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By D. B. Starkey

Investigation into the expressions of the field produced by a loop over a conducting half space or in an infinite conducting half space are well documented. Reasonably complex descriptions of the effects of stratification also are reported. However, a model which must contain all of these complexities because of transmission to depths of 15,000 feet and also include the pertibation of the field by a verticle cylindrical steel casing loses its facility in the field or for quick, accurate approximation to field magnitudes and phase. This paper describes the results of two field tests to determine the attenuation and phase versus depth and frequency of an electromagnetic wave (induction field). A simple two-layer model is postulated to predict the magnitude and phase of the induced field which does not require sophisticated computing tools. Correlation of the model with experimental results show agreement of most amplitude measurements to within 3 db and most phase measurements to within five degrees. The tests were conducted in a 7400 foot deep well in Nevada and an 11,000 foot deep well in Wyoming which had conductivities ranging from .0025 mhos/m to .25 mhos/m. The surface transmitting dipole had an area of ~ 10 6 feet squared and constant frequency signals of 1.5 Hz to 20 Hz were transmitted through the earth utilizing less than 65 watts of power. Model Description The magnetic field intensity components generated by a magnetic dipole immersed in an infinite homogeneous medium can be expressed in spherical coordinates as: [ ] where N, I, and (p a ) are the transmitting antenna turns, current, and effective area, respectively, and r is the range from the loops circumference to the measurement point. The case of interest for these experiments, however, is the special case of coaxial dipoles, i.e., ? = 180° . For this case H?= 0 and H reduces to: [ ]

Jan 1, 1973

By D. A. Hill

Introduction The fields of an infinite line source in the presence of a conducting half-space have been examined by Wait and Spies (1971). In any real communication link using a current-carrying cable for the transmitting antenna, the cable is of finite length. Here we examine the fields of a finite length cable carrying a constant current in the presence of a homogeneous conducting half-space. The constant current assumption is valid at sufficiently low frequencies when an insulated cable is grounded at the end points (Wait, 1952; Sunde, 1968). Here we examine both surface and buried cables since both downlink and uplink communication links are of interest. Also, we examine both frequency and time solutions since either CW or pulsed communications may be used. Finally, it is necessary to include both magnetic and electric field solutions since reception could be with either loops or dipoles. Since the finite cable solution is more complicated than both the infinite line source and the short dipole solutions, we explore under what conditions a cable appears to be either infinitely long or very short. Some special cases, such as- the low frequency limit, permit analytical solutions which exhibit the dependence on various parameters, such as cable length, quite clearly. Frequency Domain Subsurface Fields The geometry of a line source of length 2[l] located on a conducting half-space with the observer in the half-space is shown in Figure 1. The fields

Jan 1, 1973

By Barbara Fotta

According to the Bureau of Labor Statistics (BLS), workforce estimates of median age suggest that the median age of the mining workforce, which has been experiencing overall declines in numbers of employees, is rising more rapidly than for the overall U.S. civilian labor force. In the absence of detailed demographic data for the mining industry, the current study uses injury and illness data reported to the Mine Safety and Health Administration (MSHA) to examine differences, over time and by commodity, in the proportions of injured or ill workers aged 45 years and older. These data indicate that from 1988 to 1998, the percentage of injured or ill older workers (aged 45 years and older) have been steadily increasing. The most notable increase occurred at coal mining operations where the proportion of injured/ill older workers increased from 24 to 44 percent. A more detailed breakdown of the industry by commodity for 1998 showed the highest proportions of older injured/ill workers (over 40%) occurring in coal, iron ore, alumina mills, cement, and trona operations. In coal operations, as the employment size of the mine operation increased, so did its proportion of older injured/ill workers. Also, higher proportions of older injured/ill workers were observed at surface coal work locations than at underground locations. The distribution of older injured/ill miners by occupation for several select commodities shows the highest proportions for supervisors, electricians, mechanics, and surface equipment operators, and the lowest proportions for surface laborers and for underground coal roof bolters and scoop operators. With few exceptions, older injured workers have the highest median number of days lost per injury when examined by type of mining operation and by occupation. Given the high proportions of older injured or ill workers in many sectors of the mining industry, health and safety programs must consider the physiological changes associated with aging when evaluating job tasks and the working environment.

Jan 1, 2004

By S. J. Hussey

The Bureau of Mines investigated the applicability of carbon-in-pulp pro-cess for recovering silver from low-grade ores. The reasons for the research were (1) to illustrate a practical procedure for the process design of carbon-in-pulp adsorption circuits using leach slurries and simple equipment; and (2) to illustrate how equations of adsorption theory relating rate data and equilibrium adsorption curves can be helpful in process design. Carbon-in-pulp silver adsorption tests were made on Banner, Idaho; mine-run ore samples with silver contents ranging from 2.0 to 8.5 oz/ton and variations in cyanide leach extraction from 48 to 93 pet. The lower recoveries were attributed to the presence of complex silver sulfide minerals. Carbon-in-pulp batch adsorption tests provided rate data for the estimation of a silver equilibrium adsorption curve. Process design procedures in which the rate data were related to an equilibrium adsorption curvey by equations of adsorption theory were used to plan a four-stage pilot plant cascade. The pilot plant was successfully operated for 45 hr of countercurrent flow, producing a carbon product containing a mean silver loading of 571 oz/ton from a pregnant solution of 1.7 oz/ton of silver. Virtually all of the dissolved silver was recovered on the carbon.

Jan 1, 1978

By A. L. Johnson

In this Bureau of Mines report, time-resolved infrared emission spectra and corresponding pressure and temperature histories are reported for large-scale propagations of CH4-air, CH4-air-N2, and CH4-air-CF3Br ignitions in a 12-ft-diam sphere. Absolute spectral radiances were obtained throughout combustion over the 1.6- to 4.8-gym range, and the radiance growth patterns for the H20 (2.5-µm) bands are presented as a function of methane stoichiometry and diluent concentration. Flame temperatures were determined from the C02-band emissions, which approximated unit emissivity shortly after ignition. Burning velocities are also given for some of the test-mixture compositions. Measured flame temperatures were in excellent to fair agreement with theoretical adiabatic values for the CH.-air and CH4-air-N2 mixtures; the best agreement was for the stoichiometric CH4-air mixture. The CH4-air-CF3Br mixtures with =2 pct CF3Br gave poor agreement with theory. The measured temperatures were significantly lower during the early stage of combustion; furthermore, the later stage of combustion was uninhibited and yielded unexpectedly high pressures. Supplemental data from a 2-ft-diam sphere at various initial pressures confirmed that the CF3Br inhibition effectiveness decreases with increased pressure. The possible effects of buoyancy, turbulence, and changing kinetics are discussed.

Jan 1, 1977

1. In 2001, a total of 281 metal mining operations reported employment to the Mine Safety and Health Administration (MSHA) (down from 309 metal mines in 2000). Metal mines were the smallest mining sector, 1 comprising 1.9% of all mining operations. This was the lowest percentage of all mining sectors. • The median number of operator employees per metal mine was 17.5.2 • Gold mines comprised 43.1% (n = 121) of all metal mining operations. Other types of metal mines were copper ore (n = 37, 13.2%), iron ore (n = 27, 9.6%), and lead and/or zinc ore (n = 24, 8.5%). • Nearly 20% (n = 55) of metal mines were located in Nevada.

Jul 1, 2003

By S. B. Levin

"INTRODUCTION An exposure of large beryl crystals in pegmatite on Beryl Mountain, in Sullivan County, N. H., was the basis for investigation by the Bureau of Mines to determine the extent of the beryl mineralization and to expose other parts of the same zone that were favorable for additional beryl-rich shoots. Testing by surface cuts, trenching, and tunneling was conducted by the Bureau of Mines from August to December 1943.ACKNOWLEDGMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to the national security and economy. The Mining Division, Lowell B. Moon, chief, conducts preliminary examinations, does the actual investigative work, and prepares the final report. The Metallurgical Division, O. C. Ralston, chief, analyzes samples and makes beneficiation tests. The field work was supervised by Paul M. Tyler, regional engineer, and John D. Bardill, district engineer. S. B, Levin was in direct charge of the project.LOCATION AND ACCESSIBILITYThe deposit is on the northeast slope of Beryl Mountain, 1 mile south of the village of South Acworth. The village, on State Highways 101 and 123a, is 12 miles northeast of Bellows Falls, Vt. The deposit is reached from South Acworth over a gravel-surfaced road and about 1,000 feet of good truck trail (fig. 1).The nearest railroad siding is at Cold River, on the Boston & Maine Railroad, where there is also a fairly modern, but now idle, feldspar mill."

Mar 1, 1948

The notion of wayfinding, as conceptualized by planners, geographers, and psychologists, denotes the ability of an individual to move from one point to another through physical space. In order to achieve this movement, a person relies on a cognitive map of spatial representations [Passini 1984]. Which features of this cognitive mapping will be stressed depend, in part, on the researcher's perspective. A planner, for instance, would tend to emphasize the effect of physical structures on mobility. A psychologist, on the other hand, might focus on individual differences in how human minds encompass and represent physical space [Evans et al. 1984]. There is yet another dimension to wayfinding that needs consideration, and it rests upon the idea that reality, as experienced by human beings, is mediated: "[People] have preselected and preinterpreted this world by a series of commonsense constructs ... which help them find their bearings in their natural and socio-cultural environment and to come to terms with it" [Schutz 1967]. These "common sense constructs" are arrived at socially and constitute the agreed-upon schemas that guide people's everyday activities. According to this principle, cognition is governed by some nonlogical factors that reflect not only individual procedures but collective ones as well. These group strategies, which are shaped by shared rules and values, influence "the information gathered, the ways it is processed, the inferences that are drawn, the options that are being considered, and those that are finally chosen" [Etzioni 1992]. From this perspective, cognitive maps, rather than being individual-centered templates of environmental images [Rovine and Weisman 1989] or representations of spatial relationships [Evans 1980], are partially group-centered schematic processes. As such, they are subject to reinterpretation, revision, and outside intervention [Kaplan and Kaplan 1982]. As intermediaries between the environment and behavior, cognitive maps serve as bases for decision-making. Traditionally, it has been assumed that good maps facilitate correct decisions, which in turn leads to optimal performance during wayfinding [Hunt 1984]. Given the argument that there is a social (non¬cognitive) facet to cognitive mapping, however, this image of a cognitive map as some sort of static reference construct that motivates individual action is too narrow and mechanistic. If cognition involves less a knowledge of the environ¬ment than it does the process of "giving it meaning through imposing an order on it" [Rapoport 1976], then wayfinding behavior is not j ust a function of setting and individual differences, but is also a function of one's "normative-affective" structure [Etzioni 1992]. Rapoport [1976] used such an assumption as the base for a set of hypotheses about the connection between "external demands" and "organismic factors." One significant assertion deriving from Rapoport's ideas is that environmental

Jan 1, 2000

By James Westfield, S H. Ash

Because of the increasing shortage of fuel in the United States, especially of residential fuel in the Eastern and New England States, it was essential that the maximum production of anthracite be obtained to help win the war and to prevent human distress. The nine railroads that depend on the anthracite region for a substantial portion of their business were not congested unduly with other traffic, because the region was not participating in industrial activities to the same degree as in many other sections of the United States; consequently, transportation of anthracite to the New England States, New York, New Jersey, and eastern Pennsylvania over a shorter rail haul than for any other fuel was desirable. The prevention of floods that would cause a loss of anthracite production was important to the war program. Every shutdown deprives the northeastern section of the United States of anthracite that is needed badly. Failure to prevent inundation of anthracite mines halts production, endangers the lives of workmen, damages, sometimes beyond repair, vital underground equipment, and threatens the permanent loss of a large portion of the Nation’s anthracite reserves. Funds were made available to the Department of the Interior, Bureau of Mines, for the fiscal year ended June 30, 1945, through a supplemental appropriation for anthracite investigations, one of which was to conduct inquiries and scientific and technologic investigations that have a bearing on the anthracite mine-flood problem. As part of the investigation, the Bureau proposed to obtain the cooperation of the anthracite-mining companies and the State in effecting a program to prevent the inundation of mines in the anthracite region. No large engineering projects were undertaken by the Bureau during the fiscal year ended June 30, 1945, on the anthracite mine-flood problem. Small projects were chosen that could be completed within 1 year to prevent loss of anthracite production at a critical time. It was believed that such projects would lessen the chance that flood water would inundate active mine workings.

Mar 1, 1946

By J. Whyatt

A variety of dynamic failure cases with regional impact were described at a bump symposium held in 1958. These types of events, while rare, are of particular interest because their ability to impact a large area has disaster potential. These cases can be grouped into two broad classes of events by mechanism. These are (1) slip along steeply dipping faults and (2) fracturing of strong strata above, or below, the coal seam. Both failure modes produce dynamic or ?shock? loads on the perimeter (roof, rib, floor) of mine openings. Special consideration should be given to these failure modes in planning of deep coal mines since their occurrence is not within the professional experience of many contemporary workers, and their potential is not evaluated by many of the analysis tools commonly used to evaluate hazards in coal mine plans.

Jan 1, 2009

By Launa Mallett, Charles Vaught, Michael J. Brinich

The lack of good communication is a very real problem in mine emergencies. Sometimes critical information is not communicated to those who need it to make decisions. At other times, those on the receiving end of a warning do not think to ask the right questions. What happens in underground coal mine fires is a case in point. The authors interviewed 48 workers who escaped three serious fires in western Pennsylvania. In each case the location of the fire was known but did not get communicated to many of those who had to evacuate. Sometimes, even the nature of the problem was not clearly communicated. Some workers began their evacuation knowing nothing about what was happening. In an effort to improve emergency communication National Institute for Occupational Safety and Health (NIOSH) researchers worked with safety professionals to determine what sorts of information are critical in a mine emergency. An extensive list was generated, which proved too long to be remembered by individuals. The list was therefore collapsed into six categories. A communication protocol was derived from these categories.

NIOSH recommends that exposures to respirable coal mine dust be limited to 1 mg/m3 as a TWA concentration for up to 10 hr/day during a 40-hr workweek, measured according to current MSHA methods (see Section 5.1 and Appendix J). NIOSH recommends that sampling be conducted with a device that operates in accordance with the NIOSH accuracy criteria [Busch 1977; Busch and Taylor 198 11 and the international definition of respirable dust [ACGIH 1994; CEN 1993; IS01993; Soderholm 1991a,b; 1989].* The REL represents the upper limit of exposure for each worker during each work shift. For single, full-shift samples used to determine noncompliance, NIOSH recommends that MSHA make no upward adjustment of the REL to account for measurement uncertainties [NIOSH 1994c] (see also Section 5.6.2). NIOSH further recommends that all reasonable efforts be made to reduce exposures to respirable coal mine dust below the REL through the use of engineering controls and work practices.

Jan 1, 1997

By C. Stephan, E. Weiss, J. Trackemas, M. Sapko

The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), in collaboration with the Mine Safety and Health Administration (MSHA), the mining industry and seal manufacturers, conducted a series of full-scale experiments within the underground experimental mine at PRL's Lake Lynn Laboratory. The purpose of the experiments was to evaluate the explosion-resistant characteristics of several new seal designs for rapid deployment during mine emergencies. These seals can be deployed in less than 12 hours and are capable of withstanding explosion overpressures in excess of 140 kPa (20psi). These novel seal designs use available mine materials, do not require conventional rib hitching and, most importantly, can substantially reduce exposure time for coal miners during sealing and mine recovery operations.

By C. Travis Anderson

"A recent critical study by Ralston3 of the iron system points out the importance of and necessity for work upon the preparation of ferrous oxide. Not only are ferrous oxide samples desired for determination of the important physical and chemical properties, such as specific heats and heats of formation, bat also information on the stability and behavior of this material is of considerable technical importance. Related. problems where the properties of Fe0 are important have to do with desulphurization of iron, the formation and occurrence of magnetite in copper smelter slags, and sulphur elimination in copperFerrous oxide also has valuable catalytic properties, as is demonstrated in nitrogen fixation.Pure ferrous oxide has never been prepared in quantities large enough to furnish adequate physical and chemical data on its properties. Only two or three experiments4 have produced a fraction of a gram in a state approximating purity and have collected evidence that has been sufficient proof of their having done so. Ferrous oxide is stable only above about 570°C., and below that splits into magnetite and iron according to the reactionUp to about 1920, those who had endeavored to prepare FeO made no provision for rapid chilling, so that although their product. may have had the proper iron oxygen ratio for FeO, in reality it-probably did not consist of pure FeO. The above reaction is reversible; above 570oC. magnetite and iron are supposed to recombine almost completely, and if so, should constitute a direct and easy method of preparation. The data, however, were somewhat conflicting, and the extent to which the reaction goes in either direction needed checking. Preliminary experiments on the interaction of molten Fe304 with solid Fe gave Fe0 of about 85 per cent purity, corresponding to. the approximate purity obtained by some previous investigators. The present work is concerned chiefly with the results cf repeated interaction between partly reduced magnetite and iron, and the calculations which may be made from such results. Repeated treatments are necessary, because molten impure ferrous oxide and iron can not be kept in contact for more than short periods of time."

Oct 1, 1928

By A. T. Coumbe

The Bureau of Mines has compiled pipeline mileage every 5 years since 1926, with the exception of the war period 1941 to 1949. The present survey has been made to reflect the progress under mobilization of the petroleum pipeline industry where efforts have been made by the government to stimulate construction of those facilities that would best equip the nation for a possible major emergency. This report summarizes the total mileage change 1n petroleum pipelines for 1950 through 1952. In order to increase the value of the information gathered the reporting companies were requested for the first time to report not only the net change in mileage as formerly, but also all new and used pipe laid and the total taken up. This new information permits effective appraisal of the construction effort of the industry and relates it to steel requirements.

Jan 1, 1953

By A. R. Elliott

In the early part of the your 1919 the Bureau of Mines undertook a study of methods of handling oil after it had buon produced, with the view of pointing out the losses due to evaporation and other causes. Observations on present methods show that the oil is subject to largo losses in both quantity and quality from the time it loaves tho well until it is recoivod by the pipe-lina company. During this time it is splashed into four or more tanks of various sizes and with little or no protection over the tops. From the settling tank, where the flow of oil is tamporarily stopped in order to permit sparation of ter and sediments, through the gago tanks and leaso gathering tanks to the largo tank storage where it is hold for many days, rich gasoline vapors roadily escape, especially from tho ghor gravity oil. As no effort is made to measure the oil before it reached the storage tanks, where it is delivered to the pipe-line company, the lossos of the light products of the oil can only be approximated, and, as final results will show, are no doubt usually very much underestimated. In conducting this investigation, the Bureau has endeavored to make tests that would show quantities and values lost, in order to impress better upon those concerned what might be saved through a little more diligence. Eperiments were conducted on both California and Mid-Continent oils. The field operimental work done in California, on which a report is to be published in the near future, is cutlined briefly below: The field work consisted in collecting from operating companies data on storage of oils in large tankage and in performing experiments in the field on storing and piping oil to small lease tanks under practical conditions. Acourate Easurements were takon on the volume, gravity and gasoline content of the oil as it passed through the various stages in its removal from the lease. The work extended over the four seasons of the year in order to obtain better the effect of varying winds and high and low atmospheric temperatures during those periods. Thanks are due to the many oil operators who have taken a personal interest in the work and gave valuable information and assistance. One company furnished the oil and tanks and much of the apparatus and labor. This company also per- mitted the work to be done on its properties in the Coalinga field. This was of material aid, as the results were to be comparative and therefore it was necessary that the same gravity oil be used throughout the experiments.

Oct 1, 1920

The Bureau of Mines believes that all coal mines are potentially gassy; for the purpose of administration in the prevention of explosions and fires, the Bureau recommends: That any coal mine wherein methane or other combustible gas can be detected in amounts as much as 0.27 of 1 percent or more by frequent systematic searches shall be classified as a gassy mine. Permissible methane-indicating detectors such as are given in I.C. 7110 or subsequent lists of Bureau approved methane-indicating detectors, or conventional methods of sampling and analysis of required accuracy may be used. The concentration referred to in the decision is percent by volume.

Jan 1, 1941

By W. E. Miller, John Campbell, W. P. Yant, G. W. Jones

"Because of its interest in accident prevention, the U.S. Bureau of Mines cooperates with city officials and utilities in investigating the causes of explosions in sewers, manholes, and other underground openings and in developing means for preventing such explosions. For several years this Bureau has been cooperating with the Edison Electric Illuminating Co. of Boston and the Boston Consolidated Gas Co. in detecting and eliminating combustibles and physiologically harmful gases in manholes in the city of Boston and adjacent territory.These Bureau of Mines investigations° have shown that combustible gases from the usual sources — leakage from gas—distributing systems and from underground tanks and gasoline wastes — can be located and the dangerous conditions remedied by a well—planned, adequately supervised, systematic, and continuous manhole survey. However, other types of gas, which are termed here ""soil"" gases, also occur in manholes and are more difficult to eliminate because they have no fixed origin and because seasonal and barometric changes affect their production and passage into the manhole space. These gases appear to be produced by bacterial and fermentation or through reactions of entrapped air in the soil. Soil usually abnormally high in carbon dioxide and low in oxygen, and contain varying amounts of methane. They are especially clangorous to men entering manholes because they lack sufficient oxygen to support life. Owing to the difficulty of constructing gastight manholes the most feasible method for eliminating soil gases from manholes is by ventilation. Consequently the Bureau of Mines initiate 4 study of natural ventilation methods for the removal of these gases from manholes and also for taking care of unforeseen accumulations of combustible gases and vapors.The following factors were considered by the Bureau to be important to the natural ventilation of manholes: (1) Relation of area of ventilation opening* to the capacity of the manholes, (2) size and shape of the manhole, (3) design of the ventilation opening (4) and velocity, and (5) weather conditions."

Jun 1, 1936

By Kenneth H. Johnston

Information on oil and water production, volume of water injected, core analyses, and well completion data was collected on 28 Red Fork sand water-flood projects for comparison and evaluation of results. An average water injection efficiency of 35 percent, an average water-injected to oil-produced ratio of 16.8:1, and an average loss outside the flood pattern of approximately 45 percent of the injected fluid resulted in an oil recovery to January 1, 1969, of only 5.6 percent of the pore volume, or 9.1 percent of the initial stock-tank oil in place. The principal causes of poor oil recovery from these projects are the losses of large quantities of injection water from the flood patterns through oriented, natural fracture systems or zones of high permeability and excessive channeling of injection fluids from input wells to oil wells. For more efficient operation and a higher percentage of oil recovery from the Red Fork sand and other low-permeability-sand waterflood projects, directional orientation of both induced-and natural-fracture systems should be determined during early development. The success of a low-permeability-sand waterflood project depends to a large extent upon the orientation of the injection wells with the fracture system.

Jan 1, 1970

By R. C. Gabler

Laboratory tests on a combined nitrogen roast--two-stage leach--electro-winning approach show promise as a possible process for recovering copper, sulfur, iron oxide, and valuable minor metals (gold, silver, and molybdenum) with a minimum impact on the environment. During the nitrogen roast at 800° C, 15 to 20 percent of the sulfur together with a significant fraction of the volatile elements, such as arsenic, bismuth, lead, and zinc, are removed from the chalcopyrite concentrate. The resulting calcine, consisting of 8-chalcopyrite, troilite, and a bornitelike structure, is leached with hydro-chloric acid to remove 70 to 85 percent of the iron. The digenite in the leach residue is dissolved in an oxygen-saturated, spent sulfate electrolyte. Using a graphite 'anode plus sulfur dioxide to reduce interference from ferric iron, copper of 99.99+ purity is electrowon at current efficiencies of 88 to 92 percent and a cell voltage of 0.4 to 0.5 volt. Copper recovery for the overall process is 98 to 99 percent. Sulfur is obtained in the elemental form from the roasting and leaching steps. Iron can be recovered from the hydro-chloric acid leach solution. Gold, silver, and molybdenum are concentrated in the silica residue from the spent electrolyte leach.

Jan 1, 1975