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By Gordon M. Matheson, Charles V. Logie

The current state-of-the-art design of mine pillars can be grouped into empirical and numerical design techniques. Numerical design techniques are based on sophisticated computational techniques which analyze the stresses and strains through the interstices of a pillar. Empirical techniques are less exact, but have been widely used, particularly for coal mine pillar design, because of their ease of computation. Over the years numerous empirical equations have been proposed to calculate the ultimate strength of coal mine pillars. This paper presents a review of the various equations which are most frequently utilized and examines the fundamental assumptions, limitations and applicability of the design formulae. The review intends to provide the practicing mining engineer with an understanding of the assumptions and mathematical basis of each equation to aid in the selection of the criteria most applicable to his specific design problems. Recommendations are made of the empirical equations that are presently most acceptable for design.

Jan 1, 1983

COLORADO SECTION CHARLES M. MACNEILL, Chairman, GEORGE M. TAYLOR, Vice-Chairman, FRED CARROLL, Sec.-Treas., State Museum Bldg., Denver, Colo. WALTER W. CASE, H. E. COLLBRAN. The annual meeting of the Colorado Section was held on the evening of Jan. 24, at the University Club, Denver, Colo.; SO members and guests were in attendance and the meeting was considered one of the most interesting ever held by the local section. After the usual dinner, the officers whose names are given above were elected for the ensuing year. Dr. David T. Day and Dr. G. H. Clevenger, of the Bureau of . Mines, were present and enlightened us with short talks on oil shales and other work of the Bureau. Mr. J. V. N. Dorr was home from a visit to New York and Washington, and told us something of the war work now going on at our National Capitol. Retiring Chairman Loughridge had been insisting for months that this meeting should be given up chiefly to listening to someone who could give his personal experience in going "over the top" in western France; after a long search he succeeded in finding Sargt. F. C. Strickland, M . M., of the Second Canadian Mounted Rifles, who had very recently been discharged from the hospital with permanent disabilities and has accepted recruiting service rather than a discharge. The success of this plan was evidenced by the close attention accorded the speaker for almost two hours, during which he described conditions, hardships, successes and failures of warfare on the western front. Hardly a listener moved during this talk, and all left with a. feeling that they would have liked to hear more. FRED CARROLL, Secretary.

Jan 4, 1918

By J. A. Fulton

GOLD was discovered in the Sierra Nevada by J. W. Marshall on Jan. 2, 1848. The town: of Grass Valley soon sprang up and contained several stores in 1849; but the population of the town has always reflected the fluctuations in quartz mining. Gold-bearing quartz was found on Gold Hill in September 1850, and in the next two years most of the quartz bearing veins in the vicinity were located. At first, the quartz was crushed in mortars with spring poles; the Huff Co. took out $20,000 in this manner during the winter and spring of 1851. The first mill was put up in January, 1851. In 1866, there .were in Grass Valley 248 stamps, crushing 71,420 tons of ore with an average yield of $30 to $35; in Nevada City, there were 142 stamps, crushing 14,200, tons, with an average value of $25. But in 1918, only two properties in. this region, the Empire and the North Star, were producing. Since then, there has. been a revival of mining in the district and the following properties are being opened up: The Golden Center, Grass Valley Gold. Mines CO , Idaho-Maryland Mines Co., while the Sultana is kept unwatered and work is going on in a half dozen small properties.

Jan 2, 1926

Jan 1, 1919

Sec. 1. The membership of the Institute shall comprise six classes, namely: 1. Members; 2. Honorary Members; 3. Senior Members; 4. Associates; 5. Junior Members; 6. Rocky Mountain Members. All shall be equally entitled to the privileges of membership, excepting that no member of any class whom residence shall be outside of the United States of America, except those residing in Mexico and Canada, shall be entitled to vote. SEC. 2. Members: A person to be eligible for election or transfer into the claw of Member must be at least 27 years of age and must have had at least six years' employment in the practice of engineering, mining, geology, metallurgy, or chemistry, during at least three years of which he must have held positions of responsibility in one or more of these fields. This shall not apply to Rocky Mountain members.

Jan 1, 1936

By S.G. Bankoff

Ince1 proposed that electrostatic attraction between oppositely charged particles was responsible for slime-coating. Del Giudice2 postulated the metathetic formation of a cementing compound. Wark3 suggested that prevention of slime-coating was related to peptization of the slime. In the experiments of Table I the technique employed was essentially that of del Giudice, with the difference that the particle was examined under a film of water rather than dry.4 In general, the polished particle was agitated for 2 min. in a pulp consisting of 12.5 grams of the slime (—200 mesh) and 50 C.C. of distilled water, washed in three baths of distilled water, and examined at 220 diameters with the Leitz Ultropak. Observations of Brownian movement were made at 850 diameters with dark-field illumination. Several of these experiments do not jibe with the metathesis theory. According to published solubilities,5,6 the lead salts of the anions in experiments c through g are more insoluble than lead carbonate, there- fore should prevent the formation of lead carbonate on the galena surface. In experiment i the calcium oxalate, which precumably was on the calcite surfaces, should have permitted the formation of a lead carbonate cement by virtue of its greater solubility. Experiments j through m show that the addition of lime accelerates the deposition of quartz onto a galena surface. The writer is unable to postulate a satisfactory cementing compound, according to the metathesis theory, to explain this effect. These experiments led to the conclusion that the metathetic formation of a cement-

Jan 1, 1943

By S. G. Bankoff

INCE1 proposed that electrostatic attraction between oppositely charged particles was responsible for slime-coating. Del Giudice2 postulated the metathetic formation of a cementing compound. Wark3 suggested that prevention of slime-coating was related to peptization of the slime. [ ] In the experiments of Table I the technique employed was essentially that of del Giudice, with the difference that the particle was examined under a film of water rather than dry.4 In general, the polished particle was agitated for 2 min. in a pulp consisting of 12.5 grams of the slime (-200 mesh) and 50 c.c. of distilled water, washed in three baths of distilled water, and examined at 220 diameters with the Leitz Ultropak. Observations of Brownian movement were made at 850 diameters with dark-field illumination. Several of these experiments do not jibe with the metathesis theory. According to published solubilities,5,6 the lead salts of the anions in experiments [c] through g are more insoluble than lead carbonate, therefore should prevent the formation of lead carbonate on the galena surface. In experiment [i] the calcium oxalate, which presumably was on the calcite surfaces, should have permitted the formation of a lead carbonate cement by virtue of its greater solubility. Experiments [j] through m show that the addition of lime accelerates the deposition of quartz onto a galena surface. The writer is unable to postulate a satisfactory cementing compound, according to the metathesis theory, to explain this effect. These experiments led to the conclusion that the metathetic formation of a cement-

Jan 1, 1941

FRIENDS of the late Charles F. Rand presented in 1930 a sum of money from which the income is available to support various phases of the work of the Institute in which Mr. Rand was so deeply interested. At present the fund amounts to $10,000. The specific terms of the deed of gift are as follows: "The fund collected to establish a memorial to the late Charles F. Rand shall be placed in the custody of the Board of Directors of the American Institute of Mining and Metallurgical Engineers, to be set up as a trust to be known as the `Charles F. Rand Foundation,' the income of which shall each year be applied to a distinct purpose to be decided upon in that year by vote of the Board of Directors. This purpose shall be such as to promote the general welfare of the Institute and to constitute a permanent memorial of the usefulness of Mr. Rand, who for many years gave unstintingly of his time and talents in its service.

Jan 1, 1946

Arrangements have been completed in New York whereby the re- sources of The Engineering Foundation, under the auspices of the four principal national engineering societies, are placed at the disposal of the National Research Council, which was appointed by the National Academy of Sciences* at the request of President Wilson. The object of the Council is to coordinate the scientific research work of the country in order to secure efficiency in the solution of the problems of war and peace. The Council was without funds until The Engineering Foundation, established to further scientific and engineering research, offered to place its resources at the Council's disposal, including the services of its secretary, Dr. Cary T. Hutchinson, to act as-secretary of the Council. The offer was accepted and plans for immediate activities have been placed in the hands of an executive committee. In indicating how thoroughly, every branch bf science and engineering is represented, Dr. George E. Hale, Director of the Mt. Wilson Solar Observatory, and Chairman of the Council, when he was in New York attending to the details of the arrangement, called attention to the personnel of the body, saying that it is the purpose to enlist the cooperation, in the solution of our industrial and military problems of a scientific character, of every possible established agency. Medicine, for example, is represented on the Council by Dr. William H. Welch, President of the National Academy of Sciences, Brigadier General William C. Gorgas, , Surgeon Crenera.1 of the United States Army, Dr. Simon Flexner, Director of the Rockefeller Medical Institute, and Dr. Victor C. Vaughan, Past President of the American Medical Society; biological science by Dr. Edwin G. Conklin, Professor of Zoology, Princeton University; chemistry by Dr. A. A. Noyes of Massachusetts Institute of Technology and Dr. L. H. Baekeland; physics by Dr. A. A. Michelson of the University of Chicago; and electricity by Professor M. I. Pupin, of Columbia University.

Jan 10, 1916

By R. P. Marshall, L. P. Costas

The solid solubility of lithium in aluminum was determined by two independent techniques, electrical resistivity and microhardness, and the results are in close agreement. The solubility limits X-ray diffraction studies of the intermetallic compound LiAl indicate that its composition is nearly independent of temperature when in equilibrium with the terminal solid solution of aluminum. THE investigation of the aluminum-rich portion of the aluminum-lithium system at the Savannah River Laboratory was prompted by the observation that over-aged alloys consistently differed from the equilibrium states predicted by the latest published diagrams. Chemical analyses of these alloys showed their impurity contents to be quite low; therefore, the results obtained should have very nearly coincided with true equilibrium. A survey of the literature disclosed that previous studies had been made with metallographicig or electrical resistivity methods,4'5 but that agreement between results and technique was poor as evidenced in Fig. 1, which also includes the present results for comparison. The discrepancies have been attributed to impurities,3 and this is undoubtedly true in the early work.1'4'5 The latest Studies,''~ conducted with starting materials of higher purity, employed metallographic analysis, a technique that is quite sensitive to local homogeneity and depends strongly on subjective interpretation. In the present work the problem of defining solubility limits was approached in two ways. The first measured a physical property, electrical resistivity, at the equilibrium temperature. The second, a micro-hardness characterization of a diffusion zone, is a room temperature evaluation of a mechanical property under conditions removed from equilibrium. A close correlation between two such basically different approaches would strongly justify confidence in the results. I) MEASUREMENT OF SOLUBILITY OF LITHIUM IN ALUMINUM BY ELECTRICAL RESISTIVITY Experimental Procedure. Alloys for electrical resistivity measurements were made by melting and

Jan 1, 1962

By Noel W. Kirshenbaum, George A. Pouska, James M. Link

Literally millions of words have been written on the subject of mineral slurry pipelining. The sheer bulk of literature on the subject should be enough to convince the interested observer that the method is both viable and widely applied. It is the intent of this paper to examine typical mineral slurry applications. This examination should reveal the reasons that the slurry system was selected over other transport modes and it should provide a framework for determining the applicability of the technique to new projects. Slurry transport involves the conveyance of solid particles by suspension in a moving liquid. Almost any combination of solids in liquids may be imagined, and the conduit may be an open channel or a closed pipe. Historically, the most numerous slurry transport applications consisted of mineral particles in water. However, current research investigations are emphasizing other liquid carriers, specifically those which have greater economic value. Among these are gaseous and liquid fuels and chemical feedstocks. Another area being investigated involves the use of the pipeline as a chemical reactor system. The long residence time and turbulent flow characteristics of the pipeline make it particularly attractive for certain chemical reactions. Because these new systems involve a valuable liquid as well as a valuable solid, there is increased attention to solid-liquid

Jan 1, 1980

By Arthur Flagg

(New York Meeting, February, 1913.) THE Elk City mining district of Idaho occupies a position near the geographical center of Idaho county, a region of mod¬erate elevation in the western foot-hills of the Bitter Root mountains. The district comprises an area of approximately 350 sq. miles, bounded oil the west by the Newsome district and on the south by the Dixie and Oro Grande districts. There are no mining districts to the north or east. Elk City, the principal town and the seat of the mining office for the district, is situated in a hydrographical basin surrounded by low hills. The elevation is 4,200 ft. above sear level. Through this basin flow Elk Creek, Red river, and American river, which unite west of town to form the south fork of the Clearwater. The one township is set out from the Bitter Root Forest Reserve. Though a railroad starting from the Stites terminus of the Clearwater Short Line of the Northern Pacific railroad has been under consideration for some years, the camp is yet with¬out railroad facilities. The projected road would follow the south fork of the Clearwater on easy grades, but would be very expensive to build and maintain. While such a road would greatly benefit those who are now operating in the camp, and in a slight degree stimulate interest in its possibilities, there is hardly business enough to warrant its construction.

Jan 4, 1913

By Horace Winchell

AN EXAMINATION of the Pachuca and El Oro. districts in July, 1920, although cursory and incomplete, disclosed facts of more than passing interest to the student of ore deposits; and inasmuch as the literature on these districts is limited and some of their features are little understood, a brief account may prove valuable as reconnaissance observations to be amplified by more thorough and competent observers in the future. Where no complete monograph of important mining camps has been published a partial presentation of the data is often useful, as it sometimes leads to fuller and more accurate descriptions, by stimulating discussion. The following notes are presented with the consent of Mr. A. F. Main, managing director of the El Oro Mining and Railway Co., whose fund of information and wide acquaintance with both districts alone made it possible to cover so much ground in a short time. I have also to acknowledge gratefully the aid of Messrs. C. A. Lantz and D: S. Calland of the Santa Gertrudis and Real del Monte companies, respectively, in connection with permission to inspect geological features of interest in their mines.

Jan 6, 1921

By Michel Daghert, Michel David

In the exploitation of large porphyry type deposits where a cut-off has to be applied and where "internal waste" exists, planning people ask the geologist for the estimated grade of small blocks. Comparison with actual production figures and blast hole assays shows that any kind of weighted average of neighboring DDH (diamond drill hole) samples provides an excessingly smooth picture of reality, resulting most of the time in overevaluation of tons of ore. Solutions based on examination of Past production data exist14 but it would be necessary to have a solution which can be applied before production starts as the preceeding problem also results in an overestimation of the total reserves, often by as much as 20%, thus changing the mine life accordingly and destroying any "optimum planning" which could have been done. The proposed alternative is to forecast the grade distribution of small blocks in a larger block, sufficiently well documented. Several Possible ways to estimate these distributions are reviewed and emphasis is placed on recently developed methods (source G. Matheron) where the coefficients of the orthogonal polynomial series expansion of the distribution of any size of block are directly estimated by kriging. The efficiency of the technique is tested on a level of the Cyprus Pima open pit where the predicted recovery is compared to actual production figures.

Jan 1, 1980

By Arthur F. Johnson

THE principal costs of making a pound of aluminum are for 9 kw-hr of electricity and for 1.9 Ib of the oxide (A1203) called alumina. A pound of alumina is made by digesting 2 or 3 lb of bauxite in hot caustic solutions, settling and filtering out the oxides of silicon, iron, and titanium and precipitating and calcining the A1203 as a pure, white powder. The cost of foreign bauxite delivered at an alumina plant in the U.S. may equal or exceed the cost of its chemical treatment to make alumina. Some of the principal factors affecting costs in the utilization of foreign bauxites are: transportation from mine to market, mineralogical and physical composition of the bauxite, thickness of the bauxite beds and their clay and forest overburden, amen- ability of the bauxite to beneficiation and to caustic extraction of the alumina, and lastly size of bauxite deposits and rate of mining employed.

Jan 6, 1954

By Eugene A. Smith

Geological Relations. In his second report upon the Geology of Alabama, Prof. M. Tuomey calls attention to a rock occurring near Florence, in the Tennessee valley, the composition of which is as follows: Per cent. Carbonate of lime,.. .. .. ..16.41 Phosphate of lime,.. .. .. ..14.19 Peroxide of iron,.. .. .. .. .36 Quartz and other insoluble matters,. .. ..68.72 99.68 This rock was referred by Prof. Tuomey to the Carboniferous, because he found the Carboniferous limestones always resting conformably upon it, whilst both rest uncomformably upon the underlying Silurian or Devonian rocks. The recent discovery in Tennessee of phosphate-rock of this age (or approximately so) has stimulated the search in Alabama for similar rich material; but our search has been, up to this time, unrewarded by the finding in quantity of anything of better quality than the rock whose analysis is given above. It is, however, in high degree probable .that the rich phosphaterock of Tennessee will at some time be found to have its counterpart in Alabama. Materials of several kinds, containing a notable quantity of phosphoric acid, have been found in Alabama in both the Cretaceous and the Tertiary formations, and for our present purpose they may be most conveniently considered in their geological relations.

Jan 1, 1896

For the first time in its history the Institute will hold a meeting in the State of Arizona. A few years ago Arizona stood third in the copper-producing districts of the United States. Since that time, with the development of porphyry mines, the output has gone up with great rapidity until it not only is the leading district, but its output at the present tune is at the rate of nearly double the Montana output; which now stands second in the list. In connection with this development, most interesting departures have been made in methods of mining, concentration and smelting. Principles of mining and metallurgy of the greatest interest will be covered by papers which will appear in the Bulletin and be presented at Technical Sessions, while ample opportunity 'will ,be- afforded for those who go to the meeting to see all the points of interest to them. In addition, members will be well rewarded by the marvelous natural features to be seen on the trip, including the petrified forests, the cliff dwellings on the Apache Trail and the Grand Canyon of Arizona. It is planned to start the special train from New York, but members and guests may join the special at other points en route as indicated by the following schedule: ITINERARY Thursday; September 14th, Lv New York Grand Central Terminal 5.30 p.m. Dinner in dining car, a la carte

Jan 9, 1916

By P. A. Young

The historical background of on-strand cooling is given, together with a resume of recent practical developments. Laboratory test procedures are then considered in detail, for both productivity and quality parameters, with particular reference to the design of the Ravenscraig No 3 machine (Scotland). A heat transfer model is presented for a porous sinter with propagating cracks. The influence of cooling/sintering area ratio, sinter strength, granulometry, return fines, coke consumption and FeO levels are examined in relation to economics. A detailed comparison of capital and running costs for two different strands, designed for identical duties, but with off or on-strand cooling, is then given.

Jan 1, 1977

C. W. GOODALE, Butte, ,Mont.-While there are many points in Mr. Read's, paper which I am not prepared to discuss thoroughly, I am inclined to believe that difficulties are involved in the establishment of all employment bureau, which shall have exclusive control over the employment and discharge of workmen. I suppose you .have heard a great deal: about the so-called "rustling card? at the works of the Anaconda company. That is a very innocent sort of card, although the I. W. W. organization has made a great deal of noise about it. An applicant for a job is handed a blank on which he tells his nationality, his age, whether married or single, and the place of his last employment. The company then writes to the place where he says he was last employed to find out whether he is telling the truth; we do not ask the previous employer whether the man is blacklisted or has anything; against his record; but simply, "Was this man formerly in your employ?" A great hullabaloo has been made, about this practice by some of the men in Montana who are afraid, of their own records; but out of 53,000 applications for employment received by the Anaconda company since the employment bureau was formed, only 647 were rejected, which does

Jan 1, 1918

NEW MEMBERS The following list comprises the names of those persons who because members during the period Jan. 10, 1916 to Feb. 10, 1916. ATWATER, MAXWELL WANTON, Min. Engr Box 156, Basin, Mont. BARKDOLL, IVAN HARRY, Supt. of Mines, Old Dominion Copper Mill. & Smelt. Co., Globe, Ariz. BEAUDRY, WILLIAM A., Managing Director ....Stewart Mining Co., Kellogg, Ida. BRIGGS, CHARLES H Mill Supt., Admiralty Zinc Co., Miami, Ariz. CHURCH, L. C., Min. Engr Joplin, Mo. DAVIS, LLOYD J., Sales Engr; Ingersoll-Rand Drill Co., Joplin, Mo. DAVIS, SIDNEY H., Mgr Century Zinc Co., Joplin, Mo. DUGAN, J. H., Engr. and Contractor 65 N. Vine St., Hazleton, Pa. ELLIS, HUBERT INGERSOLL, Min. Engr., Bunker Hill & Sullivan MILL & Cons. Co., Kellogg, id..

Jan 3, 1916