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By Wilson Blake

The Bureau of Mines used a mathematical model based on the finite element method of stress analysis to calculate stresses and displacements surrounding an open pit mine in a gravity-loaded rock mass. Comparison of the finite element solution for a semicircular notch in a gravity-loaded plate with the theoretical solution for a semicircular notch in a plate under uniform compression parallel to the free boundary demonstrates the inapplicability of the latter method to openings at the free surface of a gravity-loaded medium. High stress concentrations are formed at irregularities along the boundary of an open pit in a gravity-loaded continuous competent rock; however, for this type of rock the magnitudes of the stresses are too low to be considered a major factor in open pit slope stability. High stress magnitudes will occur if, in addition to the gravity stress field, a large horizontal stress field exists.

Jan 1, 1967

By H. B. Freeman, E. J. Gleim

During the 12 months ended July 1, 1931, engineers of the Bureau of Mines examined electrical equipment in 80 bituminous-coal mines. The purpose of these examinations was to ascertain the condition of such equipment with respect to possible hazards of gas and dust ignitions, also of shock. Although only 3 of the 80 were being worked with open lights and therefore did not use explosion-proof equipment, there were others where electric cap lamps were used by the men but where it was apparently assumed that conditions as to gas and dust did not require equipment designed to give protection against ignitions. Early in its history the United States Bureau of Mines originated certain standards covering the construction and testing of electrical equipment in order to minimize the dangers of ignitions from exposed electric sparks and flashes ; accordingly, it is comparatively easy to determine wherein a machine built to these standards falls short of continuing to meet them if damaged or neglected. Many so-called flame-proof and dust-proof machines, however, have not been built to any standard comparable with that developed by the Bureau of Mines. In addition, certain machines have parts which pass Bureau of Mines tests, but do not satisfy the full requirements in other respects, and others make no pretense of inclosing the spark-producing parts. It is not uncommon to find two or more of these various types in the same mine with " permissible " machines, the type that has been built to conform to the Bureau of Mines standard. Consequently, inspection of nonpermissible machines becomes somewhat difficult without a standard of comparison. Because of its unprotected condition obviously open-type electrical equipment must be used with great care, if at all, in a mine where precautionary measures are adopted in guarding against gas and dust ignition. The unsafe nature of such equipment is widely recognized. For that reason it is to be installed only where there is no likelihood of gas being present. It is not apparent to some, however, why flame-proof and dust-proof equipment and equipment having tested parts should not be regarded in the same light as permissible equipment.

Jan 1, 1932

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

4. Preliminary Study - Remote Seal Checker 4.1 Introduction Determination of the completeness of each individual seal at the time of its emplacement is essential for an effective remote sealing system. A satisfactory seal checking technique should provide a signal which: (1) indicates percentage completion as the seal is emplaced (2) provides a definite indication of a complete seal (3) indicates the size of the unsealed area if a complete seal is not feasible This information is required to establish the need for additional seal material, the need for additional seals, and the risk likely involved in entering the mine., In many situations it is as important to know the quality of a seal as it is to build an effective one. It is likely that with repeated use the remote sealing technique developed by Foster-Miller Associates will be sufficiently reliable and predictable to preclude the seal checking requirement. It is recommended, however, that each seal be checked during construction to insure its completeness and increase the level of confidence so necessary in reopening the mine. 4.2 Description of General Problem Several characteristics of remote mine seals are important in considering techniques for evaluating the effectiveness of these seals. These include:

Jan 1, 1973

By Rose L. Ballard

This chapter summarizes data on crude nonfuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are tables that show the principal nonfuel mineral commodities exported from and imported into the United States, and that compare world and U.S. mineral production. The detailed data from which these tables were derived are contained in the individual commodity chapters of volume I and in the State chapters of volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing, the stage of measurement used in this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the output from auxiliary processing at or near the mines. Because of inadequacies in the statistics available, some series deviate from the foregoing definition. For gold, silver, copper, lead, zinc, and tin, the quantities are recorded on a mine basis (as the recoverable content of ore sold or treated). However, the values assigned to these quantities are based on the average selling price of refined metal, not the mine value. Mercury is measured as recovered metal and valued at the average New York price for the metal.

Jan 1, 1981

By Lawrence L. Davis

This chapter includes tables for 1981 that were not available in time for publication of the 1981 Minerals Yearbook, but does not include corresponding tables for 1982. The value of raw nonfuel minerals produced in the United States during 1982 was estimated at about $20 billion, a decrease of $5 billion compared with that of 1981. The decline in value is the first since 1971 and is the largest percentage drop since 1938. Although the domestic mining industry continued to be troubled by difficulties in attracting capital and by import competition from countries with lower overall production costs, the principal cause of the decline was sharply decreased demand brought on by the worldwide economic slowdown. Metal commodities were impacted most severely with only 4 of 21 metals registering production value gains and only 3 of 21 showing production quantity increases. Overall metal production value decreased 37% from that of 1981, a reflection of the domestic slowdown in the automobile and construction industries, which are major metal users, Overall production value of nonmetals decreased 12% compared with that of 1981, with only 14 out of 44 nonmetals showing increases. Nonmetal production quantities increased over 1981 for only 6 of the 44 nonmetals.

Jan 1, 1983

By Wilbur I. Duvall

The Bureau of Mines presents a theoretical solution for the stresses and displacements in an infinite elastic plate containing a circular hole whose boundary is subjected to applied shear loads over four separated arcs. The results for the applied shear loads can be superimposed on the results for applied radial loads, given in a previous publication, to obtain a complete two-dimensional approximation of the stresses and displacements induced in the rock by tunnel boring machines anchored in a circular tunnel by means of four props. Analysis of the various solutions shows that the tangential tensile stresses induced on the boundary of the circular tunnel by applied radial loads can be minimized in the roof and floor of the tunnel by the application of appropriate shear loads to each of the four props. Thus when planning tunnel boring operations, consideration should be given to the in situ stress field in the rock and the induced stresses in the rock resulting from the applied radial and shear loads produced by the props of the boring machine.

Jan 1, 1968

By J. J. Cummins

The Bureau of Mines heated at 150° to 350° C for 0.5 to 360. days Green River oil shale that had been previously extracted by benzene to provide information on in situ processing conditions, to determine the effect of low-temperature heating on the unconverted kerogen, and to determine the composition of benzene-soluble thermal products. The methods used in determining the composition of the soluble thermal products consisted of fractionation of the soluble material, elemental analysis of the soluble products, fractionation of the polar resins by ion-exchange chromatography, gas chromatographic analysis of [n]-alkanes3 and mass spectral analysis of the branched plus cyclic alkanes and aromatic oils. The methods used to determine the effect of low-temperature heating on the unconverted kerogen remaining in the oil shale heated residues consisted of carbon-hydrogen analysis, volatile material determination, carbon residue determination, and oxidation rate determination. In general, it was concluded that significant increases in the degradation of kerogen to oil occurred between the temperature range of 250° to 350° C; that the composition of the soluble products depends upon the temperature at which they are formed; and that the [n]-alkanes are pyrolytically degraded from the kerogen structure. In particular, the 250° C heating temperature is beneficial to the formation of branched plus cyclic alkanes. Also, the heated and unconverted oil shale kerogen and the soluble thermal products become more aromatic as the temperature increases from 150° to 350° C.

Jan 1, 1974

By J. J. Henn

A process is evaluated for recovering metallurgical-grade manganese are from the low-grade manganiferous iron ores of the Cuyuna Range, Minnesota. The process, developed by the Bureau of Mines, employs high-temperature sulfatization of the are to form manganese sulfate and reduction of the are to convert the iron to a magnetic oxide. The roasted ore is water-leached to dissolve the manganese sulfate, which is then separated from the leach residue, is crystallized, and is calcined to produce the manganese product. Iron is recovered from the leach residue by magnetic separation, and is pelletized and calcined to produce byproduct iron ore pellets. The fixed capital cost for a plant yielding a product containing 100 tons of manganese per day is $19.6 million on a mid-1970 basis when the raw are contains 4.84 percent manganese. The estimated operating cost of the plant is $211 per ton of contained manganese. Graphs are included to show the effects of ore cost and varying manganese content of the raw ore on the estimated operating cost.

Jan 1, 1972

By Harold C. Pierce

"INTRODUCTION During the years 1941 to 1945, the United States produced less than one-half of one percent of all primary nickel, whereas the nation's consumption of the metal amounted to nearly three-fourths of the world's supply. Although postwar nickel consumption probably will be less than wartime consumption, trade- estimates for the next 10 years are well above the average established during the 1930-1940 decade. The greatest consumption is expected in nickel alloys, particularly nickel-alloy steels. 3/ The greater use of nickel cast irons and nickel-clad metals also signifies an expanding nickel market. In anticipation of the postwar demand for nickel, and realizing the seriousness of the ""have not"" position of the United States with respect to this metal, the Bureau of Mines, sent an engineer 4/ into the lower Copper River region of Alaska during the summer of 1944 to investigate the nickel deposits near the head of Canyon Creek. Samples from the Spirit Mountain nickel prospect were sufficiently encouraging to justify more intensive exploration. As a result, a program of surface trenching, systematic sampling, and detailed mapping of the property was adopted and directed by a Bureau of Mines engineer 5/ in the summer of 1945."

Aug 1, 1946

By E. D. Eastman

The recent determination by Eckman and Rossini of the heat of formation of sulphur dioxide appears to be of much greater accuracy than any previous measurement . The value obtained by them , 70,940 cal . , is in good agreement with that of Thomsen ( 71,080 ) , but differs by about 1,700 calories from Berthelot's result ( 69,260 ) , and by 1,940 calories from the provisional figure ( 69,000 ) adopted by Lewis and Randall in their studies of the free energies of the sulphur compounds . This large discrepancy suggested the desirability of a recalculation of the free energy of sulphur dioxide . In addition it is now possiblt to fix the specific heat of S₂ gas with greater certainty than at the time of the original calculations . These two changes are incorporated in the recalculations described below , and directly affect the values of AH , and the Ar terms in the free energy equation . In the determination of the integration constant of the latter equation , the free energies and specific heats of water vapor and the oxides of carbon are required as auxiliary data . In this work these are based , with certain exceptions , upon the equations previously deduced , which differ appreciably from the corresponding equations of Lewis and Randall . 56 · The principal equilibria employed below , and the plan of calculation , remain the same as in the calculations of Lewis and Randall . Before beginning this revision a search of the literature was made , extending to August , 1930 , for studies of additional equilibria . Only one reaction was found that gives promise of increased accuracy . This is the equilibrium of sulphur dioxide with copper , cuprous oxide , and cuprous sulphide . In this case , however , certain of the subsidiary data are lacking , and until they become available , the existing studies of the equilibrium in this system can not be successfully utilized . The changes in the numerical data mentioned above , especially in the thermochemical constants , are therefore solely responsible for the rather significant differences of the revised from the original values of the free energy .

Apr 1, 1931

By James M. Spear

The U.S. Bureau of Mines and the U.S. Geological Survey conducted a mineral survey of the Black Butte RARE (I area during the summer of 1981. The study area encompasses 17,800 acres [27.8 sq mi (7,233 ha)] along the course of the Black Butte River, 13 mi (22 km) southeast of Covello, California. No mineral deposits were identified by the U.S. Bureau of Mines during this survey. Assay results of samples taken in this area indicate only trace amounts of manganese, chromium, and nickel. No radioactive or fluorescent minerals were detected. No oil and gas, coal, or geothermal leases have been recorded for the study area.

Jan 1, 1982

Develop technology for preparing thick corrosion-resistant coatings and electroforms of iron-chromium-nickel alloys. Approach To reduce the United States' dependence upon foreign sources for supplies of strategic and critical metals such as chromium, cobalt, and nickel, new technology must be devised to conserve these valuable commodities. One approach being investigated by the Bureau of Mines is the use of a modified-aqueous-electrodeposition method to prepare thick (-25 µm), complex alloy coatings (e.g., stainless steel composition) with properties similar to the commercial alloys. An alloy coating on a low-alloy steel or carbon steel substrate would require significantly less strategic and critical metals than those contained in an equivalent mass of the commercial alloy. Coatings applied to appropriate mandrel materials make possible the preparation of intricately-shaped alloy electroforms (near-net-shape parts). As a result, the loss of valuable metals associated with machining finished products would be minimized.

Jan 1, 1986

By Peter F. Steidl

As part of the Bureau of Mines methane control program, the Upper Free- port coalbed was studied in Fayette County, Pa., where this coalbed lies about 650 feet below the Pittsburgh coalbed and contains the largest remaining reserves of any coalbed in the county. Coal and overburden isopachs, structure and joint pattern maps, and a fence diagram were prepared using data from gas and oil exploration logs and coal outcrops. These maps will aid in determining the need and/or feasibility of degasifying the Upper Freeport coalbed in the study area. Much of the coalbed in this area is under 600 to 1,400 feet of overburden. By correlation with data from the Pittsburgh coalbed, the gas content at depths of this order is estimated to be between 140 to 300 cf/ton of coal, for a total of 190 to 400 billion cubic feet of methane in this coalbed in Fayette County.

Jan 1, 1977

By Michael J. Brnich

Since 1991, Pittsburgh Research Center (PRC- formerly part of the Bureau of Mines) researchers have recorded extensive interviews with 30individuals who are experts in the area of mine emergency response. These individuals, who have an average of 35 years of mining experience and 29 years of mine emergency response experience, related stories and observations from events that they experienced during their combined 850 plus years in mine emergency response. The purpose of this effort was to gather information that could be passed onto both today?s and tomorrow?s mine emergency responders to train and guide them in handling future events. This is the second of two articles which report experts responses to questions about training for future mine emergencies. During the interviews they discussed how training should be conducted, who should be trained, and what topics should be included. This article will cover the third area: Topics that should be included in training for mine emergency response managers.

Jan 1, 1997

By D. J. Parker, D. Harrington, L. H. Harrison

The necessity for protection against the hazards of lightning manifests itself from time to time in the mining industry by reason of loss of life, damage to electrical equipment, fires in surface structures at mines, and accidents in the handling and use of explosives. This paper is intended to assemble, correlate, and present some of the salient. points embodied in the available literature on the subject and at the same time give some factual data concerning instances of such loss of, life and damage to property, with special application to the mining industry The annual loss of life and destruction of property by lightning is considerable; the former may be prevented to a limited extent, though use of common sense as to exposure is required and not always followed; the latter can be prevented to a considerable degree. The manufacturers of electrical equipment,, through improved types of lightning arresters,, have done much toward the protection of electrical equipment, with consequent safeguarding of life and of property. Education based on unfortunate experiences has gone far to discourage the handling of explosives and blasting accessories during thunder storms, especially in open pits and quarries, and to a much smaller extent in underground workings. The lowly lightning rod plays an important role in the protection of certain types of buildings (especially isolated buildings), stacks, monuments, and other structures. LIGHTNING PHENOMENA In 1751, Franklin proved that lightning was simply a visible display of electricity - an extended spark; and until a generation ago little had been added to his exposition, to define the various phases of the phenomenon. Matters pertaining to lightning are discussed in the following references:

By Henry W. Busch

Determination of the aldehyde content of Diesel-engine exhaust gas has proved rather cumbersome and unsatisfactory when carried out in its entirety in field investigations; therefore, studies were conducted with a view to developing methods by which samples might be collected in the field and trans-ported to the laboratory for analysis. Experience also indicated that aldehyde samples collected in water solution and then transported to the laboratory sometimes underwent serious changes in composition if several days elapsed between sampling and analysis. Polymerization of the aldehydes, which takes place readily in dilute aqueous solutions, may have been the cause of such changes. Because of these difficulties, experiments were conducted to find a suitable stabilizer or preservative for dilute aqueous solutions of the aldehydes that occur in Diesel-engine exhaust gas, so that in field studies a known volume of gaseous sample might be collected and brought into contact with water, and the resulting solution of aldehydes analyzed in the laboratory at some later time with reasonable certainty that the results would represent the composition of the original sample,

Jan 1, 1949

By Willard L. Hunter

The Bureau of Mines smelted samples of chromite ore and concentrate from the General Services Administration (GSA) purchasing depot at Grants Pass, Oreg., in a submerged-arc furnace to establish smelting conditions and the energy requirement to produce high-carbon ferrochromium. Raw material, in the form of ore, flux, and reductant, and electrical energy are available on the Pacific coast to smelt the chromite. The concentrate can be smelted without prior agglomeration by employing hogged wood (wood chips) as a major portion of the reductant. The energy requirement is relatively low, about 3,960 kw.-hr. per ton of alloy. The ferrochromium produced will contain about 60 percent chromium. In addition to the smelting data, a statistical summary of the grade and amount of chromite purchased during the stockpile program and estimated chromite reserves and production volume are given. It is estimated that 632,000 tons of Cr203 contained in chromite of all grades is available in the western coastal States. Of this total there appears to be sufficient metallurgical-grade and beneficiable ore to sustain a smelting operation for 25 years at a consuming rate of 25,000 tons a year, utilizing material comparable to that delivered to the Government stockpile.

Jan 1, 1961

By John Owens, Wayne Howie, Hamid Maleki

After an analysis of the hazards of room-and-pillar retreat mining systems, it became apparent that safety could be significantly improved by considerations of (1) human factors, (2) remotely controlled mobile roof supports (MRS=s), (3) mine layout designs, and (4) ground monitoring systems. Initial studies of the effectiveness of MRS=s focused on their interaction with mine strata and evaluations of suitable measurements for detecting roof stability problems during pillar extraction. These studies indicated that overall stress distributions and strata movement were most influenced by the stiffness of coal-measure rocks and the design of mining layouts. Thus, to improve worker safety, mine layouts should be carefully designed and a pillar extraction method chosen for specific geologic and stress conditions. Pillar failure was often associated with an increase in pressure on the hydraulic gauges of the MRS, and roof failure was often preceded by rapid changes in the rate of roof-floor convergence. These studies led to development of a monitoring system that displays loading rate on an MRS in real time. A major MRS manufacturer cooperated in installing and testing the system on an MRS. New field studies focus on evaluating the performance of the system, measuring roof-floor convergence, and optimizing the safety of MRS operations through proper mine layout design.

To cool hot working environments in deep mines more efficiently, while substantially reducing the maintenance required by presently used cooling coil heat exchangers. Approach A mine's chilled water supply cools fresh air enroute to hot working areas, in an improved, direct-mixing heat exchanger. How It Works Warm, fresh ventilation air traveling through the mine's ventilation tubing enters the lower portion of the cooler heat exchanger through a large round opening designed to accept the ventilation duct. This air flow is turned upward and evenly distributed by egg-crate lattice and pair guide vans at the bottom of the cooler. On the diagram, warm air enters at the bottom left. As the air moves upward through the cooler, it passes through a plastic or wire mesh pad which is arranged so that it offers the most resistance to upward airflow immediately above the cooler inlet: this more or less equalizes the upward air flow along the length of the cooler. The air next moves through the cold water sprays, and then through a wire-mesh demister pad before exiting from the cooler at the top right. Cooling of the air is accomplished in several stages. As the incoming air passes through the lower plastic or wire mesh pad, it is exposed to water flowing downward through the pad to the water sump. This is water that has fallen from the sprays or dripped from the upper wire-mesh mist eliminator. This water is slightly warmer than the spray water since it has already done some cooling,

Jan 1, 1981

By S. J. Hussey

A jig tailing with gold content ranging from 0.33 to 0.43 oz/ton was leached in weak cyanide solution with extractions of up to 97 pct in 24 hours. By countercurrent batch leaching studies and laboratory pilot plant operation, minus 10- plus 20-mesh and minus 6- plus 16-mesh coconut carbon were loaded to 700 oz/ton of Au. Minor silver in the ore reported in the carbon in amounts of up to 100 oz/ton. Gold adsorption rate data and an equilibrium adsorption curve for minus 10- plus 20-mesh carbon at ambient temperatures were developed and used in the successful application of a cascade design theory. The work was performed as a part of the overall Bureau of Mines research effort to help maintain an adequate domestic supply of metals by making improvements in mineral-processing technology.

Jan 1, 1979