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By B. Ladanyi, B. Hoyaux

One of the most important problems in underground works is the assessment of the stability of underground openings and the determination of loads on eventual supporting structures. Under certain stress conditions, a hard and sound rock around an unlined opening may show a tendency to rock bursting, which can be prevented by appropriate measures. On the other hand, a less competent rock even if it fails in a less violent manner may give rise to a rock load because within limited regions surrounding the opening, the failed material may have a tendency to flow into the opening; this condition should be prevented by designing a proper supporting structure. The stability of the opening, as well as the value of the design loads acting on the supports in the latter case, depends clearly on the shape, extent, and location of the failed regions, which are often called “plastic zones.” It has been known for some time how the plastic zones develop in some very simple cases, such as in the case of a circular opening in an elastic ideally plastic medium subjected to a nongravitational stress fie1d.l However, to the knowledge of the authors, no information has been available up to now about the extent of the plastic zones in a more general case and for rocklike media. ASSUMPTIONS ON ROCK BEHAVIOR MADE IN THE CALCULATION The solution shown in this chapter is valid for a horizontal tunnel of circular cross section driven through a rock medium at a finite depth.

Jan 1, 1970

By G. S. Brooks

(New York Meeting, February, 1913.) THE tendency of the oxides of such metals as aluminum, zinc, chromium, and calcium to form compounds at high temperatures with iron oxide is well established by past investigation. Data of this reaction, as developed in laboratory research, have been contributed by Burleigh, Hofman, and Wells, in America, and by many others abroad. A partial bibliography of the subject is appended. From these authorities we learn that the ferric oxide here has the function of an acid, giving in the case of ZnO a zinc ferrite, with a normal composition of ZnOFe2O3. This formation of zinc ferrite particularly affects the success of such processes as leaching or magnetic separation, and thus becomes practically important to the metallurgist. But the meager existing data do not entirely agree; and quantitative results from muffle-practice are conspicuously absent. Furthermore, it being of some general importance to the zinc smelter in both roasting and reduction, the following few notes of operations on a commercial scale are contributed

Jan 5, 1913

By R. G. Coyle

This paper describes a model of operating policies in an underground metal mine. The purpose of the model is partly that the problem of controlling a mining operation in the face of shocks from its economic environment is interesting in its own right, and also as an input to a larger research project on policy-making in mining companies. The model includes, mining, development and milling sectors together with cash flow and finances. In particular, it shows how the policies used to control the various sectors in the face of environmental shocks from metal prices and changing state of the system are connected by feedback loops. The use of feedback theory differentiates the model from 'ordinary' simulation and assists in the design of 'robust' policies which always achieve effective control. This model is the first stage of a major project and approximations have been made, simply to get the model going. The purpose of this paper is to show the kind of output this type of model produces, to lay our explicitly what is in the model and above all, to invite contributions from mining people on what the model should show and what should be put into it. We claim no virtues for this model. It is just a research tool so that later models will be more worthwhile and useable in practice.

Jan 1, 1977

By Gregory Dybalski

The purpose of this paper is to illustrate the forecast capability of the econometric model of the cobalt industry1/ as utilized by the Federal Preparedness Agency. Forecasts from this model are illustrated from the premise that the leading producer continues production of cobalt. An alternate forecast is presented where the model structure is altered to reflect the condition where the leading producer leaves the market. All estimations and forecasts presented here are shown for illustrative purposes. The cobalt industry is highly concentrated; one company, owned by the Zaire government, accounts for approximately three-fifths of world production. The cobalt supply outside of Zaire is determined by the level of activity of copper or nickel markets, as cobalt is mined as a by-product of copper or nickel. The demand for cobalt reflects a diversified usage pattern; cobalt is used mainly in heat and corrosion-resistant materials, high- strength materials and permanent magnets. According to 1974 U.S. consumption data superalloys accounted for 22%, magnetic alloys 18%, cutting and wear-resistant materials 13%, and catalyst 7%. Foreign consumption is probably similar in terms of usage categories, but the relative order of the categories is in variance.2/ The Cobalt Model The cobalt model's object is to explain consumption, supply and price movements by utilizing statistically estimated equations. Central to the econometric model is the role of Zaire as the profit-maximizing "dominant firm". Zaire sets the price that is most profitable for itself. The price of cobalt depends on industrial demand, production of other firms, and net exogenous purchases, such as government

Jan 1, 1977

By Zavis M. Zavodni, Carl D. Broadbent

During the past 15 years, rock mass structural properties have become acknowledged as the focal point for rock slope design. Re- search into the methods for measuring and incorporating structure into the design effort has taken many directions and has produced a variety of useful techniques. Among the findings at Kennecott has been the realization that structure-controlled instability can be categorized as regressive or progressive depending on the relative geometries of slope and structure and on the strength characteristics of the structures. It was further identified that a failure condition can initiate as regressive and in time become progressive should external stimuli increase or structure characteristics be altered due to extensive displacements. The transition point has been shown to be a useful indicator of the expectable collapse time. This paper defines three fundamental failure types as dictated by structure and offers discussion on the practical value of such a classification to slope design and failure control. Several prominent examples of failures typifying the categories of structure- controlled instability are discussed. An application of f allure prediction based on the regressive-to-progressive transition point is described.

Jan 1, 1983

By F. R. S., B. Hopkinson, R. Hadfield

A short time ago Professor Stoughton askes the writer if he would present a paper for the Feburary meeting of our Institute.

Jan 1, 1915

By E. A. Lowe, C. C. Walden, D. W. Duncan, P. C. Trussell

The industrial importance of bacteriological leaching is finding increasing application in the treatment of low-grade ore and of exhausted mines. Another possible application of bio-leaching is in the extraction of ore concentrates, although here the first uses will likely be for ores that are refractory to conventional metallurgy. Biological leaching studies, which have been in progress for over ten years in this laboratory, are directed towards the more rapid and complete leaching of metals from their sulfides, particularly of copper, zinc, and nickel. The program involves not only laboratory studies, but pilot-plant operations and liaison with mining companies which are underwriting the cost of the investigations. Although the bacterial oxidation of mineral sulfides to the corresponding water-soluble sulfates has been occurring naturally for many centuries, the first documented recovery of solubilized metal from pregnant solution was at the Rio Tinto operation in Spain. At this location leaching variables were studied extensively in an empirical manner some years before the causative bacteria were first isolated from other leaching situations. Documentation of the presence of bacteria in leach waters of the Rio Tinto, Spain, operation was not confirmed until 1962.3 On this continent leaching was pioneered in the early

Jan 1, 1968

A. M. CANDY,* Pittsburgh, Pa.-According to the tables on page 532, the deposit obtained with Roebling cold-rolled steel, and Toucan electrodes contained considerably less carbon and manganese than the original electrodes; whereas very little carbon is lost in the case of the hot-rolled steel electrode. When using the hot-rolled steel electrodes, the metal apparently has a tendency, probably due to greater surface tension, to pass through the arc in larger particles than the other electrode materials. This affords greater protection against oxidation, and thereby prevents much loss of carbon. The larger globules tend to increase the arc fluctuations due to greater partial short-circuiting of the arc. Actual oscillographic records show that with the hot-rolled steel electrodes the current peaks were 70 per cent. above normal whereas the peaks for the other electrodes were only about 25 per cent. -above normal. Probably due to the larger globules, a greater proportion of slag in the electrode was carried into the weld. Some four or five test pieces made with the hot-rolled steel electrodes were all considerably below the tensile strength of the samples welded with the other electrodes. These facts indicate that an electrode may not be satisfactory even though of approximately the proper chemical composition. For example; the hot-rolled steel and Roebling electrodes are quite similar in chemical analysis.

Jan 4, 1919

By Kenneth N. McLeod, Donald W. McGlashan

In the use of free bubbles with precise temperature control and continuous pH measurement, the contact angle apparatus differs from all previous equipment. Experimental procedures differ sharply from the captive bubble method of introducing the gaseous phase in the three-phase system. When freed from the tube and captured by a solid surface, a bubble more closely conforms to the spherical ideal set up by the usual mathematical analysis of surface free energy or surface tensional relationships of the forces involved. The assembled equipment, Fig. 1, departs from the usual contact angle apparatus in providing: 1) water circulation for fixing temperature, 2) instruments to measure and record pH during testing, and 3) a system for producing and using free bubbles. The apparatus allows testing over a broad range of closely controlled conditions, and the use of free bubbles gives contact angles independent of operator manipulation, which was unavoidable in the older captive bubble method. A bubble released below the specimen rises through the liquid and contacts the mineral. If the mineral is gas-avid the bubble adheres, developing a finite contact angle.

Mar 1, 1956

By A. V. Henry, W. Harry Vaughan

THE kaolins of the southeastern United States were known to civilization as early as the latter part of the eighteenth century-and yet the [ ] commercial history of Georgia kaolins may be said to begin in the year 1900. The U. S. Bureau of Mines reported for that year a production of 6885 tons of "miscellaneous" clays in Georgia. A comparison of these figures with those of 1934, when the production rose to 284,556 tons (65 per cent of the domestic production), indicates the growing economic and technologic importance of this raw material. Fig. 1 clearly shows that a part of the increase is due to a normal growth in the use of kaolinitic clays and a part is due to replacement of clays formerly imported. Occurrence Georgia kaolin occurs in an irregular belt extending diagonally across the middle of the state, a distance of approximately 225 miles. This belt

Jan 1, 1937

By Abdel Kadir Attia, Haydn H. Murray, Adel Abdel Azin, Sabah N. Boulis

An extensive reconnaissance survey of bentonitic clays in Egypt was carried out from 1982 to 1984. X-ray diffraction, differential thermal analysis, electron microscopy, and physical property evaluations were used to identify the mineralogy and assess their industrial potential. Samples were collected from a number of localities, namely Qasr El-Sagha (Fayum), Cairo-Alexandria Desert Road (Western Desert), and Qattamia area (Eastern Desert). This paper reviews the geological occurrence, the mineralogical and chemical characteristics, and the potential utilization of these deposits.

Jan 1, 1985

By J. Wesley Pullman

It is stated by Dr. Tuttle in a paper read before the New Jersey Historical Society, that the celebrated Dickerson mine at Succasunna, Morris Co., N. J., yielded ore, about as early as 1710, for use at the Whippany forge, on Rockaway River, between Rockaway and Boonton. The ore was, for some time, free to all who chose to dig it. The tract embracing the Dickerson mine mas taken up, on account of its minerals, in 1713 or 1714, by John Reading, who sold it in 1716 to Joseph Kirkbride. John Jackson built a forge in 1722 on the Rockaway River a mile west of Dover. The ore here worked was probably chiefly from the Dickerson mine, but a portion may have been Hibernia. Hon. E. D. Halsey, of Rockaway, K. J., writes me: It is quite possible that the ore was at first taken from the outcrop of Hibernia by anybody who wanted it. The property first had an owner, May

Jan 1, 1886

By M. E. Learmont, I. Iwasaki

Grinding with steel media adversely affects the flotation response of galena. Electrochemical measurements, flotation tests, and AES, XPS, and STEM examinations were employed to identify interactions between galena and mild steel. Iron oxide, hydroxide, or sulfate species that formed on the galena surface upon contact with mild steel decreased its floatability, with the time of contact and aeration condition affecting the severity of the flotation depression. Parallel tests performed with an active metal, magnesium, indicated that floatability was also affected by the presence of a surface coating involving lead species.

Jan 1, 1985

ZAY JEFFRIES, Cleveland, Ohio (written discussion?).-The authors conclude that there is a certain average size of precipitated CuAl2 par-ticle which produces maximum strength and hardness in duralumin; that when the size of particle is smaller or larger than this particular size the hardness decreases. The writer agrees with this conclusion, because it seems to he directly indicated by the facts. Why does duralumin present this apparent discrepancy? Let us con-sider some physical aspects of the precipitation of CuAl2 from a saturated solution on cooling. When a molecule of CuAI3 is removed from the solvent, or matrix, and added to another group of CuAl2 molecules, as is known to occur on slow cooling, the forces of adhesion between the CuAl2 molecule and the solvent have been exceeded. Since a. change in tem-perature only is sufficient to cause precipitation, it must also be sufficient to cause the loss of adhesion bonds between the excess CuAl2 molecules and the solvent, or matrix. Lost adhesion bonds means loss of cohesion of the mass as a whole. When duralumin is cooled from 500° in a furnace, globules of CuAl2, large enough to be seen easily with a high-power microscope, are formed. There are, however, globules so small as to be hardly distinguishable, and others too small to be resolved are suggested by the non-uniformity of the surface appearance of the section. As the smallest globule of CuAl2 resolvable with a high-power microscope contains about 2,000,-000,000 molecules, it is evident that with rapid cooling submicroscopic particles of CuAl2 must be present in large numbers; in fact, after quench-

Jan 12, 1919

By Guy A. Johnson

In 1976, The Bureau of Mines developed a prototype system to sense and extinguish fires in shafts and shaft stations in underground metal and nonmetal mines. Subsequent work modified this technology to include fueling areas, spontaneous combustion zones and coal mines. This paper updates IC-8783 "In-mine Fire Tests of Mine Shaft Fire and Smoke Protection Systems," which was published in 1978 and summarized the design and in-mine, actual fire testing of the first prototype mine shaft fire and smoke protection system. This paper also updates related work from IC-8775 "Spontaneous Oxidation and Combustion of Sulfide Ores in Underground Mines," (also published in 1978) and IC-8808 "In-mine Evaluation of Under- ground Fire and Smoke Detectors," (published in early 1979).

Jan 1, 1982

By Thomas Watson

Introduction THE occurrence of zircon in pegmatites of acidic composition is recorded by many observers both in this country and abroad, and they form one of the most important geologic modes of occurrence of the mineral.' As is well known, commercially the most important American locality for zircon is near Zirconia in Henderson County, North Carolina, where many tons of the mineral have been obtained from a kaolinized pegmatite dike 100 ft. wide and traced for 1 ½ miles along the direction of strike N. 50° E. Zircon may be developed in pegmatites as inclusions in the principal rock-forming minerals, chiefly quartz and feldspar, and as a separate megascopic constituent in the form of grains and crystals not exceeding, as a rule, 2 in. in size, and usually smaller. In the Henderson County, North Carolina, pegmatite, zircon occurs in prismatic crystals with pyramidal terminations measuring up to 30 mm. in diameter, associated chiefly with the feldspar. In some of the apatite veins of Canada, which are closely allied to pegmatite dikes, zircon is reported in crystals upward of 6 in. in length and 2 in. 'and more in thickness. Zircon in large masses occurs in Virginia in the well-known pegmatites near Amelia in Amelia County, and near Gouldin in Hanover County. Both localities are in the middle eastern portion of the Piedmont Plateau province, and are separated by a distance of about 40 miles in a northeast-southwest direction. The rocks of both areas, including the pegmatite bodies, are in an advanced stage of decay, and, the hard and moderately fresh rocks are concealed beneath a cover of variable thickness of rock decay derived by the normal processes of weathering. Exposures, there-

Jan 7, 1916

By W. R. Johnson

In the spring of 1935 the writers undertook to compare the geomagnetic and direct-current earth-resistivity methods of tracing a concealed dike along its strike. As far as they are aware no such direct test has been attempted.# The area surveyed lies along United States Highway number 15 about one and one-half miles east of Chapel Hill, North Carolina, and northeast of Bolin Creek (Fig, 1). To the south of the highway is the flood plain of Bolin Crook, and to the north is a hill that rises almost to the elevation of Chapel Hill. A diabase dike, which strikes slightly west of north, out-crops in a. gully just south of the highway. Southward it has been covered by alluvium but northward outcrops again on the southeastern slope of the hill north of the highway. South of the highway the country rock is Triassic shale and sandstone, the northern limit of which is slightly north of the road. On the Geological Map of the United States I the pre-Triassic formations are shown as lower Glenarm and assigned a pre-Cambrian age. Since the ago of the Glenarm has been called into question in Pennsylvania 2, the writers prefer not to commit themselves as to the ago of these rocks further than to say that they are definitely pre-Triassic.

Jan 1, 1937

By Jill Dill Pasteris

Several mineralogical prospecting techniques are used in diamond exploration. Most are concerned with identifying indicator minerals such as pyrope garnet and magnesian ilmenite, which are derived from mantle xenoliths hosted by kimberlites. The first goal of such prospecting is to locate kimberlite intrusions; the second goal is to identify the diamond-bearing kimberlites. Explorationists have worked much less on the indigenous kimberlite phases. The kimberlitic opaque oxides, ilmenite and particularly spinels, promise to be useful in discriminating between intrusion episodes in identified kimberlites, and perhaps in the evaluation and prediction of diamond grades. Several petrologists have showed that spinel compositions and zoning patterns are specific to certain intrusive facies in South African and Canadian kimberlites. Careful evaluation may indicate a correlation between spinel parameters and diamond content.

Jan 1, 1984

The Library of the above-named Societies is open from 9 A.M. to 10 P.M. on all week-days, except holidays, from Sept. 1 to June 30, and from 9 A.M. to 6 P.M. during July and August. The Library contains about 55,000 volumes, including sets of technical periodicals and the 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 can render valuable service through correspondence; letters requesting information will receive special attention. The Library is prepared to furnish references and copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information as to 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. The members of the Institute can be of service to the Library by forwarding copies of mining reports, maps privately issued, and similar material, which will be classified, indexed, and made available to other members. Suggestions for additions to the Library, either by purchase or personal solicitation as gifts, will be welcomed. It is hoped that members while in the city will use the Library, freely, and assurance is given that most careful service will be rendered to them.

Jan 5, 1916

By E. J. Schmitz

Coming from San Antonio, Texas, and following the Galveston, Harrisburg and San Antonio Railroad westwards, one enters soon the Cretaceous formation, which forms a belt of several hundred miles, extending westwards to the boundary of Arizona and across the Rio Grande into the State of Coahuila, Mexico. The members of this formation are very numerous and in petrographical character very diverse—from a whitish or bluish, slaty, impure limestone to a hard, beautiful blue-and-red striped, and a compact heavy-bedded,

Jan 1, 1885