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By Nick Barton, Stavros Bandis

The descriptive term "rock mass" encompasses individual block dimensions ranging from centimeters to many tens of meters. Strength and deformability vary both qualitatively and quantitatively as a result of this size range. A key issue is therefore the appropriate size of the test sample. A large body of test data was reviewed to determine the influence of block size on the displacement required to mobilize peak strength. It is shown that the shear strength and shear stiffness reduce with increased block size due to reduced effective joint roughness, and due to reduced asperity strength. Both are a function of the delayed mobilization of roughness with increasing block size. A method of scaling shear strength and shear displacement from laboratory to in situ block sizes is suggested. It is based on the assumption that size effects disappear when the natural block size is exceeded. This simplification appears to be justified over a significant range of block sizes, but is invalidated when shearing along individual joints is replaced by rotational or kink-band deformation, as seen in more heavily jointed rock masses. Recent laboratory tests on model block assemblies illustrate some important effects of block size on deformability and Poisson's ratio.

Jan 1, 1982

Jan 1, 1884

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Jan 1, 1938

OFFICERS AND DIRECTORS President and Director HOWARD C PYLE, '61, Los Angeles, Calif Past President and Director AUGUSTUS B KINZEL, '60, New York City President-elect and Director JOSEPH L GILLSON, '62, Wilmington, Del

Jan 1, 1959

PROF RICHARD ÅKERMAN Stockholm, Sweden DR. FRANK DAWSON ADAMS Montreal, Canada PROF RICHARD BECK Friberg, Germany ANDREW CARNEGIR New York, N.Y. DR. JAMES DOUGLAS New York, N.Y. PROF HATON DE LA GOUPILLIERE Paris, France SIR ROBERT A. HADFEILD London, England PROF HANS HOFFER Leoben, Austria JAMES FURMAN HOEFER Leoben, England PROF HENRI LOUIS LE CHATELIER Paris France

Jan 1, 1917

No. 243. Superintendent for operating Virginia, manganese mine. One experienced with wet concentration, labor and general management. Opportunity for advancement for right man. Write fully concerning experience, references and salary expected to start.

Jan 11, 1917

By R. S. Rickard, H. D. Peterson, M. C. Fuerstenau, J. D. Miller

The flotation characteristics of the oxide copper minerals, malachite, azurite, and cuprite, have not presented the difficulty for concentration as have those of the copper silicate, chrysocolla. The copper carbonates and oxides respond reasonably well to flotation with conventional collectors, whereas chrysocolla will not respond to flotation with fatty acids or xanthates under normal flotation conditions. In this view then, other reagents will have to be devised to function as collectors for chrysocolla. The most obvious general class of reagents for this purpose would seem to be the organic copper chelating compounds. The utility of chelating agents as collectors in flotation systems has already been demonstrated.1-6

Jan 4, 1966

By A. T. Schwennesen

(Wilkes-Barre Meeting, June, 1911.) EVERY engineer has occasion to trace or copy a map, plan, or other drawing on paper too thick for the ordinary way of using tracing-cloth or tracing-paper. When the figure is small and simple a copy may be made by holding the original against a window-pane, covering it with the paper, and tracing direct by the aid of the strong sunlight from outside. The need of utilizing this principle on a larger scale and in a more convenient position led Dr. J. C. Branner to plan the table of which the following is a description: This table was first made in the form of an adjustable glass-top table with a mirror beneath, in 1887, while Dr. Branner was State Geologist of Arkansas. Later it was modified as experience suggested until the form as here described was evolved. The device consists essentially of a drafting-table with a plate-glass top, upon which the original drawing and the paper are laid, and a mirror mounted underneath to reflect the light of the sky up through the drawing. The glass top is hinged and fitted with two arms and thumb-screws, so that it can be raised and fixed to any position, either inclined or horizontal. The mirror is pivoted and revolves about a horizontal axis, so that it may be tilted to any angle. The hood of cardboard or black cloth prevents the reflection of light from the tracing, and may or may not be attached to the table. The apparatus is set up before a window through which part of the unobstructed sky is visible. The mirror is then adjusted like the reflector of a microscope, so that the skylight is reflected up through the drawing. If the mirror can be so located that the direct rays of the sun are reflected through the drawings, thicker paper can be used. The map or drawing may be held in place by clips screwed

May 1, 1911

Use of rock grinding media in a mill at Tennessee Copper Corp. was mentioned in the MINING ENGINEERING Annual Review. (February 1953, page 158). Because interest in use of self-grinding media continues high we asked F. M. Lewis, Superintendent of Concentration at Tennessee Copper, to supply more details on this trial, and of plans to expand use of rock media in their mills that grind marble. Here is what he reports.

Jan 5, 1953

Jan 1, 1892

By Allen Rogers

IT IS universal practice for corporations, at the end of the fiscal period, to call in a firm of chartered accountants to audit the books. The effect of this is to put an independent organization's seal of approval on the accounting of the business done by the management. Their report lets the stockholders know that the accounts rendered truly present the results of the year's business. This is as it should be; the average stockholder has no personal contact or even acquaintance with the managers of his enterprise and the approval of their stewardship by an indepen-dent agent is very desirable for maintaining confidence in their honesty and ability. But such an examination deals only with what may be called the arithmetic of the business; even the most elaborate audit, as the practice is at present, goes no further than to verify the items of the inventory. In other words, while checking up the entries showing the transaction's of the year and certifying to the correct-ness of the items of the balance sheet, such a report gives the stockholder no idea of the ability with which his affairs have been managed. If the profit and loss balance is satisfactory, as certified by the public accountants, he assumes that the management has been able; where it is not, he turns to the president's report and usually finds an explanation. Such an explanation never takes the form of admission of mis-takes in business judgment or of bad technical manage-ment. It could hardly be expected that it would. The stockholder is generally furnished, therefore, with a certificate of the honesty of his management, but never one of its ability. He does not worry about the latter as long as dividends come in; when they cease, his action generally finds expression in replacing the management. In other words, so long as profits are realized, he assumes the management to be good, even though its success is a matter beyond its control and better management would make larger profits. When there is no profit, the stockholders have no means of knowing whether it is due to conditions beyond the control of the management, as the annual report is sure to allege, or whether, by better management, profit is possible. Here is where the technical audit comes in.

Jan 6, 1922

Jan 1, 1902

By Simon D. Handelsman, Reg M. M. Rowe

The mechanism of using gold as the basis for a loan was suggested to the treasurer of a mining company operating two gold heap leach mines at a time of high interest rates. Due to the seasonal nature of cash flows from operations, and the relatively low cost of funds this scheme was attractive. The paper describes the agreement with the bank, gives an example of the transactions, and describes other types of gold loans.

Jan 1, 1985

By Robert Glass Cleland

THIS IS a history of a company whose roots run deep into the nation's past and whose field of operations has never been narrowly confined. The men who founded Phelps Dodge were men of initiative and imagination. They were men of strong convictions and upright character. They held fast to the simple virtues and traditions of the days when America was young. This heritage they passed on to their successors. From the very beginning, under such leadership, Phelps Dodge became a company of large affairs. It bought and sold, exported and imported, built factories and organized railroads, converted great forests into lumber, and operated coal and iron mines. Much of the iron, copper, and tin plate used in the United States for a generation was under its control. Its business abroad was extensive enough to warrant the organization of a separate partnership in England. Then, almost half a century after its foundation, the company began to substitute new activities for old and eventually transferred its major operations to the West, primarily to Arizona. The family partnership became a corporation. Exporting and importing gave place to mining and metallurgy. Phelps Dodge became one of the largest

Jan 1, 1952

[Alabama, University of, University, Ala California, University of Berkeley, Cal Carnegie Inst, of Technology, Pittsburgh, Pa Case School of Applied Science, Cleveland, Ohio Colorado School of Mines Columbia University, New York City Harvard University, Cambridge, Mass Idaho, University of, Moscow, Idaho Illinois, University of, Urbana, Ill Iowa State College, Ames, Iowa Kansas, University of, Lawrence, Kan Lafayette College, Easton. Pa ]

Jan 1, 1928

Jan 1, 1948

Jan 1, 1939

Jan 1, 1956

Jan 1, 1944

Jan 1, 1939