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By P. G. Winchell, R. J. Russell

The distribution of displacements of originally plane surfaces by an invariant-plane strain has been analyzed statistically. The displacement ratio (the magnitude of the displacement of a point originally a unit distance from the invariant plane) can be determined from an analysis either of tilts of random surfaces or of displacements of random scratches scribed on a randowz surface. In either case the mean of the tangent of the observed displacement angle is related to the displacement ratio, and the number of observations used in determining the mean is related to the confidence limits placed on the estimate of the displacement ratio. In estimating the effect of applied stress on a phase transformation whose displacement effects can be approximated as an invariant-plane strain,* the dis- placement ratio of the invariant-plane strain is of primary importance. Two procedures for determining such displacement ratios are considered here. In the tilt method the measured quantity is taken to be the angle through which a random polish plane is rotated by the invariant-plane strain. In the scratch method the measured quantity is taken to be the angle between the original direction of a random scratch in a random polish plane and the projection of its final direction in the polish plane. In order to obtain precise results from either of the methods, it is necessary to measure the relative volume change associated with the strain in a separate experiment. TILT METHOD A locally homogeneous invariant-plane strain, P, with displacement ratio, S, may be written&apos; where ; and < are unit vectors indicating the displacement direction and invariant-plane normal, respectively, as pictured in Fig. 1. Eq. [I] describes a uniaxial strain if the direction of displacement is parallel to the invariant-plane normal and a pure shear strain if the displacement direction is perpendicular to the invariant-plane normal. The original orientation of the random polish plane relative to the invariant plane and to the displacement direction is shown in Fig. 2. The angle 03 between < and u is related to the relative volume change, ?V/V, and to the displacement ratio by As a result of the invariant-plane strain, the polish plane is rotated about its intersection with the invariant plane by the angle y, which is always taken to be positive. The tangent of this angle in terms of the above parameters is

Jan 1, 1967

By Sidney H. Loram

As the work carried on by this Company, of which the writer has been in charge for the past two years, is somewhat unique, the following account of it may be of interest, and, on that account, is offered to the Institute without any attempt to claim this practice as the best. Mines. The mines supplying ore to the Company arc situated in three groups: the Guanaco field,.about 80 miles N.E. of the port of Taltal (lat. 25" S., long. 70" 30&apos; W. of Greenwich); the Sierra Overa, about 63 miles S.W. of Taltal; and Paranao, about 42 miles due N. of Taltal (12 miles N. of the small town of Paposo, once famous for its copper-output). Guanaco. This field lies in the center of an absolutely waterless mountainous desert, where not a sign of vegetation can be found for miles. The dryness is such that ivory and horn crack and open, while raw-hide must be used in place of leather, which -would become worthless in a very short time. Water is brought about 21 miles by piping from the Cordillera, but only in small quantities, and costs in the Guanaco $7 (= $1.78 gold) per cubic meter. All supplies and food are sent from the port of Taltal, which in turn draws its supplies from the south of Chile, the

Jan 1, 1900

By B. C. Allen

Liquid surface tensions of copper and 18 Group IV-A to VIII transition metals (Ti, Zr, Hf, V, Cb, Ta, Mo, W, Re, Ru, Rh, Pd, Os, Ir, Pt, Fe, Ni. Co) have been measured by the static pendant-drop and dynamic drop-weight methods on the same rod sample. The drops were formed by electron-bombardment heating in high vacuum. Application of necessary corrections enabled determination of surface tensions to k2 pct and agreement between methods to * 1 to 4 pct for all the metals studied. Evidence is presented that the liquid surface was well screened by metal vapor, suggesting negligible adsorption of gaseous impurities and that the surface tensions measured are characteristic of the metals involved. Correlations between liquid surface tension and melting point, molar volume, heat of vaporization, and atomic number are presented and discussed. Temperature coefficients of surface tension were calculated using Eötvös&apos; law. SURFACE tension and interface energies of metals are the result of incomplete atomic coordination resulting in a force perpendicular to the boundary, tending to minimize its area. These energies are important in many phases of metallurgy, including microstructure, sintering, joining, electronic emission, and lubrication, which in turn affect many physical and mechanical properties of metals. Liquid surface tension refers to the interface between the liquid and its own vapor or nonreactive atmosphere, and is considered a physical property of the liquid. Since equilibrium shapes can be readily obtained with liquids, the units of surface tension (force per length) and interface energy (energy per area) are interchangeable. Thermo-dynamically, the surface tension ?LV is given by the change in free energy F with surface area A at constant pressure P, temperature T, and composition N: for commercially important refractory metals, vanadium, columbium, tantalum,13,14 molybdenum,14 and tungsten,l5 and none for the rare platinum-group metals and rhenium. Measuring the surface tensions of transition metals is difficult because of their high reactivity and melting points. Of the many techniques available,16-18 the pendant-drop 19-21 and drop-weight methods17,22 are considered superior because they can be modified to eliminate persistent sources of contamination such as supports and capillaries necessary in the popular sessile drop, capillary rise, and maximum-bubble-pressure techniques. The necessary modification is to melt a drop on the tip of a vertical rod, which provides support through a solid of the same composition.13,15 The object of the work was to study the surface-tension behavior of copper and transition metals, having reasonably low vapor pressures. Liquid surface tension of each pure metal was systematically determined by using a combination of the static pendant-drop and dynamic drop-weight methods on the same rod. Liquid drops were formed by electron-bombardment heating in high vacuum. EXPERIMENTAL WORK As indicated in Table I, the metals studied were high purity and generally were obtained in rod form. The exceptions were titanium and zirconium, which were machined from crystal bars, and molybdenum (tot 11, osmium, and ruthenium, which were sintered and arc cast into rods. All the metals were ground or swaged to desired sizes between 1- and 7-mm diam, and centerless ground round and smooth to a finish better than 50 µ in., rms. Each rod was thoroughly cleaned with steel wool, degreased, acid etched, and dried. In a typical run, the rod was vertically clamped in a modified floating-zone electron-bombardment furnace designed after Calverley23 and Carlson.24 The specimen was outgassed and maintained positive at several kilovolts in a dynamic vacuum of 10-5 to 10-7 mm. The bottom end was enclosed by a tantalum pillbox and heated by electrons emitted from a hot concentric tungsten filament mounted on a movable bracket. The bombardment power was slowly raised until melting was observed. Power requirements ranged from 30 w for copper to 1300 w for 4-mm tungsten. The stabilized and out-gassed drop of near-maximum size was photographed at 4. 1X on panchromatic film at desired time inter-

Jan 1, 1963

By Henry S. Burnholz, Charles Y. Clayton, Francis B. Foley

This work was first undertaken for the U. S. Bureau of Mines, in 1919-20, by C. E. Julihn, superintendent of the station at Minneapolis. Learning of the interest, in this subject, of B. F. Tillson, of the New Jersey Zinc Co., Mr. Julihn and Mr. Foley went to Franklin, N. J., and discussed the matter with him. A conference in Chicago, in November, 1920, was attended by Dr. F. G. Cottrell, who was then Director of the Bureau of Mines, and representatives of the Bureau of Mines and of the hlissouri School of Mines and Metallurgy; at this time a cooperative plan of work was agreed upon by the Bureau of Mines and the Missouri School of Mines. In February, 1921, Mr. &apos;Tillson arranged a conference on this subject at the time of the annual meeting of the American Institute of Mining and Metallurgical Engineers, at which several technical papers were presented. In a paper, the Breakage and Heat Treatment of Hock Drill Stcels, he suggested a program that might be carried out in connection with the investigation of the problem. At this conference Mr. Manning, former Director of the Bureau of Mines, suggested the formation of an advisory committee to the Bureaus of Mines and of Standards for prosecution of this investigation. On Feb. 20, 1922, a secoud conference in New York, at the time of the annual meeting of the American Institute of mlining and Metallurgical Engineers, was attended by representatives of various technical societies. At this meeting, the report of Nov. 20, 1921, of the Chiefs of Divisions of Metallurgy of the Bureaus of Mines and of Standards, was discussed and it was agreed: 1. That the survey recommended by the two bureaus should be undertaken, which survey would have for its object the ascertaining of the present status of the practice of the heat treatment of drill steels, the extent to which the breakage occurs, etc.; and 2. That a report should be presented, of the findings of those who made the survey, to the Advisory Board to the Bureaus of Mines and of Standards. The Bureau of Standards assigned $4000 to the prosecution 01 a three-months&apos; survey, which was carried out in April, May, and June, 1922, of about sixty mines

Jan 1, 1923

By Charles Y. Clayton, Henry S. Burnholz, Francis B. Foley

This work was first undertaken for the U. S. Bureau of Mines, in 1919-20, by C. E. Julihn, superintendent of the station at Minneapolis. Learning of the interest, in this subject, of B. F. Tillson, of the New Jersey Zinc Co., Mr. Julihn and Mr. Foley went to Franklin, N. J., and discussed the matter with him. A conference in Chicago, in November, 1920, was attended by Dr. F. G. Cottrell, who was then Director of the Bureau of Mines, and representatives of the Bureau of Mines and of the hlissouri School of Mines and Metallurgy; at this time a cooperative plan of work was agreed upon by the Bureau of Mines and the Missouri School of Mines. In February, 1921, Mr. &apos;Tillson arranged a conference on this subject at the time of the annual meeting of the American Institute of Mining and Metallurgical Engineers, at which several technical papers were presented. In a paper, the Breakage and Heat Treatment of Hock Drill Stcels, he suggested a program that might be carried out in connection with the investigation of the problem. At this conference Mr. Manning, former Director of the Bureau of Mines, suggested the formation of an advisory committee to the Bureaus of Mines and of Standards for prosecution of this investigation. On Feb. 20, 1922, a secoud conference in New York, at the time of the annual meeting of the American Institute of mlining and Metallurgical Engineers, was attended by representatives of various technical societies. At this meeting, the report of Nov. 20, 1921, of the Chiefs of Divisions of Metallurgy of the Bureaus of Mines and of Standards, was discussed and it was agreed: 1. That the survey recommended by the two bureaus should be undertaken, which survey would have for its object the ascertaining of the present status of the practice of the heat treatment of drill steels, the extent to which the breakage occurs, etc.; and 2. That a report should be presented, of the findings of those who made the survey, to the Advisory Board to the Bureaus of Mines and of Standards. The Bureau of Standards assigned $4000 to the prosecution 01 a three-months&apos; survey, which was carried out in April, May, and June, 1922, of about sixty mines

Jan 1, 1923

By H. Landssberg

Subsidence caused by mining operations has been a matter of interest for the mining engineer for just 111 years, since the Belgian committee for study of subsidence in the city of Liege submitted its first report in 1825. This interest is fairly expressed in the enormous amount of literature that has since appeared on this subject. A bibliography, probably far from being complete, which preceded this study as a preliminary survey, comprises more than 800 titles. In spite of this fact the problem remains today as acute as it has ever been. The questions of as good a recovery as possible of the national resources, the safety of the operations, and the protection of private and public property are the important angles from which to look at the problem. The Problem To systematize an investigation regarding the effects of mine excavations two different aspects have to be dealt with: (1) the subsidence of the immediate roof above the workings, affecting the safety of the workers and the progress and efficiency of the operations; (2) the subsidence of the surface, which is also, from the point of time, the second event. The immense importance of surface subsidence as regards the impairment of surface structures of every kind in a mining area is self-evident. Both effects result from reactions of the strata overlying the excavations and they depend mainly on the extent of the excavations and the structure and geological condition of the strata. It has been stressed repeatedly, in this country principally by G. S. Ricel,† that for the understanding of the phenomenon of subsidence accurate surveys are the most urgent necessity. In the past, however, at least in the normal course of mining operations, these surveys have been very crude. The control of the roof in the mine is left to the observation of the behavior of the timber, warning cracks and sounds in roof and walls and to the general judgment and experience of the worker and his supervisors. In any given case this may or may not be sufficient to prevent fatalities but certainly it does not give any accurate information as to what is happening in roof and strata. On the surface, principally in endangered areas, surveys have been conducted more frequently, but also in this case usually weeks or even

Jan 1, 1936

By H. Landssberg

Subsidence caused by mining operations has been a matter of interest for the mining engineer for just 111 years, since the Belgian committee for study of subsidence in the city of Liege submitted its first report in 1825. This interest is fairly expressed in the enormous amount of literature that has since appeared on this subject. A bibliography, probably far from being complete, which preceded this study as a preliminary survey, comprises more than 800 titles. In spite of this fact the problem remains today as acute as it has ever been. The questions of as good a recovery as possible of the national resources, the safety of the operations, and the protection of private and public property are the important angles from which to look at the problem. The Problem To systematize an investigation regarding the effects of mine excavations two different aspects have to be dealt with: (1) the subsidence of the immediate roof above the workings, affecting the safety of the workers and the progress and efficiency of the operations; (2) the subsidence of the surface, which is also, from the point of time, the second event. The immense importance of surface subsidence as regards the impairment of surface structures of every kind in a mining area is self-evident. Both effects result from reactions of the strata overlying the excavations and they depend mainly on the extent of the excavations and the structure and geological condition of the strata. It has been stressed repeatedly, in this country principally by G. S. Ricel,† that for the understanding of the phenomenon of subsidence accurate surveys are the most urgent necessity. In the past, however, at least in the normal course of mining operations, these surveys have been very crude. The control of the roof in the mine is left to the observation of the behavior of the timber, warning cracks and sounds in roof and walls and to the general judgment and experience of the worker and his supervisors. In any given case this may or may not be sufficient to prevent fatalities but certainly it does not give any accurate information as to what is happening in roof and strata. On the surface, principally in endangered areas, surveys have been conducted more frequently, but also in this case usually weeks or even

Jan 1, 1936

COLORADO LOCAL SECTION Executive Committee CHARLES A. CHASE, Chairman S. A. IONIDES, Vice-Chairman C. LORIMER COLBURN, Secretary-Treasure, 614 Ideal Bldg., Denver, Colo. F. H. BOSTWICK, W. G. SWART. The annual meeting of the Colorado Local Section of the Institute was held at the Savoy Hotel, Denver, Jan. 15.- The Chairman, Frank Bulkley, presided and made a short address on the work of the Section. The following officers were elected:

Jan 3, 1915

By F. S. Sinnatt

This paper is the outcome of an extended investigation carried out in association with Dr. L. Slater. The inquiry had been continued in various directions and a number of results are quoted from an investigation recently completed by S. H. Jenkins. In projecting the work some five years ago, the author had in view a general attack on the problem of the spontaneous combustion of coal from an angle that had received little attention. The basic idea was to obtain a "slow motion study" of the active combustion of coal. This included an examination of the conditions prevailing in a mass of coal at the moment when active combustion ceases. It was thought that, if the factors governing the extinction of combustion in coal could be definitely established, it might offer an explanation of the manner in which the spontaneous combustion of coal originates. The inquiry arose from a detailed study of the properties of fusain that the author began in 1918. Fusain seemed to possess characteristics quite distinct from the coal with which it was associated, for if it were collected into a heap and one portion were heated by a small flame the combustion would traverse the whole mass. This combustion was not accompanied by smoke and passed slowly through the heap of material. Later, it was found that coals, including anthracites, would behave in a similar manner provided they were in the form of powder and that the particles were smaller than a certain size. The limiting size of particles is a definite characteristic of the coals investigated. In view of the fact that fusain exists with coal in a state that enables it to undergo this particular form of combustion, it must be assumed, sometimes, to play a definite part in the spontaneous combustion of coal in the goaf (waste). Tables 1 and 2 contain the analyses of samples of dust collected from a mine and from a dust collector. Some idea of the degree of fineness of the particles of fusain may be obtained from a study of the analyses of the dust from the dust collector; 80 per cent. of the dust would pass through a 200-mesh screen while the fusain was concentrated in the finest dust. The material that passed through a 90-mesh screen contained 54 per cent. of fusain while that between a 30- and a 90-mesh only con-

Jan 1, 1925

For the year ending February, 1923 PRESIDENT ARTHUR S. DWIGHT, District 0 NEW YORK, N. Y. PAST PRESIDENTS HERBERT HOOVER, District 4 WASHINGTON, D. C. EDWIN LUDLOW, District 0 NEW YORK, N. Y. FIRST VICE-PRESIDENT J. V. W. REYNDERS NEW YORK, N. Y. TREASURER CHARLES F. RAND NEW YORK, N. Y. SECRETARY FREDERICK F. SHARPLESS,. . . . . NEW YORK, N. Y. ASSISTANT SECRETARY PERCY E. BARBOUR NEW YORK, N. Y.

Jan 7, 1922

The most extensive oil shale development program ever undertaken in the United States has been that carried out by Colony Development Operation at Para- chute Creek in western Colorado. Field development goals were completed this spring, with the remainder of the $24 million joint venture program, primarily engineering, environmental and economic analysis, due to be finished by the end of 1972. Upon completion of the overall program, a decision concerning a commercial venture is expected. This program points up the increasing attention being focused on oil shale as a source of crude oil and energy for the U.S. at a time when the nation&apos;s supply of oil produced by conventional methods is far from adequate to meet the demand. The oil shale reserves of the Green River formation in Colorado, Utah and Wyoming are the largest hydrocarbon reservoir. The Piceance basin of Colorado, alone, contains some 80 billion bbl of shale oil recoverable by modern methods in reserves more than 30 ft thick and containing at least 30 gal of oil per ton. The U.S. Geological Survey has estimated that the total shale oil reserves of the Green River formation in the states of Colorado, Utah and Wyoming is more than 600 billion bbl of oil in deposits containing at least 25 gal per ton of shale oil.

Jan 10, 1972

By T. O. Breitling

Two significant problems In mill design are environmental control and cost reduction. Environmental control is predicted to be 5-10% of total plant costs in some parts of the U.S. Operating and design companies will assign this new "unit operation" a place in the early flow sheets. More advanced environmental control will add to both capital and operating costs, so mill designers will strive to reduce other costs.

Jan 1, 1970

By C. C. Harris

A critical literature review leads to a descriptive model of tumbling mill operation based upon energy partition concepts and the necessary requirements for particle fracture. As grinding proceeds into the ultra-fine region, conditions which are of little significance during normal operations gradually become controlling. These involve increasing resistance to fracture and an increasing tendency to aggregate as particles become smaller, and a growing fraction of the power input being consumed fruitlessly. The result is that fineness asymptotes to a maximum value as comminution proceeds indefinitely; thus where t is time, p and n are experimentally determined parameters, and Ø is a measure of fineness, which is presumed to be proportional to specific surface area, or proportional to the reciprocal of the size modulus (provided that the distribution modulus remains constant with time), or both. Ø, is the asymptotic value of Ø and is a measure of the grind limit. A method for its graphical determination is given. In a previous paper1 the physical and mathematical principles requisite to a study of the role of energy in comminution were reviewed. The micro-process of comminution — or the comminution event — can be investigated in terms of (a) the magnitude of the force-field localized around the individual particles which gives rise to the stresses generated in the particles, which in turn induces their fracture, and (b) the distribution of fragment sizes, should the event prove fruitful. The entire fragmentation operation can be considered to be the totality of its individual events, and in order to obtain a single independent variable of the process it is necessary to transform and sum the local stresses in terms of energy.1 This energy, however, will account for only a fraction of the energy input to the comminution process, the actual magnitude depending upon the kind of mill and several related factors. From the comminution viewpoint the primary function of a mill is that of stressing as many as possible of the individual particles of the charge to failure, with the maximum economy of energy expenditure. This is difficult indeed to achieve, for stressing a particle does not always break it, while the overwhelming portion of the energy input is involved with various internal mill processes which — almost incidentally — determine the magnitude, frequency, and manner in which the forces are applied to the particles. Essentially, these processes depend upon the mill dimensions, loading and speed, and they may be little affected whether fracture occurs or not. These processes must be delineated if a complete description of the role of energy in comminution is to be given; the energy account sheet1 (Fig. 1) in showing how the energy is partitioned for the requirements of the several functions it performs, provides a framework for the development of a model of the comminution process. Actual numerical values for the variables appearing in Fig. 1 will depend upon the mill, materials, and operating conditions. A possible general relationship between the variables will be suggested in this paper. Before proceeding further, a cautionary note must be issued. It was pointed out in an earlier paper&apos; that while energy input is not changed by increasing the power and decreasing the time in the same proportion, and vice versa, the results of the process in terms of particle fineness may be different. Thus, although energy is chosen as the independent variable of a comminution process, it is not absolutely independent, and care must be exercised to ensure that it is used within its range of valid application. Time has the necessary independence, and it will be used in place of energy where it is appropriate. The residence time in a mill is usually of the order of minutes. Under these conditions the particles are subjected to "... a relatively constant fracture producing environment".2 However, under the more rigorous conditions of greatly extended time, which pertain in ultra-fine grinding, indications are that the fracture producing environment no longer remains constant; this is the major subject of this paper. At this extreme limit the mill is probably taxed to its utmost, and at the same time the bulk material properties are becoming closer to ideal, while the physico chemical effects associated with surfaces, edges and corners are multiplying. (The edge length per unit volume is proportional to the square of the specific

Jan 1, 1968

By W. J. C. Venter

The use of activated carbon to improve the selectivity in the separation of base metal minerals from bulk concentrates played an important role in the development of separation techniques employed at Tsumeb Corp.&apos;s Tsumeb and Kombat mines. The Kombat mill fiowsheet and metallurgical data are given with particular reference made to the separation techniques using activated carbon. The mine&apos;s historical background, geology, and mining methods are described briefly.

Jan 1, 1974

By Pete Turcic, Wade E. Cooper

Many factors influence radon-222 influx and radon-daughter concentrations in underground uranium mines. A brief review of some of these factors is presented. Current radon-222 and radon-daughter control principles and practices for U.S. underground uranium mine atmospheres are discussed and a brief review of the applicability of other possible control methods such as rock sealants, radon-222 removal, and radon-daughter removal is given.

Jan 1, 1982

Brushy Creek mine is located near the center of a linear, 40 mile long belt of mineralization that extends south from St. Joe Minerals Corp.&apos;s Viburnum division. The mine area includes a segment of 5.4 miles long of this new mining region along which eight mines are presently operating. The geology of the area is relatively simple; the rock formations have not been disturbed through folding or extensive faulting.

Jan 7, 1973

(This list. includes only those who have entered military service within the past month, or whose entry has only recently become known to us; it also includes a few names of those whose titles or assignments have been changed within the month. A complete list will he found in the Year Book mailed with this Bulletin. Another Honor Roll is maintained in the reception room of the Institute.) ALDEN, HERBERT W., Lieutenant-Colonel, Ordnance Dept. ALDER, ALFRED; Engineers&apos; Reserve Corps. ALFORD, NEWELL G., Sergeant, Bureau of War Risk Insurance, Headquarters 84th Division. AMBLER, HARRY A., Lieutenant, 30th Infantry. ANDERSON, GEORGE K., JR., Sec. C, 1st Co.; 3d Officers&apos; Training Camp. AYER, -FRANK A., 1st Lieutenant, 43d Squadron, 3d Prov. Regiment, Aviation Camp.

Jan 3, 1918

By J. T. Ryan

SiR Humphry Davy&apos;s epoch-making treatise delivered on Nov. 9, 1815, before the Philosophical Society of London, first announced and demonstrated a flame safety lamp for detecting methane in mine air. Coal mining was known in England as early as 1180, more than 600 years before the advent of a safe lighting and gas-detecting appliance. Mining, no doubt, took place first in outcrop coal, and danger from gas did not become apparent until the workings became deeper and more extensive. Davy&apos;s lamp did much to increase the safety of miners, and a modified Davy lamp is still widely used for detecting the presence and approximate amount of combustible gas in mine air. No factor in coal mining has improved more rapidly during the past 15 years than safety measures. This progress came about not only as a result of the workmen&apos;s compensation laws now in force in most of the states of the Union, but because the research work of the U. S. Bureau of Mines had demonstrated some dangers incident to coal mining which were not considered to be serious matters prior to that time. Electric power and explosives are necessary but potential hazards in American coal mines. A general mechanization program is now under way, while the mines are growing deeper and more extensive. Consequently ventilation problems are more complex and a demand has been created for positive detecting devices for carbon monoxide as well as methane. Scientists and manufacturers, working hand in hand during the past 10 years, have invented and developed appliances which make systematic and effective examination of mine air possible. The object of this paper is to describe briefly the approved testing devices in use today, with the hope that they may lead to the saving of life. Two Groups of Dangerous Coal Mine Gases Dangerous coal mine gases may be placed in two groups: (I) those that are dangerous because of their explosive properties, and (2) those that are dangerous because of their toxic properties. Methane (CH4) is the important gas of the first group, and in so-called gaseous mines constantly exudes from the coal and rock; it may accumulate and form an explosive mixture. The explosive range of methane-air mixtures is well defined. The low limit is 5 per cent., the high limit 15 per cent., and the most explosive

Jan 1, 1927

By Phillip J. Maddex, Ole Skaarup

The quite diverse backgrounds of the authors and their mutual interest in reducing transportation costs has produced some interesting innovations. A few words about their background will tell the reason for this joint paper. . . One is a shipping executive with a background of shipowning, ship management, ship and cargo brokerage and chartering, and most facets of the steamship industry, both American and International. The other is a chemical engineer, thoroughly brought up in the American chemical and mineral industries, with several top managerial positions behind him. They began cooperating when U.S. Borax was contemplating a change in its export shipping program and studying the freight cost for shipping borax from The mines in the Californian desert to Europe, and eastern U. S. markets. In the 20 Mule Team days, borax was exported in 50 pound bags. In 1960 it was still shipped in 50 pound hags. Three main products were shipped: two were anhydrous, and all three were sensitive to impurities. The products were bagged at the plant in the Mohave Desert, and shipped about 150 miles by rail to the port in Los Angeles. From Los Angeles, shipment was made by Conference steamship lines at Conference rates. Anyone who has shipped bagged material to Europe by steamer knows that the tab is anywhere from $20 to $30 or more per ton.

Jan 1, 1970

By Richard J. Mainiero

INTRODUCTION Because of the hazards associated with flammable methane gas and coal dust, the shooting of mudcaps (adobes) or other unconfined explosive charges in underground bituminous coal mines is prohibited; all explosives must be fired in stemmed boreholes. However, there are situations where it would be advantageous from a safety standpoint to fire open shots. This would be in the areas of dislodging loose roof slabs, overhangs, rock-fall leveling, slab or boulder breaking, crib removal, and crevice shooting. The Bureau of Mines, U.S. Department of the Interior, has been developing an explosive charge that is non-incendive; that is, detonation of the charge will not ignite a flammable atmosphere. This explosive charge could be applied to the blasting conditions mentioned above. As of this writing, the explosive charge has not yet been certified as "permissible" for use in flammable atmospheres, but the necessary protocol is being finalized with the Mine Safety and Health Administration (MSHA), U.S. Department of Labor. The explosive charge described in this paper is merely a prototype sheathed rock-breaker charge (sheathed permissible explosive rock- breaker charge) demonstrating the feasibility of such a device. Industry may modify the design and composition of the charge in producing a commercial product so long as it is still safe, as defined by a testing schedule being developed by the Bureau of Mines and MSHA.

Jan 1, 1984