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By S. M. Brisbane

THE life of refractory linings in rotary cement kilns can be shortened by uneven or inadequate support of the kiln and its shell and by variations in the conditions of operation. Alteration of these factors may, according to their nature, bring about mechanical deterioration of the lining or promote chemical attack. Chemical attack has been described elsewhere.1-4 The distortion of cement kilns has been discussed in a general manner by Rochow,6 ho indicates the amount of distortion which may occur in an unlined shell, and by Rosenblad: who states that the deformations of the shell are greatest above the trunnions. The present article indicates the extent of the distortion of a kiln to an oval shape in certain selected positions and the deviation from a straight line of the kiln along its length between two supports. The cement kiln is a long, hollow, rotating cylinder consisting of steel plates which may be either welded or riveted together. This shell is supported on tires, frequently 60 ft apart, which roll on trunnions. The large mass of the kiln causes distortion of its cross-section; it becomes slightly oval, i.e., diameters lengthen as they become horizontal and shorten as they become vertical. There is also a tendency for the shell to bow between supporting tires; this bowing may be upwards or downwards depending on the position of the weight forces and the supports. The extent of the deviations from the ideal kiln shape was investigated. Observations described in this paper were made on the shell of the clinkering zone between the first and second tires of two of the kilns at the Geelong works of Australian Portland Cement Pty. Ltd. The kilns were both 400 ft long and 10 ft diam with a welded enlarged burning zone 11 ft 6 in. diam. The shell was fabricated from mild steel and in this section its thickness was 1 in. It was lined with 41/2 in. of chemically bonded magnesite-chrome bricks which were jointed with mild steel plates. The kilns operate on a 4 pct slope and the speed may be varied between 0.75 and 1.68 rpm. The wet process is used; kilns are coal fired and are fitted with integral coolers. Temperatures within the kiln are difficult to determine with any accuracy because of the absence of black body conditions, but surface temperatures are probably in the range 1420° to 1470°C. Average shell .temperatures at the two positions at which the deformation studies were made were 370°C and 355"C respectively. Methods: In determining the ellipticity it was necessary to measure the lengths of the vertical and horizontal diameters while the kiln was in operation; data obtained from a stationary kiln would not have the same practical significance. For this purpose the four points V, W, X, and Y at the ends of two mutually perpendicular diameters were marked on one kiln. The point X is shown in Fig. 1. For the measurement of the length of the vertical diameter a vertical column, to which a horizontally aligned telescope was attached, was placed 10 ft from the kiln. The telescope could be racked up and down in a vertical plane. Two sets of readings were taken, one set when each of the points V, W, X, and Y was at its maximum height above the

Jan 1, 1957

By William P. Blake

THE use of diamonds upon a large scale in drilling rocks, and the substitution to a certain degree of rotary diamond drills for the ordinary steel percussion drills, marks a new era in the art of mining. Since the invention by Leschot of the diamond drill, it has steadily advanced in its utility and range of application, and in the appreciation of miners and engineers. It must be claimed as one of the many gifts of science to the arts ; and it is, in particular, one of the fruits of the scientific education given at the Ecole Centrale, at Paris. Members are all, doubtless, more or less familiar with the construction of the drill and of the machinery by which it is applied in boring. It is, therefore, my present purpose only to direct your attention to some recent marked improvements, made by the American Diamond Drill Company, by which the economy and efficiency of the machines have been increased. Form of Bit. The annular or ring form of the drill-head or bit was, I believe, the earliest; and it is still in use, without essential modification, wherever it is desired to obtain a sample "core" or specimen of the rock traversed. But for mere drilling, regardless of the preservation of a test-core, a solid-head bit is preferred, except for very large holes. Until recently, these solid-head bits were made with a pointed cutting face shaped like an obtuse cone. This form was assumed to be the best, being most in accordance with the experience obtained with percussion drills. It is found, however, that the exact reverse

Jan 1, 1873

By R. W. Raymond

R. W. Raymond, New York City: In his paper at the New York meeting (Trans., xix., 28), Mr. Ledyard described, among other mines, the Belmont, in the county of Peterboro, Ontario, the developments of which at that time indicated, though they did not, perhaps, completely demonstrate, a deposit of high-grade Bessemer magnetite of very great extent. Mr. Ledpard said that experts estimated the quantity of ore within 100 feet of the surface at 1,000,000 tons. But the precise data upon which this estimate was based were not furnished. We are all interested in the development of fresh supplies of Bessemer ores. I think nobody who knows how enormous is the demand can seriously fear that such deposits will be exploited too rapidly. On the other hand, I need not here enlarge on the fact that a considerable number of enterprises, in which American ironmasters have been more or less interested, for the development of Canadian iron-ore deposits, have been unsuccessful, more by reason of disappointment as to the quantity of the ore and the facilities for cheaply mining it on a large scale, than as to its quality. Of course, a Canadian nine supplying the American market is handicapped at present, to the extent of 75 cents per ton, by the duty on foreign iron-ore; but this would certainly not be prohibitory in the case of a deposit sufficiently large, rich, and accessible. Or, to put it otherwise, there might easily be, somewhere in Canada, near our borders, a mine so favored that its product could be profitably

Jan 1, 1892

Discussion of the paper of R. H: Sweetser,. presented at the Cleveland meeting, October, 1912, and printed in Bulletin No. 71, November, 1912 pp. 1327 to 1334. See also Bulletin 11 No. 72, December, 1912, pp. 1561, 1562. J. J. HOWARD, Dover, N. J. (communication to the Secretary*) :-No doubt there are as many different methods of starting a blast-furnace as there are men who assume that responsibility. Having blown-in a furnace a few years ago in a manner similar to that outlined by Mr. Sweetser, things went along so well at the start that I had time for a little reflection on what was going on inside the furnace. I saw the wood turned to charcoal practically, and it occurred to me, why should I use wood when I could put in the charcoal in the. first place, and thus save a lot of time, and also eliminate the dangerous gas from the wood, which is the cause of most of the accidents in starting up a furnace. I had a furnace out for repairs and decided to use no cord-wood in blowing in. I put in about a carload of charcoal and used no wood except some shavings and oily waste at each of the tuyeres. The furnace had 16 tuyeres and was 100 by 22 by 14.5 ft. Hot rods were put in each tuyere' and the blast started immediately at 11 a.m. Within 5 mill. the air was all driven out of the stack and the gas lighted of its own. accord at the top of the furnace. It was allowed to burn for 5 min. longer and then the bell was closed and the gas taken to the last stove and the last boiler on the gas-main. It was all clone so quietly that it was hard to realize that the gas was down. The tuyeres were as bright as if the furnace had been in blast for a long time. I have learned since that others have used the same method, but they had not passed the good advice along.

Jan 5, 1913

By Clarence Thom

This chapter presents, in summarized form, standard procedures for making separations of minerals from their ores by the froth flotation process to produce marketable concentrates. These are typical mineral separations which are being made commercially with the reagents and conditions generally used in the mining industry. Typical separations are presented for 17 metallic and 11 nonmetallic ores. The review of each includes a brief description of the mineral and the particular problem presented, general market specifications for its concentrates, an outline of treatment method, and kinds and quantities of reagents usually employed. This chapter does not include de- tails about ore preparation (crushing, grinding, and classification), elements of ore and pulp transportation (conveying and pumping), or concentrate preparation for market (thickening, filtering, and drying). In each presentation it is assumed, if not detailed further, that the ore is ground to the economical point of liberation of the minerals to be separated. Specific information, such as ratio of concentration and recovery, that depends upon the grade of ore being treated is considered beyond the scope of this chapter. Effective flotation separations that produce marketable concentrates may produce widely varying results in terms of percent recovery and still be economically profitable operations. Details of plant practice on specific ores are presented in Chapters 16 and 17. In this chapter the chemical names of the reagents are given. The extent to which different reagents are used in flotation plants in the U. S. is presented in Chapter 4. A compilation of the various flotation reagents, their trade names, manufacturers, and use has been prepared by H. T. Spedden. ANTIMONY The principal ore mineral of antimony, stibnite (Sb2 S3), is generally found in the U. S. in ore bodies in association with other valuable minerals such as galena (Pbs), sphalerite (ZnS), chalcopyrite (CuFeS2), or tetrahedrite (3Cu2 S – Sb2 S3), The sulfo-salt minerals of antimony, such as tetrahedrite or pyrargyrite, are often associated with high silver values, so that the presence of antimony may indicate economic importance even though the actual antimony content is low. Antimony is also significant to the mineral economy because of its occurrence in some ores where lead, gold, and silver are the

Jan 1, 1962

By Portland P. Fox, Berlin C. Moneymaker

THE development, within recent years, of core drills capable of drilling holes up to 72 in., or even more, in diameter, has made possible an entirely new and valuable method of geologic exploration. Although little used until recently as an exploratory tool except in the United States, by the Tennessee Valley Authority and the Corps of Engineers of the U. S. Army, for the exploration of damsites, the large-diameter core drill may be used to good advantage in other types of geologic exploration. Its principal utility is that of supplementing, rather than replacing, other means of exploration. Although core is frequently recovered intact, the greatest advantage of large-diameter drilling is that the holes produced are large enough to be entered by the geologist and engineer, and thus afford an excellent means of examining undisturbed rock. The walls of the holes are smoothly cut, and in some rocks nearly or quite polished, so that the most minute details of structure and stratigraphy are clearly disclosed. Such features as faults, joints, bedding planes, weathered "seams," and beds or layers of soft materials, which are not always amenable to disclosure by cores recovered from small-diameter holes, are conspicuously displayed in the walls of large holes. Frequent reference to the drilling of large-diameter holes is made in engineering literature, but comparatively little emphasis has been placed on their value in geologic investigation. It is, therefore, intended that the present paper acquaint the geologist, as well as the engineer, with the large-diameter core drill and the technique involved in its use, and also with its advantages, disadvantages and limitations as an implement of geologic exploration. THE EQUIPMENT The equipment generally employed in the drilling of large-diameter holes consists of a trunnion-type drill head mounted on a sliding base, which allows it to slide clear of the hole and thus permit the introduction

Jan 1, 1938

By Brian J. Gorval, Robert L. Kemeny

INTRODUCTION Financing, or providing adequate capital at low cost for developing and bringing a natural resource property into production, is a fundamental requirement for profitable operation. Under the present economic environment the cost of financing any project is gaining more importance than ever. The fundamental keys for success in mining are "the Four M's": Mineral, Market, Management and Money. In recent years, with capital and operating costs skyrocketing, increased emphasis on obtaining adequate and low cost capital funds for bringing in a prospect is essential. For a small mining company there are limited sources for raising funds. In most cases these companies have neither a substantial asset base, nor any cash flow, and they are deemed as risky investments. The issue of shares of capital stock of such a company is probably the most common method of raising funds via the public purse. Alternatively, debt could be used and a source of such capital might be private investors or financial institutions. The company which intends to raise funds from the investing public by way of the sale of equity, subsequently lists those shares for trading on a stock exchange. Going and staying public commits a company to a multitude of complex laws, rules and reporting requirements. The governing bodies are the watch dogs for the public. The largest of such an organization of this kind in the world is the Securities and Exchange Commission (SEC) in the United States. In Canada, the Securities Laws come from within provincial jurisdiction. Most provinces have their own Securities Act, and Securities Commission. It is the Commission which administers the Act, and hence controls the distribution and trading of securities within the province. Extra provincial registration is required for trading and distribution in more than one province. In British Columbia, prior to a public offering, the approval of the Superintendent of Brokers (SOB) and of the VSE must be obtained. THE VANCOUVER AND TORONTO STOCK EXCHANGES There are five stock exchanges in Canada which supply a trading forum in which mining companies may operate. The stock exchanges are located in Montreal, Toronto, Winnipeg, Calgary, and Vancouver. Of the five stock exchanges, the Vancouver Stock Exchange (VSE) and the Toronto Stock Exchange (TSE) are the most heavily used for resource-based issues and are the focus of this paper. The objective of this section is to provide a brief background on the VSE and TSE. The Vancouver Stock Exchange The VSE is Canada's predominant stock exchange for financing resource-based, junior issues. Since 1907, the VSE has acted as a source of funds for mining, exploration and energy companies throughout Canada and the world. Currently, there are over 1400 companies listed on the VSE. During 1983, over 3.1 billion shares traded at a value exceeding CDN$3.96 million. The VSE has developed a reputation as one of the few exchanges where a speculative resource venture may obtain a listing and subsequent financing in a relatively short time, generally five to ten months. The SOB, the Investment Dealer's Association of Canada (IDA), and the VSE all regulate trading at the Exchange. Any irregularities in a company's stock dealings are investigated and trading may be halted by the VSE until a satisfactory explanation has been received from the suspended company. Companies can be suspended from trading or delisted for various reasons. One reason is misrepresentation of facts in documentation submitted to the SOB, VSE, or to the public, through news releases.

Jan 1, 1985

By H. P. Leighly, J. W. Marx, H. L. Walker

A relationship between recrystallized grain size and prior deformation is predicted from elementary statistical considerations, and reasonable agreement with experiment is obtained. RECRYSTALLIZATION phenomena have received much theoretical and experimental attention, and very adequate discussions of the various mechanisms suggested have been given by Anderson and Mehl,' Cook and Richards,' and Burgers," and others. It suffices to note here that the initial concepts fitted one of two general hypotheses: I—The new crystals are nucleated within microscopic regions at which there is a concentration of internal stress, i.e., volume elements of maximum strain energy. 2—The new crystals have their inception in volume elements of minimum strain energy. In a comprehensive early review of the subject, van Arkel' considered both possibilities and came to the conclusion that hypothesis 2 was inconsistent with the experimental fact that the number of nu-cleations increased with increasing deformation. He suggested that, if allowance was made for a preliminary atomic rearrangement at the points of large internal strain, hypothesfs 1 provided the more reasonable concept. Following the initial observations of Collins and Mathewsonb nd Crussard,Y he systematic X-ray investigations of Cahn' and Guinier and Tennevin" established the existence of a polygonized structure in metals that had been cold-worked, and subsequently annealed, under conditions such that re-crystallization did not occur. This new experimental evidence by no means disproved the first nucleation hypothesis, a fact recognized by both Beck" and Cahn,10 who independently suggested nucleation mechanisms based on the idea that regions of large strain might polygonize before the bulk of the less deformed material. These mechanisms, together with others recently proposed," are dependent upon the prior existence of some degree of polygonization in the deformed material. On the other hand, a critical examination of the published data leads to the supposition that polygonization may not be the necessary precursor of recrystallization, but merely its favored energetic competitor. In regions where the lattice distortion is not too severe, the limited adjustment afforded by polygonization may permit the lattice to drop to a relatively stable low energy state in which the nucleation of a new crystal becomes improbable, even at elevated temperatures. Such structures, of course, might provide a fertile field for the growth of nuclei, if these could be introduced. In regions of concentrated lattice distortion, polygonization alone may not be able to accomplish an adequate strain reduction, and in these volume elements sufficient thermal activity permits the more drastic atomic rearrangement involved in nucleation. Completely polygonized structures are known to withstand extended heating close to their melting points," with no other effect than a slow enlargement of some of the subgrains at the expense of others. Once started, macroscopic recrystallization might be expected to go to completion in a matter of minutes under similar heat treatment. Crussard12 and his coworkers have found that recrystallization may occur in single crystals of impure (about 99.7 pct) aluminum without any detectable prior polygonization. The indication here is that large Cottrell impurity atmospheres inhibit dislocation movement, thus suppressing polygonization to such an extent that the alternative process, recrystallization, dominates the lattice restoration. Experimental studies relating recrystallization directly to stored energy have not, at the present time,

Jan 1, 1954

By S. J. Leach

The possible solution of some of the problems raised in H. L. Hartman's article "Determining Ventilation Requirements for Continuous Miners," which appeared in the March 1962 issue of MINING ENGINEERING, is offered by recent investigative work done at the Safety in Mines Research Establishment, Ministry of Power, Sheffield, England. Highlights of this research are outlined here. Accumulations and layers of methane form in a mine roadway because it is difficult to mix methane with air beneath it by turbulent diffusion. Such mixing involves work contrary to buoyancy forces. In specifying requirements for good ventilation it is not, therefore, sufficient to state that the airflow must be turbulent in the absence of methane. Fundamental work at SMRE on the behavior of methane roof layers has led to the formulation of rules for controlling methane roof layers which specify the ventilation velocity needed to ensure adequate mixing in terms of the rate of flow of methane into the layer (V = cu ft per min) and the airway width (D = ft). A "layering number" for methane and air has been defined by [U37/V/D] where U is the mean ventilation velocity in ft/min in the upper half of the airway. In a horizontal airway there is no mixing by turbulent diffusion for values of the layering number less than about 2, resulting in extensive roof layers. But with a layering number of 5, the layer is "brought under control"-i.e., a further increase in the layering number will shorten the length of the layer only slightly, and a small decrease in the layering number will cause only a small increase in the length of the layer. In a sloping roadway with uphill ventilation, higher values of the layering number are needed to achieve this "controlled" condition; the values range from about 5 at small slopes to about 8 at a slope of 1: 10. In downhill ventilation it is possible for layers to "back" against the ventilation, i.e., to flow uphill. The critical condition for preventing backing can also be expressed in terms of the layering number. Backing will be prevented if layering numbers are about 3 for small slopes and about 4.5 for large slopes; these values for downhill ventilation also give good control of the layer.

Jan 10, 1962

By M. W. Legatski, D. L. Katz

The best currently available description of the longitudinal mixing properties of a porous medium is an equation of the form which relates the effective longitudinal dispersion coefficient Dp to the molecular diffusion coefficient Do, the electrical resistivity factor F, the porosity <f> and a Peclet number. If the parameters dpa and m are determined for a porous medium of known porosity and electrical resistivity factor, then a dispersion coefficient may be estimated for a given flow rate and a given gas pair. A new method, featuring on-line gas analysis by thermal conductivity and on-line data reduction by analog computation, was developed and used to determine these mixing parameters for eight naturally occurring sandstones and two dolomite samples. The exponent m of the above equation was found to vary between 1.0 and 1.5. The characteristic length dpa in the above equation was found to vary between 0.25 and 1.9 cm, with an average value of 0.4 cm for sandstones. Measurements were made on two cores in which paraffin wax had been deposited by evaporation from a pentane solution. They indicated that the presence of an immobile phase such as connate water could increase the dispersion coefficients significantly. INTRODUCTION While the petroleum and chemical industries have studied the mixing of miscible liquids flowing in consolidated porous media and of miscible gases flowing in unconsolidated porous media, relatively little data have been presented to describe the mixing of gases flowing through consolidated porous media. Such data are of particular interest to the gas storage industry. For instance, the U. S. Bureau of Mines is storing large quantities of a rich helium-nitrogen gas in contact with a natural gas in a dolomite reservoir. Since the rich gas occupies only 15 percent of the total reservoir volume, it is essential that the extent of rich gas-natural gas mixing be predicted and understood as a function of rock properties, pressure and rate of movement. This investigation was concerned only with the determination of longitudinal dispersion coefficients. It is understood that a transverse dispersion coefficient, which characterizes mixing perpendicular to the direction of flow, may be an order of magnitude less than the coefficient characterizing mixing in the direction of bulk flow.5719 It should also be recognized that the use of any dispersion coefficient is in itself a simplification. It is necessary to assume that mixing in a porous medium may be characterized by the equation for flow in a single direction. A number of authors1 l8,19 have pursued the mixing problem, not in terms of the so-called "dispersion model" described by Eq. 1, but in terms of a "mixing cell model". This model supposes that a porous medium is constructed of a large number of small mixing chambers and that the concentration of the diffusing component within each mixing chamber is uniform. Fick&apos;s law (Eq. 1) assumes that there is no gross by-passing of one fluid by another, and that there are not stagnant pockets of gas in the system under consideration as discussed by Coats and Smith.8 These assumptions are not always valid for flow through porous media and it is important to recognize the limitations upon Eq. 1. The most serious limitation upon the assumption of Fick&apos;s law mixing in a porous medium is

By E. DeGolyer

PROSPECTING for new deposits is a part of the ordinary routine business of the petroleum industry to an extent that is not true for any other mineral industry. The health of the industry depends upon whether we are successful or unsuccessful. How many know what it costs to find oil today and what it has cost in the past? Very few, I will wager. The industry is not well informed upon this extremely important point. We cannot deal in averages for lack of information. Does it cost more or less than previously? Prospect wells are increasingly deeper and, since the introduction of the core drill, prospecting techniques have required increasingly expensive field oper-

Jan 1, 1939

The first National Industrial Conference was disbanded without accomplishing the results hoped for. A second conference is to be called in the near future. In response to suggestions of members of the Founder Societies, the following telegram was sent, Oct. 29, to the President and each member of his cabinet. "Engineering Council respectfully recommends appointing on new Industrial Conference two or more engineers familiar with industrial problems. Council represents five national societies of professional engineers having forty-one thousand members. Washington office in McLachlen Building."

Jan 12, 1919

By W. Denham Verschoyle

IN designing a pocket instrument whereby any given horizontal or vertical angle may be closely approximated, the following points should be kept in view, if general utility is aimed at 1. The instrument should be light and compact, so that it can be carried in the pocket, or in a sling. 2. It should be capable of observing any angle whatever, horizontal or vertical. 3. Since time is often an important consideration in making a preliminary survey, it should be capable of giving the horizontal and vertical angle at one observation. I do not know of any instrument that will fulfill these requirements, except the one here described. Where the depression- or elevation-angle of the distant object, whose bearing is required, exceeds 50 or 60 degrees, it becomes difficult or impossible with a prismatic compass, for instance, to obtain accurate results; and since it frequently happens, particularly in mining, that much work requires to be done beyond that limit, it is obvious that an instrument which can be used to observe a high angle just as easily as a low one, if not absolutely a necessity, will at least be a great convenience. How this " pocket transit " attains to the required degree of universality will be understood from the diagram, Fig. 1, in which B is a beveled, graduated circle, attached to and freely revolving about the center of the magnet A. Light falling on B is reflected through a window in F (the compass-box), along the line AC, and is again reflected back to the eye at D by the prism C. By a simple arrangement, the sight-line DCE can be completely revolved in the vertical plane DE, which is normal to AC. It is clear, then, that no matter through what vertical

Jul 1, 1907

By James W. Neill

The occurrence of minerals of nickel and cobalt at Mine La Motte is probably known to every mineralogist. I will not attempt to describe these minerals, but, before entering on my subject, will briefly mention the ores, etc., which call for metallurgical treatment and enter into the composition of our mattes. Our staple lead-ore, the dressed galena, is the chief source of nickel and cobalt. It carries but a small percentage of these metals, viz.: 0.2 to 0.3 percent. usually, though when much copper pyrites is contained in the gangue, the amount of nickel and cobalt may be as great as 1.0 to 1.5 per cent. Next in importance is the ((middle product" of the dressingworks, consisting of the sulphides of iron (and copper) with gangue and galena. This usually carries 20 to 23 per cent. of lead, 0.5 to 1.0 per cent. of copper and 2.5 to 3.5 per cent. of nickel and cobalt. A larger percentage of copper always carries with it an increase of nickel and cobalt. In some few cases 12 to 15 per cent. of copper gives 6.5 to 8.0 per cent of these metals. Resides these products of the dressing-works, there is a small quantity of true nickel-cobalt-ore

Jan 1, 1885

By G. J. Wilson

Difficulties experienced in correlating vertical and lateral locations of subsurface features that are encountered in directional wells prompted critical review of the tangential method of computing directional surveys. Inherent discrepancies were indicated to cause small incremental but significantly large cumulative errors in computed vertical depth and horizontal departure. A radius of curvature method, developed for planning and analyzing directional wells, was studied as a means of more accurately calculating survey data. Errors incurred in the tangential method were not present in the radius of curvature method. Conflicting assumptions in calculating dog-leg severity by the tangential method were resolved by a new procedure that was derived from the radius of curvature method. Results of the investigation showed the radius of curvature method to be an improved method for computing directional surveys. Introduction Many improvements in directional drilling tools and techniques have been made in the past 10 years,&apos; but the method of computing survey data has remained virtually unchanged. While use of computers greatly aids the process of calculation&apos; and eliminates many human errors, manual and computer calculations are still made with the assumption that the wellbore consists of straight-line segments. This paper points out discrepancies in the method and presents an improved method in which the wellbore is assumed to be curved. Tangential Method The method presently used to calculate vertical depth, horizontal departure and direction coordinates with measured values of well depth, inclination angle and direction angle is termed the tangential method. This term stems from performing calculations with a series of straight-line segments, with each segment assumed to be tangent to the wellbore at a corresponding survey point. A segment is defined by inclination and direction angles measured at only the lower or deeper end. Consequently, a discrepancy or error is introduced for each segment. Errors are not of extreme magnitude, but cumulatively are significant due to the need to define as accurately as possible the vertical and lateral location of subsurface features such as pay tops, fluid contacts and fault cuts encountered in expensive directional well bores. In Fig. 1, the curved-line segment ab represents a portion of the actual borehole as viewed in the vertical plane. Points a and b are survey stations and +, is the inclination angle at point b. The curved-line segment ab is assumed to be the straight-line segment arb of a length equal to ab and tangent at point b to the curved-line segment. Lengths a&apos;c&apos; and c&apos;b are equal to a&apos;b cos +, and a&apos;b sin +,, respectively. Point a already has been fixed by calcillations performed with survey data obtained at point a, and calculated lengths m&apos;c&apos; and c&apos;b are projected as lengths from point a, rather than from point a&apos;. Point b1 is thus fixed and assumed to represent the actual point b. Calculated length ac" is shorter than actual length ac, and calculated length c"bl is longer than actual length cb. Since b1 is the point from which the next deeper segment will be projected, errors are cumulative. Cumulative error continues to increase as long as the inclination angle continues to increase. When the inclination angle decreases (Fig. 2), calculated length ac" is longer than actual length ac, and calculated length c"bl is shorter than actual length cb. These errors also are cumulative, but differences between calculated and actual lengths are opposite in mathematical sign to differences demonstrated in

Jan 1, 1969

By L. H. Robinson

Triaxial compression tests have been performed to determine the strength characteristics of limestone, sand-stone and shale rocks subjected to controlled stress conditions. This control tuns exercised by varying the liquid pressures within and around a plastic-encased rock specimen. The pressure in the pores of the rock was varied throughout the range from atmospheric to 15,000 psig; the external pressure was changed over the same range with various positive pressure differences between is and the intertnal pressure. The data show that the rock strength increased and the mode of failure changed as the pressuire. surrounding the rock became greater than the pressure in the pores of the rock. These observations and the resu1ts of microbit drilling experiments indicate that the increased rock strength under pressure may bc an important effect in reducing drilling rare, but that other factors are probably of even greater importance. INTRODUCTION A large part of the research conductcd to reducc thc cost of drilling is directed toward improving present drilling technology and dcveloping new drilling methods. In spite of the fact that drilling is essentiaIly the act of making rocks fail, many details of the mechanism of failure are not known. It seems probable, therefore, that continuing studies of the fundamentals of rock failure can lay a foundation for future improvements in drilling technology. One of the factors which affects rock failure is the stress applied to the rock. This effect has been known for many years.&apos;.&apos;.; As an example, stress studics have been published by engineers&apos; concerned with the strength characteristics of concrete in large dams. More recently, a number of investigators4-12 have explored the effects of stress on the strength of geologic formations and the geologic implications of their findings. During the last few years some research&apos;" on rock strengths has also been conductcd in an attempt to gain additional insight into the factors which affeet rock drillability. In detcrmining the strength characteristics of rocks under different stress conditions, investigators have conventionally used triaxial compression equipment. wherein a jacketed rock cylinder is uniformly loaded from all directions and then compressed longitudinally. The results of this work have demonstrated that the mode of failure (brittle or malleable) is dependent upon the loading pressure, and that the strength of the rock increases as the loading pressure increases. These results clearly manifest that the stress, which is determined by the loading pressure, affects rock strength, and this implies that rocks under stress should be stronger and hence harder to drill. During the drilling of a porous rock the stress conditions are determined not only by the pressure surrounding the portion of the rock undergoing failure (confining pressure) but also by the pressure of the interstitial fluids within the rock (pore pressure). The importancc of both these pressures on the drilling rate of rocks has already been demonstrated by a number of investigators. Murray and Cunningham" found in microbit drilling expcriments that at constant pore pressures the drilling ratc decreased as the hydrostatic pressure surrounding an unjacketed, impermeable rock increased. Later Eckel" found that for jacketed Iimestone specimens the differcnce between hydrostatic (wellbore) pressure and formation (pore) pressure had an important effect on drilling rate. These observations of the effect of pressure on drilling rate emphasize that for drilling studies triaxial compression tests should be conducted under conditions of confining and pore pressure which simulate conditions underground. In the past, triaxial tests have been made under conditions which do not reproduce those underground. In particular, most of the tests on porous materials have keen made at varying confining pressures but with atmospheric pore pressures. In only one group of tests&apos; was any data on the effect of pore pressurc reported, and these few data were on materials not representiltive of those encountered in drilling earth formations. The research described herein was initiated to deter-mine the importance of both internal pore pressure and confining pressure on failure characteristics of limestone. sandstone and shales. Triaxial loading equipment was used to obtain strength data at pressures up to 15,000 psig. An additional objective of this research was to apply these results to drilling rate studies by comparing them with the previously published drilling data of Murray and Cunningham" and of Eckel12. The work reported here is but one step in determining and evaluating the fundamental mechanisms which control drilling rate. Additional research is needed to clarify other aspects of the drilling process. The better

By William Bent

MORE than twelve years were spent by Wöhler at the instance of the Prussian Government in experimenting upon the resistance of iron and steel to repeated stresses. The results of his experiments are expressed in what is known as Wöhler&apos;s law, which is given in the following words in Du Bois&apos;s translation of Weyrauch :* "Rupture may be caused not only by a steady load which exceeds the carrying strength, but also by repeated applications of stresses, none of which are equal to the carrying strength. The differences of these stresses are measures of the disturbance of continuity, in so far as by their increase the minimum stress which is still necessary for rupture diminishes." A practical illustration of the meaning of the first portion of this law may be given thus : If 50,000 pounds once applied will just break a bar of iron or steel, a stress very much less than 50,000 pounds will break it if sufficiently often repeated. This is fully confirmed by the experiments of Fairbairn and Spangenberg, us well as by those of Wöhler; and, as is remarked by Weyrauch, it may be considered as a long-known result of common experience. It partially accounts for what Mr. Holley has called the "intrinsically ridiculous factor of safety of six." Another "long-known result of experience "-although this has not, as the writer believes, been investigated by scientific experimenters-is the fact that rupture may be caused by a succession of shocks or impacts, none of which alone would be sufficient to cause it. Wrought iron will crystallize by repeated blows in service and become weaker than cast iron. Iron axles, the piston-rods of steam-hammers, and other pieces of metal subject to continuously repeated shocks invariably break after a certain length of service. They have a " life" which is limited. Iron rods in bridges sometimes crystallize and break, although the rods in most of our iron bridges * Strength and Determination of Dimensions of Structures. By Dr. J. J. Weyrauch. Translated by Du Bois, New York, 1877.

Jan 1, 1880

By Rudolf K. Berkhard

Static soil investigations with more or less heavy loads and extensive borings do not always have efficient results; also, they are very expensive. The new geophysical method of dynamic tests described herein is simple and cheap and avoids several disadvantages of the routine investigation, thus forming a useful supplement to the older methods and even at times replacing various static tests. The fundamental principle of dynamic soil tests consists in the application of artificial vibration. The technique employed is essentially geophysical in nature and in some respects is akin to seismic studies. Artificial vibration may be excited by centrifugal forces resulting from eccentrically supported rotating masses. The reactions of soil and structures caused by these vibrations may be measured. Their dynamic constants, such as amplitudes, phase speeds, damping, reflection, and interference effects, can be investigated. This geophysical method has been used for several years with increasing success. The results of these tests, summarized at the end of the paper, indicate that this method opens a new field for the pkactical engineer in investigating soils (capacity and formation), foundations, dams and structures, and especially buildings that must withstand earthquakes. Methods Static Method.—The first and oldest tests to investigate the bearing capacity of the soil were carried out by static weights. The penetration of these weights, however, depends not only on the soil but also on the size and the form of their lower surface. The length of time the load acts is also important. To imitate actual field conditions, heavy weights and lengthy tests are required, both of which are expensive. Furthermore, the influence of static weights affects only the surface and does not penetrate into deeper strata, therefore substitutes and supplements for static tests have to include the time factor and consequently lead to dynamic investigations. Such dynamic investigations also affect

Jan 1, 1940

By Rudolf K. Berkhard

Static soil investigations with more or less heavy loads and extensive borings do not always have efficient results; also, they are very expensive. The new geophysical method of dynamic tests described herein is simple and cheap and avoids several disadvantages of the routine investigation, thus forming a useful supplement to the older methods and even at times replacing various static tests. The fundamental principle of dynamic soil tests consists in the application of artificial vibration. The technique employed is essentially geophysical in nature and in some respects is akin to seismic studies. Artificial vibration may be excited by centrifugal forces resulting from eccentrically supported rotating masses. The reactions of soil and structures caused by these vibrations may be measured. Their dynamic constants, such as amplitudes, phase speeds, damping, reflection, and interference effects, can be investigated. This geophysical method has been used for several years with increasing success. The results of these tests, summarized at the end of the paper, indicate that this method opens a new field for the pkactical engineer in investigating soils (capacity and formation), foundations, dams and structures, and especially buildings that must withstand earthquakes. Methods Static Method.—The first and oldest tests to investigate the bearing capacity of the soil were carried out by static weights. The penetration of these weights, however, depends not only on the soil but also on the size and the form of their lower surface. The length of time the load acts is also important. To imitate actual field conditions, heavy weights and lengthy tests are required, both of which are expensive. Furthermore, the influence of static weights affects only the surface and does not penetrate into deeper strata, therefore substitutes and supplements for static tests have to include the time factor and consequently lead to dynamic investigations. Such dynamic investigations also affect

Jan 1, 1940

By George W. Bain

Some problems concomitant with commercial exploitalion of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service department wants defects rectified and the cause determined to avoid recurrence The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character. Geological Problems The geological problems deal almost exclusively with the size of blocks. Size across the deposit is limited by thickness of individual beds. and along the strike by the space between crosscutting joints. Frequently the vertical depth of a block is reduced by exfoliation shells arising from spontaneous expansion. All these factors require consideration in developing a deposit to fill an order. Thickening of Marble Beds The limestone beds that became the marble deposits of the northern Appalachians and of the Yule locality in Colorado were seldom homo-

Jan 1, 1941