinal centerline

Jan 1, 1968

By Roswell Johnson

WHAT becomes of the water which must have filled the oil and gas sands at the time of deposition, has long puzzled students of oil and gas and has found expression in Munn's well known article on the hydraulic theory. Both Munn and Clapp have pointed out that in the Appalachian field the deeper sands carry increasingly less proportionate amounts of water. It seems to me probable that the principal source of oil and gas has been in the shales in proximity to the sands which now contain these products. The sand spits which mark off the lagoons from the sea comply particularly with the requirements of a limited sand imbedded in shales rich in organic matter. Cunningham Craig has objected to this view that the rich organic muds of lagoons are found only at the surface. That such muds do extend to considerable depth 1 am assured by Prof. Douglas W. Johnson, who has made an extensive study of the Atlantic Coast marshes. As any particular sand body becomes weighted by a heavier and heavier overburden, the result of increasing deposition, a part of the very large percentage of water in the uncompacted sand and mud is forced pout. The water percentage of freshly settled mud is vastly higher than that of the resultant shales, or even of a very porous sand. If beds of less compressible material meet or underlie the shales in question, there will. frequently be a lateral motion along such beds to some point where the upward movement will be resumed. We find in our laboratory work here that oil, gas, and water have extremely slight capacity for gravitational sorting while in a state of rest but when moving the gravitational sorting is readily accomplished. As the oil, gas, and water pass a body of larger pores, the gas, owing to its lack of capillary attraction, is retained in .the large pores.

Jan 2, 1915

By K. L. Ludeke, A. D. Day

For many reasons, it appears that deep rooted, perennial shrubs offer potential for improved stabilization and provide maintenance free vegetative cover to harsh sites where perennial grasses have not been successful. The major objective was to select various shrub species of arid plants for initial soil stabilization of disturbed mining areas. The very fact that a drought-adapted shrub has a massive root system that can use moisture from a greater volume of mineral waste soil materials suggests that arid environment disturbed soils may be vegetatively stabilized using desirable forage shrubs. A secondary effort is underway to assemble information and plant materials of promising species from many arid regions of the world for reclamation of mined lands. Surprisingly, many of the better plants for arid sites are quite high in protein content. With proper management, breeding, and selection, they may prove to be very desirable livestock feed when mined lands are used in range land areas. Advancements in arid land solid waste stabilization hold favorable promise for many industries that mine and mill in arid regions for effective reclamation of disturbed areas. Particularly exciting is the possibility of establishment of high density maintenance free vegetative cover of climax vegetation that reclaims the disturbed area back to its original land use. Due to high shrub productivity, stabilization potential, nutritional quality, and reclamation success, greater use should be made of shrubs in disturbed land reclamation associated with mining and milling operations in harsh aril environments.

Jan 1, 1986

By Joseph E. Pogue

The prices of crude petroleum and its derivatives have shown an upward trend from 1915 to 1920, and a downward trend from 19'20 to 1923, see Table 1. Over the former period, oil prices were dominated by the rapidly increasing demands and inflation incident to the war and its aftermath, while over the latter period oil prices were influenced at the outset by deflation and then by the conditions of overproduction that have characterized the past three years. he purpose of this paper is to analyze the broader features of the more recent price movements in the petroleum industry and to relate these features to basic economic conditions in the industry. Index Numbers of Oil Prices The analysis and comparison of price movements may be facilitated by converting actual prices into relative prices, or index numbers, with 1913 taken as a base of 100. In this way, the various price groups are expressed as percentages of the 1913 prices and may thus be readily compared with one another or with the average prices of other commodities similarly expressed. Table 1 gives the index numbers representing the average prices of crude petroleum, gasoline, kerosene, fuel oil, lubricating oils, and all commodities. The last named is the index of all commodities as published by the U. S. Bureau of Labor Statistics and is widely accepted as the official measure of the general price level. The index numbers of oil prices were calculated by the writer from weekly quotations published in trade journals. Fig. 1 shows in graphic form the trend of oil prices by months over the period 1920-23. It may be observed that the prices of crude oil and its derivatives move in rough conformity with one another; tend to follow

Jan 1, 1924

By Read Winterburn

This discussion covers only one method of pressure drilling—that developed in the Kettleman Hills field. Thus it is probable that many departures from the procedure herein described would be advisable, and perhaps necessary, in using this method of drilling wells in other localities. Purpose of Pressure Drilling By the early part of 1936, formation pressures in the heavily produced north end of the Kettleman North Dome field had declined to range from 1000 to 1500 lb. per sq. in. This low pressure, combined with the depth of the wells (8000 to 9000 ft.) permitted water to be filtered out of the mud into the producing sands during drilling operations. The loss of water was indicated by loss of fluid from the suction tank while drilling, accompanied by an increase in mud weight. It was found that when water was added to the mud stream at such a rate as to keep the fluid level in the suction tank constant, the mud weight would not vary. This indicates that water only was forced into the sands. The rate of this loss at various wells ranged from 2 to 5 bbl. per hour. At some places complete loss of circulation occurred, and drilling mud to the extent of 200 to 1000 bbl. had to be pumped into the sands before returns were regained. It was believed that these conditions had already begun to harmfully affect production, and that such effect would become more pronounced as formation pressures continued to decline. Pressure drilling with oil was introduced because it eliminated the danger of loading the formations with mud and water. The method also afforded a convenient means of testing as drilling progressed, lessening the amount of formation testing, which had become necessary because of encroaching edge water.

Jan 1, 1938

By William Vietti

WEST TEXAS and New Mexico has been overshadowed by the develop-ment in East Texas to such an extent that the area has been placed on a settled production basis by most of the operators. Considerable develop-ment work on both proven and unproven acreage remains to be carried on, but the incentive, a ready and profitable market, has been lacking. The main characteristics of the fields in this area are so well known that they are not described again in this paper, which thus resolves itself into a statistical review of the more important production features of the area. Proration has been in effect during the year and has been rigorously applied with the full cooperation of all producers. Proration in West Texas and New Mexico is based in the more pro-ductive fields on a potential and acreage distrbution of the allowance to the individual wells or acreage units. Potentials are determined generally by a short production test of from 1 to 4 hr.; and the hourly rate is multiplied by 24 to obtain the 24-hr. production or rated potential of the separate wells. The potential values thus set up have been questioned by many production men who are not willing to concede that the instantaneous (hourly) capacity of a well to produce is its potential capacity for a day with all other wells in the pool producing at their capacity. However, the potential of a well determined as above remains its chief rating as a measure of the permeability in place and as an indication of the possible reserve feeding that well. , The acreage factor has made it unnecessary to overdevelop properties in order to obtain an allowance proportionate to neighbors who are willing to drill an excessive number of wells on a piece of acreage in the hopes of a quick drainage and a corresponding profit. Proration has resulted in an orderly development of many of the pools in this area on the base as out-lined above, resulting in more reasonable spacing of wells and the more even withdrawal of oil and the ensuing expectation of high recoveries.

Jan 1, 1933

By J. R. Mihalisin

THE application of electron-microscopic techniques to the study of high-temperature alloys has met with considerable success.' This is due, in part, to the submicroscopic nature of the phases present in this type of alloy making high resolution methods necessary. Among the newer electron-microscopic techniques, the extraction replica technique' has proven to be of great value. This method allows phases to be examined in situ in the microstructure and permits their identification by means of electron diffracticn. This technique eliminates the main disadvantage in using electrolytic extraction of residues as a means of phase identification; that is, the uncertainty of relating constituents identified in the residue to what is observed microscopically. In the course of work relating microstructure to physical properties in high-temperature alloys, it was found that the formation of grain-boundary carbide phases and intragranular precipitation of an age-hardening phase greatly influence strength and ductility at high temperature. In particular, it was found that the formation of a unique type of precipitate in Nimonic "80" (a nickel-chromium-aluminum-titanium type superalloy), termed cellular or discontinuous precipitate, at grain boundaries generally results in poor ductility at high temperature. However, this mode of precipitation can be avoided by proper heat-treatment. It was assumed that this precipitate was either a carbide or age-hardening type of phase. Using various etching procedures with the extraction-replica technique, it was found to be possible to extract the carbide and age-hardening phases preferentially in this type of alloy. Previous work has shown that the age-hardening phase can be extracted from superalloys merely by

Jan 1, 1959

By R. L. Brown, A. C. Fieldner

Committee it supports pioneering research on the development of a coal-burning gas turbine and through the Mining Development Committee it promotes research on a new type of continuous mining machine that operates without using explosives. Other organizations have contributed major publications on fundamental and applied coal research in the last two decades, including the Minerals Industries Experiment Station of Pennsylvania State College, the Illinois Geological Survey and University of Illinois, the University of West Virginia, the University of Michigan, the University of Alabama, the University of North Dakota, the Massachusetts Institute of Technology, the Koppers Company, the U. S. Bureau of Mines, and, in recent years, the Institute of Gas Technology. Engineering development work, which is included in the overall estimate of $20,000,000, is conducted largely by manufacturers of equipment, and this portion of the estimate is difficult to gage. It represents a large proportion of the estimate and probably is too small rather than too large. For example, the development of mobile coal-loading machines and continuous mining machines, outstanding in recent mining research, undoubtedly involved a high cost. Coal Mining From an economic point of view, the greatest research development in the coal industry obviously has been the growing degree of mechanization in mining. The percentage of underground-mined bituminous-coal output mechanically loaded has risen from 3 pct in 1926 to 67 pct in 1949. Coal operators and equipment , manufacturers have united in designing machinery. Loading machines of large capacity and astonishing flexibility are in common use. Shaking conveyors transport coal from producing faces to transfer points from which it may be carried long distances underground and on the surface; and in many mines rubber-tired shuttle cars carry the coal from the loader to the

Jan 1, 1952

While coal was undoubtedly seen by the early travellers within the state, the first mention of it was in the late 1820's when hunters put some stones from a creek bed under the logs of a large camp fire, and awoke later to find the stones on fire. The stream was later named Coal Branch; the location was at the eastern side of the present Bibbs County.1 In the Louisville Daily Journal of Feb. 11, 1831, the following short editorial note appeared: "Tuscaloosa Coal.-A small quantity of this article has reached Mobile, and has been tried in the office of the Patriot; it is said to be an excellent article. We invite such of our friends as desire economy in fuel, love a cheerful and constant fire, or would eschew a smoky room, to call and examine." On a geological map published in 1832, the "Carboniferous group" is shown and a spot near Tuscaloosa indicated as showing bituminous coal,2 and this is again alluded to in Morton's Synopsis, 1834. A brief description of the coal fields in the state in 1834 said that in winter coal was brought down the. Black Warrior River to Mobile and sold there at the same price as Liverpool coal, $1.00 to $1.50 per barrel, ($10 to $15 per ton) and that the writer was using it in his laboratory.3 At that time it was in local use by smiths and an iron foundry was using it in Shelby County.4 In 1836 some coal was mined in the Birmingham district, chiefly in the northern portion of the Coosa basin, where it was loaded on barges and taken down the Coosa Rivers.5 "William Whitman dug coal out of Wolf Creek (Walker County) in 1837," and in the same county, in 1839, the first coal shaft in the state, was sunk. This was near the mouth of Lost Creek and was known as Frierson's Shaft. It was operated by a hand windlass, using two tubs.1

Jan 1, 1942

By John Birkinbine

The early history of the mining and metallurgical industries of Pennsylvania is so intimately associated with the section of the State in which we meet, that a brief resume of a few of the important historical facts, and a reference to some of the more modern enterprises, in which members of the Institute have been largely concerned, seem appropriate to this occasion. It is just two hundred years since the publication of the earliest mention of the manufacture of iron in Pennsylvania. What kind of iron this was, or where or by whom it was produced, is uncertain. The only record of it is the following verse, quoted in the admirable work of Mr. James M. Swank,* from a poem published in 1692: " A certain place here is, where some begun To try some Mettle, and have made it run, Wherein was Iron absolutely found, At once was known about some Forty Pound." One who stood one hundred and seventy years ago on the summit of this Neversink Mountain † (had the atmospheric conditions been favorable, and the timber somewhat removed) might have noticed in the daytime the smoke, or at night the reflection, from the fires of the first successful Pennsylvania iron enterprises, scarcely 15 miles to the south, viz.: Rutter's bloomary forge, built in 1716, and the Colebrookdale blast-furnace erected in 1720, respectively 3 and 8 miles distant from Pottstown. Here the pioneers of iron production in the State which has so long led, and still leads all others in this manufacture, had their trials and successes ; and it may be a satisfaction to some who bewail a present depression in trade, and the low prices now ruling, to recall the fact that in 1731 pig-iron is reported to have been sold ''in large quantities" at the Colebrook-

Jan 1, 1893

By James Quigley

As the outcrop mines in the West developed into underground operations, systems of ground sup- port were gradually evolved. In the early coal mines there was little need for support except near the dirt line in portals, where stone masonry was common. Where the top was shaley or broken, native pine props with light cross bars and legs furnished enough support even in Utah's 25-ft coal seams. As depth of workings increased, roofs and backs of the same general nature as those near the surface became more and more unstable and required more and more support. Some coal airways show this tendency very clearly. From the surface down the same type of roof shows deterioration which an experienced eye can translate into a measure of depth under surface rather than change in rock characteristics. Rock bolts, developed by various companies and by the U. S. Bureau of Mines, have become an effective substitute for timber in sections of some metal and nonmetal mines formerly requiring excessive timber support, and further use of war surplus landing mats, chain link fencing, and a new punched channel developed by one of the steel companies has enabled other mines to operate deposits where costs of timber and lack of clearance for timber support would have prohibited mining. The block caving mines have made extensive use of reinforced concrete underground to achieve similar ends under difficult conditions. Steel sets are standard in many Bureau of Reclamation projects, although these are usually covered in with concrete to make the permanent structures the Bureau's reclamation projects require. But the use of steel in mining operations is limited and has been confined principally to the iron ore mines of Michigan, Wisconsin, and Minnesota. Some mines have installed used rail as posts, caps, and crossbars, but a rail section is not suited for load carrying, and used rails are generally brittle, having a tendency to fail without warning when overloaded.

Jan 7, 1959

By Alden B. Greninger

Although the crystallography of lattice transformations has been studied extensively during the past few years, these studies have been limited, with few exceptions1'2, to specimens in which the transformed lattice appears as a segregate phase. A realization of the technical importance of the segregation mechanism, especially in the formation of martensitic structures and in age-hardening phenomena, has undoubtedly stimulated research in this direction. In the crystallographic studies of segregation, the general problem has been to relate the orientation of the parent crystal to that of the segregate crystals. The technique has been complicated by the fact that it has been necessary to deal with the presence of as many as 24 ideal segregate orientations within one parent lattice; furthermore, the segregate lattices are invariably scattered (seldom less than ±2º, often as much as 15" or 20') about these ideal positions. It is probable that a more complete picture of phase transformations may result from a study in which complete lattice relationships between individual grains are evaluated, thereby providing an additional parameter which when it is necessary to work with multiple segregate orientations, cannot be evaluated. The present paper presents the results of such a study, ? wherein a peritectic reaction is made use of to produce the transformed lattices. Matebials and Methods Pem'tectic Reaction.—In Fig. 1 is reproduced a portion of the copper-zinc equilibrium diagram, which includes the peritectic reaction a + liq. —ß. A liquid of composition between B and D upon solidifying will

Jan 1, 1937

By J. Mizrahi, A. Brillantshtein, A. Mitzmager, O. Schächter

The separation of synthetic mixtures of heavy minerals by hindered settling classification and jigging was comparatively tested in water and five organic heavy liquids, of various specific gravities and viscosities. It was found that in the hindered settling classification process the separation efficiency was directly proportional to the concentration criterion, the liquid viscosity being a minor factor. There is therefore a decisive advantage in using heavy liquids as classification medium. In the jigging process the advantage of using a heavy liquid is masked by the detrimental effect of a higher liquid viscosity, which, in this case constitutes an important factor. Considerable interest has been aroused lately by the development of mineral beneficiation techniques 1,2 using TBE (tetrabromoethane), a heavy liquid of specific gravity of 2.96, which has been made available for industrial use by a new process3 producing TBE directly from the Dead Sea brines at a reasonable price. Most of the applications investigated until now were based on the sink-float separation of minerals in a heavy liquid of intermediate specific gravity. The TBE can be conveniently diluted with many organic solvents, and thus sharp separations are possible in a wide range of specific gravities up to 2.96. Although this maximum specific gravity is sufficient on most cases for the elimination of the bulk of the barren gangue and the production of marketable concentrates, some practical problems came up for investigation in which the separation of two (or more) minerals, heavier than TBE, was required.* *Among the cases studied in the IMI Laboratorles which fall into this category we can mention: alluvial deposits, such as heavy minerals in sea sand, tin deposits, or ground coarse-grained rocks, such as pegmatites. In such cases where, due to the petrographic structure, further fine grinding is required in order to achieve the liberation of the heavy components, the

Jan 1, 1964

By R. Pakalnis, J. P. Savely, R. D. Call

A simple and inexpensive clay imprint core orienting device has been developed by Dr. R. D. Call. It has a minimum of moving parts, is durable and easily used by drillers, and adds only 15 minutes to a core run. Conventional wire-line drilling and a drill hole inclined 30° to 60° from the horizontal plane are required. The device will not operate in a vertical hole. The orientor is an eccentrically weighted downhole device which can be constructed in a mine shop from an old inner core barrel and lead. Modeling clay is packed in the core lifter case, which is screwed on the downhole end of the orientor. A clay imprint of the bottom of the hole is taken after each coring run. This imprint is matched to the top of the succeeding core run, the drill core is pieced together, and a reference line representing the drill hole is scribed on each core. Fracture attitudes are measured relative to the reference line and the core axis. On recent drilling projects, tests for imprint reproducibility were conducted. The results of these tests show an average variation of f3" in location of the scribed reference line between imprints. Comparisons of surface mapping data with oriented core data are good. It is rare that the entire length of drill core in intensely fractured zones can be oriented because it is impossible to piece the core together. However, if a triple tube set-up is used, a modification in the scribing procedure can result in a good statistical sampling of the fracture population. Attitudes of major structures have been oriented with this technique.

Jan 1, 1983

By Theo W. Robinson

The evolution of the modern blast-furnace from the embryonic stages of comparatively few years ago, has been the work of wide praetiee and experiment. That much is still to be desired, the experience of every furnace-manager mill testify. Mr. Walsh's paper on "The Irregularities of the Blast-Furnace Process, and a Practical Way to Avoid Them" (Trans., xv., 419), proposes a new solution of the problem of interior lines, and one that has given rise to not a little speculation and controversy. The investigation described in this paper was undertaken to test experimentally the theory of Mr. Walsh as to maximum reducing capacity. Briefly explained, Mr. Walsh's views (outside of his claim for increased efficiency due to having the bosh wholly within the meltingzone) are, that a furnace of contracted stack and throat, on his lines. may equal in product one of considerably greater cubical capacity. The explanation offered for the theoretical greater capacity per cubic foot of his furnace is, that the increased tension of gases caused by passing through the small area mill promote transpiration, thus facilitating reduction and permitting more rapid driving. This alleged relation will appear from a hypothetical case in which a furnace, A, constructed on Mr. Walsh's lines, has but 1/x of the cubical contents of a furnace, B, of modern type; the two being equal in height. In order that A shall have the same capacity as B, both working normally with the same mixture and burden, and

Jan 1, 1889