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By B. Etkin, A. A. Haasz

The Infrasizer Mk III, developed at the University of Toronto, is capable of sizing particles of a few pm to hundreds of pm according to particle terminal velocity, which is a function of particle density, size and shape. The factors limiting the performance of the Infrasizer Mk III have been presented and analyzed. It has been established theoretically and experimentally that the device has excellent potential as a laboratory instrument. The principle is applicable to a continuous production classifier, a prototype of which is now under development.

Jan 1, 1980

By W. G. Moffatt, J. Wulff

BRAZED joints and their strength have for some time been of great practical as well as theoretical interest. A good summary of the previous work in this field may be found in the reports of the Armour Research Foundation. In spite of excessive scatter in test data, the fact that the strength of a brazed joint may exceed the ultimate strength of the brazing material itself by many times continues to be of interest and of value in engineering. That this is qualitatively due to plastic constraint of the brazing material by the faying surfaces of the base metal is not in dispute, yet no complete interpretation of the data exists. The purpose of the present work is not to provide such a new interpretation, but to report new experimental data which we hope may lead to a better understanding of the important variables concerned. The work of Bredz' definitely shows that the thinner a brazed joint is, the greater is its strength. Dianeter of a joint has seldom been taken into

Jan 1, 1958

By Wilson Blake

Rock deformation and failure taking place around underground openings is usually both accompanied and preceded by the phenomena of rock noise or microseismic activity. These small-scale releases of seismic and acoustic energy can be detected with special geophysical monitoring equipment. Use of this equipment allows one to look inside a rock mass to determine how an opening is behaving under the applied loading system. Microseismic equipment and monitoring techniques are briefly reviewed, and use of the microseismic method as an engineering tool in monitoring rock structure stability is illustrated by case histories. Examples cited range from evaluating roof stability using single-channel portable equipment, to rock burst monitoring using sophisticated computer controlled, multichannel monitoring systems.

Jan 1, 1983

By I. J. Jansen

Introduction The Surface Mining Control and Reclamation Act (PL 95-87) lays a new challenge before the surface mining industry by requiring that prime farmlands must be reclaimed to equivalent or higher levels of yield as nonmined prime farmland in the surrounding area (section 510d). We must now evaluate the situation and plan a mining and reclamation program that will achieve that objective. We must recognize that soil and land needs vary with intended land use and climatic setting. Also, various site conditions determine the potential for constructing a productive soil and the best procedures to accomplish that end. It is necessary to plan the land reconstruction program on a site by site basis in order to achieve the best results. Discussion The Prime Land Concept Terms like prime agricultural land have been used loosely for many years to refer to lands that are highly productive and well suited to agricultural use. The concept of what qualified as prime land varied considerably from one geographic area to another and from one person to another. The term prime farmland, as used in PL 95-87, has recently been defined quite

Jan 1, 1982

By Carville E. Sparks, Rollin Farmin

TRIAL installations of rock bolts, of the slit-rod- and-wedge type, were under way at several units of Day Mines, Inc., when Korean hostilities interrupted the already slow deliveries of steel bars to the Coeur d'Alene district. Factory-made bolts had not yet been put on the local market, so the program was halted for lack of supplies. Interest was revived by a visitor's description of wooden roof bolts. These were said to have been used briefly with apparent success in a coal mine, until apprehension voiced by the U. S. Bureau of Mines caused the practice to be suspended

Jan 9, 1953

Jan 1, 1879

By John R. M. Hill, Gerald Zink, Fun-Den Wang

The work described in this paper is sponsored by the Bureau of Mines for the purpose of accelerating the drilling of roof bolt holes and reducing the quantity of materials needed to fill each hole. A high-speed, small-hole drill has been fabricated and tested in the laboratory. High Priority has been given to safety, reliability, and compatibility with underground coal mining practice. The combination of drag bits and erosion jets is designed for high penetration rate, long wear life, and uniform hole size in a variety of sedimentary strata. A reliable high-pressure, high-speed swivel feeds water to the bit at about 4 L/min (1 gpm). The duplex hydraulic intensifier which drives the jets has a 40-kW (30-hp) capacity. Results of recent full-scale laboratory testing (Now. 1977) are presented.

Jan 12, 1979

By Arthur F. Colombo

The selective flocculation, desliming and flotation process developed by the U.S. Department of the Interior, Bureau of Mines, as part of its goal of maintaining an adequate supply of minerals to meet national economic and strategic needs is described. The application of the selective flocculation and cationic flotation process to three oxidized taconites from the western Mesabi Range in Minnesota is discussed. Data from the operation of a 408-kilogram-per-hour (900 lb/hr) pilot plant employing reclaimed water are summarized for the three types of oxidized taconites.

Jan 1, 1980

By B. H. G. Brady, C. M. St. John

Computational schemes for analysis of rock mass response to excavation, loading and other imposed changes, are employed pervasively in rock mechanics practice. Applications range in complexity from determination of stress and displacement distributions around openings, to prediction of the thermo-hydromechanical behaviour of a saturated fissured mass. While this may be taken as apparent sophistication in rock mechanics design activity, the indiscriminate use of computer methods may sometimes conceal inferior and inadequate engineering procedures. These inadequacies may not always be recognized, due to the general uncertainties which are inherent in rock mechanics investigations. This paper seeks to identify some common deficiencies in rock mechanics applications of computational schemes, and to propose ways of eliminating them. It also indicates some specific developments and applications of computational procedures, which are required to address persistent design problems in geomechanics practice.

Jan 1, 1982

By Frank C. Appleyard

Southwest of the town of Saltville in western Virginia is Plasterco, a small village that has been a source of gypsum production since 1815. Boasting the deepest underground gypsum mine in the world, Plasterco has been the site of mining operations by United States Gypsum Co. for more than half a century. And although its own ore supply is dwindling, Plasterco's position as a source of gypsum and gypsum products has been ensured by the recent opening of the nearby Locust Cove mine, one of U.S. Gypsum's newest projects. In the early days, production of gypsum at Plasterco was very small, the primary use of the mineral limited to that of "land plaster"-ground gypsum spread on the land to sweeten the soil. Initial mining was confined to surface outcrops containing gypsum, but the construction of a local plaster-producing calcining plant in the late 1800's coupled with al- most total depletion of the surface rock spurred the start-up of underground operations.

Jan 3, 1965

By H. M. Garrett

The basic cement making process is outlined relative to the fuel but chemically sensitive suspension preheater (SP) kiln which made its debut in the early 50s. The SP history is trailed through the process disasters of the late 50s; identification of chemical sensitivities in the 60s; and resurgence of the SP together with development of its stepchild process, the precalciner (PC) kiln, in the 70s. The current energy problem and related conversions to coal re-emphasize the process chemical sensitivity. Attention is focused on the basic problem of coal sulfur and ash variations and several solutions are presented.

Jan 1, 1981

By James J. Scott

A four-year program of research, development, and field testing has led to the refinement of a ground support system utilizing friction rock stabilizers, or "Split Sets," as they are known by their patented trade name. These rock anchors are a distinct departure from conventional anchors or fully grouted anchor systems, and allow control of ground movement internally in a manner that permits controlled deformation during the early phase of rock "relaxation" around a mine opening, increased anchorage per unit length during the secondary creep stage, and have the ability to strengthen and stabilize mine openings for extended periods of time.

Jan 7, 1977

By Robert C. Emmett, Donald A. Dahlstrom

FOR many years gravitational classification has been employed as a basic tool in beneficiation of minerals and coal. While improvements have been made to increase efficiency and fields of application, the basic flow pattern has remained relatively unchanged in most gravitational classifiers. Feed slurry is introduced into a settling pool wherein the coarser solids settle against either an upward or horizontal fluid current, or a combination of both, and are withdrawn in a concentrated underflow stream. The finer solids below the classification point possess too low a settling velocity and thus are primarily swept out through a weir overflow by the bulk of the fluid. Because of its simplicity, efficiency, and low power and maintenance costs, gravitational classification finds a wide acceptance for separations in the range of 20 to 325 mesh.

Jan 10, 1953

By R. A. Vik, C. B. Daellenbach, W. M. Mahan

The influence of reduction roasting and thermal shock on the grindability of a refractory low-grade Michigan iron ore was examined in bench-scale tests. The quantitative effects of the various treatments were evaluated at three sieve levels, 48, 100, and 400 mesh, with ball-mill-grindability and work-index parameters as response indicators. Data from the testing program were statistically analyzed to isolate the effects of cooling rate, roasting temperature, mesh level, and ore chemical condition. All four variables were found to have an important influence on the grindability of the treated ore. Ore chemical condition and roasting temperature had the most pronounced effects.

Jan 1, 1972

Discussion of the paper of WALTER 0. SNELLING, presented at the New York meeting, February, 1915, and printed in Bulletin No. 100, April, 1915, pp. 695 to 704. A. F. LUCAS, Washington, D. C.-Are the results of the experiments in practical operation? WALTER 0. SNELLING.-There have been no large-scale operations up to the present. The necessary conditions of temperature are easily arranged for, but the required condition of pressure, 800 lb., is not so simple a matter. The company has been working on this problem, and at the refinery in Oklahoma work of this kind is now being carried on. The way in which an ordinary still will leak at 50 lb., and more at 100 lb., leaves some doubt in the mind of many as to what can be clone at a continuous working pressure of 800 lb. On the other hand, the fact that they are making ammonia abroad by a method which employs higher pressures and temperatures than anything involved in this method, leads me to believe that the difficulties, which will undoubtedly arise when this is attempted on a commercial scale, can be overcome. WILLIAM N. BEST, New York, N. Y.-Is there any change in the calorific value of these oils?

Jan 5, 1915

By S. F. Emmons

[The following notes of observations made during a visit of a few days in the month of October, 1886, which was cut short by a sudden summons East, are offered, in spite of their incomplete and tentative character, in the hope that they may aid the members of the Institute, in their coming visit to this region, to a clearer understanding of the general geological conditions under which the ore-bodies occur.] The Butte mining region lies in a sort of a depression in the mountains which is drained by Silver Bow creek and its various tributaries. On the east it is bounded by high north and south ridges of granite, and on the west by lower ridges, also running north and south, which, as far as examined, were found to consist of rhyolite. High mountains also inclose the depression on the north and south, but at a greater distance than the more immediate bounding ridges on the east and west, the distance between which is hardly more than six miles.

Jan 1, 1888

By Stefan Boshkov, Malcolm T. Wane

The validity and accuracy of velocity measurements underground have been questioned repeatedly by those in mine ventilation work. The general disagreement on the subject is well illustrated in an AIME publication.' Although the presence of errors is readily admitted, their magnitudes are not known and often are described by practical operators merely as "great," "small," or "of no importance." The belief that errors are of academic interest only prevails because of a justifiable claim that actual volumes of air circulated are well in excess of those required by law and safe mining practices. Poor understanding of the source and nature of errors inherent in velocity measurements, coupled with questionable determination of cross-sectional area, result in faulty techniques for the purpose of expediting ventilation surveys and render doubtful the calculated volume. Often consistency of readings is confused with accuracy. A succession of check readings showing a maximum deviation of 5 pct in the measured value of velocity usually signifies nothing more than diligent application of technique in a stable ventilating current.

Nov 1, 1955

By W. D. Robertson, R. E. Reed-Hill

Slip on (11221 planes, which do not contain a close-packed direction, has been identified on crystals strained at —190°C. Evidence is also presented to show that (1071) pyramidal slip is a mode of deformation at 25ºC in a limited orientation range. PYRAMIDAL slip (l011) <1120> in magnesium at elevated temperatures has been established for some time.1-2 More recently, Burke and Hibbard reported this mode of deformation at 25ºC, but their results were questioned by Craig.&apos; Also, as far as the present authors know, slip in magnesium on pyramidal planes of the second order, Type II (1122)) has not previously been reported, although Gilman"," identified (1122) slip in another hexagonal metal

Jan 1, 1959

By C. R. Sundeen, C. W. Nicolson, J. D. McAuliffe, C. A. Campbell, P. D. Pearson

SHAFT SINKING SYMPOSIUM is a weighty term that could mean any number of things. However, in, this case it has been possible to utilize the transcription of the Annual Meeting Session of the same title and present it in much the same manner as the experts on the panel presented it to their audience Wednesday afternoon, February 18, 1953, at the Los Angeles Statler Hotel.

Jan 8, 1953

By Sydney H. Ball

MINERALS used primarily for personal adornment and decorative purposes are called precious stones. To be so prized, the stones must possess beauty of color, must not be too common, and must be hard enough to withstand ordinary wear. If transparent, they must have brilliancy and fire. Almost one hundred minerals have been used as precious stones, the noble gems being the diamond, emerald, ruby, and sapphire; pearls are frequently included by courtesy. These gem stones, however, are sometimes equaled in beauty by fine opals, aquamarines, ourmalines, spinels, chrysoberyls (both cat&apos;s-eye and alexandrite), and spodumenes (hiddenite and kunzite). The Greeks, Romans, and medieval Europeans grouped together gem stones according to color and degree of transparency, and only as the niceties of mineralogy began to be known, about a century ago, was it realized how many different minerals have the beauty required of gem stones. Pliny, for example, did not distinguish between rubies and the red varieties of spinel and garnet, although he conjectured that the beryl and emerald were one mineral. GENERAL SURVEY Early man treasured bright colored berries, attractive shells, white teeth of wild animals and brightly colored pebbles, and used them as personal ornaments. In the eastern hemisphere, the earliest stones used were members of the quartz family (100,000 to 75,000 B.C.); then obsidian and amber (50,000 to 25,000 B.C.); the jade minerals, fluorspar and jet (22,000 to 7000 B.C.); turquoise (7000 to 3400 B.C.); lapis lazuli and garnet (prior to 3500 B.C.) ; emerald (2000 to 1800 B.C.) ; sapphire, ruby and diamond (800 to 500 B.C.). Indeed, gem mining is the oldest form of mining, and before any metals were known primitive man recognized about 18 gems and decorative stones. At first he sought them in stream gravels and residual deposits but by 3400 B.C. the turquoise mines of the Sinai Peninsula were operated. This was the world&apos;s first important hard-rock mining enterprise. The Afghanistan lapis lazuli mines may

Jan 1, 1949