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[A Aall, Christian H., M49 B VP, Dir of Smelt & Refin, Am. Metal Climax Inc., 1270 Ave. of the Americas, N.Y. Aaroe, Stanley L., A54 B VP, The W. S. Tyler Co. of Can. Ltd., St. Catharines, Ontario, Canada Abalos, Toodulo Q., J57 A Prod Foreman, Lepanto Cons. Mng. Co., Mt. Province, Philippines Abbass, G., M55 P. O. Box 680, Hong Kong, China Abbitt, James M., A54 770 Sole Blvd., Bartow, Fla. Abbott, Raymond C., J59 3442 Greenwich Ave., Columbus 24, Ohio Abdullah, N. Y., J53 Dept. of Mines, Res. Div., P. O. Box 1016, Tiger Lane, Ipoh Perak, Malaya Abel, John F., Jr., J53- 100 Maple, Littleton, Colo. Abell, Leo M., M31 B Conc Supt, Phelps Dodge Corp., Morenci, Ariz. Abendroth, Harry E., A57 A Geol, Union Carbide India, 183 Brabourne Rd.. Calcutta. India]

Jan 1, 1961

By R. G. Hudson, L. Yang

In electrochemical separation of metals, it is necessary to control the potential applied between the electrodes so that only the desired electrode reactions can occur. A knowledge of the minimum potential needed for a given electrode reaction to take place continuously is therefore pertinent to the success of the process. In molten chloride systems at high temperatures, activation polarization is believed to be small,1,2 so the minimum potential needed for the electrolytic decomposition of a molten metal chloride MC1n (n = valence of the metal ion) is therefore essentially the equilibrium electrode potential E of the metal-chlorine galvanic cell in the solution. If the decomposition products are pure M and chlorine at a pressure of p atm, E*Eo-rt/nf in [i] Since EO (the standard electrode potential of MCln) is a constant at a given temperature and R (the gas constant), and F (the Faraday's constant) are all constants, the variation of E with the electrolytic bath conditions is largely determined by the effect of the latter on the activity of the metal chloride amcln (standard state = pure MC1,). Measurement of E and study of how amCin varies with temperature and concentration, the nature of the solvent, and that of the coexisting solutes are therefore pertinent in the selection of optimum operating conditions for the electrochemical separation of metals. Because of its low melting point, high decomposition potentials of its components, and the low solubility of heavier metals in it, the LiC1-KC1 eutectic melt is a useful solvent and has been used in the electrodeposition of Mo,3Ce,4 and u5 metals. Senderoff and Brenner3 measured the potentials of Zn/Zn++, Fe/Fe++, Cu/Cu+, Mo/Mo+++, and Ag/Ag+ against an Ag/AgCl (pure) reference electrode at 600°C and a concentration of 4.1 mole pct of each chloride and came to the conclusion that complex ion formation occurred in some of the melts. Laitinen and LiUe gave an electromotive force series at 450°C for a number of {Metal/Metal ions (unit activity)) electrodes in LiC1-KC1 eutectic melt, the {pt/pt++ (unit activity)) electrode being chosen as the reference. Walker and Danly7 studied the ther-modynamic properties of NiC12 in LiC1-KC1 eutectic melt over a wide range of temperatures and concentrations by measuring the electrode potential between a nickel electrode and a chlorine electrode in the melt. Since potential measurements made by using the chlorine reference electrode are of more direct significance both in the study of electrochemical separation and in the evaluation of the thermodynamic properties of the melt, it is therefore decided to measure the electrode potentials of cells of the type {M/MCin (mole fraction = N) in LiC1-KC1 eutectic melt/Cl2 over a range of N values and temperature for a number of metal chlorides. The results should indicate the order by which the various metals plate out on the cathode and how this order is affected by temperature and the concentration of the metal chloride in the solu-

Jan 1, 1960

Jan 1, 1881

Oct. 8 to 13, inclusive, 1917 COMMITTEES Committee on Arrangements H. A. BUEHLER, Chairman W. E. MCCOURT, Secretary C. J. ADAM L. L. HUTCHISON VICTOR RAKOWSKY J. A. CASELTON EUGENE MCAULIFFE J. D. ROBERTSON .F. W. DEWOLF P. N. MOORE ARTHUR THACHER E. F. GOLTRA MRS. P. N. MOORE H. A. WHEELER Committee on Ladies', Entertainment MRS. PHILIP N. MOORE, Chairman MRS.. W. E. MCCOURT, Vice-Chairman MRS. D. M. ARMISTEAD MRS. R. G. HALL MRS. A. A. BONSACK . MRS. J. W. HEGELER MRS. B. F. BUSH MRS. J. N. HOUSER MRS. G. 0. CARPENTER MRS. EUGENE MCAULIFFE MRS. F. V. DESLOGE MRS. RUDOLPH PORTER MRS. F. W. DEWOLF MRS. N. P. ROOD MRS. A. W. DICKINSON MRS. ARTHUR THACHER

Jan 12, 1917

By E. Hornbogen

The deformation mechanisms of a iron-phosphorus alloys were compared at 20oand —196°C. Alloying with phosphorus increases the resistance to slip, but has little effect on the resistance to twinning. The stress for onset of twinning is nearly independent of temperature, but there is an increasing tendency for cleavage along (112) twin boundaries with decreasing temperature and increasing phosphorus content. FIVE iron-phosphorus alloys and one high-purity iron (0.004 pct C, 0.004 pct N, 0.05 pct O) were vacuum melted and cast, then homogenized for 6 hr at 1100oC and water-quenched. Single crystals were cleaved from the coarse grains produced in this manner. The hardness was measured* on polished (100) surfaces of the crystals at 20" and -196°C. Laue back-reflection patterns indicated a deviation of not more than 3 deg from coincidence of the {100} plane with the surface. The deformation mechanisms were studied by relief effects on the polished surfaces. Yield points in compression (0.5 pct offset) were measured with polycrystalline material. At 20°C the addition of phosphorus to a iron leads to a change from slip to twinning as the main deformation mechanism, Figs. 1(a), (b). Between 2 and 4 at. pct P slip and twinning occur simultaneously. In alloys with more than 4 at. pct P twinning is the main deformation mechanism and slip was observed only in the neighborhood of twin intersections. All cracks at 20oC were on (100) planes, some initiated by twins.' From measurements made at-196oC, hardness and yield points of all the alloys were nearly constant and the same as the hardness of high phosphorus alloys that deformed by twinning at 20°C, Figs. 2 and 3. In the high-purity iron, plastic deformation at -196°C occurred by both slip and twinning, but deformation in the iron-phosphorus alloys appeared to be entirely by twinning. In the high phosphorus alloys a large number of cracks formed along the (112) twin boundaries and at intersections of twins, in addition to the (100) cleavage, Fig. 1(c). DISCUSSION In , iron, plastic deformation can occur either by slip or by twinning, depending upon composition,

Jan 1, 1961

By Philip Davidson, Wm. B. Price

The object of this paper is to present, a survey of some of the physical properties of sheet nickel silver when subjected to cold rolling and when annealed at temperatures extending from 350" C. throughout the coininercial annealing range.. A number of alloys were taken from stock and analyzed. Four of these, representing low nickel and high nickel both with and without lead, were chosen for the tests. The analyses were as follows: Alloy Copper, Lead. Iron. Nickel, ManGanese, Zinc, PeR Cent. Per Cent. Per Cent. Per Cent. Per Cent. PEr Cent. A................ 64.68 Trace 0.194 6.73 0.06 remainder B................ 65.82 1.27 0.227 6.17 0.06 remainder C................ 65.44 Trace 0.345 17.83 0.08 remainder D................ 65.60 1.08 0.238 17.77 0.06 remainder These alloys were lolled in accordance with regular mill practice to approximately No. 6 R. & 6. gage. The bars (which were then coiled) were annealed together in a mill muffle and afterwards pickled in a 10 per cent. sulfuric-acid solution and cold rolled in stages of approximately one number (B. & S.) at a time to No. 18 B. & S. gage. After each stage, suitable samples were set aside for physical tests. Additional samples were chosen for tests after the bars were rolled to Nos. 8, 10, 12, and 14 gage. These samples were annealed together in the mill muffle and, after pickling, were finished on 0.050-in. gage, yielding a series of specimens 2, 4, 6, and 8 numbers hard for the subsequent annealing tests. Tensile test pieces 9 by 1 in. (22.9 by 2.5 cm.) were cut from both lots and the central portion was milled to give a test section 2 1/2 in. long by 1/2 in. wide. A distance of 2 in. was marked off on the edge of each specimen with light punch marks. In the case of the annealed alloys, Erichsen test pieces 4 by 235 in. were also taken.

Jan 1, 1921

NEW MEMBERS. The following list comprises the names of those persons who became members during the month of June, 1913: Members. ANGERER, VICTOR, Vice-Prest. and Genl. Mgr., Wm. Wharton, Jr. & Co., Inc., 25th St. and Washington Ave., Philadelphia, Pa. BULLOCK, ALLYN, Min. Engr Hazleton, Pa. CUNNINGHAM, NOEL, Met. Engr., Hollinger Gold Mines, Ltd., Timmins, Ont., Canada. ESTABROOK, EDWARD L., Supt. of Colliery 436 Center St., Ashland, Pa. GATES, A. 0., Instructor Purdue Univ., La Fayette, Ind. LUDLUM, ALBERT C., Prest., New York Engrg. Co., 2 Rector St., New York, N. Y. MILLER, HERBERT F., Met. Engr P. 0. Box 142, Verona, Pa MORTON, ELMER T., Min. Engr Clifton, Ariz. MURFIT, RICHARD H.. Fdv. Asst Hess Steel Castings Co., Bridgeton, N. J. QUAYLE, THEODORE W., Chief Sampler, Metcalf Mines, Arizona Copper Co., Metcalf, Ariz.

Jan 7, 1913

By L. V. Wade

Abstract-US Bureau of Mines efforts under longwall research programs to develop the capability to predict support requirements for longwall/shortwall support systems are discussed. Ground control studies are being conducted in conjunction with several longwall/shortwall demonstration projects. Geologic, support performance, and strata behavior are being documented on these projects. A hypothesis is presented for the prediction of support requirements.

Jan 11, 1978

By Reed S. C. Rogers, Robin P. Gardner, Kuruvilla Verghese

The development and use of short-lived radioactive tracer methods for the onstream determination of residence time distributions in large-scale ball mills is described. Tests are reported on a pilot-plant ball mill with 0.43 m diameter and 0.86 m length and on an industrial mill with 1.83 m diameter and 2.74 m length. Tests with different tracer feed sizes indicate that the residence time distributions on both mills are independent of charge particle size. Similar tests are planned for a large ball mill of 4.57 m diameter and 9.30 m length. No safety problems were encountered in these tests and none are anticipated in tests of the larger mill.

Jan 1, 1981

By Henry S. Munroe

The earliest accounts we have of Japan represent the country as having great mineral wealth, especially of precious and useful metals. Marco Polo, the Venetian traveller, in the thirteenth century, writes of "Zipangu:" " They have gold in greatest abundance, its sources being inexhaustible. The king does not allow of its being exported. To this circumstance we are to attribute the extraordinary richness of the sovereign's palace. The entire roof is covered with a plating of gold.. .. The ceilings of the halls are of the same precious metal; many of the apartments have tables of pure gold of considerable thickness, and the windows also have golden ornaments." Marco Polo also gives an account of an unsuccessful Tartar expedition against Japan, prompted by the supposed great wealth of the country. Columbus also, as well as many other explorers, were attracted and encouraged by these prevalent reports of the wealth of the islands of Zipangu. Kaempfer, writing in 1727, speaks of the great mineral wealth of Japan, and especially of the abundance of gold, which, he says, is found in many provinces. The Portuguese and Dutch, while they had trading-posts in Japan, furnished tangible evidence of the truth of the early reports. Between 1550 and 1639 the Portuguese merchants sent home from Japan nearly three hundred million dollars' worth of bullion, most of which was gold. As the relative value of equal weights of gold and silver was then six to one, while in Europe, at the same time, it was nearly twelve to one, the exchange of silver bullion for gold was by no means an unimportant part of their Business. After the Portuguese, the Dutch continued the exportation of bullion, and the exchange of silver for gold, though with less profit, as the relative value of gold increased with the demand. Between 1649 and 1671 the Dutch traders sent home over two hundred million dollars in bullion, of which, however, nearly two-thirds was silver. In 1671 the Japanese government, alarmed at the rapid rate at which the precious metals were leaving the country, issued an edict forbidding the exportation of gold or silver, under heavy penalties, which had the immediate effect of stopping this trade. Besides bullion, copper formed at this time a most important article of export. According to Dr. Geerts,* who has examined the old

By AIME AIME

IN furtherance of the policy of acquainting those members of the Institute who live at a distance from New York with all the details of administration, the thirty delegates sent by the local sections and the technical divisions were invited to attend the meeting of the Directors on Tuesday evening as well as the Directors' dinner immediately preceding. Including the Directors and officers, new and old, the members of the Papers and Publications Committee and the section delegates, more than 70 sat down at the dinner table in the Engineers Club. The attendance at the business meeting that followed was not quite so large, doubtless for the reason that the ladies' fashion show, held in connection with the informal dance, offered attraction that eclipsed that of watching the wheels of Institute business go around.

Jan 1, 1930

By Herbert Kilburn Scott

The information in this paper was collected by the author during a five years' residence in the State of Minas Geraes. Outside the State itself, very little is known of the gold-field. Such accounts as have been published are antiquated and contained in publications mostly out of print. The increased attention now attracted to the natural resources of Brazil, and the probability that American capital will be, in the near future, largely invested there, will make an up-to-date account specially useful at this time. I. Historical and General. Soon after the Jesuits founded what is to-day the city of S?o Paulo, gold was discovered in the streams of the neighborhood; and this incited the natives, known as paulistas, to look for it farther afield. After many expeditions into the interior, gold was found in quantity in placer-deposits in the vicinity of Ouro Preto, in 1699, by a prospecting party headed by Antonio Dias. The name of Ouro Preto (black gold) was given because of the superficial dark coating of the gold, and the inhabitants of the district were known as mineiros (miners). Later on, the placers of Cuiaba, in the State of Matto Grosso, were discovered in 1718, and those of the State of Goyaz in 1724. All this territory was at the time a private colony, but on account of its increasing importance it was taken over by the Crown, and in 1739 a royal governor was appointed, with his nominal capital in S?o Paulo, though for a number of years the real capital was Ouro Preto. In 1711 Ouro Preto was raised to the rank of a city, with the name of Villa Rica de Ouro Preto (" rich city of black gold"); and in 1720, by reason of administrative difficulties, Minas Geraes was constituted a separate colony from S?o Paulo, with Villa Rica as its capital. The site of this city

Jan 1, 1903

By David B. Burrows, Francis R. Conley

INTRODUCTION A prerequisite to the evaluation and management of oil properties is accurate information derived from the analysis of core samples; but reliable data, such as porosity and permeability, can result only if all oil and water have been removed from the core samples analyzed. The most common method of core cleaning used to date has been Soxhlet extraction—a somewhat static technique, which depends upon the slow diffusion of hot solvent through the core sample. Soxhlet extraction performs satisfactorily only with highly permeable samples and at best requires long cleaning periods. The centrifuge method was developed in 1951 by Continental Oil Co. to overcome the inefficiencies inherent in the Soxhlet method. The new method is basically an operation in which hot solvents are caused to flow through the samples under the influence of centrifugal force. The centrifuge unit has proved so successful that samples which formerly required days for partial extraction can now be completely cleaned in approximately one hour. The original idea was conceived in 1950 by Elmer S. Messer, whose early experiments consisted of flowing solvent over sandstone samples suspended in a revolving basket and driven by a vertically mounted vacuum cleaner motor. Results were so outstanding that more permanent units were constructed. A modified model using this basic design was recently built by Core Laboratories, Inc., and is now used regularly in their operations. DESIGN Fig. 1 shows a photograph of the two extractors routinely used to clean small core plugs in the Production Research Div. of Continental Oil Co.'s Ponca City laboratories. For illustrative purposes, the basket from one of the units has been removed, and because both extrac- tors are of identical design only one is described in the following discussion. Each extractor unit consists of a centrifuge and a solvent still. The core basket of the centrifuge is made of mild cold rolled steel 7 1/2 in. in diameter and 1 1/8 in. deep. The basket holds 18 1-in. samples (cubical or cylindrical) and is attached directly to a cone fitted to the shaft of the motor. Both the outer rim and the hollow hub of the basket contain perforations for the passage of solvent and extract. The solvent is delivered to the perforations by means of a copper tube inserted into the hollow hub. The motor is a vertical tool post grinder motor; (115 v, 5.6 amp, 0-60 cycles, AC-DC, rated at 1/3 hp). It has a rated speed of 10,000 rpm under full load and 15,000 rpm with no load. Variation of speed is obtained by the use of a variable transformer. The solvent still was constructed from one end of a stainless steel oxygen bottle by inserting a heating element, sight glass, and piping as shown on the schematic diagram, Fig. 2. The heater used was a three-position, 1,000 w, 115-v, immersion type. Intermittent flow of solvent to the centrifuge is obtained by means of a siphon bottle inserted between the condenser and the centrifuge.

Jan 1, 1957

By Frederick Jr. Prime

THE first catalogue of Geological Reports of the United States was prepared by Prof. O. C. Marsh, and published in the American Journal of Science and Arts for 1867, vol. xliii, second series. Since then the list has more than doubled, and it was thought that the publication of a new catalogue, brought down to date, would be useful to many of the members of the Institute of Mining Engineers. The compiler will be most thankful to have any omissions or inaccuracies in the list sent to him, to be published as a supplement in the next volume of the Transactions. Especially to have the correct title, number of pages, plates, and maps of any volume on the list to which an * is prefixed, as he has been unable to personally consult such works. A preliminary list was issued last February, which has been almost doubled by the kindness of many friends. The writer desires more especially to express the obligations he is under to the following gentlemen The Chief of Engineers, U. S. A.; Principal Dawson, Mr. G. M. Dawson, Drs. B. J. Harrington and T. Sterry Hunt, of Montreal; Mr. H. Engelmann, of La Salle, Ill.; Dr. F. V. Hayden and Prof. J. W. Powell, U. S. Department of the Interior ; Prof. E. W. Hilgard, University of California; Prof. Henry Y. Hind, Windsor, N. S.; Prof. C. H. Hitchcock, of Dartmouth College; Mr. Henry A. Holmes, State Librarian, Albany; Maj. Jed. Hotchkiss, Staunton, Va. ; Prof. W. C. Kerr, Raleigh, N. C.; Dr. J. S. Newberry, of Columbia College ; Prof. W. H. Pettee, of the University of Michigan ; Dr. Samuel H. Scudder, Prof. N. S. Shaler, and Prof. J. D. Whitney, of Harvard College ; Mr. Sanderson Smith and Prof. J. J. Stevenson, of New York ; Mr. Addison Van Name, of Yale College, and Lieut. Geo. M. Wheeler, U. S. Engineers. PHILADELPHIA, 907 Walnut Street, October 1st, 1879.

Jan 1, 1879

By Henry Schwellenbach

LABOR shortages, rising wages, and changes in moisture and fines content of the ore necessitated a review of the flowsheet at Warren Foundry & Pipe Co's. Mt. Hope, N. J. Mines Div. This plant had been designed prior to World War II, and started operations in January 1945. When this operation was designed there was an oversupply of labor in the area, wages were at a reasonable level, the run-of-mine ore was low in moisture, and there was a limited amount of fines. These factors all favored use of hand picking for cleaning rougher lump concentrate. Since that time, many changes have occurred. The proximity of defense industries and large military installations, has created one of the most acute labor shortages in the country. This labor shortage together with present wage levels, and the increase in moisture and fines in the ore created several problems. The increase in moisture and fines may be attributed to changed mining methods, the extensive use of sprays, and the opening of new mining areas bringing an increase in ground water. [ ] Two problems were presented by the increase in moisture and fines. The first was that lump ore arrived at the open hearth in an unacceptable condition, due to the segregation enroute of the large amount of fines that had adhered to the lumps. The second problem was that high magnetite content fines coated the large lumps, making it difficult for pickers to distinguish middling by other than the relative weight. [ ]

Jan 1, 1952

By J. S. Kirkaldy, R. J. Brigham

AS part of a program to investigate the diffusive properties of dilute ternary austenites we have made a determination of the effect of chromium on the activity of carbon in ? iron. Samples of pure iron and Fe-Cr alloys were simultaneously equilibrated at 1000°C with atmospheres of controlled CO/CO2 ratio following the procedures of Darken and Gurry 1 and smith.' The 0.020 in. thick samples were analysed for carbon by microcombustion analyses3 to yield a set of isoacti-vity curves. The latter were converted to activity coefficient (standard state at infinite dilution) plots by combination with Smith's data2 for the activity of carbon in pure iron. Table I shows the compositions of the base alloys used while Fig. 1 shows the experimental results superimposed on a set of curves generated by the relation In?C=6.9NC- 10.7 Ne In the notation of wagner4 the interaction parameter is the second coefficient on the right, Sgr = - 10.7 This can be compared with a rather inaccurate value deduced from the transient equilibrium diffusion data of Kirkaldy et al.' as The authors are indebted to the American Iron and Steel Institute for financial support. This material is condensed from a B.Sc. Thesis submitted to Mc-Master University by R.J.B.

Jan 1, 1963

Jan 1, 1968

By AIME AIME

A THOROUGHLY satisfactory crowd turned out at the fall meeting of the Industrial Minerals Division and took an active part in the entire program. On Thursday afternoon, Sept. 24, a limestone plant was inspected, technical sessions occupying the attention of the visitors all day Friday and Saturday morning. Headquarters were at the Nittany Lion Inn, an attractive hostel on the Penn State campus, at State College, right in the center of Pennsylvania. We are still in the dark, despite inquiries, as to just what breed of lions Nittany lions are. As nearly as we could find out, Nittany is not a Biblical name, as it sounded to us, but a corruption of the name of an Indian princess, or maiden, or maybe just girl that haunted those parts in bygone times and after whom a near-by mountain was named. Penn State athletes are "lions" and there you are. The meeting was supposed to be a joint one with the American Ceramic Society's Materials and Equipment Division; but it was quite evident that the Institute had a much better publicity agent than the Society, which bothered Ross. Purdy, the aggressive secretary of the ceramic people, no end. However, Secretary Purdy saw to it that everyone present fully understood that the Ceramic Society was present, so that that contingent all but stole the show, its representatives presiding at every meeting. The Pittsburgh Section of the American Ceramic Society was also supposed to be holding its fall meeting there at the same time, but made no trouble at all for anybody, as one of the speakers remarked.

Jan 1, 1936

Discussion of the paper of THEODORE P. HOLT, presented at the Salt Lake meeting August, 1914, and printed in Bulletin No. 91, July, 1914, pp. 1699 to 1708. F. S. SCHMIDT, Salt Lake City, Utah.-Any furnace that can make a chloridizing roast to yield an extraction of 92 to 93 per cent. and do this at a cost of less than 24c. per ton in a 10-ton unit opens great possibilities for the treatment of certain classes of ores. This cost does not include the salt and will be reduced to about 16 1/2c. per ton in the 35-ton furnace which are now being designed. On a trial run the roaster treated 9.6 ton: of Ontario stope fillings crushed to pass a ¼ -in. opening. The ore is well adapted to chlorination with the exception of insufficient sulphur and occasional days of high lime, but is not adapted to any other process The following is an analysis of the crude ore: Ag, 9.52; Au, 0.029 oz. Pb, 0.71; Cu, 0.11; SiO, 79.4; Zn, 0.57; S, 1.00; Fe, 7.9; Mn, 0.89 CaO, 1.20 per cent. The composition of the mix was: Per Cent. Dry crude ore : 83.4 Moisture 4.4 Salt 8.3 Coal dust 2.3 Pyrite, 70 per cent. pure 1.6

Jan 11, 1914

By S. D. Thompson

An AIME transaction by P.L. Allsman (1960), "Analysis of Explosive Action in Breaking Rock," contains many useful concepts applicable to blast design. Of special interest was the derivation of a heave blasting burden formula, which is important in establishing the maximum burden. Unfortunately, its derivation contains a fundamental error and then a compensating one. This formula was: [bImpulse _P d At max =nwuwu where: bmax = maximum burden in m (ft). P= average detonation pressure in N/m2 (lb per ft2). A= duration of the average detonation pressure in sec. n= 3.1416. w= specific weight of rock in N/m3 (lb per ft3). u= minimum velocity that must be imparted to the rock in m/sec (ft per sec). d= borehole diameter in m (ft).] The derivation used the impulse-momentum principle, with a 0.3 m thick (1 ft thick) radius of rock mass being acted on by an explosive impulse. However, the rock weight was not converted to mass by dividing by the gravitational constant. This mistake can be verified by checking the units in the formula, which resolve into m1/2-sec instead of meters. Adding the gravitational constant corrects this: [P d Atbmax =gu g = gravitational constant equal to 9.81 m/sect (32.2 ft per sec2).] If the minimum velocity is now taken as 0.3 m/sec (1 ft per sec), as was recommended, excessively large burdens result. Any appropriate rock velocity should be capable of throwing the rock mass a minimum distance so that the swell needed for breakage can occur. Unless the burden is extremely small and the bench height is very high, it is unlikely that a velocity of only 0.3 m/sec (1 ft per sec) will be sufficient. A review of the literature indicates that average rock velocities observed by camera studies typically range from 15 to 30 m/sec (50 to 100 ft per sec) (duPont deNemours and Co., 1977; Tansey, 1979). On this basis, a minimum rock velocity of about 15 m/sec (49 ft per sec) would be expected and not 0.3 m/sec (1 ft per see). When a velocity of 15 m/sec (49 ft per sec) is inserted into the corrected formula, the results approximate those of the original formula with a velocity of 0.3 m/sec (1 ft per sec). The errors were approximately self-compensating [(9 = 1.24)]. ? References Allsman, P.L., 1960, "Analysis of Explosive Action in Breaking Rock," Transactions, AIME, Vol. 217, pp. 475-476. E. I. duPont deNemours and Co., 1977, Blasters' Handbook, 175th Anniversary Edition, Dupont, Wilmington, DE, pp. 233. Tansey, D.O., 1979, "The DuPont Sequential Blasting System," CIM Bulletin, Vol. 72, July, p. 80. Thompson, S.D., 1981, "Critical Review and Revision of Surface Blasting Practice," MS thesis, West Virginia University, pp. 308-316.

Jan 1, 1986