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By Laurance Reid

HIGH compression ratios, resulting from high injection pressures and relatively low recovery process pressures, constitute a major problem, which has confronted those engaged in gas recycling for condensate production since the beginning of that practice. Despite the numerous process developments and improvements, no entirely satisfactory solution for this prob-lem has been presented to date. Often, where the residue gas from the recovery process must be recompressed for subsurface injection, there is a substantial difference between the required injection pressure and the plant-operating pressure required to produce maximum recovery of condensate. These limitations result in high compression ratios, which, in turn, neces-sitate excessive compressor investment and operating cost. As an alternative, the operating pressure may be increased in order to lessen the compressor requirements but such a saving often is purchased at the expense of decreased condensate recovery, caused by operation at the higher pressure. Regardless of the choice, the net result is a diminished return on the capital invested in the project. The goal of future development in this field must be the complete recovery of all valuable hydrocarbon components in the reservoir fluid at pressures that, regarded as compressor suction pressure, will require minimum compressor horsepower to inject the residue gas into the formation. A com-pression ratio of 1.5 has been established as an optimum for modern compressor equipment." Therefore, in order to con-form to this optimum condition, a 3000-lb. injection pressure would require that the condensate recovery process be operated at 2000 lb. per sq. inch.

Jan 1, 1940

By W. R. Johnson

In the spring of 1935 the writers undertook to compare the geomagnetic and direct-current earth-resistivity methods of tracing a concealed dike along its strike. As far as they are aware no such direct test has been attempted.# The area surveyed lies along United States Highway number 15 about one and one-half miles east of Chapel Hill, North Carolina, and northeast of Bolin Creek (Fig, 1). To the south of the highway is the flood plain of Bolin Crook, and to the north is a hill that rises almost to the elevation of Chapel Hill. A diabase dike, which strikes slightly west of north, out-crops in a. gully just south of the highway. Southward it has been covered by alluvium but northward outcrops again on the southeastern slope of the hill north of the highway. South of the highway the country rock is Triassic shale and sandstone, the northern limit of which is slightly north of the road. On the Geological Map of the United States I the pre-Triassic formations are shown as lower Glenarm and assigned a pre-Cambrian age. Since the ago of the Glenarm has been called into question in Pennsylvania 2, the writers prefer not to commit themselves as to the ago of these rocks further than to say that they are definitely pre-Triassic.

Jan 1, 1937

By Thomas Wilson

IN a single-crystal cube of iron the arrangement of the atoms is that characteristic of iron at room temperature: the body-centered cubic lattice. X-ray investigation has shown this structure to be characteristic of iron, as it has shown the atomic arrangement of other metals to be characteristic of those metals also. Rarely do substances have more than one characteristic atomic arrangement. Many physical properties of metals are directly connected with their atomic arrangements, so that changes of arrangements produce changes of properties. Only chemical change influences atomic arrangement. If a difference in the physical properties of a metal is caused by a process which involves no chemical change, the cause of the difference in properties must be sought elsewhere than in the atomic arrangement. Frequently this cause can be traced to alteration of crystal orientation. The orientation of a crystal may be defined as the relationship which the crystallographic axes bear to some quantity of reference. A cube of iron appears cubic whether it is regarded from a face, an edge, or a corner. Yet these three positions represent three different orientations of the cube with respect to the observer. It is evident that the orientation of this cube of iron, unlike the atomic arrangement, is not characteristic of iron but is entirely dependent on the previous history of the cube. Most of the processes of metal working, such as wire-drawing, rolling, and bending, change the orientation of the crystals present in the worked metals. These processes usually tend to produce rotation of the crystals into positions approaching a mean. Specimens of metals show-ing this characteristic are said to possess a preferred, orientation. Tensile strength, ductility, and many other properties are influenced by orientation changes; therefore two specimens of the same metal may show different values of these quantities. In metal specimens possessing a narrowly limited preferred orientation, these quantities will vary in magnitude in different directions throughout the specimens. The investigation of the influence of manufacturing operations upon crystal orientation, and hence upon physical properties of metals, is an important

Jan 1, 1929

By Donald H. McLaughlin

THE primary function of the mining engineer is to find mineral deposits and fuels in the accessible rocks of the earth and to recover them for the vast needs of our complicated civilization. On him has been placed the responsibility for the exploitation of the nation's and world's mineral resources. The degree to which the minerals of the earth have been utilized serves to an extent as a measure of man's material advancement, as well as an index of the relative strength of nations. The natural endowment of lands, varies greatly, but the intellectual energy of a people is revealed by the way in which they take advantage of their heritage of minerals or reach out to less developed regions by exporting their engineering skill as well as capital to secure the raw materials they need.

Jan 2, 1953

The following discussion occurred on the afternoon of Sept,. 22, 1930, as part of the fall meeting of the Iron and Steel Division at Chicago. About seventy-five men attended this session. C. B. Murray opened the meeting, as follows: C. B. Murray, Cleveland, Ohio.—It is very encouraging to see so many here this afternoon to discuss this important matter of beneficiation. The producers of ore, I am sure, are anxious to furnish the grade of ore that the consumer wants. The consumer sometimes wants that which cannot be economically produced and often the producer cannot understand why the consumer wants certain things. It was to bring together these two interested parties that this meeting was proposed. I was appointed the chairman of the meeting, chiefly because I happened to be the chairman of the Iron Ore Committee of the Institute. I know a little about iron ore but have not perhaps kept up with the times in blast-furnace practice. I am asking Mr. Sweetser, who is well informed from both sides, to take over the meeting and carry on the discussion. R. H. Sweetser, Columbus, Ohio.—We want to have a free discussion between the iron-ore men and the blast-furnace men as to just what we are trying to reach in the beneficiation of iron ores. Many of those present have had a great deal of experience. There are men here from the ranges who have been passing through the experimental stage of beneficiation of iron ores, and there are some who have already gone on to commercial production. We have reached the point where the beneficiation of iron ore is important to the whole iron and steel industry. The connection between iron-ore beneficiation and the cleaning of coal is so close that I think we can profit by working very close to the coal people. Some Aspects of the Iron-ore Situation W. G. Swart, Babbitt, Minn.—I was very much interested in Mr. Richards'* paper on tonnages and the 20-year life. There is one interesting thing about the ore reserves; that is, the irregular distribution of that tonnage. On the Mesabi Range, for example, the United States Steel Corpn. owns between 70 and 75 per cent. of the reserve tonnage. They ship bctween 40 and 50 per cent. of the annual Lake Superior

Jan 1, 1930

By Persifor Frazer

I DESIRE to say that, owing to the number of papers which have been more or less crowded at this session of the Institute, and the fact that, as one of the Local Committee, I have the distinguished honor to feel somewhat like one of the hosts, I should not tax the patience of members at this late hour, but would have my paper read by title were it in any way possible to do this. But the task I have set myself this evening is to present to the eyes of the members of the Institute certain objects which have occupied more or less of my time during the last eighteen months or two years. The objects I allude to are some of the igneous rocks of this country, which, until quite recently, have been less understood than any others. It will be well known to some of the members that some of the cooled lavas of a previous age of our planet, when not directly coarsely crystalline and granular, were considered and spoken of as " natural glasses," or perfectly uncrystalline, vitreous, or hyaline masses of matter. Among the first results of the use of the microscope was the dispersion of this fallacy. Sir David Brewster, Mr. H. C. Sorby, and William Nichol (the discoverer of the celebrated calcite prism, which bears his name), had, with greater or less success, examined sections of various rocks and minerals, both by transmitted and reflected light, and also in the form of powder. But, until the genius of Vogelsang undertook the subject, these investigations had no permanent value, nor did they constitute an independent line of mineralogical and geological research. Since the close of his labors, by Vogelsang's premature and much-lamented death, the subject has been made one of renewed interest by his brother-in-law, Ferdinand Zirkel, as well as by Rosenbusch, Tschermak, and many others abroad, and at home by the commencement of a systematic study of the traps of Connecticut by Messrs. E. D. Dana and G. W. Hawes, of New Haven, and by the splendid set of described sections of the traps of the West which have been furnished by Zirkel to illustrate Clarence King's report. I had the honor of presenting a large number of thin sections of our traps at the Washington meeting, for the inspection of the members, with the aid of a table microscope belonging to the Smithsonian Institution. Here I propose to project these sections upon the

By Grover R. Castle

INTRODUCTION "Project Financing" or "Project Loans" have become increasingly popular in recent years, and commercial banks are being asked to consider more and more of such financing. However, the analysis of this type of loan is quite different from the analysis of a loan to a financially sound corporation based on the company's balance sheet. For this reason Chemical Bank did a study of project loans in an attempt to be more sophisticated in our approach to them. As part of this study, we examined 29 project financings for which information was available. In this article I shall describe project loans and set forth the guidelines we developed, as an aid to credit officers who might have occasion to analyse this type of financing. DEFINITION OF "PROJECT FINANCING" OR "PROJECT LOAN" The terms "project financing" and "project loan" commonly describe the various methods that banks and institutional lenders use to finance the construction of new projects on a basis whereby payout is anticipated from the revenue stream generated by the project. A project financing often involves a loan to a new entity formed specifically to own the project. The analysis of a project loan proposal is quite different from the analysis of other term-loan proposals since it involves a credit decision based on the review of a projection or forecast rather than of historical earnings and/or it involves the reliance on contractual obligations of third parties. Lenders are asked to assume the added risks associated with project loans because: 1. Project financing may permit a company to obtain additional leverage. It is possible for companies to arrange financing on a project basis that could not be arranged as a direct borrowing. For example, a company may not be permitted to borrow more money directly, due to a limitation in a bond indenture. However, a project financing can sometimes be negotiated on a basis not prohibited by the indenture. 2. Often the sponsors of, or the stockholders in, the project are seeking an off-balance-sheet financing. For example, 11 of the 29 projects in our study were arranged on an off-balance-sheet basis and one showed on the balance sheet as a deferred income item. An off-balance-sheet financing, for the purpose of this article, is a financing which does not show as a direct liability on the balance sheet of the sponsors of or stockholders in a project. 3. Projects are often located in a foreign country. The financing is arranged so that the lenders assume the political risk on the loan because many companies rightly believe that this arrangement affords a degree of insulation from political risk not otherwise obtainable. 4. Many projects are jointly owned by several sponsors. This form of financing lends itself well to a situation where a new entity is formed to own a project and do the borrowing. Project loans can be used to finance a variety of activities including development of iron-ore deposits and associated pelletizing plants; development of coal reserves; construction of pipelines, alumina plants, fertilizer plants and refineries; etc. The specific areas of analysis can be quite different, depending upon the type of project being financed. It is important, therefore, to classify the proposal according to the type of project, and also by the nature of the financing - nonrecourse financing, financing covered by a guarantee of completion and financing supported by an undertaking lasting for the life of the financing. I will discuss each of these types in more detail later, but first, I should like to make some

Jan 1, 1985

By Willis H. Carrier

PARTICULAR interest in the ventilation of deep mines, especially those in South Africa, has been created by a very complete system of cooling of the world's deepest mine, the Turf shaft of the Robinson Deep in Johannesburg. The writer visited this mine in January, 1936, and again in 1937. During these visits and subsequently, a considerable part of the theory involved in rock cooling in tunnels was developed and this has been checked by practical observations of the rates of rock cooling made within mines. The purpose of this paper is to set forth the method of attack of the mine problem. The cooling or air conditioning of mines by the use of mechanical refrigeration was not wholly new 1-5 when the Robinson Deep installation was made. The first mine to be cooled was the Morro Velho mine, in Brazil. The first installation in this mine was put into operation in December 1920, the refrigerant being ammonia.5 The surface cooling gave considerable benefit but it proved inadequate as greater depths were reached, therefore in 1929 two centrifugal refrigerating machines were installed at the 6000-ft. level. These were used in conjunction with the surface cooling system to furnish additional cooling at the lower levels. This later installation used Carrene as a refrigerant. This nonflammable refrigerant, having a boiling point of 104º at sea level, insured reasonable safety, since all parts of the machine operated at subatmospheric pressure. Very favorable reports have been received on the effectiveness of this installation, but no recent data are available. An interesting feature of that plant is that the condenser water is cooled by spraying it into the exhaust air from the mine at the base of the ventilation upcast, which permits the water to be cooled within a few degrees of the wet-bulb temperature of the air entering the upcast, and the only water that has to be supplied for condensing purposes is that lost by evaporation, or about 0.5 per cent of the volume circulating through the condenser. This plan affords an ideal means for the removal of the heat load from the refrigerating system, and of course also from the mine itself. In many mines, however, especially those in South Africa, there is no

Jan 1, 1938

By D. A. Farmen

INTRODUCTION In early 1978, engineering personnel at The Carter Mining Company began using photogrammetry coupled with a computer modeling technique to aid in mine planning efforts. The decision to develop this approach was based on the following needs: 1. A method to accurately capture excavated quantities for reporting purposes, 2. A method to produce accurate up-to-date maps for planning purposes, and 3. A computer-based mine-planning technique that would be compatible with techniques used in the past. The system developed utilizes a photogrammetric contractor to provide thousands of aerially-surveyed data points for input into the computer system. Each month the Rawhide and Caballo mines are flown by the photogrammetric contractor. The terrain of the active pit area is digitized and punched out on computer cards. This information is read into The Carter Mining Company's computer facilities, and an updated two-dimensional topographic grid model of the pit is generated. This surface is used to generate quantities moved during the month, to update isopachs, and to update quantities contained in fixed block progression polygons used for forecasting purposes. The system has greatly reduced the amount of manhours spent in field surveying and provides a useful tool for expeditiously evaluating many different forecast cases. It also provides the

Jan 1, 1983

By Frank Kneeland

SAFETY FIRST is a popular motto-most mining companies have adopted it. It is probable, however, that in the majority of cases it is only a motto and gets no further than the office stationery or the bulletin board at the mine's entrance. In but few industries is there employed a greater diversity of machinery and mechanical devices than in coal mining. The list ranges all the way from mechanical stokers to wood-working machinery and undercutters. Many of these devices, particularly those employed in wood working, are extremely dangerous. In 1913, 23 per cent. of all fatalities occurring in coal mining in the U. S. were caused by machinery of some sort or other. Although the forms of accidents occurring with mining machinery are legion, they generally arise from one or more of five causes: (a) Falls from ladders, platforms, etc.; (b) coming in contact with moving machines or parts thereof; (c) electric shocks; (d) failure of some machine part; (e) mismanipulation of valves, levers, switches or other hand-operated controlling devices. The steps which may be taken to prevent accidents from the above causes are almost as numerous as the accidents themselves. There is, and can be, no panacea for all mishaps, nor for any one class of accidents. There is no mathematical or other formula that will bring immunity under any set of conditions. Common sense is the only guide. The remedy for the first-named class of accidents is simple and generally effective-namely, make the staging, ladder, platform, or other support, abundantly strong to carry any possible weight that it may be called upon to bear; provide ample railings on platforms or runways, and non-slipping feet on movable ladders.

Jan 1, 1915

By H. W. Morse

THE CHAIRMAN (H. W. MORSE).-Gentlemen, for the first time in the history of the American Institute of Mining Engineers, we have a full session on the subject of leaching-especially on the leaching of copper ores.. This branch of metallurgy is rather in its infancy. We have had one big plant running for a year or more, and pretty successfully; and another one which will be started in February or March, the New Cornelia. We have another one at Garfield for the Utah company, which is just designed and construction begun; and from several other points come reports of interesting test work. The first paper on the program this evening is one of some of the test work on the New Cornelia ore by myself and Mr. H. A. Tobelmann. LAWRENCE ADDICKS, New York, N. Y. (written discussion).-The Ajo proposition has had, as I understand it, two great advantages: it has not been obliged to measure leaching against flotation or some other metallurgical process, and it deals with a copper content high enough

Jan 12, 1916

By R. P. Rothwell

THE first difficulty mentioned is that in some instances two or more beds of coal separated by sandstone or slate rocks of considerable thickness in one part of a basin, are found running together in another part. Of course, we may happen to strike first the part of the basin where there is but a single seam, and in this case the bed would appear to divide into two or more branches within a short distance. Such cases are not rare in the anthracite coal-fields. I would suggest as an explanation of this phenomenon the gradual sinking of the peat-marsh-the embryo coal-bed-on one side, and the moving forward of the marsh, so that on one part of the bed the formation of peat would still be progressing, while another part, being under water, would be covered with mud and sand. Thus we have different portions of the same bed of different ages. Now if the sinking of the marsh be stopped for a time, the bed will become thicker in the portions left exposed, and if the sinking now changes in direction, so that the part that had previously gone down com¬mences to rise, we should have the phenomenon of a bed, continuous throughout, with one portion overlying another, and separated from it by rock strata. These are exactly the conditions observed in splitting beds. While one side of the lake is sinking, and the peat-marsh moving on in that direction, the other side may be rising,

Jan 1, 1873

By C Gunther

The term metamorphism as commonly used means any change in a rock in either form or composition, from whatever cause. By metasomatism, according to Lindgren, is meant a metamorphism that involves a change in the chemical composition of a rock by the addition or subtraction of substance. Certain types of metamorphism are due to the action of mineralizing solutions, and are closely connected with ore deposition; they form, therefore, valuable guides in the exploration for ore-deposits. Other types of metamorphism are due to regional processes, and are not connected with ore deposition. By dynamo-regional metamorphism is meant a primary alteration of rocks over large areas under conditions of pressure, flow- age, and heat. This process produces schists and gneisses from either sediments or igneous rocks. It is thought that there is little migration of minerals or of elements in dynamo-regional metamorphism, and that the changes are due chiefly to recrysallization and rearrangement of original minerals in bands with their major axes oriented normal to the direction of greatest pressure. Under these conditions limestones are commonly altered to marble, and sandstones to quartzite, basic igneous rocks to greenstone or serpentine, while rocks of normal or acid com- position commonly yield the usual types of schist or gneiss. Dynamo-regional metamorphism, extending over large areas, has no connection with mineralizing processes, and is, therefore, no guide to ore deposits; while this process has certain features, such as characteristic mineral associations, in common with contact metamorphism, the results of the two processes may usually be distinguished without difficulty.

Jan 1, 1932

By Charles Barrett

THE orientation of metal crystals and grains, both large and small,. can be determined conveniently and accurately without the use of X-ray apparatus. This seems to be appreciated by so few metallurgists that it may be useful to explain in detail the method we have found most satis-factory in the laboratory the reflection of light from crystallographic etch pits. This note includes a description of a suitable inexpensive instrument and instructions for etching various metals and for plotting the data. As the stereographic projection is used to facilitate handling the data, this note may be considered as an appendix to an earlier review of the metallurgical uses of the stereographic projection.1 Various methods involving etch pits have been used by other investi-gators, Bridgman's method2 consists of attaching the specimen to a sphere (a transparent sphere is convenient4), holding it at arm's length, and marking a spot on it when it has been turned so that the etch pits reflect light into the eye of the observer from a lamp standing behind him. It has an accuracy of about 2° and is extremely rapid. A greater accuracy can be obtained by having the reflected light fall on a screen, as has been done by Czoehralski, 5 Chalmers,6 and Schubnikov.7 All of these methods have been intended for undeformed single crystals. Tammann and his coworkers"' developed a method for estimating the number of grains in a polycrystalline aggregate having orientations in a given region of the stereographic triangle and thus obtained statistical information about deformation and recrystallization textures. While the method has had some use in recent years,9 it is not applicable to the majority of problems in physical metallurgy. Smith and Mehl10 determined orientations by plotting the directions of the sides of individual etch pits on a stereo-

Jan 1, 1940

Secondary minerals are the result of a process of concentration and enrichment and are commonly richer than the primary minerals of the same deposit. Secondary ores that contain abundant sulphides are commonly distinguishable in the field from primary ores; this distinction is more difficult with ores that carry a small quantity only of sulphide minerals, and microscopical examination of the ore in thin section is advisable in all doubtful cases. It is frequently difficult, and in some cases impossible, to determine the primary or secondary character of quartzose gold ores. The safest guide is the presence or absence of gaseous or fluid inclusions in association with the ore minerals; such primary association coupled with a lack of traces of oxidation is indicative of primary origin. Any ore that carries traces of oxidation, such as iron stains, endritic oxides of manganese, kaolin and so forth must be considered to have been acted upon by surface agencies, and secondary enrichment must be suspected. Further examination, however, may indicate that the contained value is primary, and, therefore, persistent in its vertical distribution. The manner of occurrence of secondary minerals is frequently characteristic; secondary minerals, being due to the action of surface waters, are commonly found in cracks through earlier minerals, or as crusts lining vugs or surrounding nucleal masses, or in general, in some distribution later than and not conforming to the arrangement of the primary minerals. Secondary sulphides are often found as soft black pulverulent masses or coatings, although they frequently occur well crystallized or as

Jan 1, 1932

By B. Bernstrom

A 22-ft diam, 7-ft long, wet autogenous grinding mill was installed in the new Cretaceous plant of the Jones & Laughlin Steel Corp. to prepare crude iron ore for concentration in spirals and flotation cells. The paper describes the flowsheet and gives a description of the operating and metallurgical results that have been obtained. These results include capacity, horsepower, operating problems and a comparison of pilot plant results with those obtained in commercial operation. The Cretaceous plant at the Hill Annex mine of the Jones & Laughlin Steel Corp. was designed with a wet autogenous mill for grinding low grade iron ore so that it could be concentrated by spirals and flotation cells. The plant, on the west end of the Minnesota's Mesabi Range, went into operation in June 1961, and preliminary operating and metallurgical information describing the performance of this mill can now be given. The crude is lean ore from the Cretaceous iron foundation. This formation is a beach deposit of Cretaceous age that overlies the Precambrian direct shipping and concentrating ores. This rock in nature is not extremely hard but is quite resilient, resisting blasting in mining and size reduction in milling. It contains hematite as water-rounded particles and other fragments of the underlying iron formation and adjacent rocks cemented together by a high alumina-silica ferruginous matrix. It is interspersed with hard dense hematite agglomerates and also contains granite pebbles and boulders that were not cleaned off during removal of the surface. It has a 3.48 sp gr and in the stockpile the material consists of frag-

Jan 1, 1962

By L. S. Darken, H. A. Wriedt

THE constitution diagram of the iron-copper system derived by Daniloff' exhibits, at the iron-rich end, phase fields similar to those of the iron-carbon diagram. At 1484° 1094°, and 850°C there are, respectively, a 6-y-L peritectic, a y-E-Lperitectic, and a a-y-E eutectoid. The phase designated E is copper-rich, containing 4 pct Fe or less according to the temperature. The composition of copper-saturated ferrite (a-solid solution) has been determined previously only twice as a function of temperature. By electrical conductivity measurements, Buchholtz and Köster2 found 3.4 pct Cu in ferrite at a eutectoid temperature of 810°C. They represented the composition of saturated ferrite by the equation, log (%Cu) = 4.32-4125 (1/T) Gregg and Daniloff3 reported that Köster later modified his opinion, raising the indicated eutectoid temperature to 833 °C and the copper content of eutectoid ferrite to 3.7 pct. The literature contains several indications4-7 that the work of Köster and his co-workers is not reliable. Norton,8 using an X-ray method, found that 1.4 pct Cu dissolved in ferrite at the approximate eutectoid temperature of 850°C and that the solubility decreased to about 0.3 pct at 700°C. Below 700°C his experimental data show almost no change in solubility. These findings, although inconsistent with the work of Ruer and Goerens4 and of Smith and Palmer,7 have been used generally since their publication. In investigations involving the observation of arrests in temperature during continuous heating or cooling the precise location of the eutectoid temperature has been obscured by a large hysteresis. The more reliable work 579 where the results are not effected by this hysteresis indicates a eutectoid temperature between 840° and 850°C. The foregoing discrepancies, along with a few observations in this Laboratory relating to the precipitation of copper from ferrite, prompted us to rein-vestigate the lower temperature portion of the Fe-Cu system. In this investigation the solubility of copper in ferrite was obtained by the chemical analysis of high-purity iron equilibrated with copper-silver alloys. This method eliminated the necessity for retaining by a quench the physical state of the specimen existing at the equilibration temperature. EXPERIMENTAL The reaction of the iron with the copper alloy was

Jan 1, 1961

By C. W. Spencer, J. Singer

A PARTIAL phase diagram for the As-Te system is given in Hansen.' The only compound reported is As2Te3, melting at 362°C. Stoichiometric quantities of reagent-grade elements were reacted in evacuated quartz and directionally cooled. The resulting ingot consisted of very thin threadlike crystals from which only very small single-crystal fragments were isolated. A powder diffraction diagram disclosed nonisomorphism with the analogous V-VI compounds insofar as these have been reported; Sb2S3, As2S3, Bi,S,, and Bi2Te3 data in the ASTM index of powder patterns, together with the single-crystal data on Sb2Se3,2 were used for the com- parison with the observed spacings. Single-crystal data confirmed the uniqueness of the As2Te3 structure. Single-crystal Weissenberg diagrams have so far yielded the following data: As2Te3 is monoclinic, space group C-m (OkO data still lacking), a = 14.4A, b = 4.05A, C = 9.92A, ß = 97". The cell volume is about 5802. The set of isomorphous ortho-rhombic cells of Sb2Se3, Sb2S3, and Bi2S, are apparently related to As,Te, in having one lattice constant close to 4.0 and with cell volumes as large as 540A8. Assuming Z = 4 for As2Te3 also, the density is calculated as 6.1 which agrees well with a roughly determined value of 6.0. A complete structure analysis is under way.

Jan 1, 1956

By Evan Just

Attempting to analyze a 25-year forecast after less than a third of the time has elapsed may seem premature. The President's Materials Policy Com- mission's report necessarily painted with a broad brush and made no claim for pinpoint accuracy in its predictions. More importantly for present purposes, it made no attempt to predict the detailed courses of production and consumption during the period forecasted. Several statistical highs and lows may very well lie between now and 1957, so comparing recent figures with points taken from the report on a straight-line basis would be illogical. Moreover, the report assumed that the general trend of consumption-domestic and foreign-would be upward. Contrarily, domestic figures were lower in 1957 than in 1950. Therefore, to project curves from 1950 through 1957 leads to conclusions that are probably false. Many in the industry would feel more uncertain about forecasting 1975 domestic conditions now than they would have been in 1950, even though nearly a third of the 25 years has elapsed. In making comparisons, several statistical problems are encountered. The Paley report figures for 1950 were estimated in several cases and corrected figures vary as much as 10 pct. For example, the report placed 1950 lead consumption at 800,000 tons, whereas actual consumption was 885,000 tons. Obviously, in comparing more recent figures with the report's projections, adjustments must be made for positions taken in error from the start. Over the long pull, such discrepancies will probably be insignificant, but they must be noted in comparing short-term changes.

Jan 10, 1959

By Francois E. Heuze

INTRODUCTION Rock slope stability typically is governed by the geological discontinuities. This stability can be improved by drainage, unloading, adjustment in slope orientation, adjustment in slope angle, and also by reinforcement such as bolts or tendons. This paper addresses the modeling of bolt reinforcement in rock slopes. Most geological discontinuities such as joints have rough surfaces; they dilate during shear displacement. Their shear strength is characterized by two envelopes (Fig. 1); the peak envelope is distinct from the residual envelope when the joints can dilate. If the dilation is restrained transversely, such as with bolts, the normal stress will increase and the joint strength also will increase. It has been demonstrated that this increase may be considerable (Obert et al., 1976). The new normal stress at peak strength is a com- posite function of the properties of the rock mass and of the steel (Heuze, 1979). Hence, the dilation and its resultant effects on joint shear strength must be included in the analysis and design of the reinforcement. We present a model which can be used to perform such an analysis. Early studies of rock reinforcement in mining and civil applications (Lang, 1957 - Panek, 1962 - Osen and Parsons, 1966 - Lang, 19721, did not consider the specific effects of bolts on joint shear strength. In 1973, Heuze and Goodman reported direct shear tests on rough sandstone joints with bolts perpendicular to the joint plane (Fig. 2). The peak shear strength of such joints was greatly in excess of the shear strength of the unbolted joints. The excess

Jan 1, 1983