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By Y. Astafyev

In applying computers at the enterprises it is necessary to develop an open-pit model which completely corresponds in its structure, properties and characteristics to real open-pit mining. This model is used for controlling open-pit operations which ultimately define the system controlling ore reserves. The preparation and reserving of the latter are highly expensive and labour-consuming, therefore the investigations are aimed at developing the ore reserve control system which is capable to provide open- pits with the necessary ore reserves on the basis of equipment relibility characteristics, and thus helps to solve the ore reserves problem which is to define their optimum dimensions under conditions of stochasticity of production processes. In accordance with the tasks of the investigation it may be conventionally divided into three parts. The aim of the first part is to develop a structural open-pit system model consisting of a set of elements which are represented here by drill-rigs, shovels, trucks, unit trains, plant receiving bins and dumps (Fig. 1). The combination of similar elements makes up technological components the sequence of which forms simple systems. The latter, in their turn, grouping according to the type of mined rocks and inter- acting in parallel, form the "Stripping" and “Mining” subsystems. In addition to this, there is the "Ore Reserves" subsystem which serves as a "store" and includes opened-up, prepared and ready for extraction ore reserves.

Jan 1, 1977

By LeRoy Scharon, P. Uhley

TEST gravity surveys were made in the Washington County barite district of Missouri on properly owned by the Baroid Sales Division of the National Lead Co. This property is located just northeast of Richwoods in the northeastern corner of Washington County, Fig. 1. The area to which the surveys were confined comprised approximately 5000 acres, of which some 525 acres were surveyed gravitationally. Gravity observations were made at 2600 points within the area, observations being confined to relatively clear and gently sloping ground. Part of the area was heavily wooded, and the terrain too rugged for either the occurrence of a commercial barite deposit or a feasible gravity survey. The relief along the central drainage, Ditch Creek, was about 140 ft, the maximum difference in elevation being 400 ft in a distance of 3½ miles. The purpose of the test gravity survey was to determine whether the gravity method of geophysical prospecting might be applied in the exploration for barite deposits in the Washington County barite district, since a satisfactory systematic procedure had not been devised to explore and ultimately determine barite ore reserves with desired accuracy. No previous geophysical work with respect to barite is known to have been done in this area. Stratigraphy: The formations over which the barite deposits occur' are Paleozoic in age, representing rocks involving sandstones and dolomites unconformably underlain by pre-Cambrain granites and rhyolite porphyries. The areas covered by the granite survey were directly underlain by almost

Jan 1, 1955

By E. I. Larsen, A. S. Doty, F. R. Hensel

The alloy under discussion is a Pig. I shows results of heat-treating tests nickel-silicon bronze and is one of many on two typical nickel-silicon bronze castings age-hardening or precipitation-hardening of the type on which the observations were copper-base alloys. The hardening constituent is a nickel-silicon compound.l The quenching temperature necessary to produce hardening by a subsequent aging treatment is a function of the composition and extends from about 700°C. to 950°C.; the aging temperature range extends from 4000 to 600°C. The work carried out by the authors of this paper was confined to cast alloys having compositions within the ranges of: 1.5 to 3.00 per cent Ni; 0.4 to 0.75 per cent Sj: balance. comer. made. A quenching temperature of 750°C. produces almost as high a hardness on subsequent aging as do quenching temperatures of 850' and 900°C. Several foundries have spent years of active and intelligent effort in trying to control the casting and heat-treating variables of nickel-silicon bronzes and finally gave up the attempts because of the inconsistencies of results.2 This undesirable characteristic was not manifest in the ultimate hardness or conductivity but primarily in tensile strength and ductility, as shown in Table I. The variation in tensile properties was often much greater than that existing on the alloys

Jan 1, 1941

By James A. Roberson

THE mechanical behavior of molybdenum has become a matter of considerable interest in recent years because it has a reasonably high strength at high temperatures. Various aspects of its fatigue behavior have been investigated previously,1-3 and the results can be summarized as follows. Recrys-tallized molybdenum exhibits a fatigue limit which decreases continuously with increasing temperature. The ratio of fatigue-limit stress to ultimate tensile stress is high (0.6 to 0.8) and reasonably constant. The present work was undertaken to determine the effect of variations in environment on the fatigue of molybdenum stressed in fully reversed axial tension compression. In order to provide a basis to which these data could be compared, a complementary series of fatigue tests were made in vacuum. All of the specimens used were made from one mill lot of unalloyed molybdenum which had been vacuum-arc melted, worked down to 1-in.-diam bar, re-crystallized, then warm-worked to 5/8 in. diam. The interstitial content by weight was as follows: C—0.022 pet, 02-0.0026 pet, Hz-0.0001 pet, and N20.0002 pct. The average grain diameter in the transverse direction was about 0.035 mm, and the average grain length was about 0.15 mm. Typical tensile-test data are shown in Table I. None of the specimens tested exhibited an upper yield point.

Jan 1, 1965

By E. Gybbon Spilsbury

In the course of the persistent and rapid advance of our country towards the goal she has set for herself, of commercial and manufacturing supremacy, there stand out certain periods or cycles of prosperity or depression, succeeding one another with a comparative regularity as to their ultimate trend, but of varying lengths and intensities. I might compare this course to that of a railroad between two points at different levels, with intervening mountain ranges and valleys, the up-grades climbing towards the final upper terminal of prosperity, while the down-grades retard the ascent, and tend to return to the valleys below. Just at the present time we are evidently at the bottom of one of these valleys, and, before starting to climb the next divide, it may be prudent for us to look into the condition of our rolling-stock, and especially into that of our brakes, and see what the experience of our downward journey has taught us, and whether we are properly equipped for the new upward advance which now lies before us. Probably no previous period of the same duration has produced in all branches of mining and metallurgy improvements SO many and so various as have the last ten or twelve years. Not that they have brought forth any such startling and revo-

Jan 1, 1898

By A. S. Doty, E. I. Larsen, F. R. Hensel

The alloy under discussion is a Pig. I shows results of heat-treating tests nickel-silicon bronze and is one of many on two typical nickel-silicon bronze castings age-hardening or precipitation-hardening of the type on which the observations were copper-base alloys. The hardening constituent is a nickel-silicon compound.l The quenching temperature necessary to produce hardening by a subsequent aging treatment is a function of the composition and extends from about 700°C. to 950°C.; the aging temperature range extends from 4000 to 600°C. The work carried out by the authors of this paper was confined to cast alloys having compositions within the ranges of: 1.5 to 3.00 per cent Ni; 0.4 to 0.75 per cent Sj: balance. comer. made. A quenching temperature of 750°C. produces almost as high a hardness on subsequent aging as do quenching temperatures of 850' and 900°C. Several foundries have spent years of active and intelligent effort in trying to control the casting and heat-treating variables of nickel-silicon bronzes and finally gave up the attempts because of the inconsistencies of results.2 This undesirable characteristic was not manifest in the ultimate hardness or conductivity but primarily in tensile strength and ductility, as shown in Table I. The variation in tensile properties was often much greater than that existing on the alloys

Jan 1, 1941

By Donald E. Crowell

In the fall of 1969, ASARCO and Newmont Mining Co. began the design of the 700tpd concentrator at their Black Cloud shaft located near Leadville, Colo. The concentractor would treat by flotation a Pb-Zn-Ag ore containing minor gold values. Flowsheet design was based on laboratory test work performed at the Minerals Research Testing Laboratory of ASARCO. Since the concentrator is located at an elevation of 11,000 ft, cold weather was a major factor in design considerations. The original capacity was designed as 700 tpd but for various reasons an ultimate capacity of 1,000 tpd was desired. This necessitated special consideration in the design of several areas, particularly the grinding circuit. The grinding circuit chosen was a single 9 X 12 ball mill operating in closed circuit with one 20-in. cyclone. The ball mill will operate at low speed and as an overflow type originally. The mill can be speeded up and converted to grate type for handling the larger tonnage when required. Thickeners and filters were oversized and space was left for additional flotation cells in order to handle the increased tonnage in these areas. Pumps were sized so that they could handle the increased tonnage by increasing their speed. Construction began in May 1970; the Black Cloud concentrator went on-stream in April 1791.

Jan 1, 1974

By Edward Thomas

THE late George S. Rice was active in the investigation of bumps, particularly in the last ten years of his career as chief mining engineer of the U. S. Bureau of Mines. Since most of his investigation was carried out in Great Britain, continental Europe, and-to a lesser extent-Canada, his thinking on prevention was influenced considerably by the experience of those countries. It is not surprising, therefore, that when he was called upon a few years before his retirement to investigate bumps in the U. S. and suggest ways to prevent them, he turned to longwall mining. A longwall method had been most successful in combating the bump hazard in mining coal under deep cover, especially in Great Britain, but the prevailing method there at the time was advancing longwall mining, which he knew was uneconomical under U. S. mining conditions. For this reason he proposed a modified retreating longwall system that he believed included the best features of the advancing method. As brought out by Rice,1 if the cover is 2000 ft and 50 pct of the coal is extracted, the static load on the remaining pillars will be about 4000 psi, which exceeds the ultimate crushing strength2 in most instances. If the pillar coal is overloaded before a pillar line is established, then the abutment zone preceding a line of extraction is no place to split pillars or extract them by any method other than an open-end system. Rice therefore advocated open-end mining, preferably by longwall, but he was willing to compromise with long-face mining if the longwall method was not acceptable.

Jan 8, 1958

By E. M. Wise

IT is known qualitatively that the recrystallization behavior of platinum is dependent upon the amount and particularly the nature of impurities present, the amount of prior cold-work and the annealing time and temperature, but published data are limited. A study of the effects of cold-work and annealing temperature on the hardness of a sample of very pure platinum was undertaken to supply part of this information. CONCLUSIONS 1. The platinum used in the experiments had a probable platinum content of 99.99+ per cent, and had the following mechanical properties in the completely softened condition: Vickers hardness number, 39.4; ultimate tensile strength, 19,340 lb. per sq. in.; proportional limit, very low; elongation, 37.5 per cent in 2 inches. 2. The effect of cold-rolling on the hardness is shown in Fig. 1. The hardness increases rapidly up to 10 to 15 per cent reduction and more slowly up to about 75 per cent reduction, beyond which it increases more rapidly. 3. The recrystallization temperatures for a 15-min. anneal, after cold-rolling 19, 39.5, 50.8, 66, 80.5 and 89.5 per cent reduction in thickness, are approximately 765°, 700°, 635°, 600°, 545° and 425°C., respectively. 4. The recrystallized grain size of this platinum is a function of the percentage of cold reduction, being larger the lower the percentage of cold-work. 5. Little or no grain growth resulted from subjecting recrystallized samples to higher temperatures or annealing for longer times.

Jan 1, 1940

By M. L. Fuller

OWING to the nature of the die-casting process, freshly cast alloys are undoubtedly not at equilibrium from the standpoint of alloy phase relationships. After casting, therefore, they tend to undergo phase changes, with the ultimate effect of reaching a state of equilibrium at the aging temperature, beyond which no further change takes place. This phase alteration undoubtedly is one of the primary causes of the changes in dimensions and physical properties that zinc-alloy die castings undergo during aging. It is planned to report on this problem in a series of papers of which this is the first. The writers have made a study of commercial zinc die-casting alloys over a period of several years, utilizing the X-ray diffraction technic of determining the phase composition changes in the alloys. Up to the present, two principal phase changes have been observed which are capable of causing dimensional changes: (1) the segregation of secondary constituents from the zinc-base solid solution and (2) the beta aluminum-zinc decomposition. The latter is the subject of the present paper and studies on the former will be reported upon at a future time.

Jan 1, 1934

By R. U. Jackson

FACED with rising costs, the mining industry is looking to new methods and equipment to supply the relief necessary for profitable operation. Conveyor transportation is rapidly taking a superior position to motor tramming in underground mines because of lower installation, maintenance, and operating costs. Haulage is always a critical problem in underground mining. The ease of operation and flexibility of a haulage system can have an important effect on ultimate mining cost. With the average tenor of ores on the downgrade, larger tonnages are required for the same metal recovery. This selection of a tramming system can be the key to a successful, paying plant. Because this shift is being made at an ever advancing rate, it may become necessary to tailor mining operations to the transportation system, rather than to select a haulage system fitting set mining methods. In choosing a haulage system, the relative costs of the various methods are of the greatest importance. Adapting the mine to one or the other type of tramming is not considered in the cost analysis, and very likely would make little difference, outside of location of drifts and raises. In the cost sheet, the problem presents recommendations for a conveyor installation and a comparison of equipment, installation, operation, maintenance, and power costs are made. Under the track haulage estimate, no allowance was made for dumping equipment at the shaft pocket or bin. If this equipment was added to the balance sheet, the additional

Jan 1, 1952

By Claude H. P. Lupis, John F. Elliott

QUITE generally an increase in the temperature tends to bring a system closer to ideality. It is reasonable as a first approximation to consider that the excess free energy will vary linearly with the temperature, or: where t may be defined as the "characteristic temperature" of the solution, or the temperature at which the system would become ideal if the results at T were linearly extrapolated. It must be emphasized that consideration of this hypothetical property is an appeal to intuition rather than an established physical concept. The order of magnitude of 7 for dilute solutions will depend on the nature of the solvent; a value of 3000° + 1000°K may be suggested for ordinary metallic solutions. In terms of free energy, entropy, and enthalpy first-order interaction coefficients, differentiation of the above equations with respect to composition leads to The concept of t offers a simple and plausible interpretation of Chipman and corrigan's3 recent empirical correlation between and a for a number of groups of ternary systems 1-24. The authors found that in each group the ratio was approximately constant. The corresponding calculated from their data by Eq. [4] are listed in Table I. The expected order of magnitude is obtained for 7. As noted by Darken,4 if a regular solution is not assumed, thus if utj) # 0, Chipman and Crrigan's results imply that, as T is increased, ultimately changes in sign, Fig. 1. Clearly Eq. [4] is valid only in a limited range of temperatures since at the temperature 7 at which the system becomes ideal not only should become null but also and . Thus, both and are functions of

Jan 1, 1967

By D. S. Cahn, D. W. Fuerstenau

Specimens of glass, plexiglass, and naturally occurring minerals were irradiated by a 15-joule ruby laser pulse to determine criteria for the fracture of nonmetallic solids by internal thermal stresses. Fracture did not occur in those specimens with either a very high or very low internal absorptance or with a high spectral reflectance. If significant amounts of melting and vaporization do not occur at the surface of irradiation, the specimen will fracture if a derived 11fracture stress" exceeds the ultimate tensile strength of the specimen. The purpose of this investigation was to determine criteria for the fracture of nonmetallic solids by internal thermal stresses which are caused by absorption of laser irradiation. A laser produces a very short pulse of light which has a high energy density distributed over a very narrow part of the visible spectrum. The laser system used in this investigation had an energy output of 15 0 joules at a wavelength of 6940 A. Fracture in a non-metallic solid, then, would be caused by the absorption of light energy by that solid, and subsequent conversion of this energy to heat or mechanical energy. Fracture is caused by internal stresses that result from rapidly imposed nonequilibrium thermal gradients. ANALYSIS OF CONDITIONS FOR FRACTURE BY LASER IRRADIATION For this analysis, the laser beam is assumed to be circular and centered on the junction of the major and minor axes of a rectangular specimen. The laser beam forms a cylinder of radius rb extending through the specimen width. The beam cylinder may be then thought of as a heated mass constrained by a surrounding unheated mass. The instantaneously heated cylinder will at-

Jan 1, 1968

Problems discussed and research opportunities identified during the workshop in the major areas of 1) flocculation, 2) flotation, 3) leaching and magnetic separation are summarized below. I. FLOCCULATION Problems Practical problems caused by unintentional flocculation or dispersion were described in the papers that dealt with iron ore processing, selective flocculation, fine coal processing, phosphate processing and potash processing. Ideas generated during the discussions ranged from the very practical suggestion that a conscious effort be made to transfer knowhow from the experienced clay industry to the metals and fuels-from-slimes industry. . . , to the familiar appeals for omnipotent theoretical developments. There was surprising recurrence of some questions in many contexts. Recurring questions are emphasized here rather than commodity-specific problems because their answers would serve a wider clientele usage. There is indeed no objection and some advantage to commodity-specific research, however, provided the proposed project is planned with full cognizance of transferable knowledge in other commodities, and of the possible usefulness of these results in other areas. Research Needs Most of the questions or research opportunities can be classified into three groups: a) water chemistry, b) dewatering, and c) flocculation theory. Other classifications are possible and probably useful. In each group there is a clear need for outwardly esoteric theoretical research a clear application of that work to current practical problems. Higher priority should be given to proposals for theoretical research which explicitly show the expected ultimate usefulness of the result. Likewise, proposals for applied research should demonstrate cognizance of applicable theory. Both of these types of projects could profit from collaboration among industrial, university and government personnel.

Jan 1, 1979

By J. L. Leland Myer

Some of the early experiments on the oxidation temperature of coal1 were undertaken in England in connection with a study of self-heating, or spontaneous combustion. It was then suspected that coals with low oxidation temperature were most likely to ignite by self-heating, but further experiments showed that many additional factors were involved. The oxidation temperature has importance as a physical property or characteristic of the coal. While only a few of the physical properties have been studied, they appear to have basic significance2 in the ultimate classification of all coals. When reliable data become available on the oxidation temperatures, as determined by standard and adequate methods, it should provide an additional basis for classification and comparative evaluation. Oxidation Temperature Defined For such a heterogeneous substance as coal is known to be, no simple definition of oxidation temperature can be established on a theoretical basis. If coals were homogeneous and of simpler structure, the accepted definition of "ignition temperature " as applied to simple gaseous mixtures might be adopted; that is, the temperature at which self-heating of the mixture sets in. But most coals self-heat slightly even at storage temperature, as evidenced by spontaneous combustion, and the definition for gases cannot be applied to coals with any exactness. By subjecting coals to suitable experimental conditions various oxidation characteristics can be obtained and examined for critical or significant stages of the oxidation process. Oxidation temperature itself must then be defined on the basis of such experimental results. Experimental Methods Attempts to determine critical points in the temperature functions of coal undergoing oxidation have resulted in the following experimental methods:

Jan 1, 1932

By Charles M. Cooley

THE continual improvements in. the two extremes of the drilling, unit, the drill and bit, have prompted critical examination of the drill steel, the weak link of this drilling unit. Obviously, little is to be gained from the betterment of the drill and bit if the drill steel which transmits the force needed for drilling from the machine to the bit cannot stand long hard service. The technology of the bit has advanced from the integral type to steel detachables, thence to the tungsten carbide insert. The carbide insert is the most significant advance in the bit, bringing it to the level of a machine tool with its performance records under constant surveillance. Long steel changes have become advantageous because the carbide bit will drill greater footages without replacement than did the steel bit: The development of the tungsten carbide insert opened new fields of endeavor in drilling with percussion drills here- to fore known, but limited by the steel bit. After the introduction of the tungsten carbide bit, drill manufacturers began promotion of long feed shells, lighter drifters and stopers, and easily handled auxiliary equipment. Ultimately this promotion of better equipment was intended to increase the bit-against-rock time of the drill shift. Advantages of the uninterrupted drilling period of a long steel change and faster setup time of lighter drill machines are lost when the shank fails in the machine, rod failure requires continual changing, or the bit breaks off in the hole. The quest for reduced

Jan 1, 1952

By J. K. Gustafson

Since prehistoric times, gold has been sought for its beauty and its unusual physical and chemical properties. Early in the dawn of civilization it became the ultimate unit of value, and for at least 6000 years it has been used to barter for other commodities. It has been prospected for, treasured and made into works of art and personal adornment. From time to time, it has even been the object of conquest. Because of its predominant role as a basis for money in recent centuries, economists have come to think of gold solely in these terms. Gold, however, has physical and chemical properties that make it one of the most useful metals in the modern world. It is the most ductile metal known. An ounce of it can be drawn into a continuous wire over 35 miles long. It is also so malleable that an ounce of it can be beaten into films 0.00001 in. thick covering 68 sq ft of surface. It has a density of 19.3 and is so heavy that 1 cu ft of it weighs more than half a ton. Gold is nonmagnetic and has a high electric conductivity that is only slightly less than that of silver and copper. Gold is so inert to all the chemicals found in nature that gold coins and jewelry buried beneath the soil or at the bottom of the sea for thousands of years appear to be as bright and perfect as when they were first immersed. Finally, gold has an extremely high reflectivity of both light and infrared rays.

Jan 1, 1971

By Klaus W. John

The geologic factor of greatest significance in rock mechanics and rock engineering is considered to be the geologic structure represented by joints, faults, and other planes of weakness. This geologic structure differentiates between the rock element and the rock system composed of these elements. Only during the last decade has the difference of the technological properties of element and system been recognized but this appears to be more in theory than in engineering practice. If rock mechanics is to achieve real significance in engineering practice, it has to provide methods of analysis which are realistic compromises between the best representation of the actual conditions and pragmatic engineering. The rock mechanics practitioner has to face the fact that many geological engineering and rock mechanics problems may be too complex to allow rigorous analysis but at the same time are deemed satisfactory for the construction of major structures. Ultimately, the geotechnical engineer or the engineering geologist has to express the effect of geologic factors in quantitative, even if approximate, terms and provide numerical data on strength and deformability of rock systems to be utilized in construction. Qualitative evaluations, quantitative descriptions of geologic features as such, and comparisons of specific test results are always of interest but may not suffice as basis for engineering decisions and designs. The present efforts of the rock mechanics group at the Karlsruhe University, Federal Republic of Germany, are based on a systematic combination of geomechanical models and numerical analyses based on the finite element approach. This group considers that at the present stage

Jan 1, 1970

By Valentine R. Garflas

The Mexican oil fields, during 1921, produced in round numbers 203,000,000 bbl. of which 176,000,000 bbl., or 86 per cent., were exported, the bulk of these exports, or about 73.3 per cent., going to the United States. The Mexican exports were divided by grades as follows: Light crude, 47.0 per cent.; heavy crude, 22.0 per cent.; tops, 3.5 per cent.; fuel oil from light crude, 24.0 per cent. The balance, or 31/2 per cent., includes the bunker fuel shipments and the coastwise trade in Mexico, which is not classified as to grades. The figures show that, in importance, the light-oil fields form about 75 per cent. of the Mcxican petroleum industry. The production of the Panuco field has followed the general history of the American fields, and its gradual decline, which is at present foreshadowed, may be estimated as well as its ultimate economic life. On the other hand, the behavior of the light-oil fields to the south is unlike any in the world so far discovered, and as a result we have concentrated overproductions followed by sudden droughts, both sometimes equally unexpected. The coming in of two or three gushers within adequate pipe-line facilities will flood the market with 100,000 bbl. or more a day, while the flooding by water of a particular pool will, in a few weeks, remove from the market one-half the total production of the Mexican fields.

Jan 1, 1923

By E. A. Wieselmann

This chapter presents a successful approach for achieving mine entry stability at the Cane Creek potash mine by the utilization of closure measurements. The mine is located in southeastern Utah (Fig. l). Mining is being conducted at depths in excess of 3000 ft under structurally complex geologic conditions typical of the Paradox salt basin. The closure measurement systems described have definite application for determining relative entry stability in other nonelastic rocks which are similar in behavior to potash. Similar types of closure measurements have been taken in various underground openings throughout the United States, Canada, arid Europe. Application of this closure data has previously met with varying degrees of success as a tool for design of under- ground openings in both elastic and nonelastic media.1-32 Closure measurements can be made easily and economically and they provide a practical solutiori to a practical problem. They are in-situ measurements which do not necessarily require laboratory correlation. Simple closure measurements have special significance in potash because "steady-state" ' closure rate, or creep, of the entries is measured. These closure rates can be utilized because nonelastic media such as potash will never achieve absolute stability around a mine entry. The potash will tend to creep or deform until all entries are closed and the overburden stress is redistributed over what was previously the mine area. The time for this ultimate effect to occur is dependent on a number of mining and geologic variables. Percentage of mine extraction, mining

Jan 1, 1972