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By H. I. Aaronson, C. Wells

THIS is a preliminary report on a detailed metal- lographic investigation of the bainite reaction in a plain carbon hypoeutectoid steel. In view of the current interest in the bainite reaction and of the controversies which still exist about even the basic phenomenology of this mode of transformation, it was considered desirable to present a summary of the more important results obtained to date prior to the completion of this investigation. The steel used contained 0.29 pct C, 0.76 pct Mn, 0.25 pct Si, 0.005 pct P, and 0.007 pct S. The alloy was homogenized for 48 hr at 1250°C. Individual specimens were then austenitized for 30 min at 1300°C and isothermally transformed for various times at temperatures above and within the bainite region, ranging from 775" through 500°C at intervals of 25°C. These specimens were carefully examined on a research metallograph; a few specimens of especial interest were also studied electron microscopically.' Bainite may be defined as the aggregate structure resulting from the precipitation of carbides from supersaturated ferrite which formed by nucleation and diffusion-limited growth. Two groups of experimental observations made during the present study provide support for this mechanism of the bainite reaction: 1—at 625°C, partial conversion of pro-eutectoid ferrite to bainite began after more than 99 pct of the austenite had decomposed and 2—the precipitation of bainitic carbides occurred only within the ferrite phase. The proeutectoid ferrite and the bainite reactions in the steel studied were found to be morphologically continuous. Following the classification scheme of Mehl and Dube,2 three principal morphologies of proeutectoid ferrite were identified in the temperature region (625" to 550°C) in which the two reactions blend—grain boundary allotriomorphs," * Grain boundary allotriomorphs are crystals which nucleate at and grow preferentially along matrix grain boundaries. Widmanstaetten side plates, and intragranular plates. Carbide precipitation converted these morphologies into their bainitic equivalents with increasing isothermal reaction time. Conversion took place more rapidly as the reaction temperature was reduced. The replacement of supersaturated ferrite by bainite, however, did not occur uniformly even within individual austenite grains and was noticeably incomplete at higher transformation temperatures, e.g., 625° to 575°C. The ferritic and bainitic forms of a given morphology thus were frequently found to coexist, often inextricably intermixed, in a given specimen. At 625" and 600°C, the conversion of ferrite to bainite was clearly seen to have occurred entirely by the nucleation of carbides at ferrite/ferrite boundaries, as shown in Fig. 1. The nature of the loci at which carbides formed at lower temperatures was often difficult to ascertain with a light microscope, although the alignment in rows of many of the carbides, illustrated in Fig. 2, suggested that nucleation had again occurred at grain boundaries or subboundaries within the ferrite. Application of the electron microscope confirmed this deduction for bainitic structures formed at these temperatures, as shown in Fig. 3. The dense black appearance of bainite formed at very low reaction temperatures in higher carbon steels3 indicates, however, that isolated lattice defects within ferrite crystals prob-

Jan 1, 1956

By Walter E. Mingramm

The construction of rescue-apparatus on the principle of furnishing the wearer with air from a tank containing it under high pressure was given up by inventors about 20 years ago. Such an apparatus must supply continuously, for not less than two hours, nearly 50 liters of pure air at atmospheric pressure per minute, or a total of 6,000 liters (210 cu. ft.); and a cylinder containing this amount of air, under 2,000 lb. pressure, would weigh 180 lb. or more. Although apparatus has been recently constructed utilizing liquefied air, no experiments have been made to determine the regularity with which the air is generated, nor has its chemical composition been determined. Moreover, the chief objection to such an apparatus is the difficulty and cost of keeping on hand a large quantity of liquefied air. The system of furnishing the wearer of a breathing-apparatus with air which has given the best results, and has found

Jan 1, 1909

By A Sainoki, D Fukuda, K Shioya, C Zhang, M Sharifzadeh, T Yamaguchi, S Saydam, J Kodama, C A. Amagu, Y Fuji

In an open pit mining, ensuring stability of rock slope has been one of the major challenges. As the instability of rock slopes can results in slope failures; consequently, endanger the lives of workers, affect mining operations, and often lead to economic losses. Therefore, it is practical important to study the stability of rock slopes to ensure safe, smooth, and effective mining. The stability of rock slope of about 130 m height at Higashi-shikagoe limestone quarry, which has experienced slope failures four times since 1996, was assessed. The rock mass at the quarry is consists of mainly limestone, schalstein and slate rocks intersected by clay seams of about 70 m thick at footwall of the rock slope. Previously, the effects of limestone excavation at the foot of the rock slope and shear failure due to rainfall infiltration have been investigated. Although clay is widely known to plays a vital role in the stability of slopes in engineering projects including mines, but its impacts on slope deformation at the study quarry are not adequately examined. Therefore, the present study addressed the impact of presence of clay on slope deformation at Higashi-shikagoe limestone quarry by employing both field displacement measurements and numerical simulation. Firstly, surface displacements measured by automated polar system (APS) for over eight years were analysed to understand the overall characteristics of the slope deformation. The measured results show that the displacement gradually decreases with time. The maximum displacement of about 100 mm was observed at middle of the rock slope. Secondly, the effect of deterioration and plastic behaviour of the thick clay layer were simulated using two-dimensional finite element method (2D FEM). The simulated results reveal that the clay exhibited deterioration by water contact and plastic behaviour arising from mining activities at the footwall of the clay zone. Based on the characteristics of the measured and simulated results, it was found that the displacement induced by the effect of deterioration of clay is more noticeable at the north side of the quarry whereas displacement induced by excavation is quite significant at the south side of the quarry if clay behaves as an elasto-plastic material.

Nov 29, 2022

By Samuel S. Wyer

Discussion of the paper of SAMUEL S. WYER, presented at the New York meeting February, 1916, and printed in Bulletin No. 110, February, 1916, pp. 263 to 279. DAVID T. DAY, Washington, D. C.-I would like to ask whether the court decisions quoted in the paper are general, or do they represent one side of the case; if so, are there any decisions that represent more than one side of the case? Are they of general application, or do they affect only one side? Also, what is the difference between a pump and a compressor from the standpoint of the natural-gas industry? I notice stress is laid on the word "pump" in. connection with some of the legal decisions, and then it is stated. that they must not pump or compress above 300 lb. The question is, is a pump a compressor and a compressor a pump, under certain conditions? SAMUEL S. WYER, Columbus, Ohio.-Answering the first question, I will say that the decisions cover both sides of the case very thoroughly, and are uniformly on the side that a company is justified in the use of gas compressors; in other words, there are no decisions holding it to be illegal to use gas compressors, with the exception noted in Indiana, Kansas, and Oklahoma where you cannot go below atmospheric pressure. In regard to the second question, I think the engineers and the gas operators themselves are responsible for the confusion. It is because the use of the term "pump" is almost universal, and so many people have obtained the idea that the primary function of a gas compressor is to pump air into the gas, in order to increase the consumers' gas bills. I appreciate that it is very hard to draw a clear line of demarcation. between a pump and a compressor. The distinction I have always made myself, and which I think is a logical one, is that you do not get the pumping action until you get below atmospheric pressure. As far as the compression end is concerned, there is only one State, namely, Indiana, that has any statutory limitation with regard to how high the pressure may be increased in order to put the gas into the transmission lines. The State law in Indiana limits the maximum pressure to 300 lb. per square inch.

Jan 5, 1916

By Stephen J. Harven

Geologic conditions in eight northern operating sections of Jane Mine, Keystone Coal Mining Complex. Armstrong County, Pennsylvania are defined by utilizing drillhole data and underground geologic mapping. Three of the eight sections are experiencing difficult mining conditions in the Shelocta "0" coal seam (formerly the Lower Freeport). The five remaining productive sections will exhaust their reserves within one year. Coordinating mine planning with future production levels is aided by indicating areas that appear favorable and lack the geologic conditions that cause difficult mining. Roof rock 1 ithologies, lithologic variations in and below the floor, jointing, overburden thickness, coal splits, paleochannels. and clay veins are the principal geologic factors believed to influence mining conditions in Jane Mine. Careful definition of each cause allows for a reasonable assessment of future mining conditions.

Jan 1, 1987

By W. A. Walker, G. W. Ostroot

An increase in the number of deep wells being drilled where extreme bottom-hole temperatures are encountered, and the anticipated drilling of wells where temperatures in the range of 500°F or higher may occur, has brought about a comprehensive investigation of cementing materials and of the techniques involved in their proper usage at these elevated temperatures. Included are developments in cements, retarders, weighting materials and other cement additives which make it possible to formulate a variety of compositions to help resolve the cementing problems of these extreme well conditions. The problems associated with the selection and testing of cements are discussed, and a resume of field results is included. Previous studies on strength retrogression indicate that caution should be exercised in the selection of a cementing composition for use in high-temperature wells. It now appears that, by the addition of silica flour as a stabilizing additive to certain cements, compositions covering a wide range of slurry densities can be designed to meet extreme well conditions without strength retrogression. Improvements in cement retarders make it possible to produce a four-hour thickening time at static temperatures up to 500°F. This temperature is considerably higher than conditions presently being encountered in drilling and completion work. Inert weighting materials, used to produce 20-lb/gal or heavier cement slurries, are reviewed. INTRODUCTION As the search for oil continues, the number of wells being drilled to depths of 10,000 ft or below has continued to increase over the past decade. During 1959, there were 50,893 wells drilled in the United States for a total of 209 million ft of hole. Of this total, approximately 4.45 per cent were drilled below 10,000 ft and 0.30 per cent below 15,000 ft, with a record depth of 25,340 ft recorded (Table 1). With the drilling of this record-shattering hole comes the question, "How deep can wells be drilled?".' Limitations with respect to equipment (surface and subsurface), cementing materials and techniques would cause some concern; however, a panel of experts have agreed that the U. S. oil industry has the equipment and know-how to drill a 50,000-ft hole. The greatest deterrent would be the 700°F temperature they would anticipate encountering at this depth. Although the number of wells drilled under what is generally considered hot-hole conditions (230°F and higher) has been relatively high, each well often presents distinctly individual problems and requires separate consideration and selection of special materials, techniques and equipment. At the present time there are over 30 additives and special cements available for use in "tailoring" a cementing composition for a specific well. It is not uncommon to use three or four different additives with the basic cement to produce the desired slurry characteristics. A generally accepted procedure is to make laboratory tests on selected cementing compositions prior to pumping them into wells deeper than 12,000 ft, or where static temperatures are in the range of 260°F or higher. In some instances, it is recommended that laboratory tests be made where less severe well conditions are encountered. Prior to selecting a cementing composition for a particular well, key personnel representing the operator, drilling contractor and service company should meet to determine that each individual is acquainted with every detail which might influence cementing results and to discuss the execution of the job. For cementing hot-holes, a number of factors must be evaluated before proceeding with the operation. Consideration must be given to the following. 1. Thickening time—The slurry must remain fluid for a sufficient length of time to allow displacement down the casing and up the annular space in a primary cementing job or, in squeeze-cementing, adequate thickening time for both the build-up of a satisfactory squeeze pressure and the reversing out of excess cement. The thickening time of standard retarded cements will often be too short under extreme temperature conditions, thus involving special formulations and requiring laboratory tests to determine the proper amount of additional retarder to obtain the desired pumpability.

By A. J. Schindler, F-P Sawyer, T. Logan, M. L. Shutey-McCann, R. M. Perry

"Test work on biooxidation pretreatment of low-grade refractory gold ores has been ongoing at Newmont Gold Company since 1988, including laboratory testing and pilot biooxidation heaps (360 to 23,000 tonne). Metallurgical results of the biooxidation process utilizing Thiobacillus ferrooxidans (T. ferrooxiddans) have culminated in the design, construction, and operation of a biooxidation demonstration facility. The facility has processed 708,000 tonnes of refractory ore, using a batched process with separate pads for biooxidation and ammonium thiosulfate gold extraction. Siliceous sulfidic refractory (SSR) and carbonaceous sulfidic refractory (CSR) ores are treated separately during biooxidation pretreatment unit operation. Following biooxidation, the ores are neutralization with lime and placed on oxide leach pads or stacked on the ammonium thiosulfate leach pad. Gold is leached with either cyanide for SSR ores or ammonium thiosulfate for preg-robbing CSR ores.This paper will only address the biooxidation pretreatment process of the SSR and CSR ores.AcknowledgmentsThe authors appreciate the cooperation and approval of Newmont Gold Company Carlin Operations management for its support and permission to publish this paper. The paper draws on efforts and assistance of the following people and several others which are to many to list who participated over the past five years in bringing this project to its fruition: Dr. James A. Brierley, Chief Microbiologist, Newmont Metallurgical Services; Dr. Rong-Yu Wan, Metallurgical Manager, Newmont Metallurgical Services."

Jan 1, 1997

By Deno M. Pappas

The purpose of this Bureau of Mines study of U.S. roof and rib (roof- rib) accident statistics and related accident costs is to define current accident trends (1980-84) associated with fatal and nonfatal roof-rib fall accidents. Data were retrieved from a data base containing all recorded U.S. mining accidents, then sorted and normalized utilizing a computer software program. The statistics indicate that roof-rib accidents have significantly declined in the 5-yr study period. Moreover, they indicate that there have been increases and/or patterns of roof-rib accidents associated with specific mine characteristics, such as seam height, mine size, geographic location, and seasonal variations. Also, roof-rib injury characteristics produced pattern changes involving worker activity, lost workdays, types of injury, and severity of injury. A conservative estimate indicates that there has been a 30% adjusted increase in the cost of a roof-rib accident over the 5-yr study period.

Jan 1, 1987

By Forrest T. Moyer

Injury experience in the mineral mining and processing industries during 1968 was slightly improved in the nonfatal-injury record but worse in the fatality record. The resulting frequency rate of all injuries was slightly better, whereas the injury-severity rate retrogressed appreciably from the figure for 1967. Overall operating activity, as measured by man-hours of worktime, was slightly higher in 1968. However, there were several major segments of the mineral industries in which activity was lower owing to reduced demand for mineral products and to several major work stoppages. These statistics comprise the injury and work experience of all personnel engaged in production, exploration, development, maintenance, repair, and force-account construction work, including supervisory and technical personnel, and working partners and owners at mineral-producing and mineral-processing establishments in the United States. Data concerning officeworkers are excluded except for the oil and gas industry for which such information is not separable. All injury rates and totals are calculated from data before rounding. The data for 1968 are preliminary except for the anthracite, coke, petroleum and natural gas, native asphalt, peat, and slag industries, which are final. The figures represent full coverage for all industries except oil and gas for which coverage is not complete, particularly with respect to small companies.

Jan 1, 1970

By A. D. Hughes

A relatively small area in Malaya, about 200 miles long by 40 miles wide, is the most important source of tin in the world. Some tin is recovered in other parts of the peninsula. Of the tin mined, 98 pct is recovered from alluvial deposits. From 1935 to 1941 the average annual world production of tin was 190,000 tons. The average annual production from Malaya during the same period was 62,000 tons or about one third of the total. Other producing countries, in order of importance, were the Netherlands East Indies 34,000 tons, Bolivia 30,000, Belgian Congo, Nigeria, Siam, Burma, China, and a few others with smaller amounts. The serious shortage of tin during the war period was due to the fact that the Japanese were occupying Malaya, Netherlands East Indies, Siam, Burma, and China which, together, formerly were producing 65 pct of the world supply. Because of the importance of tin in the world economy, and because of the fact that little is generally known in this country regarding the methods of recovering the tin in Malaya, it is believed that a short description of the industry, as carried on there, may be of interest to many of the readers. In addition you may be interested in the effect of the Japanese occupation, subsequent recovery of the properties and conditions existing at that time. The Malay Peninsula lies at the southeast tip of Asia. Singapore, a British colony, is situated on a small island at the southern end of the peninsula. It is a city of nearly a million population, an important world port, the site of a large British naval base and of one of the tin smelters. The Federation of Malaya consists of nine states, plus Penang, Malacca, and other small areas formerly part of the Straits Settlements, and it now covers the entire peninsula. The civil administration is controlled by the British. A constitution was adopted recently after reaching agreement with the Malay Sultans of the various states, who retain control of religious matters. The Capital is at Kuala Lumpur, a city of about 200,000 population, 250 miles north of Singapore and about half way to Penang. The country covers an area of 51,000 square miles, an area about equal to that of Florida and about one third that of California. It has a population of about seven million consisting of Malays, Chinese, East Indians, and a relatively small number of Europeans. The principal products are tin and rubber. There are over three million acres of planted rubber. The country is not self-supporting agriculturally as about one third of the necessary food supplies is imported. Rice is the principal food of the Asiatic population and some of the recent unrest is caused by a shortage of rice and the consequent high price. Good highways have been built through the settled part of the country. A railway, Government owned, extends from Singapore northward through the entire peninsula. The climate is tropical but health conditions are good for a tropical country. I was in Malaya from 1939 until January 1942, during the time of the simultaneous air attacks on Pearl Harbor, Manila, Hongkong, and Singa-

Jan 1, 1950

By Ian Wark

IT has been shown1 that in the absence of heavy metal salts, the nature of the alkali used to promote differential flotation-whether caustic soda, lime or sodium carbonate-is unimportant. The hydroxyl ion is the active depressant upon which differentiation depends, and the pH value determines whether a film of collector forms on any given mineral surface. Even when sodium cyanide is used in conjunction with alkalies, it is the pH value and not the nature of the alkali or its concentration that is important, for upon the pH value alone depends the fraction of the added sodium cyanide that is present as cyanide ion, which is the true depressant. When heavy metal salts become dissolved from partly oxidized ores, or are added intentionally as activators, conditions are different, and metallurgists have found that lime and sodium carbonate do not give identical results, even when added in amounts sufficient to produce the same pH value. In the few instances in which we had attempted to confirm this view, we had failed to do so, for, with nothing to guide us, we had inadvertently chosen solutions that gave contact curves of a "stand-ard type," which correspond to conditions of ready floatability. Now, however, we find that, in the presence of copper salts, and within a restricted range of reagent concentrations, the nature of the anions present is important, and that sodium carbonate does influence the results, apart from the usual effect due to its influence on pH value. With the recognition of this anion effect, and with the control of temperature already introduced,' it appears that the factors of major importance in connection with this set of reagents have been taken into consideration, and that the results obtained and the conclusions drawn from contact tests will be of more immediate value to the operator.

Jan 1, 1939

By G. M. Behrend

"AbstractMeasurement and control systems in minerals processing plants are usually well thought out and designed. The criteria and design parameters have been interpreted correctly.However, these systems often fail to perform satisfactorily or break down altogether as a result of in-plant conditions which are unpredictable and over which the instrument systems designer has no direct control. The foresight necessary to anticipate the problems and allow for them in the systems design can only be generated by experience.This paper lists the most common of these problems and offers practical methods for their solution. It then follows with an analysis of instrument installation practices and comments on special points that need watching.Finally, instrument maintenance is discussed with a view to achieving good maintenance at the best possible economy.Good MeasurementGeneralTHE MINES and mineral processing plants of the nineteen seventies, after decades of sensible caution, have now committed themselves to extensive automatic control. X-ray analyzers are freely specified. Sample acquisition systems are efficient and automated, computers are reliable and relatively cheap, and computer control systems in conjunction with the new analyzers are operating in a good many plants and are proving to be profitable.The sight of shift foremen and floor operators assembled in front of a TV-tube and taking a computer data display as gospel truth is quite common now, and yet was quite unthinkable only ten years ago."

Jan 1, 1977

By Whitehead A. B

INTRODUCTIONDuring the past few years there has been considerable interest in developing the so-called direct reduction processes for treating iron oxides. The various methods proposed were recently reviewed by Scortecci and Palazzi (1960).In particular the application of fluidized bed techniques received considerable attention and, on first examination, this seems to be the ideal method 'of dealing with fine iron oxides. Several difficulties (e.g. product agglomeration) require the method to be investigated further before its potentialities can be fully assessed.PROPOSED FLUIDIZED BED REDUCTION PROCESSESBrassert and De Jahn (1951) were among the earliest to suggest the use of fluidized beds for the reduction of iron ore to metallic iron. Their patent was followed by many others proposing similar concepts, mainly from Lewis (1955), Ogorzaly (19.56), Shipley (1956), Agarwal (1960'), Osborn (1958), Texaco Development Corporation (1956) and Stelling (1957).The H-iron process (Squires and J ohnson, 1957; Lubker and Bruland, 1960) is the only scheme that has been an economic success. This process, mentioned later, manufactures a 'premium quality product in the form of sized iron powder.AIM OF THE PRESENT WORKThe work reported here was performed to assist in the formulation of a comprehensive pl'ogramme of research into fluidized bed reduction processes to be undertaken at the...

Jan 1, 1962

By Bhudeo N. Sinha, Paul Dean Proctor

Heavy metal contents in stream waters, sediments, and selected aquatic algae were determined for the upper Meramec River basin, Missouri, of 3905 km2 (1508 sq mi) area and site of the proposed and controversial Meramec dam and reservoir. Six distinct drainage areas within the basin are: (1) a lightly industrialized and farm area, (2) a primitive forested- ranch area, (3) an area which includes the Northern New Lead Belt, (4) the westward drainage of an old and extensive barite mining area, (5) the main trunk of the Meramec River, and (6) short north-divide tributaries of the Meramec River. Lower Paleozoic sediments rest nonconformably upon eroded and hilly Precambrian igneous basement. This locally rises as major inliers and also makes up the St. Francois Mountains to the east. Major lead, and lesser zinc, copper, cobalt, and nickel mineralization occurs in the buried Cambrian Bonneterre dolomite. Residual barite is present along the eastern fringe of the basin and is derived from the Potosi formation. Some 62 water samples, active stream sediments (AS), bank samples (BS), and 11 selected aquatic algae samples were collected in the various drainage areas and analyzed for copper, lead, zinc, cadmium, nickel, arsenic, and mercury contents. Heavy metals in water have a maximum range of 1-120 ppb (parts per billion), and this for zinc. The AS and BS sediments have orders of magnitude greater acid leachable metal contents in the -80 mesh fraction, with lead hawing the greatest range of 11-1028 ppm. Heavy metal content of stream-algae approaches that of the sediments in which they grow. Most anomalous heavy metal accumulations occur near mining and milling activities and in the streams draining such areas. Significant distortions of the primary dispersion pattern militate against geochemical exploration for hidden ore zones, but do demonstrate the mining, milling, and smelting activities of man, and sporadic mineral occurrences in younger horizons.

Jan 1, 1980

By M. J. Virnig, Christopher A. Fleming

THE CIP PROCESS "IN THE RIGHT PLACE AT THE RIGHT TIME? After its tentative introduction to the precious metals mining industry in the earlier part of this century, the carbon in pulp (CIP) process has now come of age, and is the process of choice on all new gold mills. Well over 50 percent of all gold that is mined each year is recovered by adsorption on activated carbon, and the percentage will increase in the years ahead, when old mills using Merrill Crowe technology come to the end of their lives, and as the proportion of world gold production from low-grade resources increases. The pioneering process development work in this field, which was mainly concerned with carbon elution, was carried out by Zadra and his colleagues at the United States Bureau of Mines in the early 1950's (Zadra et al., 1950, 1952), and led to the commissioning of the first large-scale, industrial CIP plant, at the Homestake Mine in South Dakota, in 1973 (Hall et al., 1974). From there, the process spread rapidly, firstly in South Africa in the late 1970's. and then throughout the rest of the gold producing world in the 1980's. There were several factors that led to the meteoric (by gold industry standards) acceptance and successful implementation of this new technology into gold processing operations worldwide. Firstly, and perhaps most fortuitously, the development of the technology closely paralleled the 1968 release of the gold price from the rigid constraints of the $35/oz. gold standard. With the value of the metal allowed, for the first time in modern history, to fluctuate in response to free market supply and demand forces, the gold industry witnessed an unprecedented boom as the price of their commodity increased ten-fold in a remarkably short period of time. This had several important spin-offs as far as new process developments were concerned: The profits realized by established gold-mining companies increased enormously and, consequently, there was more to spend on research and development and exploration for new deposits.

Jan 1, 1993

By Yoon-Bong Hahn

A mathematical model has been developed to analyze and predict the reduction process of iron ore particles in a two-stage fluidized bed system. This model includes the effect of particle degradation to elucidate its effect on reduction of iron oxides. Although the particle degradation is dependent on kind of iron ores, it was found that eighty to ninety percent of overall degradation is occurred in the prereduction stage mainly due to thermal stress and volume expansion. The degradation of particles in the?final stage is not much, but is mainly due to interparticle collision and abrasion. It was also found that to obtain a target reduction degree, it is of great importance to control the bed temperature and the residence time of paarticles in R1 rather than in R2. Optimum range of residence time was 15-20 minutes in the prereduction stage; 30-35 minutes in the final reduction stage.

Jan 1, 1996

By Aïda Espinola

This work is part of a research program concerning the study of heavy metal removal and selective recovery from electroplating waste waters in the Guanabara Bay ecosystem, preventing the potential noxious retarded effect of landfill, specially in a country of heavy rainfall. A flow-throw cell was employed to adapt to the limits established by the local legislation for disposal in rivers and seas. The cell design is presented and preliminary results show that this cell may be applicable for the decontamination from copper.

Jan 1, 1994

By Hamid Maleki

The U.S. Bureau of Mines implemented a monitoring program in a western U.S. coal mine for the evaluation of both conventional and alternative support systems. The conventional support consisted of 2.5-m-long vertical bolts installed in an 5.5-m-wide entry. The alternative system consisted of 2.5- and 3-m vertical and inclined bolts installed at a higher density during widening of a cut from 3.6 to 5.5 m. Roof deformation, roof stress, rib deformation, and bolt loads were monitored during the 2-month test period. In addition, roof failure patterns and lithology were characterized within the six-entry main test section. Results were analyzed using roof deformation and failure profiles, roof stress profiles. bolt loading and bending moment diagrams, and numerical models. The mechanics of roof deformation, failure, and support reaction in three zones in the mine roof were characterized. Significant improvements were shown in roof stability in the section using the alternative system. Results are encouraging and indicate the effectiveness of alternative support systems and excavation techniques for limiting inelastic deformation of roof in highly stressed underground mines.

Jan 1, 1994

By Sven Petersen, Berit Lehrmann, Bramley J. Murton, Paul A. J. Lusty

"INTRODUCTIONToday’s metal mining focusses on land based ore deposits which only consider one third of the Earth’s surface. Through an increasing global demand of strategic metals used in the electronic and green industry (Zepf et al. 2014), ‘uneconomic’ sites of lower grade in more technical challenging grounds such as greater depth and/or more remote areas are developed by the mining industry often resulting in higher environmental impact. However, considering the steady growth of the Earth population a shortage of certain metals may occur (Krausmann et al. 2009). In 2010, the United Nations allowed commercial exploration for seafloor massive sulphides (SMS) in international waters with currently six contractor licenses being granted.Although the number of discovered vent sites has steadily increased since the first discovery of hydrothermal venting at the Galapagos Rift in 1977 (Corliss et al. 1979) with more than 600 sites being known today, their economic potential is poorly constrained. So far Nautilus Minerals Inc., a Canadian mining company, is the only company having conducted a NI 43-101 resource estimate for the Solwara site, located in the territorial waters of Papua New Guinea. Other studies using bulk geochemical data from 95 sites published in literature do exist (Hannington et al. 2011, Monecke et al. 2016) suggesting a global resource potential for today’s known SMS deposits of 600 million tons with a median grade of 3 wt.-% copper, 9 wt.-% zinc, 2 g/t gold and 100 g/t silver. However, the geochemical data being used originated mainly from easily recoverable, mainly non insitu surface grab-samples and are under current mineral resource classification schemes such as JORC code or NI 43-101 not even accepted for resource estimations. Furthermore surface samples such as high-temperature sulphide chimney and talus material are not representative for the entire deposits with information regards thickness and continuity of individual sulphide layers obtained through drilling being scarce. In addition, it remains unknown what geological processes occur once hydrothermal activity ceases and whether metal tenor becomes enriched, depleted or disappears."

Jan 1, 2017

By Steven J. Page

The increasing concern for dust control in metal and nonmetal mining prompted the Bureau of Mines to investigate the dust suppression technique of applying foam to face drilling and crushing operations in a gypsum mine. Previous attempts to achieve effective dust control on face drills using other techniques, such as dry collection and boom-mounted external water sprays, have not been successful. The largest problem encountered when using these techniques has been the lack of sustained effective dust capture at the face. Results for two faces studied show that injection of the foam through the drill steel provided an average dust reduction of 95 pct. However, the use of foam on the crusher provided no dust reduction at the operator's position (because of good local ventilation) and a 27-pct average dust reduction for two feeders at a location midway between the operator's position and the crusher. The conclusions obtained from this study are that (1) foam can be an extremely effective dust control technique when used on localized dust sources such as dust generated within a blasthole during drilling, and (2) foam is only marginally effective as a dust control technique when used on nonlocalized dust sources such as dust generated during the feeder-and-crusher operation.

Jan 1, 1981