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By Philip McKenna

WHEN a new material becomes available to industry, it is useful to describe its properties as a guide to its most effective application; and when the new material may be produced in compositions having a series of graded properties, tests to select the combination of properties best adapted for various uses are helpful. The class of materials to be con-sidered in this paper are hard tool materials produced by processes of powder metallurgy from hard carbide constituents and various matrices of iron, nickel or cobalt, or alloys of them with tungsten, or tungsten and carbon. The customary use of carbide hard alloys is for metal-cutting tools; although wire-drawing dies, lathe centers, follow rests, grinding rests, burnishers, rolls, extrusion dies, measuring gauges and micrometers, and a number of other tools are also made with these hard alloys as the essen-tial wear-resisting parts. The properties and tests to be considered are those affecting these uses. In the development of tool, materials since the industrial revolution we have had carbon tool steels, Mushet steel, high-speed steels, stellites, and now cemented carbide compositions. For an understanding of the latter category of materials their properties and uses relative to the older and more familiar tool materials will be considered.

Jan 1, 1938

By Persifor Frazer

(Read at the Wilkes-Barre Meeting, May, 1877.) A CLASSIFICATION of natural objects is usually based either upon some fundamental and permanent attribute of the thing itself (as in the case of scientific classifications), or it embraces one or more generalizations convenient for use in ordinary life. Thus, it suffices for the statistician to, know that so many tons of fish are annually taken by our fishermen, and that they realize so many thousands of dollars, whereas to the student of natural history the anatomy, habits, and relationships of the animals are of chief interest, as settling their respective places in the scale of animate nature. Many different classifications of coals have been attempted, as one would naturally anticipate from the immense extent of the coal trade, and the different localities whence the supply was derived. The English divisions were prevalent up to the date of the publication of the last geological survey of the State, except so far as they were modified by local designations. Indeed, Rogers' classifications made very little alteration in the English nomenclature, as may be seen by comparing. the tables given below. To commence with the different kinds mentioned in Ure's Dictionary of Arts, Manufactures and Mines of 1845 " 1. Cubical Coal.-Black, shining, compact, moderately hard and easily frangible. Comes out in rectangular masses, of which the

Jan 1, 1878

By John W. Frey

[Minerals, generally of great geological age, are to a very large extent the material basis of what we know as modern civilization. In most of the so-called civilized world the use f minerals has become such a commonplace that it is easy to se sight of their importance. It was the use of minerals, obably more than anything else, that made it possible for e American people to expand from the Atlantic seaboard the Pacific in a little over one hundred years. As the 1 to use the natural wealth at hand constitutes a funda¬ental element in American life, there seems to be justification for the thought that American geography is largely mineral geography. Of all American environmental reactions, the most striking are those which have come about through the use of the metals and the power fuels. If we turn to the ancient industry of agriculture, we find very little that is unique in North America except those developments which have come about through the use of machinery and transportation, both of which are contingent upon the use of minerals. Practically every crop now grown n North America was grown in some part of Europe before merica was discovered. One can point out exceptions to statement but in general it is true. Analysis of the es of North American agriculture shows that the outstand¬ characteristics are: regional specialization (i.e., the Economic Geographer; Chief, Petroleum Section, Minerals Division, u of Foreign and Domestic Commerce.]

Jan 1, 1932

By Charles E. W. Bateson

The Mojave mining district is situated in a group of small hills centering around Soledad peak, in the Mojave desert, Kern county, Cal. These hills are about 4.5 miles SSW. of Mojave, a railroad town at the junction of the Santa Fé and Southern Pacific railroads. The town of Mojave is about 50 miles north of Los Angeles, to which it is connected both by telegraph and by rail. The distance on the Southern Pacific railroad is 102 miles, covered in 3 hr. and 45 min. by express train. A sketch-map of this region is shown in Fig. 1. The Mojave district is relatively isolated. The only other mining towns in this section of California are Randsburg and Johannesburg, in a district (containing the well-known Yellow Aster mine) at the northern end of a low range of hills, which begins about 20 miles NE. of Mojave, runs nearly N. for 35 miles, and varies in width between 3 and 6 miles. As will be seen later, the origin and formation of these hills are not the same as those of Soledad peak. II. Climate and VEgetation. The climate and vegetation of the Mojave district are typical of the arid regions of the southwestern United States. During the winter and spring there is some rainfall, and the tempera ture is generally from 60" to 70" F. in the day-time. The rainfall in the spring is often very considerable for short spaces of time, and cloud-bursts are not infrequent. In summer there is continual sunshine, with temperatures, as a rule, exceeding 100" F. in the day-time, while 115" F. in the shade of a house is not at all unusual; but at night the temperature falls considerably. No rain falls during the summer. The vegetation

Jan 1, 1907

Jan 1, 1879

By Robert F. Winkle

A detailed breakdown of mining costs, available to management on monthly and year-to-date bases, is mandatory for a controlled and efficient mining operation. A simple lump sum reporting of costs may indicate a profit or loss differential, but it does not allow an effective search for areas of possible cost reduction. Moreover, functional reporting is necessary on a timely basis so as to note trends of increasing costs In specific areas, which in turn allow possible preventive action by management. Definitive cost information helps to eliminate the tendency to overlook areas where cost Improvements can be made. A good cost control system points out salient operational weaknesses by: ( 1 ) allowing comparison of functional costs with similar costs of other mines and (2) pinpointing sudden increases over unit empirical costs within the organization. In general, the cost accounting structure is relatively uniform within large open pit mines, but surprisingly some systems will overlook the need for detailed breakout in comparatively high cost areas. In some other systems, unrelated costs will be lumped together, preventing careful analysis of cost accrual.

Jan 1, 1979

By H. M. Roberts

H. M. ROBERTS, Minneapolis, Minn. (communication to the Secretary*). -The rifling of drill cores is a frequent source of interest to men engaged in diamond drilling. Previous to the appearance of Dr. Crane's paper, there has been little record of connected observation or rigid speculation as applied to the cause of rifling. Replying to one of Dr. Crane's letters of inquiry, I ventured my opinion that the cause of rifling was a complex problem in physics, which I had not attempted to solve up to that time, except to ascribe it to the general cause of rotation and vibration of the rods. The question is worth attention not only as a matter of curious scientific interest but also for the reason that it stimulates thought on

Jan 10, 1916

By J. E. Kemp

1. Situation.—From Monterey in the State of Nuevo Leon, the Sierra Madre mountains stretch away to the southeast and present a steep front to the northeast. The Monterey and Mexican Gulf railway. which connects Monterey with Tampico. follows their general line with its road-bed a few miles out from the foothills. At a distance of 100 miles from Monterey it passes through the town of Linares. and from Linares one can see far away to the southeast the peaks of another group of mountains rising from the general plateau and forming a more eastern

Jan 1, 1906

By J. David Lowell

For his contributions to the field of mining geology, a striking example being his brilliant inte.rpretation of the complex geologic history of the San Manuel District (Pinal County, Arizona) which resulted in the discovery of the Kalamazoo orebody, and for his lecture, "Copper Resources in 1970." On a low desert ridge six miles south of Cairo lie the remains of the world's earliest known mining town, Maadi of predynastic Egypt. Copper artifacts, including ingots and an ax head which was spoiled in casting, indicate that copper ore was smelted in Maadi, and radiocarbon dating has placed the activity at least as early as 3300 B.C. This is the oldest documented date for the use of smelted copper, the first industrial metal used by man. Copper was mined and smelted almost as early in Asia Minor and on the island of Cyprus, but the greatest development of the budding copper industry was in Egypt, where specific historical records show that about 10,000 tons of copper metal were produced in the period from 1850-1580 B.C. Contrast this production of 35 tons per year with the present world production of about 7 million tpy. Evolution of the Copper Industry The copper ore mined by the ancients was high grade, and the copper produced was expensive. The copper industry began with narrow high-grade veins, but has evolved to the point where massive earth-moving equipment can be operated in huge, low-grade open pits. Indian pits dug before 3000 B.C. in the Lake Superior district were in ore which averaged 15% Cu. His- torical research done by Arthur Brant has shown that copper cost in the Middle East in 1840 B.C. in terms of 1970 labor dollars was about $25 per lb. The copper mined in northern Europe in 1540 in the time of Georgius Agricola averaged about 8% Cu, and the cost in 1970 labor dollars was about $10 per lb. Average ore grade had dropped to about 6% Cu in 1890, and the cost of copper in the U.S. in 1970 dollars was about 45¢ per lb. Butte, Mont., was a good example of the efficiently operated vein mines of this time. In 1906, Daniel Jackling made a dramatic entrance into the copper scene with the Bingham Canyon open-pit copper mine and proved that more profit was possible mining 2% porphyry copper ore on a

Jan 1, 1971

G. O. SMITH,* Washington, D. C.—This program is itself a demonstration of the widespread interest in the subject of more efficient development and operation of oil fields. The statements of fact already presented and the views expressed are sufficient evidence that the engineering and economic principles fundamental to the idea of unit operation are much more generally accepted than they were even one year ago. And real progress has been made in putting these principles to the test. No one realizes better than I that the fight against waste, whether physical or economic, must be waged in the front-line trenches: Washington at best is only an observation post. Yet viewed from this distance the advance made in the last few months has been notable and to a high degree encouraging. Five years ago the Federal Oil Conservation Board, in its first contacts with the industry, raised the question, "How can new pools be explored without exploitation until new production is warranted by the country's needs?" Three and one-half years ago the Board, in its first report to the President, paid largest attention, among what it listed as fundamental conservation measures, to "cooperative methods in sane development of new fields." A year ago, in its third report, the Board again endorsed as the essential factor in conserving the nation's reserves of oil, "full cooperation in unit control, whether by voluntary agreement or by state enforcement." The function of this federal agency has been purely fact-finding and educational. The Oil Conservation Board early declared that the major part of its task was to help the industry "formulate the broader by-laws in the sense of conservation." And now, after these five years of eventful history in the oil industry, may I size up the situation as I see it from the Washington point of view? First of all, and fundamental to a successful issue, I have observed in the industry a gradual acceptance of technical opinion as the guide to executive action; and this has at last led to some agreement as to what procedure offers most promise. Analyzed in more detail, this highly desirable progress has consisted in "self-restraint actuated by enlightened self-interest." We see emerging the general desire of oil producers for efficiency in operation, which means low costs and high recovery. As shown by facts presented at this meeting, competition in drilling is in direct opposition to efficiency in oil production, in that such competition increases costs and lowers recovery. The only route to conservation of this natural resource and also of the capital and labor involved in making it available is through unit control, which substitutes cooperative, well-planned action for competitive, unregulated activity, forced by the individualism of a small minority of landowners or perhaps by a single operator. Or, in terms of actual experience, development of an oil field and its subsequent operation under unit control means the substitution of majority rule for minority rule, yet the minority enjoys to the full the resulting economic benefits. So far as it affects the public interest, unit operation of oil properties deserves unqualified approval. It means more oil from the same area over a longer period

Jan 1, 1930

By F. W. Bremmer

The experiments described in this paper constitute the preliminary work of an investigation outlined to determine the combined effects of steam and temperature on the endurance properties of certain steels. Essentially of a fundamental nature, it was found necessary, in order to make the investigation comprehensive, to test materials treated to give a wide range of properties. The work reported deals chiefly with nickel steel with one series of tests including nitriding steel. Such a study involves numerous variables, and requires an endurance-testing machine of rather special design. Testing Machines The testing machines used were designed by C. E. Weaver;l they are a modification of the White-Souther and McAdam types. Each was driven directly by an individual 1/2-hp. 115-volt direct-current motor, running at a speed of 2200 r.p.m. Fig. 1 shows the assembly drawing and Fig. 2, a photograph of one of the machines. Specimen B is held by the rotating specimen holder A inside the steam box F, which is closed at the top by a tight-fitting, elliptical cover G. The load is applied to the specimen through the rod D and bearing C. E is an oil pipe leading fromthe lubrication system to the bearing C. The steam, which comes from the power house, is admitted through an inlet (not shown in Fig. 1) at the side of the box, the drain being at the bottom. Steam packings were placed around the rod D and the rotating shaft at H, from which the water was drained by means of a vacuum, which usually showed a gage reading of about 10 in. The temperature was measured by a mercury thermometer, and the pressure by a steam gage. Method of Applying Load After the motor has been started and the specimen as a consequence put in rotation, the load is applied by placing the foot pedal A (Fig. 2) in contact with electromagnet B, the winding of which is connected electrically in series with the motor. This operation releases the support under the weights that constitute the load. By this means the load

Jan 1, 1930

By Hjalmar W. Johnson

IT has long been accepted that blast-furnace practice varies to some degree with the coke used. While the qualities desirable in iron have been known for some time, the qualities in coke that produce such iron have not been established. There are no objective standards for blast-furnace coke, which is usually described in general terms, as good or bad. Many experienced operators believe that coke cannot be measured objectively except by using it in the furnace, noting the result, and labeling the coke according to furnace operations. This is admittedly unscientific, and besides is useless for the two main purposes for which a measure of coke quality is needed: (I) to produce the best possible coke from the coals and equipment on hand; (2) to test new coals and determine their value for blast-furnace coke. In seeking such an objective measure, much work has been done on tumbler tests, shatter tests, sizes of coke, porosity, specific gravity, reactivity or combustibility and other tests, but as yet very little has been published in which conclusive correlations have been established between such objective measures and furnace operation. In our study of the problem during the past 8 years we have developed no new measures of coke quality, but we have collected data that are presented here in the hope that they may assist in further work, so that at some future time there may be developed such positive measures. The purpose of this paper is to show that there are variations in coke and that such variations do influence the operation of blast furnaces. At the same time we must remember that there are variations in blast-furnace operation and it may be the blast furnace that is at fault. This correlation of coke properties with blast-furnace operation will be worked out in the following steps: I. Discussion of a period when a change in the coke resulted in an increase in efficiency on one furnace and a decrease in efficiency on another. 2. Adaptation of the inefficient furnace to the available coke so that normal efficiency was restored. 3. The use of radial distribution: a discussion of the effect of size of ore layer in adapting blast-furnace operation to the coke. 4. An example of a change in size of coke and the detrimental influence on the production of one furnace. 5. An example of a change in size of coke, together with manufacturing data, to show why it changed, the conclusion being that coke is a product with an optimum value. 6. Illustration of the fact that coke has different optimum values on two furnaces, with discussion on adaptation of operation so the optimum values will be the same. 7. Limitations of the use of screen tests as an objective measure of coke quality. 8. Importance of uniformity in coke. FUNCTIONS OF COKE AND QUALITIES REQUIRED TO PERFORM THESE FUNCTIONS Coke has three important functions in a blast furnace: (I) to furnish most of the

Jan 1, 1941

By P. W. Bridgman

During the war, the Navy undertook the construction, under my direction, of an experimental gun embodying features designed to lessen the cost and time of production. These experiments were initiated after representations as to their desirability had been offered by myself, by the Naval Consulting Board, and by the National Research Council. The first drawings were made in June, 1917, and the experiment was completed in November, 1918. For the sake of clearness it will pay to recapitulate briefly the fundamental idea of gun construction. It is well known that if a hollow cylinder is subjected to internal fluid pressure, the maximum stress occurs in the inside layers, the outer parts carrying much less than their due share of the stress. This inequality of stress is more pronounced the thicker the walls of the cylinder. If such a cylinder is pushed to the elastic limit, failure in elasticity will take place long before the outer lagers have reached the limit of their capacity. Economical use of the material would demand, however, that all parts of the cylinder reach the limits of their capacity simultaneously. This may be brought about, at least in cylinders of not too great thickness, by producing in the inner layers an initial compression, and in the outer layers an initial tension. The effect of internal pressure is at first to relieve the compression of the inside layers, while increasing the tension of the outside layers. If the initial stresses are properly distributed, all parts of the cylinder will reach their elastic limits simultaneously, thus giving a cylinder of maximum strength for its weight. In gun construction as hitherto practiced, this initial distribution of stress is produced either by winding the inner tube with wire, a common English practice, or by shrinking hoops over the inner tube, which has been the standard American practice. Either process is long and expensive, particularly with the larger guns, 12- or 14-in., which require

Jan 1, 1922

By M. L. Requa

This paper is abstracted from the report of the Appraisement Committee of the Independent Oil Producers' Agency, of which the writer was Chairman. The other members of the committee were M. V. McQuigg and R. S. Haseltine. To Thomas Cox, engineer in charge of the investigation, and to his efficient staff of assistants, is due the credit for the detail work necessary in carrying out the plan of the Committee. It treats only of the valuation of the lands, wells, and piping, without going into details of equipment and other features. It was recognized, early in the operation, that the value of oil lands was the value of oil to be extracted, and marketed, less the costs attendant thereon. Referring this back to the costs in cents per barrel, it became obvious that surface improvements, absolutely necessary in the production of oil, from wells then drilled; had no separate and independent value aside from the value of the land, but that any excess equipment, not necessary for the production of oil from present wells, such as drilling tools, well casing, etc., should be given a present condition value. In valuing the properties of the Independent Oil Producers' Agency, the Committee has considered the following facts: 1. That from each property there will ultimately be. produced a certain total quantity of oil. 2. That in the production of that oil a certain total quantity of money will be expended. 3. That a certain total amount of money will be received from the oil. 4. That the total net receipts will be the total gross receipts less the cost of development and production. 5. That the present value of the net receipts must be such an amount that when invested by a purchaser it will be returned with 8 per cent. interest additional during the life of the property.

Jan 2, 1918

By Richard E. Chism

SAN DIMAS, in the State of Durango, Mexico, on the frontier of the State of Sinaloa, is the centre of an extensive and rich mining region, which has been exploited for over a hundred years; and the patio process for working silver ores has there attained the highest perfection of which it is capable. Local modifications have been engrafted upon the underlying principles of the process, but, as a whole, the San Dimas practice so fully illustrates its typical capabilities, that I have undertaken to describe its workings in the hope of lightening, to some degree, the labors of my professional brethren who may have occasion to visit Mexico." As is tolerably well known, the patio process, like all other systems of free amalgamation, is not successful with ores containing more than a trace of zinc or lead, the presence of zincblende being especially obnoxious. Iron and copper in small quantities are not particularly disadvantageous. The process succeeds very well with all sulphide ores which do not contain much more than a trace of arsenic and antimony, provided the tailings are concentrated, although, of course, it is best adapted for free milling ores. For suitable silver ores that contain small amounts of free gold the process is still a good one, but where the gold is combined with sulphurets, a considerable and even an excessive loss is inevitable. Hitherto the Mexicans have submitted to this loss, but, since the introduction of American mills, they are gradually abandoning the patio process in favor of the other. The San Dimas ores have a gangue of quartz and feldspar. They are composed principally of silver sulphides, with some chloride and

Jan 1, 1883

By David Baker

Our large modern blast-furnaces, equipped with ore-bins, larries and mechanical means for putting stock into storage, withdrawing it therefrom, and charging it at the tunnel-head, are indeed wonderful in capacity; yet, it is admitted that, with some notable exceptions, they have disappointed us in economy—that is, in the items of low fuel-consumption, uniformity of product, freedom from slips, and reduced cost of repairs and relining. The manager who estimated the cost of pig-iron to be made in a modern plant, by taking the costs of the hand-filled furnace and deducting the amount to be saved by the mechanical appliances, has been surprised, in many cases, to find that unfavorable results in these items of economy have greatly reduced his expected gains. Is there any reason why the fuel-consumption should be greater for a modern furnace than for an older stack using the same mixture ? Certainly the equipment is much more complete, and the trouble, therefore, must lie in the management or in the character of that equipment. Everybody knows that intelligent and vigilant management is a prime requisite: that any neglect of a detail, though it may not be felt that day or week, will surely sooner or later make its appearance as an increased item of cost. But to hold the furnace-maaager responsible for the relatively poor work of the modern blast-furnace would be, I am convinced, a great injustice. For its management has received much more study and care than was given to the older types. Many furnace-managers have lost their health through worrying over this problem, and some hare lost their positions, being held responsible for results made inevitable, as I believe, by the equipment provided for them.

Jan 1, 1905

By P. W. Bridgman

During the war, the Navy undertook the construction, under my direction, of an experimental gun embodying features designed to lessen the cost and time of production. These experiments were initiated after representations as to their desirability had been offered by myself, by the Naval Consulting Board, and by the National Research Council. The first drawings were made in June, 1917, and the experiment was completed in November, 1918. For the sake of clearness it will pay to recapitulate briefly the fundamental idea of gun construction. It is well known that if a hollow cylinder is subjected to internal fluid pressure, the maximum stress occurs in the inside layers, the outer parts carrying much less than their due share of the stress. This inequality of stress is more pronounced the thicker the walls of the cylinder. If such a cylinder is pushed to the elastic limit, failure in elasticity will take place long before the outer lagers have reached the limit of their capacity. Economical use of the material would demand, however, that all parts of the cylinder reach the limits of their capacity simultaneously. This may be brought about, at least in cylinders of not too great thickness, by producing in the inner layers an initial compression, and in the outer layers an initial tension. The effect of internal pressure is at first to relieve the compression of the inside layers, while increasing the tension of the outside layers. If the initial stresses are properly distributed, all parts of the cylinder will reach their elastic limits simultaneously, thus giving a cylinder of maximum strength for its weight. In gun construction as hitherto practiced, this initial distribution of stress is produced either by winding the inner tube with wire, a common English practice, or by shrinking hoops over the inner tube, which has been the standard American practice. Either process is long and expensive, particularly with the larger guns, 12- or 14-in., which require

Jan 1, 1922

By J. Burns Read, Charles H. Fulton

A previous article1 by the authors contained a general description of the new roasting furnace herein described but it did not go into detail as to the metallurgical behavior or the results obtained. Believing that such information would be of great value, they have elaborated on the subject and have given many unpublished details. The furnace described applies the principle of roasting finely divided zinc-sulfide ores, now produced in large quantity by the flotation process, in gaseous suspension; that is, the ore particles are carried, in suspension, in a current of air and gaseous products of the roast. The relatively great fineness of flotation concentrate presents difficulties and problems of roasting in furnaces of the ordinary type; the fine ore is forwarded through the furnace in the form of a shallow bed and its very fineness leads to dense impervious bedding which prevents oxygen from reaching the interior of the bed, thus unduly lengthening the time of roasting and preventing the elimination of the last of the sulfur. The fineness of the concentrate, normally, should lead to a rapid and complete roast, for the speed of roasting is a function of the surface exposed to oxygen, which surface is greatest, per unit of weight, in very fine material. The difficulty in bed roasting is to get the oxygen to the particle. If the fine ore, during the roasting, could be freely suspended in oxidizing gases, full advantage could be taken of the great surface conferred by its fineness. This fundamental idea, of course, is not new, for the Stedtefelt furnace, familiar to the older metallurgists, is an example of it; but the manner in which this is accomplished may be new. The numerous efforts to roast in gaseous suspension show that the idea is attractive; in fact, an analysis would indicate that it is the most reason-

Jan 1, 1925

By Yap Chu-Phay

Although chronologically the Sb-Bi system was the first one studied by the writer, the theoretical basis of the equations used in this paper is fully discussed in the writer's paper on the iron-carbon system,' because he believed that many would be more interested in the iron-carbon alloys. He suggests, therefore, that the reader consult that paper to familiarize himself with the theoretical aspect of the thermodynamic treatment outlined herein. This paper is divided into two parts: Part 'I deals with the Sb-Bi system and Part II deals with the lead-rich side of the Sb-Pb system. Although the former system has not much practical interest now, it has great theoretical interest in that it is the one system that for a long time was thought to have (and under specific conditions still has) an anomalous solidus, which no amount of physical investigation could adequately account for. The latter system, of course, is particularly interesting in the lead-rich end. It will be shown that the thermodynamic method is capable of predicting reliably the equilibrium position of the solidus, and thus acts as a check on the experimentally derived solidus. PART I.—THE ANTIMONY-BISMUTII SYSTEM In connection with his studies in thermoelectric phenomena,-the writer was naturally interested in the system Sb-Bi. In consulting the International Critical Tables2 he found the constitutional diagram shown in Fig. 1 (not including Ôtani's solidus), essentially after Cook,³ who investigated the system carefully by thermal analysis. Note the isothermal crystallization of alloys varying in composition from about 48 per cent, (by weight) to pure Bi. This is anomalous, because, according to the phase rule, in a binary system when only two phases coexist, there is univariant equilibrium; that is, the composition changes with the tempera-

Jan 1, 1931

By J. Lyndon Rosenblad

This chapter describes the development of a rocklike model material for use in tests with a rock-blocks model to investigate the failure mechanism of a discontinuum. In order to provide reliable results, the model material must be characteristic of natural rock and obey the laws of similitude. Initially, the development of such a material does not appear to be a difficult problem. Only when one undertakes such a task does he realize how little is actually known, and that there is considerable work yet to be done. A material that simulates rock in all of its physical properties probably will never be developed. There is now and probably always will be room for improvement. Improvement is needed not only in the component materials but also in the technique of preparation. The material developed and subsequently described in this chapter simulates rock in general and a schistose gneiss rock in particular. The material possesses many rocklike physical properties not found in previously used model materials. One of the most significant improvements of this material is that there is an increase of Young's modulus with an increase in confining pressure as determined by triaxial compression tests. A change in the usual procedure of material preparation was used to develop this material and is also described. MODEL MATERIALS USED IN THE PAST Intact Materials Numerous materials have been used by investigators in models in the past to simulate a wide range of prototype materials. Some of the materials used include cork, plastic, concrete, plaster of Paris, portland

Jan 1, 1972