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By John W. Bell

IN the introduction to an excellent pamphlet, John Gross1 makes the following statements: Although marked progress has been made along mechanical lines, the theory and conception of underlying principles have not advanced so rapidly. This lack of advance in theory may be attributed to the unfortunate situation resulting from the controversy as to whether the Rittinger or Kick law is applicable to crushing. Many pages of the technical literature are burdened with theoretical discussions in favor of one or the other of these laws, which have tended to cloud rather than to clear the atmosphere. Realizing the situation, the Milling Committee of the American Institute of Mining and Metallurgical Engineers, through its secretary, E. A. Hersam, studied the milling industry and, because of the apparently hopeless lack of agreement in the Kick versus Rittinger dispute (5, 13, 14, 16, 18, 19, 21, 22, 23, 24, 30. 34), concluded that a foundation for the theory of crushing was of primary importance. The numbers in the paragraph quoted refer to papers listed by Mr. Gross in his Bibliography on Crushing and Grinding.1 One is obliged to infer that these papers show "hopeless lack of agreement in the Kick versus Rittinger dispute." No. 22 is a paper by Arthur O. Gates2 and No. 23 is one by the writer.3 Employing the subject matter contained in papers Nos. 22 and 2323 the writer will show that their authors formulated identical conclusions, based solely on experimental evidence. Exactly the same defect in the Stadler hypothesis was described in each of the two papers, although entirely different experimental methods were employed in uncovering it. Both of the authors, independently, formulated the conclusion that Rittinger's was a. true hypothesis and Stadler's false. The evidence in a third paper4 will be employed to prove that Stadler's hypothesis, when examined experimentally, is worthless. STADLER'S HYPOTHESIS WORTHLESS It is the writer's opinion that the evidence available in 1915 and the corroborating evidence in 1916 was amply sufficient to eliminate the need for any further consideration of Stadler's hypothesis. Certainly the evidence produced in 1918 dealt this hypothesis its coup de grace. It follows, therefore, that in the year 1918 there was only one credible hypothesis left-the Rittinger hypothesis. Gates' Opinion What information is available in Mr. Gates' paper?2 His conclusions are not consecutively summarized, none the less they are perfectly clear. On page 876, Gates says, and it is a very significant utterance: But my results show, among other things, that many more of Stadler's energy units are obtained per foot-pound-applied in coarse than in fine crushing. This suggests a doubt as to the correctness of his unit, since one would expect a foot-pound-applied to produce the same number of "energy units," whether the feed and resulting product were coarse or fine. When Rittinger's theory is applied, the number of mesh-tons (my unit of surface produced) is

Jan 1, 1942

By Zden[e]k P. Bažant

Due to their heterogeneity, most rocks fracture with a zone of distributed cracking ahead of the fracture front. This makes linear elastic fracture mechanics inapplicable. The present study describes a mathematical model in which the progressive microcracking is taken into account by strain-softening stress-strain relation. In a simpler version of the model, the triaxial strain-softening stress- strain relation is obtained by direct adjustment of the elements of the compliance matrix. This formulation is rigorous only if the principal stress directions do not rotate during fracture formation within the fracture process zone. As a more sophisticated and generally applicable model, the so-called microplane model which is an analogue of the slip theory of plasticity is outlined. Comparison with fracture data for various rocks are given.

Jan 1, 1984

By B. K. Parekh, W. M. Goldberger

A novel process is proposed for continuous removal of ash and unreacted solids which become suspended in the oils obtained during coal liquefaction. The proposed method uses water in direct contact with the oil under conditions which cause the suspended residue solids to transfer from the oil to the water phase. Separation of the phases yields a product oil essentially free of suspended solids. The water is cooled, clarified or filtered by conventional low-cost systems, and recirculated. The paper describes experimental work leading to development of the novel concept and includes the result of batch experiments that establish the feasibility of the process.

Jan 1, 1980

By C. B. Barlow, T. A. Mekelburg

Due to a tight ash constraint on the clean coal product and difficult middlings washability characteristics, a considerable amount of coal was being lost in the jig middlings at the Monterey No. 2 Mine. An investigation was conducted into circuitry to recover this lost coal with minimal effect on the total clean coal ash. A reverse two-stage hydrocyclone system cleaning at low specific gravities was selected. This system is currently recovering approximately 5.8 kg/s (23 stph) of 11.5% to 12.5% ash coal. The specific gravity of separation for the system is about 1.5 and the probable error is 0.13.

Jan 1, 1986

By Irvin Mayes, Maher E. Tadros

The effects of particle properties and dispersion on the filtration behavior of magnesiumhydroxide, silica, and polystyrene suspensions in aqueous media were examined. It was found that effective separation of particles can be achieved using filter media with larger pore diameters than the size of the particles. The addition of electrolytes, at concentrations lower than the critical coagulation concentration, to suspensions of polystyrene or silica resulted in an increase of the cake resistance. This result was interpreted in terms of a decrease in the effective particle size due to the increase in ionic strength. For magnesium hydroxide, an increase in the absolute value of the surface charge was associated with an increase in cake resistance and a decrease in cake compressibility. Low cake resistance values were obtained with suspensions of large particles with low surface charge and blocky morphology.

Jan 1, 1980

By L. Adler

Analysis of a mine roof can be based on fixed-end beam behavior. The author here analyzes the effects of zero restraint at deflecting beam supports. Formulae are given for determining permissible support deflections. Analysis of a mine roof in a bedded deposit usually follows the assumption that the behavior of the roof is analogous to a beam with both ends fixed. Yet it is recognized that the end restraint itself varies with the thickness of cover, so that at shallow depth the restraint is minimum, and at great depth, maximum.' Consequently, an analysis on the basis of fixed ends or full restraint represents only one extreme in the possible range of conditions. Since the actual amount of restraint is difficult to ascertain, a more rational approach is to consider the two extreme cases of end restraint. Such situations regarding uncertainty of the restraining effects of supports are not uncommon in structural analysis, and are handled in a like manner.' Since previous studies9)4 have dealt with full restraint, this paper will analyze the effects of zero restraint at deflecting beam supports. In such a case a mine roof with several intermediate supports becomes analogous to a uniformly loaded continuous beam on simple supports, as shown in Fig. 1A. Such a structure is statically indeterminate to a degree equal to the number of intermediate supports, n. Therefore, with the three equilibrium equations, n additional equations are needed. A number of methods exist to analyze this problem, but The Theorem of Three Moments is Simplest. The continuous beam is divided at each support into a sequence of simply supported single span beams, with the unknown end moments, as appears in Fig. 1B. Continuity requires that the common ends of adjacent beams have the same slope (Fig. 1C). eiB= B(i+l)~= ei(i+l)and MiB= Mti+I)A= Mi(i+i). [1I A Glossary of all terms is given in Table I. Furthermore, if we first consider that the supports do not deflect, the slope at a support is the sum of the slopes due to each of the individual loads shown in Fig. 2, yielding:

Jan 1, 1961

By Luis E. Vallejo

Experimental and theoretical analyses are presented to study the mechanics of growth and interaction for three inclined left-stepping, three inclined right-stepping and two inclined non-stepping cracks in a brittle material subjected to uniaxial compression. It was found that the non-stepping cracks did not interact and they propagated individually in a direction parallel to the uniaxial compressive stress. The propagating cracks formed in regions where tensile stresses developed. The left-stepping cracks interacted and formed branching cracks as a result of failure in tension of the material between them. Also, they propagated from their tips in a direction parallel to the uniaxial compressive stress. The right stepping cracks did not interact, but extended themselves from their tips following a direction parallel to the uniaxial compressive stress. The extended cracks formed in areas of compressive stresses.

Jan 1, 1984

By Richard D. Dick

The Los Alamos National Laboratory was involved in an oil shale fragmentation research program in cooperation with a Consortium of industrial companies to investigate the feasibility of using modified in-situ (MIS) recovery of oil from oil shale. Field tests were conducted at the Anvil Points Mine, Colorado, in the thick oil shale beds of the Green River formation. Part of the program included obtaining data about fragmentation by instrumenting the tests with accelerometers, velocity gauges, and the CORRTEX technique (Continuous Reflectometry for Radius versus Time Experiments). Some of the rock motion data from accelerometer and velocity gauges is presented, along with some conclusions. In addition, the signal recording system is briefly explained. The CORRTEX technique is discussed, and some results on explosive performance and stem behavior using the method are discussed.

Jan 1, 1984

By Eugene A. Stephenson

In November, 1932, Dr. Lacey, of the California Institute of Technology, presented before the American Petroleum Institute some of the results of his research under Project 371. The investigations described dealt particularly with changes in the physical properties of petroleum that result from the solution of natural gas therein. The solubility of Santa Fe Springs dry gas, containing 87 per cent methane, 8 per cent ethane and 5 per cent propane, had been determined in various crudes at 100' F., and 2000 lb. pressure per square inch as shown in Table 1 and Fig. 1 herewith. Originally the computations were made in terms of cubic feet per barrel, but' for a more uniform basis of comparison the results are also shown as cubic feet of gas2 per cubic foot of oil.

Jan 1, 1935

Until a comparatively few years ago, interest in tantalum was limited almost wholly to its scientific investigation, but its extreme resistance to the action of even the strong mineral acids, its great avidity for the common gases, hydrogen, oxygen and nitrogen, and its capacity for transforming alternating to direct current are winning for it a place in our industrial life. Tantalum is not attacked by any single acid except hydrpfluoric, nor is it affected by solutions of alkalies. Aqua regia, which readily dissolves both platinum and gold, has no action on it. This resistance to the common corrosive agents is an outstanding property of tantalum and accounts for many of the applications to which it has been put. When heated, tantalum reacts readily with oxygen and nitrogen and absorbs large volumes of hydrogen, 740 volumes being taken up at a dull red heat. This capacity for absorbing gases is being utilized to an increasing extent in the manufacture of vacuum tubes, in which tantalum is used for the metal parts, especially for grid wire. It is said to be a superior metal for this purpose, particularly in power and sending tubes, because of its low secondary emission. The use of tantalum in the manufacture of electrodes, dishes, spatulas and other laboratory apparatus appears to be fairly steady. There has been some development in its use for dental instruments, surgical tools, pen points, hypodermic needles and acid-proof pumps. Recently it has been used in the manufacture of spinnerets for the rayon industry, of nozzles for the manufacture of artificial casings for sausages and of lining for plant equipment. Tantalum in Electrolysis It has been known for some time that certain substances permit the passage of an alternating current in one direction more readily than in the other. Tantalum possesses this property to a marked degree.' When an alternating current is passed through a cell with tantalum electrodes and sulfuric acid electrolyte, a thin film is soon formed at the

Jan 1, 1930

By D. R. Colton, W. V. Youdelis

The maximum segregation, as a function of alloy composition, is calculated for the aluminum-zinc system using the theory of inverse segregation based on the mechanism of volume contraction and interdendritic flow. The results show good agreement with experiments on aluminum-zinc ingots. The significance of the mass calculations of the segregation theory in discussing the metallography of the cast aluminum-zinc alloys is considered. THE occurrence of inverse segregation in rapidly cooled castings has been reported on previously by various authors, and several theories have been proposed to explain this phenomenon. It is now generally accepted that the mechanism of inverse segregation involves volume contraction on solidification followed by interdendritic flow of enriched residual liquid to the contraction volumes. This increases the concentration of the lower-melting-point constituents in regions of first solidification to above the mean concentration, which is con-

Jan 1, 1961

By A. M. Johnson

Dewatering is a major operational cost at some mines. Under certain conditions, costs associated with water disposal may continue beyond the productive bye of the mine. For mines with mineralized waters, this is of special concern. Since 1974 experience has been gained from examination of a number of closed underground metal mines that exhibited drainage problems. It was observed, in certain cases, that had appropriate steps been taken prior to closure, the resulting drainage problems could have been largely avoided. Reclosure steps would have involved alteration to the 'plumbing system" of the mines; i.e., the drifts and crosscuts interconnecting the mine workings. This could have best been accomplished by the placement of bulkheads and/or selective drifting. In addition to reconfirming that hindsight is 20-20, a lesson learned from these case studies shows that a relatively simple hydrologic evaluation prior to mine closure may avoid a troublesome and costly drainage problem.

Jan 1, 1985

The history of surface mining is essentially that of mining coal, copper, and iron ores and the non- metallic minerals, i.e. clays, gypsum, phosphate rock, sand, gravel and stone. The accompanying table comparing world production with that of the U. S. indicates that two thirds of the 8.8 billion tons of ores mined throughout the world come from surface operation. Assuming that the stripping ratio for surface mining in the U. S. applies equally to world production, then over 21 billion tons of waste, or a total of nearly 27 billion short tons of material are mined annually in the world by surface methods. Several factors are significant indicators of economic and technologic trends in surface mining. Among these are increasing production, a shift in emphasis from underground to surface mining, a decline in the grade and quality of some crude materials and, with few exceptions, an increase in the productivity of labor.

Jan 10, 1967

By J. A. Dresser

The controlling supply of asbestos for the world is obtained from southern Quebec, 150 miles or less north of the international boundary line between Canada and the United States, and about 75 miles south of the city of Quebec.

Jan 1, 1915

By Geoffrey Purcell

Although the extractive metallurgist has not yet tackled the problem of getting blood out of a stone, he must, when faced with the mini- metal values of today's ores, believe that this ultimate miracle will soon be expected of him. Even assuming that some plausible professor at one of the few remaining minerals industry schools could persuade the National Science Foundation to sponsor such a sanguine research project, the funds might have to go begging for want of a graduate metallurgist. Falling enrollment in fields devoted to nonrenewable mineral resources, long a matter of grave concern to educators, is now recognized as a problem of great national consequence urgently needing a solution. While the law of supply and demand might eventually be expected to right the imbalance of engineers, time is not on our side and action to correct the shortage is required now.

Jan 1, 1970

By Irvin Lavine

THE discovery of several large deposits of natural sodium sulfate (Glauber salt) in the northwestern part of North Dakota during the summer of 1934 might have been anticipated from a knowledge of the topography and geology of this territory and from the presence of natural C A N A D A FIG. 1.-LOCATIONS OF GLAUBER SALT DEPOSITS, NORTHWESTERN NORTH DAKOTA. North Lake (deposit No. 7) is not shown on this map. It is approximately 13 miles north of Miller Lake (deposit No. 3). sodium sulfate deposits in western Canada, which have been known for several years. In the northwestern part of North Dakota is a chain of shallow lakes, which continues northward into Saskatchewan. Over twenty million tons of Glauber salt has been proved present in these North Dakota deposits. (See Fig. 1.)

Jan 1, 1936

By Bernard Rachlin

In the mineral industry measurement of density or specific gravity of slurries is often necessary or highly desirable. To date the most successful method of measuring the specific gravity of various media is to hand weigh a constant volume sample of the slurry. This method is time-consuming, however, and is intermittent rather than continuous. Most density measuring instruments in use today are variations of three basic systems: air bubble tube systems, radioactive methods, and displacer systems. The high cost of the radioactive cell, combined with the precision electronic measuring that is required, limits the practical utility of this procedure to a small percentage of critical processes. In the air bubble systems clogging of the bubble tubes with solids has rendered this type of measurement completely ineffectual for many applications. Continuous or intermittent purging of the bubble tubes with air or water to prevent tube clogging has been tried but has not been very successful, especially in the heavy media process.

Dec 1, 1956

The Library of the above-named Societies is open from 9 A.M. to 10 P.M., except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 3, 1918

By J. B. Scuffham, G. A. Rowden

The use of ammonia as a leaching agent has been well-documented but only recently have its advantages been fully exploited on a commercial basis. When compared with conventional sulfuric acid leaching processes, the major advantage of ammoniacal systems is their ability to reject iron and many acid consuming gangue materials. Although metallic copper, nickel, zinc, etc. are dissolved rapidly in ammoniacal liquors at ambient temperature in the presence of air the sulfide ores of these metals are more resistant to this treatment. Sherritt Gordon Mines in Canada treats sulfide concentrates at its Fort Saskatchewan plant under pressure with ammoniacal am- monium sulfate solution to solubilize the non-ferrous metal values. Typical leach operating conditions are 80-95°C and 115- 128 psig. Although the metals present in the ammonical solution could be recovered via solvent extraction techniques, Sherritt Gordon Mines currently operates a pressure reduction process using hydrogen to yield metal powders directly from the ammoniacal solution. The basic Sherritt Gordon technology has been applied world wide for the treatment of nickel/cobalt concentrates.

Jan 12, 1973

By K. V. Lindell

THE 70-mile serpentine belt of eastern Quebec, producing 70 pct of the world's chrysotile, has 11 operating mines, two of which are underground, eight are open-pit, and one is both open-pit and underground. The combined operation, the Jeffrey mine, of the Canadian Johns-Manville Co., Ltd. is the largest producer in the group. Haulage All four of the separate operations falling under transportation at the Johns-Manville Jeffery Mine at Asbestos, P. Q., is handled by the company owned Asbestos and Danville Railway. A variety of equipment is operated over the 25 miles standard gage railway. Included in the scope of transportation are: 1-Hauling mill rock to the mill. 2-Hauling stripping and waste rock to the waste dump. 3-Hauling mill tailings to the tailings dump. 4-Hauling supplies from, and finished products to Danville. Main line tracks are permanent, but those within the pit and on the dumps have to be relocated constantly to follow the mining face and dump edges. Tracks within rock areas in the mine are laid on steel ties and can be moved by a bulldozer. Standard mechanical track shifters move tracks in dirt areas in the mine and on the dumps. Train-movements, both within the mine and over the out-lying tracks are controlled by a dispatcher located at the southwest rim of the pit. Steam locomotives haul all stripping, waste rock, and ore from the mine to the gathering yard at the northwest rim of the pit. Normally, two trains per operating shovel are used, with adjustment for optimum loading. In the event of shovel loading on the bottom level or in good stripping, service may be increased to three or four trains per shovel. From the gathering yard a 100 ton diesel-electric locomotive hauls the mill rock to the mill slips, a distance of about three miles. Electric or steam locomotives haul the waste rock and stripping to the waste dump located about two and one-half miles from the mine. Stripping cars are sprayed with a chloride solution and "gravelled" to prevent wet stripping from freezing in the cars during the cold months. Cars pass under a shaking screen which distributes an even

Jan 1, 1952