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By K. D. Jacob, H. L. Marshall, D. S. Reynolds

All types of commercial phosphate rock produced throughout the world contain fluorine in quantities ranging from approximately 0.4 to 1.3 per cent in the Curacao and Christmas Island phosphates to 3.1 to 4.2 per cent in the phosphates of the United States and North Africa1. For a given type of rock, the fluorine content is usually roughly proportional to the phosphorus content. Significance of Fluorine in Phosphate Rock On the basis of chemical and X-ray diffraction studies, Hendricks and co-workers2 concluded that fluorapatite, Cal10F2(PO4)6, is the essential phosphatic constituent of the commercial types of domestic phosphate rock. On the other hand, Bredig and co-workers3 have recently advanced the opinion, also based on X-ray diffraction studies, that the mineral phosphates usually contain carbon dioxide in the apatite lattice, and that the phosphate rocks of the United States are really fluorcarbonate apatites. However, the domestic types of phosphate rock do not seem to differ greatly from coarsely crystalline fluorapatite in their behavior toward chemical reagents in general, and for the purpose of this paper it will suffice to consider fluorapatite as being the essential phosphatic constituent of these types of rock. The available data1 indicate that the different commercial types of domestic phosphate rock usually contain about 12 to 52 per cent more fluorine than theoretically is required to form fluorapatite with all the phosphorus. Calcium fluoride (fluorite) has been definitely identified in only a very few of the samples that have been examined1,2. Bredig and co-workers4 state that fluorapatite can take into its crystal lattice excess calcium fluoride to the extent of approximately 70 per cent of that theoretically required by the formula Ca10F²(PO4)6 without causing more

Jan 1, 1938

By D. S. Reynolds, K. D. Jacob, H. L. Marshall

All types of commercial phosphate rock produced throughout the world contain fluorine in quantities ranging from approximately 0.4 to 1.3 per cent in the Curacao and Christmas Island phosphates to 3.1 to 4.2 per cent in the phosphates of the United States and North Africa1. For a given type of rock, the fluorine content is usually roughly proportional to the phosphorus content. Significance of Fluorine in Phosphate Rock On the basis of chemical and X-ray diffraction studies, Hendricks and co-workers2 concluded that fluorapatite, Cal10F2(PO4)6, is the essential phosphatic constituent of the commercial types of domestic phosphate rock. On the other hand, Bredig and co-workers3 have recently advanced the opinion, also based on X-ray diffraction studies, that the mineral phosphates usually contain carbon dioxide in the apatite lattice, and that the phosphate rocks of the United States are really fluorcarbonate apatites. However, the domestic types of phosphate rock do not seem to differ greatly from coarsely crystalline fluorapatite in their behavior toward chemical reagents in general, and for the purpose of this paper it will suffice to consider fluorapatite as being the essential phosphatic constituent of these types of rock. The available data1 indicate that the different commercial types of domestic phosphate rock usually contain about 12 to 52 per cent more fluorine than theoretically is required to form fluorapatite with all the phosphorus. Calcium fluoride (fluorite) has been definitely identified in only a very few of the samples that have been examined1,2. Bredig and co-workers4 state that fluorapatite can take into its crystal lattice excess calcium fluoride to the extent of approximately 70 per cent of that theoretically required by the formula Ca10F²(PO4)6 without causing more

Jan 1, 1938

By W. M. Bertholf

To establish the minimum or break-even efficiency of a preparation plant it is necessary to determine the ratio of production costs per ton of run-of-mine coal to sale price per ton of clean coal. This ratio is then divided by the percentage of plant recovery. Assume, for example, that washability data indicate that 80 pct of the run-of-mine coal may be recovered as clean coal selling for $5.50 per ton. If the same plant incurs $4.00 per ton mining costs and $0.25 per ton preparation costs, the cost to sale price ratio would be 4.25/5.50, or 77.3 pct. Since the plant is capable of recovering 80 pct of the run-of-mine coal the minimum plant efficiency would be 77.3/80, or 96.6 pct. If the plant efficiency were increased to 100 pct the limit on preparation costs would be increased to $0.40. Therefore, the washing operation must be accomplished at a cost of $0.25 to $0.40 per ton and the efficiency must be 96.6 pct or higher. By plotting a curve of efficiency vs preparation costs and taking into consideration the plant cost, feed rate, operating costs, and yields of the various flowsheets it is possible to select a financially sound process. Table I classifies preparation processes according to their nature of separation. It must be remembered that what is thought to be ideal does not always prove practical under actual operation. An outstanding example is the work done on the plunger-type jig. It was determined by the law of equivalence that this unit could treat satisfactorily only sizes differing by no more than a ratio of 2. Yet these same plunger-type jigs are successfully treating sizes considerably greater than this ratio.

Jan 12, 1957

By Bartlett W. Paulding

Since its introduction to the petroleum industry in 1949 by Clark,1 hydraulic fracturing or "hydrafracing" has developed into a widely respected and useful technique for increasing production from petroleum reservoirs. Even then, Clark described production increases of from 6 to 100 barrels of oil per day (bopd). Since that time, others have described treatments in which production increased from 12 to 456 bopd, from only a show to 40 bopd;2 from 48 to 219 bopd; 3 from 500 to 1400 bopd and from a show to 192 bopd.4 Although representative of only a few of many successful hydraulic fracturing operational6 these increases in production attest to the past and potential value of the hydrafracing technique to the petroleum industry. The technique has received a considerable amount of theoretical and experimental attention.1, 5-20 Unfortunately, however, the degree of general understanding of the mechanics of hydraulic fracturing is still inadequate to solve many recurring problems. The practicing engineer is plagued with difficulties in predicting such factors as: (1) the required pressure and viscosity of the fracturing fluid to not only induce the fracture but to control the extent of its growth, (2) the strength characteristics and amount of proppant to include in the fluid so that the fracture is held open once the fluid pressure is decreased, and (3) the volume of the reservoir influenced by the induced fractures and the resulting increase in production. A major cause of these difficulties is the uncertainty associated with determining the orientation of the hydraulically induced fractures. One's natural conclusion in considering the problem is that the orientation of the fracture would depend on several variables, as, for example, the relationship between the viscosity and injection rate of the fluid and the

Jan 1, 1968

By Ole Singstad

THE legislatures of New York and New Jersey, determined in 1919 that a vehicular tunnel should be built under the Hudson River. On July 1, 1919, an engineering staff was organized with the late Clifford M. Holland as chief engineer, and this staff was given a number of problems to solve, such as location, size, type of tunnel, method of construction, method of ventilation and cost. After a period of preliminary investigations and studies it was decided to build the tunnel at Canal St., New York, connecting 12th St., Jersey City. This is the center of the heaviest traffic across the Hudson River. It was also decided to build two tunnels-one for west-bound traffic and one for east-bound traffic-the tunnels to be of cast iron, built up of segments and bolted together, each tunnel to have a roadway 20 ft. wide and a clear heat room of 13 ft., 6 in. This is to provide for two lines of vehicles in each direction. The tunnels have an exterior diameter of 29 ft., 6 in. The interior lining is of concrete, the sidewalls tiled with a vitreous white tile and the roadways paved with granite block. The entrances and exits at both ends are separated by two blocks so as to reduce traffic congestion. BASIS OF VENTILATION It was recognized very early that one of the most important problems confronting the engineers was a proper ventilation system. It was estimated that each tunnel as planned would have a traffic capacity of 1900 vehicles per hr. The tunnels are 8500 ft. long between portals, and it was considered that the ventilation should be based on all of these vehicles being operated by gasoline engines. That presented a problem in ventilation unlike any other either in magnitude or character.

Jan 8, 1926

By F. E. Bash

WHENEVER electric and open-hearth steel men discuss the relative advantages of their respective methods, the question of temperature is always discussed, so that this paper is written in the hope that definite data may settle some of the questions and encourage further investigations along these lilies. The writer has had the opportunity of taking the tapping temperatures of steel from electric furnaces of different sizes in various plants and from a number of open hearths handling the same kind of steel. All temperature measurements were made with the same disappearing-filament type optical pyrometer and the corrections for emissivity applied were those worked out by Burgess,1 which are 0.40 for steel streams and 0.65 for slag. The correction is applied by calculating the curve giving the relation between the true and apparent temperature in the following formula: Log E = CZ log e( 1 _ 1 x \T2 T1) in which E = emissivity; C2 = 14,500; e = base of Napierien logarithms; ? = wave-length of light used = 0.65/4; T2 = true temperature, in degrees absolute; T,1 apparent temperature, in degrees absolute. The curve showing the relation between true and apparent temperature for steel and slag arc given in Fig. 1. For the purpose of comparison of open-hearth and electric furnaces, there are given in Table 1 the tapping temperatures of two 25-ton Heroult electric furnaces and one 6-ton with one 50-ton acid, one 40-ton basic, and one 65-ton acid open-hearth furnace, all making nickel ordnance steel for guns. The two 25-ton Heroult electric furnaces were finishing steel refined by the triplex process and the 6-ton Heroult finished steel that was partly refined in an open hearth.. In this table, the tapping temperature and the temperature of the steel stream into the first ingot

Jan 9, 1919

By A. Hansson, G. E. Tardiff

WHILE it is generally known that cold-worked low-and medium-carbon steels exhibit substantial increases in tensile rupture ductility with increased deformation velocity172 (up to the von Karman limit), the observations for annealed or normalized steel do not permit simple generalization. Various investigators, for example, have reported both small increases1,3 and small decreases4,5' in rupture ductility with increased rates of deformation of normalized low-carbon steel. The purpose of the present note is to report on the dependence observed for strain-aged steel since preliminary work here indicates that strain aging results in the development of a consistent type of behavior that is understandable in the light of current knowledge of the lower yield dynamics for steels which deform inhomogeneously.6 This realization throws additional light on the influences responsible for the behavior of normalized steel. The results presented here were obtained for a 0.21 pct C, 0.012 pct N sheet (0.012 in. thick) steel which was received in a temper-rolled condition (approximately 3 pct reduction in thickness after process annealing); the as-received material had a spherodized structure with a ferritic grain size of ASTM 8. The material was selected for testing after 6 months room temperature aging, at which time the static lower yield and ultimate tensile strength measured 79 and 82 kpsi, respectively. ASTM 2-in. reduced section, 1/2-in.-wide specimens were used in smooth bar tests and 3/4-in.-wide specimens containing two 60-deg opposed edge notches (root radii = 0.002 in.) were used in notched bar tests. To facilitate strain measurement, the smooth bars were blued with ink and marked at 0.1-in. intervals along the gage length; the notched

Jan 1, 1968

By F. F. Aplan

INTRODUCTION The production of coal is a major part of the mining industry. In recent years the production of clean coal has exceeded 600 million tons per year and is reported to have reached 660 million tons in 1977. Some data on the magnitude and utilization for the year 1975 is given in Table I. In that year 648 million tons of soft coal were produced and of this 267 million tons or 41% approximately was produced by mechanical cleaning. Of the 374 million tons of raw coal sent to the preparation plant, 28.6% or 107 million tons was discarded as refuse. In the same year approximately 6 million tons of anthracite were produced and nearly all of this was cleaned. Table I also gives coal utilization statistics for 1975. Excluding the approximately 20% that goes to the coke ovens or to export, the vast bulk of our production is used for steam power generation and a lesser amount for captive production of industrial power and process steam. While much of the nation's coal (e.g. strip mined western, sub-bituminous coal) may be removed from the ground in relatively pure form by modest selective mining techniques, other coal requires preparation in order to remove ash and sulfur constituents and produce an acceptable steam or coking coal. Preparation is often a valuable adjunct to mining in that rather non-selective, low cost, bulk mining techniques may be used underground while the preparation plant is used to reject refuse at low cost above ground. The principal reason for the use of coal preparation is to convert raw coal into an acceptable commercial product by removing the high ash and high sulfur refuse material.

Jan 1, 1979

By D. E. Swets, R. C. Frank

It is well known that hydrogen is introduced into iron or steel as a result of many chemical processes (acid pickling, electrolytic cleaning, plating, etc.). One of the reactions that has been of recent interest1 is the reaction between an iron surface and water vapor. It was shown a few years ago2-4 that hydrogen can be introduced into steel at an accelerated rate during abrasion as a result of this reaction. Grun-berg and Scott have also observed that water in mineral oil lubricants increases pitting failure in ball bearings5 and they have suggested that hydrogen from the water is the primary cause of this effect.' In this laboratory, the question was raised as to whether or not hydrogen is also introduced into the metal surface of a bearing as a result of the decomposition of the hydrocarbon lubricant itself, and an experiment was performed to try to find a satisfactory answer. All steel parts contain some residual hydrogen. Therefore, it appeared that the best way to carry out this experiment without the need for highly accurate quantitative analyses was to use deuterium as a tracer. The natural abundance of deuterium in H2 is only 0.015 pct. The tracer was obtained in the form of deuteroparaffin (CD,(CDJ, CD,) and 0.25 g were dissolved in 20 cc of mineral oil to form the lubricant to be used in the tests. The bearings used were New Departure Type QOLOO ball bearings with a ball diam of 0.187 in. Prior to adding the mineral oil-deuteroparaffin lubricant, the bearings were cleaned in warm trichloroethylene to remove the packing grease. After packing with the new deuterated lubricant, the bearings were operated in a bearing fatigue test machine under a radial load of 190 lb and a thrust load of 190 lb at a speed of 3800 rpm. The expected life under these conditions is about 500 hr. Two tests were made; one for a period of 27 hr and the other for a period of 102 hr. The bearings achieved a temperature of 120o F during the tests. When the tests were stopped the balls were mechanically removed from the bearings and were immediately placed in liquid nitrogen to reduce degassing until the analysis for deuterium could be made. Before analyzing, the balls were warmed to room temperature and scrubbed with several degreasing agents to remove all traces of the deuteroparaffin mixture. This cleaning procedure was shown to be satisfactory by running a control test in which one ball bearing was subjected to all parts of the test except running in the fatigue machine. The hydrogen and deuterium were removed from the balls using a hot extraction apparatus attached to a mass spectrometer. Four balls from each bearing were analyzed. Each one was analyzed separately by removing it from a cold storage volume of the hot extraction apparatus and transferring it to the oven tube with a magnet. As the gases were evolved they were analyzed with the mass spectrometer. Since the hydrogen and deuterium pass through steel in the atomic form and since there are many more hydrogen atoms than deuterium atoms in the sample, the probability of forming an HD molecule is greater than forming a D2 molecule. For this reason the evolution of HD and H was followed as each ball was placed in the oven. The results showed that as each ball from the test bearing was dropped into the oven, the mass spectrometer recording of the HD evolution increased by about ten divisions. When balls from the control test bearing were dropped into the oven, the increase was about one division or less. The hydrocarbon background in the mass spectrometer was also monitored to see if hydrocarbons or deuterocarbons were given off when the balls were dropped into the oven, but no change in the hydrocarbon peaks was observed. Since the balls contained a fair amount of residual hydrogen, isotope ratio measurements were made on the gas obtained from each ball. The D/H value found for those balls which had been operated in the fatigue testing machine was consistently about 0.3

Jan 1, 1962

By N. J. Gran, W. R. Opie

HYDROGEN in molten aluminum and aluminum alloys, which precipitates during cooling and solidification, is the principal cause of pin hole porosity in ingots and castings. Much attention has been given to determining the effect of temperature and pressure on the solubility of hydrogen in pure aluminum, but little data are available on hydrogen solubility in aluminum alloys. This investigation was undertaken to check results reported for pure aluminum and to show the effect of silicon and copper additions on the amount of hydrogen contained by molten alloys. Previous determinations of the solubility of hy-drogen in molten pure aluminum are plotted in fig. 1. The most reliable data appear to be those of Ransley and Neufeldl and of Baukloh and Oester-len.' The latter authors also report some results on the effect of copper and silicon additions. Up to 6 pct these elements decrease the solubility of hydrogen quite rapidly, with a definite minimum noted at 6 wt pct for both copper and for silicon, although no reason is apparent for these minima. Experimental Procedure The solubility of dry hydrogen in pure aluminum, aluminum-silicon, and aluminum-copper alloys was determined by the method of Sieverts.8 This consists of determining the volume of the gas system above the molten metal at a given temperature and pressure by using an insoluble gas. This volume is referred to as the "hot volume." The system is then evacuated and the soluble gas is introduced at the same temperature and until the same pressure is reached. It is necessary to introduce enough of the soluble gas to fill the space above the metal plus the soluble amount. The difference in the volume of soluble gas and the "hot volume" is the solubility. The accuracy of solubility measurements by the Sieverts' method is primarily depend-

Jan 1, 1951

By Donald N. Rosenblatt

I would like to commend the author on his description of Pinto Valley's plant, and its interesting innovations. The author's discussion of 18 ft in diameter by 21 ft long primary ball mills (the largest wet ball mills made to date) is of considerable importance to those who have been engaged in the field of studying ball mill liner wear as it relates to various grinding installations. While it is stated that the mills have operated on a fixed tonnage and therefore it has been difficult to determine the best liner pattern, calculations from the data in the paper indicates that for mills 1, 2, 5, and 6, the tonnage per hour varies from a low of 223 for mill No. 1, up to a high of 314, for mill No. 2, while mills 5 and 6 calculate 285 and 246, respectively. Analysis of the wear patterns for the single wave liners used in mill No. 1 as compared to the double wave liners in mill No. 2, suggests that the author's data may tell more than he suspects about liner wear to be expected and thus what should be a best pattern selection from what may appear to be only limited hours of operation. [Fig. A] is a reproduction of author's [Fig. 10], to which wear forecast patterns [F-1 and F-2] have been added. Forecasts are based on many previous studies of large diameter ball mill operations over many years of field service. Calculations from the first-wear pattern provide an initial wear rate of only 13 lb of liner per 100 sq ft of shell liner surface per day, or 0.031 lb per to: ground. However, the second wear pattern is ac-

Jan 1, 1978

By George Sachs, J. Spretnak

The process of recrystallization has not as yet been explained satisfactorily. Some definite conclusions could be drawn from recent investigations, such as, for example, that recrystallization is a process of nucleus formation and crystal growth1 and that the orientations of the nuclei correspond to some fragments of the original crystals, which have been considerably distorted during deformation.2 There are, however, a number of metals and alloys crystallizing in the face-centered cubic system, which form a particularly simple orientation if recrystallized as a sheet.3 Such a shect is almost a single crystal with the cubic axes parallel to the rolling, transverse, and normal directions of the sheet. This preferred cubic or (100) orientation of the recrystallized sheet has been considered to be very different from the rolling structure of the same metals,4 but there are two reasons why this last supposition remains open to controversial discussion. The first reason is academic: In practically all cases except the one mentioned above, close correlations and similarities between rolling and annealing orientations have been observed; for instance, in iron and steel sheet.6 Secondly, no deformed metal actually forms a simple orientation. In any thoroughly investigated case a number of different orientations and considerable scattering or deviations from the ideal orientations have been found.6 It is generally true that investigations on single crystals have shown that a definite orientation is approached in stretching or in compression of an originally undisturbed crystal.7 In the special cases, however, where the initial orientation was close to an important crystallographic direction that differed from the final "ideal" orientation, the resulting orientation changed very little by deformation, staying somewhere in the vicinity of the initial orientation.8 Such deviations

Jan 1, 1940

By George Sachs, J. Spretnak

The process of recrystallization has not as yet been explained satisfactorily. Some definite conclusions could be drawn from recent investigations, such as, for example, that recrystallization is a process of nucleus formation and crystal growth1 and that the orientations of the nuclei correspond to some fragments of the original crystals, which have been considerably distorted during deformation.2 There are, however, a number of metals and alloys crystallizing in the face-centered cubic system, which form a particularly simple orientation if recrystallized as a sheet.3 Such a shect is almost a single crystal with the cubic axes parallel to the rolling, transverse, and normal directions of the sheet. This preferred cubic or (100) orientation of the recrystallized sheet has been considered to be very different from the rolling structure of the same metals,4 but there are two reasons why this last supposition remains open to controversial discussion. The first reason is academic: In practically all cases except the one mentioned above, close correlations and similarities between rolling and annealing orientations have been observed; for instance, in iron and steel sheet.6 Secondly, no deformed metal actually forms a simple orientation. In any thoroughly investigated case a number of different orientations and considerable scattering or deviations from the ideal orientations have been found.6 It is generally true that investigations on single crystals have shown that a definite orientation is approached in stretching or in compression of an originally undisturbed crystal.7 In the special cases, however, where the initial orientation was close to an important crystallographic direction that differed from the final "ideal" orientation, the resulting orientation changed very little by deformation, staying somewhere in the vicinity of the initial orientation.8 Such deviations

Jan 1, 1940

By J. F. Shirley, H. K. Burke

In January, 1964, three years of laboratory and pilot plant test work reached its culmination. The San Manuel Div. of the Magma Copper Co. switched its molybdenite extraction circuit from the sodium hypochlorite-ferrocyanide process to the new process described in this paper. The San Manuel Div. Concentrator of the Magma Copper Co. is located near San Manuel, Ariz., approximately 45 miles northeast of Tucson. The concentrator treats approximately 35,000 tons of ore per day containing about 0.85% copper and 0.025% molybdenite. The San Manuel ore body is a disseminated copper deposit in quartz monzonite and quartz monzonite porphyry. The primary copper mineral is chalcopyrite; minor amounts of chalcocite, bornite and covellite are also present in varying degrees. Pyrite makes up somewhat more than half the sulfide content of the rock. The molybdenite is nearly always found on fracture faces or associated with quartz veinlets.' On January 9, 1964, the sodium hypochlorite-ferrocyanide process that had been used for molybdenite recovery was replaced by the following process: 1) A conditioning step with hydrogen peroxide, sulfuric acid, sodium cyanide and zinc sulfate. 2) A two stage rougher flotation step with stove oil and sodium ferrocyanide. 3) One cleaning step with sodium ferrocyanide. 4) One cleaning step with sodium hypochlorite and potassium ferricyanide. 5) Four cleaning steps with an anti-foam Exfoam 636 and potassium ferricyanide. COPPER CONCENTRATOR Since molybdenite recovery is closely allied with previous steps in the operation, the copper concentrator will be briefly described first. The ore is ground to approximately 5% plus 65-mesh and 65% minus 200-mesh in a two-step grinding circuit consisting of rod mills in open circuit and ball mills in closed circuit with rake classifiers. A straight forward rougher circuit producing only one concentrate is used. The rougher concentrate is combined with the discharge from the regrind ball mills and is then cycloned, with the overflow going directly to the cleaner circuit and the underflow going to the regrind mills. The feed to the cleaner circuit is approximately 90% to 94% minus 325 mesh. The cleaner circuit consists of two stages in which the tailing from the final cleaner stage is returned to the primary cleaner and the primary cleaner tailing is returned to the rod mill discharge at the head of the circuit. Approximately 0.013 lb of the allyl ester of amyl xanthate (S-3302) per ton of ore is added to the rod mills and approximately 0.006 lb of sodium isopropyl xanthate (2-11) per ton of ore is stage added down the rougher banks. The frother used is methyl iso-butyl carbinol (MIBC) and it is added at various points in the grinding and the rougher flotation circuits. Lime is added to the ball mills and/or to the rod mills to maintain the desired pH in the rougher flotation. The rougher flotation has been operated at various pH levels between 10.5 and 11.5. Fuel oil is added in the regrind mills at a loading of approximately 0.01 lb per ton of ore. Factors Which Directly Affect Molybdenite Recovery: It has been found at San Manuel that, to obtain maximum molybdenite recovery, an oily type flotation collector must be added in the grinding circuit. When molybdenite is crystallized in the characteristic platy form, which appears to be the case almost all of the time at San Manuel, its surface has a greater tendency to adhere to oils than water. 2 Of the several oily type collectors available on the market, the allyl ester of amyl xanthate seems to be the best molybdenite promoter. The floatability of San Manuel's molybdenite does not appear to be affected, at least up to a pH of 11.5, by lime. It has been reported that at several plant operations high lime alkaline circuits have adversely affected the molybdenite recovery.3,4 It has been found through microscopic studies that the bulk of the chalcopyrite will float before the molybdenite in both the rougher and cleaner circuits. It is necessary to add fuel oil to the regrind mills to enhance the

Jan 1, 1965

By Herbert Hoover

I HAVE been greatly honored as your unanimous choice for President of this. Institute, with which I have been associated during my entire professional life. It is customary for your new President, on these occasions, to make some observation on matters of general interest from the engineer's standpoint. The profession of engineering in the United States comprises not alone scientific advisers on industry but, in great majority, is comprised of the men in administrative positions. In such positions, they stand midway between capital and labor. The character of your training and experience leads you to exact and quantitative thought. This basis of training in a great group of Americans furnished a wonderful' recruiting ground for service in these last years of tribulation. Many thousands of engineers were called into the army, the navy, and civilian service for the Government. Thousands of high offices were discharged by them with credit to the profession and the nation. We have in. this country, probably, one hundred thousand professional engineers. The events of the past few years have greatly stirred their interest in national problems.' This has taken practical. form in the maintenance of joint committees for discussion of these problems and support to a free advisory bureau in ,Washington. The engineers want nothing for themselves from Congress.. They want efficiency in government, and you contribute to the maintenance of this bureau out of sheer idealism. This organization for consideration of national problems has had many subjects before it, and I propose to touch on some of them this evening.

Jan 1, 1920

By Jacques B. Wertz

Detailed structural studies in southeast Arizona have successively revealed (1) the local attitudes of individual fractures (with lateral and/or vertical displacements), (2) the patterns exhibited by groups of fractures, and (3) the trends and directions shown by fracture groups or zones on a regional scale. The results of the studies have been twofold: First, domes were locally determined from these fracture arrangements, even where other criteria failed; and, second, fundamental breaks brought out the breadth of the Texas lineament in southeast Arizona as well as major northwest- and northeast-trending fracture zones. Coincidence of one or several domes with the major intersections of fundamental breaks can be centers of important mineralization, as in the instances of Bisbee, Ajo and Morenci. THE OVER-ALL STRUCTURE OF ARIZONA A northwest-southeast trending anticlinorium has been suggested as the structural setting of Arizona. Starting in Triassic and culminating in late Cretaceous times, this deformation resulted from stresses of considerable magnitude with varying ratios of com pres sional and uplifting forces. However, the series of parallel flexures could just as well have been caused by isostatic movements involving dilation under tension with only incidental compression, as later emphasized by dike filling and block faulting (Fig. 1). The anticlinorial deformation, which is also suggested by the fact that the Pre-cambrian rocks to the southwest are all concealed by sediments, could be somewhat reminiscent of the conditions that affected the classical swarm of parallel dikes of wager.' ANALYSlS OF DATA As a first step in this analysis, all structural information obtained on such features as fractures and their relative displacements, faults, dikes, anticlines, synclines, and Precambrian and Laramide-Tertiary intrusives were plotted on maps along with structural trends inferred from aerial photographic mosaics. Next, the faults in southwest Arizona were classified according to time of occurrence and relative importance. The fault assemblages were then examined as to geometric or spatial arrangement and correlated with the occurrences of domes and existing Finally, the conjunction of fracture intersections and domes was analyzed and compared with locations of known ore deposits. Differentiation of Faults According to Time and Relative Importance: The faults encountered were grouped as follows: (1) Basin and Range faults, latest in time; (2) secondary faults; (3) primary faults; and (4) lineaments, earliest in time by inference. BASIN AND RANGE FAULTS- Generally concealed by alluvium, the Basin and Range faults are normal

Jan 1, 1969

By E. P. Pfleider, W. G. Pariseau

This paper reports the theoretical and experimental results of an analysis of ore pass drawdown as a problem in soil plasticity. The method of analysis developed appears to be a promising technique of investigating the mechanics of fragmented materials. A reconstructed plasticity theory brings experiment and theory into reasonable agreement, and hence may provide the foundation needed for rational ore pass design. The gravity-induced movement of broken rock through ore passes is an economical method of transporting fragmented materials through large vertical distances in underground mines, provided the ore pass is well designed. Unfortunately, the design procedures now followed do not very often result in ore passes that function properly. On the one hand, the huge accumulation of empirical data pertaining to the movement of materials in gravel bunkers, storage bins, deep grain silos and other structures that have features in common with ore passes remains uncorrelated. On the other hand, there is a dearth of experimental data substantiating theoretical models of material behavior. Consequently, reliable generalizations encompassing the broad spectrum of problems involved have not been forthcoming. AS an initial step towards improving the situation, a detailed case study of two-dimensional ore pass drawdown was made. The mechanics of the process were analyzed theoretically as a problem in soil plasticity and tested experimentally through observations of a laboratory ore pass model. THEORY Taylor1 defines a soil as a "mass commonly considered to consist of a network or skeleton of solid particles, enclosing voids of varying size." Broken rock in an ore pass is such a material. In plasticity theory this material is replaced by an idealized substance that deforms elastically up to some state of stress at which slip or yield occurs,2 For com-pressive states of stress, the Mohr-Coulomb criterion is a satisfactory yield condition. After the yield point is reached, the ideal soil deforms in accordance with the concept of plastic potential.4 Under plane strain conditions the governing equations separate into a system of stress equations and a system of velocity equations.' Only stress variables appear in the stress system. The velocity system, however, contains a stress variable. The two systems are, therefore, coupled. Both systems are hyperbolic, and each has two real, distinct families of characteristic curves that coincide according to the classical theory of ideal soil plasticity. The

Jan 1, 1969

By J. F. Tavernelli, L. F. Coffin

The deformation and fracture characteristics of eight metals subjected to fully reversed cyclic strain ranging from 0.2 to 50 pct were investigated at room temperature. Strain-hardening characteristics unique to the interna1 structure of a particular metal were found. Complete removal of the strain-hardening effects resulting from prior deformation was brought about by subsequent cyclic strain. Further support for the validity of the inverse relationship between the plastic strain range and the square root of the number of cycles for failure is given. THE resistance of materials to cyclic plastic strain is of interest both from a fundamental and practical point of view. It is now a well-accepted fact that fatigue failure in metals is a consequence of the localized slip deformation which occurs within the individual crystals of metal.'-' Hence the failure process should be strongly dependent upon the magnitude of the gross cyclic plastic deformation of the metal under conditions where this is a measurable quantity. Therefore, an experimental investigation of metals in which the cyclic plastic strain is the independent variable should shed new light on some of the basic aspects of the problem. From the practical point of view, there are many uses for information relating to the cyclic strain resistance of metals. One is the case of thermal stress fatigue where fatigue failure can occur as a consequence of a com- paratively few cycles of thermally induced mechanical deformation. Another is the mechanical working of metals where large cyclic strains are employed. In recent years several publications have appeared relating to the cyclic-strain resistance of metals,8-11 dealing mostly with the fracture aspects where the temperature is cycled simultaneously with the mechanical strain. Some work has been reported on the cyclic-strain resistance of metals at constant temperature, again oriented more toward the fracture aspects of the problem than the deformation aspects. 12-16 The present research investigation was undertaken to obtain information regarding the deformation characteristics of several metals whose structure-property relationships were simple and straightforward under conditions of both cyclic and monotonic strain. It has been shown for example that under cyclic-strain conditions some materials will strain harden, while other materials, particularly cold-worked structures, strain soften and these effects required further clarification.8,17-19 It was also de-

Jan 1, 1960

By John T. Galey

In all, 210 wellst were completed in southwestern Pennsylvania during 1939, which is 59 more than were drilled during the preceding year. Of this number, 137 were gas wells, which is a considerable increase from the 81 completed during 1938. Only 25 oil wells were completed, as against 28 in the previous year, and 28 dry holes, 6 more than last year. Shallow Development—Gas The increase in the number of gas wells is largely the result of a search for additional gas in Armstrong and Indiana Counties. Although a considerable number of wells were drilled in the latter county, the majority of them produced less than 100 M cu. ft. initial open flow. In Armstrong County, a new pool was opened in Cowanshannock township, producing from the third Bradford sand. Several large wells were obtained there, one of which produced an initial of nearly 12 million cu. ft., with a reservoir pressure of 1100 Ib. However, the productive area has been fairly well outlined by further drilling and shows that the pool covers only about 800 acres. The sand is 20 to 30 ft. thick, and probably has 5 to 6 ft. of pay. Thus this reserve is not an important one. Several wells were found in Menallen township, Fayette County, where the Big Injun sand has been having a play for the past three years, but the activity there is much less than a year ago. Oil On the west side of the Bradford sand gas pool, Cowanshannock township, Armstrong County, a well was drilled which flowed 100 bbl. the first day from the Tiona sand. The probability is that this well is a freak, as the Tiona has been drilled within a fairly close distance on every

Jan 1, 1940

By John T. Galey

In all, 210 wellst were completed in southwestern Pennsylvania during 1939, which is 59 more than were drilled during the preceding year. Of this number, 137 were gas wells, which is a considerable increase from the 81 completed during 1938. Only 25 oil wells were completed, as against 28 in the previous year, and 28 dry holes, 6 more than last year. Shallow Development—Gas The increase in the number of gas wells is largely the result of a search for additional gas in Armstrong and Indiana Counties. Although a considerable number of wells were drilled in the latter county, the majority of them produced less than 100 M cu. ft. initial open flow. In Armstrong County, a new pool was opened in Cowanshannock township, producing from the third Bradford sand. Several large wells were obtained there, one of which produced an initial of nearly 12 million cu. ft., with a reservoir pressure of 1100 Ib. However, the productive area has been fairly well outlined by further drilling and shows that the pool covers only about 800 acres. The sand is 20 to 30 ft. thick, and probably has 5 to 6 ft. of pay. Thus this reserve is not an important one. Several wells were found in Menallen township, Fayette County, where the Big Injun sand has been having a play for the past three years, but the activity there is much less than a year ago. Oil On the west side of the Bradford sand gas pool, Cowanshannock township, Armstrong County, a well was drilled which flowed 100 bbl. the first day from the Tiona sand. The probability is that this well is a freak, as the Tiona has been drilled within a fairly close distance on every

Jan 1, 1940