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By W. F. Brace, James D. Byerlee

Although prediction of failure of rocks may be ultimately possible without knowing in detail how failure occurs, understanding of this process is certainly of fundamental interest in rock mechanics. Of the various failure mechanisms, probably brittle fracture is of greatest interest. Recent reviews have brought this subject nearly up to date (Hock,1 Price,2 and Jaeger 3) and here, we summarize certain recent developments. As our understanding of brittle fracture is derived almost solely from laboratory studies this will amount to a review of certain laboratory experiments. New studies in four areas are pertinent; these concern 1) the volume changes which accompany brittle fracture, 2) the propagation of cracks in compression, 3) certain frictional characteristics of rocks and minerals at high pressure, and 4) the law of effective stress for crystalline rocks. Our objective here is less to present an entirely consistent, complete picture of how a rock fractures than it is to emphasize gaps in our understanding and, thus, suggest areas that need further study. Progress is still painfully slow in this field and perhaps this approach will stimulate new work. OBSERVATIONS Although the behavior of large rock masses is most often the concern in rock mechanics, the number of large-scale experimental tests is still vanishingly small. Our experimental observations arc, by and large, still made on small, relatively flaw-free, rock samples. Here also we report the behavior of small samples.

Jan 1, 1967

By Charles T. Holland

In connection with the problems of bumps in coal mines, much has been written concerning the manner in which roof action and methods of mining enter into the pressure effects observed but little has been written upon the relationship between the physical properties of coal and associated rocks and the cause of bumps. The question of the strength of bituminous coal, of its elasticity, and the energy it can absorb and store has been neglected to a considerable extent in connection with this problem. It is generally agreed that one of the necessary conditions for bumps is a strong coal.' Therefore, since the strength of coal is an important factor, a study of this property should be made. several investigators have conducted laboratory experiments upon the strength of coal, using small cubical or rectangular test pieces. An attempt will not be made to go into all of these investigations, but they are briefly summarized in Table I. Experiments of the U. S. Bureau of Mines and of Lawall and Holland (pp. 27 and 34 of ref. 9), however, indicate that regardless of whether the coal is a soft and weak semihituminous (Pocahontas No 3) or a hard and strong bituminous (Stockton) coal, the maximum ultimate unit stress developed in laboratory tests is higher in small cubes than in larger cubes of the Same coal.

Jan 1, 1942

By M. W. Bartley, Hugh M. Roberts

SUBSTANTIAL deposits of Bessemer hematite have been found recently by drilling beneath Steep Rock Lake, Ontario, which is situated in the northern part of the Lake Superior Region. It will be practicable to divert the waters flowing into this lake and develop open pits on the upper part of two large ore bodies by damming off and pumping out the water in the part of the lake in which they occur. Ultimately, the bulk of the ore will be mined by underground methods. Owing to the generally massive nature of the rocks in the area, no underground flows of major consequence are anticipated after diversion of the lake. The Steep Rock deposits are attributed in origin to hydrothermal replacement. They were formed, for the most part, along an unconformable, brecciated contact between the Steep Rock limestone and an overlying younger volcanic series. The replacing solutions came in as igneous after-effects, following upon the intrusion of basic igneous rocks that invaded the hanging-wall volcanics. It is believed that this took place in a geological period roughly equivalent to late Middle Huronian, which was the period when the most extensive iron-bearing rocks of the Lake Superior Region were formed. Comparison is made with other deep-seated iron-ore bodies in the Lake Superior Region, the origins of which are ascribed in the discussion to hydrothermal replacement.

Jan 1, 1943

By Charles T. Holland

In connection with the problems of bumps in coal mines, much has been written concerning the manner in which roof action and methods of mining enter into the pressure effects observed but little has been written upon the relationship between the physical properties of coal and associated rocks and the cause of bumps. The question of the strength of bituminous coal, of its elasticity, and the energy it can absorb and store has been neglected to a considerable extent in connection with this problem. It is generally agreed that one of the necessary conditions for bumps is a strong coal.' Therefore, since the strength of coal is an important factor, a study of this property should be made. several investigators have conducted laboratory experiments upon the strength of coal, using small cubical or rectangular test pieces. An attempt will not be made to go into all of these investigations, but they are briefly summarized in Table I. Experiments of the U. S. Bureau of Mines and of Lawall and Holland (pp. 27 and 34 of ref. 9), however, indicate that regardless of whether the coal is a soft and weak semihituminous (Pocahontas No 3) or a hard and strong bituminous (Stockton) coal, the maximum ultimate unit stress developed in laboratory tests is higher in small cubes than in larger cubes of the Same coal.

Jan 1, 1942

THE power requirements of the Mount Lyell Mining and Railway Company at Queenstown, Tasmania, have, since the inception of smelting operations in June, 1,,896, been derived continuously from the extensive forests in the watershed of the Queen River, adjacent to -the works, the firewood being of good quality, mainly composed of myrtle or beech (Fagus Ounninghami), eucalypts, and manuka (Leptospermum ericoides).The country is very rugged and mountainous, indented by numerous ravines and gullies, and intersected by many creeks, which are subject to periodical floods, under the influence of a heavy and persistent rainfall. The areas so far exploited aggregate a total of about 42 sq. 'miles, and this denuded country gives promise of ultimately becoming very valuable pastoral ground for cattle-raising. The tonnage of wood yielded per acre varies from 40 to 100 tons on stack measurement of 80 cub. ft. per ton, 60 tons per acre being considered a good average yield. The gross amount of firewood handled during the past 13 years approximates 1,200,000 tons, the greater portion of which has been obtained by ordinary tramming methods. The company's main line of railway, 3-ft. 6-in. gauge, has served as a trunk line for all supplies derived from the Queen River valley, south of the reduction works, while the northern and western areas have been exploited by means of...

Jan 1, 1911

By Brinkmann J. R

The relative effects of the two basic mechanisms contributing to rock breakage during blasting, shock and gas penetration, are neither well understood nor well characterized, and need further clarification. Blasthole liner (BHL) tests separate the two effects, and by enabling direct measurement of borehole expansion give insight into the shock/gas energy partitioning in rock confinement. The hydrodynamic code DYNA2D is used to simulate the shock effect of the detonation of emulsion in a stainless steel lined hole, and the predicted expansion is compared with experiment. Workers in the past have neglected near-blasthole phenomena and have calibrated models based on stress measurements remote from the blasthole. Extrapolation back to the blasthole has inherent limitations, and indeed, one of the deficiencies of these models is that they have not been able to predict correct borehole expansions, as observed in BHL experiments. DYNA2D has been enhanced by the ICI group with a detonation model which resolves the explosive reaction zone. As a preliminary step towards the ultimate goal of devising a practical damage model, simulations are used to predict the maximum expansion that would take place if the rock were to remain undamaged. Various material parameters are investigated and it is shown that calculated liner expansions are appreciably lower than measured values for high rock yield strengths, while greater than values for low yield strengths.

Jan 1, 1990

By Charles T. Holland

IN connection with the problems of bumps in coal mines, much has been written concerning the manner in which roof action and methods of mining enter [ ] into the pressure effects observed but little has been written upon the relationship between the physical properties of coal and associated rocks and the cause of bumps. The question of the strength of bituminous coal, of its elasticity, and the energy it can absorb and store has been neglected to a considerable extent in connection with this problem. STRENGTH OF COAL It is generally agreed that one of the necessary conditions for bumps is a strong [ ] coal.1 Therefore, since the strength of coal is an important factor, a study of this property should be made. Several investigators have conducted laboratory experiments upon the strength of coal, using small cubical or rectangular test pieces. An attempt will not be made to go into all of these investigations, but they are briefly summarized in Table I. Experiments of the U. S. Bureau of Mines8 and of Lawall and Holland (pp. 27 and 34 of ref. 9), however, indicate that regardless of whether the coal is a soft and weak semibituminous (Pocahontas No. 3) or a hard and strong bituminous (Stockton) coal, the maximum ultimate unit stress developed in laboratory tests is higher in small cubes than in larger cubes of the same coal.

Jan 1, 1942

CONTENTS PAGE Ross, J. M. and WAYLAND, R. G.-Mining Methods at the Homestake. Discussed by Benjamin F. Tillson, R. M. Raymond, I, H. Barkdoll, Arthur Notman 1 EMMEL, RUDOLPH.-Mining Methods in Zaruma District, Ecuador. Discussed by Rudolph Emmel, George A. Packard, Fred Hellmann, R. M. Raymond, Arthur Notman 2 MISHLER, R. T. and BUDROW, L. R.-Methods of Mining and Ore Estimation at Lucky Tiger Mine. Discussed by Fred Hellmann, Benjamin F. Tillson...4 PARK, JOHN FURNESS.-Mining Methods of Jarbidge District. . Discussed by R. S. Lewis : 5 Mining Methods at the Homestake Discussion of the paper of A. J. M. Ross and R. G. WAYLAND, presented at the New York Meeting, February, 1925, and issued, as Paper No. 1408-A, with MINING AND METALLURGY, February, 1925. BENJAMIN F. TILLSON, * Franklin, N. J.--It requires a good deal of timber to operate, especially the caving systems. An important function in mine operations now seems to be forestry and to operate a timber tract in order to insure a supply of timber. By depleting the timber resources of your section, you only increase your costs later when timber must be brought in from the Pacific Coast or the East. Our experience has been that any square-set method of timbering is the most expensive. Timbering for stoping systems, top slicing if you will, although it uses a large volume of time does not require as expensive timbering as the square-set method; also it does not require as long a life for-the timber, so that such wood as birch and maple, which have strength but not long life under the fungus conditions in the mine, may be used. All the drifts in the orebody are thoroughly timbered, and it has required a lot of timber. If we had it to do over, we would spend a lot more money in the development of rock drifts; as a matter of fact, we must ultimately come to that any way.

Jan 6, 1925

By J. J. McDougall

The Windy Craggy copper-cobalt-bearing massive sulfide lies in the Tatshenshini map area of northwestern British Columbia, where British Columbia joins Alaska and the Yukon. The area is covered with numerous glaciers and ice fields that mask geologic detail and hamper ground access. In 1957, Ventures Ltd., the predecessor of Falconbridge Ltd., undertook a reconnaissance of the area using a float-equipped Supercub. At that time, large lakes and glaciers were unnamed and little was known of the geology. The prospecting team was led by J.J. McDougall with Stan Bridcut as pilot-prospector. Prospecting was directed at the St. Elias Mountains between the rich Kennecott copper deposits to the northwest and the Maid of Erin silver-copper mine on the Haines Road, BC. Reconnaissance flying in 1957 and early 1958 eliminated vast segments of the Kennecott-Haines Road terrain as being too inaccessible for mining. In 1958, the Supercub landed at an unnamed lake and the terminal moraine of an unnamed 12.9-km (8-mile) long glacier was prospected. The lake was called Tats Lake and the glacier named Tats glacier (short for Tatshenshini). Float of sulfide was found in the moraine. Follow-up investigation along Tats glacier led to the discovery of several small sulfide deposits and these were staked. Prospecting active glaciers in this area can be complicated because of drainage capture by eroding valley glaciers. Glacier capture resulted in the float from one mineralized area being deposited at different times in three widely separated moraines. Float of the Windy Craggy deposit, therefore, occurs along the course of older glaciers and at the base of the currently active ones. The problem of sourcing caused much additional Supercub reconnaissance. It is interesting to note that about 40 geographic names were given various features in this unmapped portion of the St. Elias Range, and these names were ultimately officially adopted.

Jan 1, 1991

By Jorj O. Osterberg

The practice of using side shear resistance in the design of drilled shafts socketed in rock is discussed. In the absence of field test data for the particular rock involved, the designer often neglects the side shear altogether or uses an extremely conservative value. The uncertainty of using strength data from compression tests on rock cores is discussed. Examples of full scale load tests are given which illustrate that even in the weakest of rocks, considerable side shear resistances are obtained, enabeling reductions in the depths of the sockets and consequent savings. Existing Practice. The existing design practice in using side friction/bond between a drilled shaft in rock or hard soil varies very considerably in different areas of the U.S., in different areas of the world, among different Geotechnical Engineers, and in the requirements of different building codes. In fact, the variation is so great that it is inconsistent and contradictory. For example, in Florida where fairly weak coral limestone and sandstone is prevalent, the general practice is to use side friction only and to allow no end bearing. In Chicago, Detroit, Boston and other areas where soft clay overlies stiffer clays, hardpan and limestone or other hard rock, the common practice is to allow for no friction and to use end bearing only, even though the lower portion of a shaft frequently penetrates stiff to hard clays and hardpan (glacial till) before bearing on hardpan or rock. In Hong Kong, if the hole is stabilized with drilling mud, no end bearing is allowed. In Boston (Thompson, Erikson, and Smith, 1989), two tests at two sites on 18 inch pipe piles penetrating 100 feet of soft clay and driven only inches into an argillite, tested 140 and 210 tons in ultimate side shear resistance. Certainly, with long drilled shafts, no matter how soft or weak the soil or rock is, some if not considerable side friction occurs, and where drilling mud is used, there must be considerable end bearing.

Jan 1, 1991

By John Henry Harden

It appears that in the earlier days of anthracite coal mining, 1824-25, the Lehigh region mined 76 per cent. of all the coal sent to market. During the same period Wyoming sent 12 and 5 per cent. respectively, whilst the Schuylkill sent 11 and 18 per cent., the number of tons marketed being in those days very small indeed. In the year 1828 the Schuylkill region mined over one-half of all the coal sent to market, and continued to do so for thirty years (with the exception of the year 1831), until 1858 ; since that date the production has declined very steadily in comparison with the other regions, until, in 1876, it was only 34 per cent. Wyoming, in the year 1820, was mining 40 per cent., but the production of all the regions was very small; in six years it declined to 5 per cent., increased to 34 per cent. in 1831, declined to 10 per cent. in 1838. Since which time the increase has been gradual, until 1873-75 Wyoming produced over 50 per cent. of all the anthracite coal sent to market. In 1867 the production exceeded that of Schuylkill, and has continued to do so since that time. In the year 1876, during the existence of the "coal combination," Wyoming lost 9 per cent.; during the same time Lehigh gained 7 and Schuylkill 2 per cent. over their relative production of the preceding year, the decrease of Wyoming being two and a half million tons, the increase of the Lehigh one million, the decrease of the Schuylkill nearly three-quarters of a million. The extraordinary production of the Lehigh region at a time of decreased demand and in opposition to an agreement with the other regions to limit the supply to the supposed demand mas the cause of the disagreement which ultimately broke up the combination of the great coal-producing and carrying companies. The Lehigh region produced very steadily, from 1829 to 1854, an average of about 22 per cent. of the whole production. From 1854

By S. R. Elliott

THE Spies mine is located in the eastern half of the northwest quarter of section 24-43-35, near the village of Iron River, Mich., and is operated by The Cleveland-Cliffs Iron Co. Speaking generally, the jasper hanging walls of most of the deposits in the Iron River district dip at a steep angle and are exceedingly strong, standing without caving, even after mining has been continued for years and after large excavations have been made. The ore is fairly hard and tough and contains no slippage faces. It occurs in large masses, which are often egg shape, with the smaller end down, and can be mined in, open stopes without the use of timber. The common system employed in the district is the shrinkage stope, or some modification of it. The Spies system was developed to utilize the advantages of the open-stope method and to avoid the disadvantages of the shrinkage stope. The Spies shaft was sunk to such a depth that the bottom, or third level, was in rock at a short distance below the bottom of the orebody, the shape and extent of which had been previously determined by diamond drilling. This is shown in plan and by the ore contours at the first, second, and third levels in Fig. 1, and in section in Figs. 2 to 7. In order to provide the necessary mills and raises, three parallel crosscuts were driven on 25 ft. centers on the bottom level. Drifts on the second and first levels were driven to the orebody and followed the foot wall in a southerly direction to the end of the ore. In crosscut 3, Fig. 1, raises 30, 40, 50, and 60 were carried up on the foot wall and holed into the second level, and were ultimately carried up and holed into the first level. These foot-wall raises carry the pipes and ladders, provide a means of ventilation, and furnish safe communication to all working places in the stope.

Jan 3, 1922

By Ronald D. Hill, Elmore C. Grim

1. Potential groundwater pollution resulting from large-scale surface mining in western states should be evaluated. 2. Criteria should be developed for the design, construction, operation, and abandonment of sediment ponds for maximum removal of suspended solids. 3. Methods should be developed for reducing suspended solids discharges from surface mines to less than 30 milligrams per liter. 4. A manual should be developed in the form of guidelines for sediment and erosion control planning and implementation. These guidelines must be designed to cover all phases of the coal surface mining operation (i.e., before, during and after mining). 5. A mine road manual should be developed for use by surface mine operators and State and Federal Agencies. Erosion, water control, and dust control should be covered in detail. 6. The block-cut, head-of-hollow fill, and mountain-top removal methods and techniques of contour mining should be evaluated, designed, and ultimately demonstrated in steep, mountainous terrain. Designs should be prepared for single and multiple seam applications. The demonstrations must show that these mining systems will secure rapid achievement of reclamation require¬ments and provide maximum, safe, economic coal recovery in an environmentally safe manner. 7. A Blasting Manual should be developed for use by industry and enforcement agencies. Stress should be placed on how to keep vibration levels and air blast pressures well below accepted safe criteria. Also, methods that can be used to control noise should be listed. 8. Investigations should be conducted on the effect of continued vibrations from blasting on structures that are near quarries. 9. Additional guidelines need to be developed for sampling and analysis of overburden material and associated coals for trace elements and noxious strata. Samples are extremely sensitive, and the source and manner of their collection, handling, storage, and treatment, as well as the techniques of analysis, need to be developed and described. This information can be used to predict possible future problems.

Jan 1, 1974

By Stefan Mutz, Thomas Pretz, Jörg Julius, Frank Hilbk-Kortenbruck, Aachen, Hartmut Harbeck

"The annual global production of primary aluminium was about 22 million tons in the year 2000. This represents the second largest production rate in the world market after steel. Experts are predicting that the global demand for aluminium will rise in the near future.In contrast to other metals such as copper, the recycling of aluminium is considered relatively difficult. There are two main alloying groups, namely cast and wrought. In the case of aluminium it is important that the constituents within the scrap aluminium to be smelted are clearly identified. Within the secondary remelting process alloying does take place, but a removal of unwanted metal constituents is problematic. Therefore mixed aluminium scrap (not genuine in-house collected material) can only be used to produce cast aluminium. Thus, in other words a down-cycling of wrought (extrusions and rolled) products occurs. However, in spite of these difficulties there is an increasing trend to produce aluminium from secondary scrap (approx. 35% in Germany). Similar trends have been identified in the USA and other industrialised countries. This development is mainly caused by the high energy consumption for the production of aluminium from bauxite. Producing aluminium from scrap is saving about 95 % of the energy in comparison to the processing of primary raw materials.An improvement in sorting technology is necessary to separate wrought and cast alloys of aluminium as the absolute amount of recovery from old scrap is higher than the demand for cast.This contribution presents some alternative methods, utilizing automatic picking technologies, which will be used to separate secondary aluminium in the future. During the recent years, some major progresses have been made in automatic picking technologies for different applications in the processing of primary and secondary materials.For the sorting of aluminium scrap a special additional sensor will be necessary. The best detection will ultimately be based on online elemental analysis of single particles. First investigations in the field of laser based systems for these applications have already been performed several years ago. One of the laser based techniques is the laserinduced breakdown spectrometry (LIBS)."

Jan 1, 2003

By K. Konialis

In the last twenty years, the mining industry has made marked efforts to improve its reputation in regard to its social performance. These efforts have been expressed in the 9th ICMM (International Council on Mining and Metals) principle as a commitment to contribute to the social, economic and institutional development of the local communities. Towards this goal, which has been increasingly highlighted because of its importance for sustainable development, a number of practices and methods have been developed. The international development literature describing these practices is full of so-called development buzzwords, such as stake-holder participation, empowerment, capacity building. This paper argues that none of these development catchwords are neutral, but contain assumptions based on a specific view of development. Since capacity building is a central task in development, the paper focuses on this concept and takes a critical look at the assumptions that underlie this concept and influence strategies employed by the mineral sector. It suggests that the notion of capacity building in some earlier approaches implies a set of asymmetric power relationships between developed and developing countries where capacity is transferred from the developed countries to the developing ones. The developing countries are seen as passive recipients while the experts, i.e. the developed countries through their mining companies ultimately control the capacity-building process. The paper also points out that the mainstream capacity development approach has been based on the assumption that local or indigenous communities are mainly made up of needs and capacity gaps. The goal of development projects should then be to address these needs, which are perceived and prioritized by the ?experts?. Critiques of this development model suggest that in order for the mining industry to embrace more successful and sustainable practices, it should rethink the notion of capacity building. It should move towards alternative approaches that see it as a two-way learning process which will serve to enhance not only the capacities of the communities, but also of the development practitioners and which will build on the strengths of the community, and move away from attitudes of superiority and practices of dependence.

Jan 1, 2007

By A. Redfern, B. G. D. Smart

The ultimate objective of the development work presented in the paper is to devise an appropriate method for relating powered support specification to geological conditions and mining practice, thus enabling the longwall method of coalmining to be successfully implemented throughout the varied coalfields of the world. The paper begins with a review of various methods previously used to determine support rating, each method being analysed with regard to its source, the logic and theory which constitute the method, and subsequent recommendations. An alternative approach is then proposed, the Powered supports being considered to be one of three foundations, sharing load with coal ahead of the faceline which acts as another foundation, and the waste behind the supports which acts as the remaining foundation. The load/deflection characteristics of the coal and waste, which in turn are related to geological conditions and mining practice, are shown to affect the load transfer on to and hence the specification of the powered support. In particular the characteristic of the waste foundation is shown to be affected by the caving mechanism, an alternative form to that mechanism accepted for British conditions being proposed and designated "parting-plane-controlled" caving. A finite element solution for a beam on elastic foundations was used to translate the above concepts into numerical results, these results being compared with data from Indian and Chinese operating conditions. The Indian case study examines the effect of using a conventional chock type of support in a one-web back mode when mining towards a roof break generated ahead of the face, while the Chinese case study compares measured subsidence over a longwall with "blocky" roof conditions with the model results. The comparisons are encouraging, suggesting that the approach used is worthy of further development.

Jan 1, 1986

By Charles A. Ashburner

The petroleum industry of western Pennsylvania and southwestern New York lias been one of phenomenal development. Greater and more sudden flucuations hare occurred in the price* of crude oil, and in all the collateral interests dependent upon its production, than in the case of any other mineral product which has been extensively exploited in the United States. This was more particularly so from the commencement of drilling for oil in 1859 down to the end of 1877. The experience gained during these early years has enabled the oil men to operate more intelligently since; the business is not now attended with the hazardous risks with which it is generally credited. The most important questions connected with the oil industry are those of (a) the oil-supply, and (6) the possible ultimate exhaustion of the field. Since 1876 my attention has been directed to the study of the statistics of the product of the oil regions. In January, 1880, in order to slow some interesting points connected with these questions, I prepared a graphic chart which was used to illustrate a lecture on petroleum delivered before the Franklin Institute. This chart was afterwards reconstructed in two distinct forms for publication in the census report. on Petroleum and its Products. These latter I have redrawn in a condensed form, and have extended them to include the statistics up to 1885, for publication in the Transac tions of the Institute, in conjuction with a map of the oil-re&'~IOIIS prepared by Mr. John F. CarII and myself. It is hoped that these illustrations will be found interesting to the members of the Institute, and of practical utility to oil-men, without any extended discussion, since it is my desire to make only such brief references to them and give such additional detailed facts as may serve to make the prominent features understood.

Jan 1, 1886

By A. Hansson, G. E. Tardiff

WHILE it is generally known that cold-worked low-and medium-carbon steels exhibit substantial increases in tensile rupture ductility with increased deformation velocity172 (up to the von Karman limit), the observations for annealed or normalized steel do not permit simple generalization. Various investigators, for example, have reported both small increases1,3 and small decreases4,5' in rupture ductility with increased rates of deformation of normalized low-carbon steel. The purpose of the present note is to report on the dependence observed for strain-aged steel since preliminary work here indicates that strain aging results in the development of a consistent type of behavior that is understandable in the light of current knowledge of the lower yield dynamics for steels which deform inhomogeneously.6 This realization throws additional light on the influences responsible for the behavior of normalized steel. The results presented here were obtained for a 0.21 pct C, 0.012 pct N sheet (0.012 in. thick) steel which was received in a temper-rolled condition (approximately 3 pct reduction in thickness after process annealing); the as-received material had a spherodized structure with a ferritic grain size of ASTM 8. The material was selected for testing after 6 months room temperature aging, at which time the static lower yield and ultimate tensile strength measured 79 and 82 kpsi, respectively. ASTM 2-in. reduced section, 1/2-in.-wide specimens were used in smooth bar tests and 3/4-in.-wide specimens containing two 60-deg opposed edge notches (root radii = 0.002 in.) were used in notched bar tests. To facilitate strain measurement, the smooth bars were blued with ink and marked at 0.1-in. intervals along the gage length; the notched

Jan 1, 1968

By D. Harrington

ONE of the main functions of the United States Bureau of Mines is to obtain and disseminate information that will promote safety in and around mines, and the health and safety of employees engaged in mining. Serious health and safety conditions arising out' of contamination of air in metal mines by dust, fumes from explosives and fires, and absorption of oxygen by timber and other causes, led the Bureau of Mines to cooperate with the United States Public Health Service in the study of dust occurrence and ventilation in metal mines in various parts of the country. Dr. A. J. Lanza, of the U. S. Public Health Service, and Edwin Higgins, mining engineer of the U. S. Bureau of Mines, in 1915, made a detailed study in the mines around Joplin, Mo., their reports1 are now available. In 1916, 1917, and 1918, a similar study was made in the Butte, Mont., region by Doctor Lanza and D. Harrington, mining engineer of the Bureau of Mines; the reports of this investigation will be available soon. In 1919, the study was continued in some of the Arizona mines by D. Harrington, of the Bureau of Mines, and G. E. McElroy and Dr. R. A. Koronski, of the U. S. Public Health Service, the underground work being completed in June, 1920; these reports are now being prepared for publication. In the spring of 1920, the scope of the work was extended, with D. Harrington in charge as supervising mining engineer, and short studies made in the mines of the Coeur d' Alenes in Idaho and around Oatman, Ariz. It is hoped soon to extend the work into mines of California, Nevada, Colorado, Michigan, and Minnesota, and ultimately to other states should the mining companies be willing to cooperate.

Jan 2, 1921

By R. H. Matjie, J. R. Bunt, C. A. Strydom

"A number of conventional and advanced analytical techniques (proximate and ultimate analysis, low-temperature oxygen-plasma ashing, X-ray diffraction, X-ray fluorescence spectrometry, coal petrography, and lightelement electron microprobe analysis) have been integrated and crosschecked to provide detailed characterization of coals from the Highveld coalfield in South Africa, as a basis for better understanding of the mineralogical and chemical properties of the individual coal sources that are blended as feedstocks for combustion and carbon conversion processes. The techniques included methods to quantify the abundance and composition of the mineral matter (minerals and non-mineral inorganic elements), and also the abundance and chemical composition of the individual macerals in the individual coals concerned.Kaolinite is the most abundant of the minerals in the coals studied, with lesser but still significant proportions of quartz, mica and/or illite, dolomite, calcite, and pyrite. Small but variable proportions of anatase, goyazite, and siderite are present in some coal samples. Electron microprobe analysis, based on a special configuration for light-element study, shows that the vitrinite contains less carbon and more oxygen, and has significantly higher concentrations of nitrogen and organic sulphur, than the inertinite macerals in the same samples. Minor proportions of organically-associated inorganic elements, including titanium, were also identified in some of the maceral components.A comprehensive knowledge of the minerals and non-mineral inorganic elements in the coals used for feedstock preparation, obtained by integration of data from these advanced analytical techniques with more conventional analyses, may be of benefit in understanding the processes that take place during coal utilization, and also in avoiding or ameliorating some of the operational and environmental problems that may occur in different sectors of the coal utilization industry."

Jan 1, 2016