Search Documents

By Fun-Den Wang

A two-dimensional plane strain analysis by the stiffness matrix method was used to analyze two basic pit slope configurations. The magnitudes and the directions of stresses are given for a V-shape and for a flat-bottom pit with the slope angle varying from 30° to 90° at 10° intervals, Stress effects due to irregular pit configuration or to in-situ forces are discussed. Equations of similitude for gravity loading are given. Expressions are also given for the stresses at the toe as a function of slope angle. Procedures are given for finding the stresses in any geometrically similar pit slope of different dimensions and material properties from the stresses and equations presented in this report. Numerical results show that the V-shape pit slopes have lower stresses than the flat-bottom pit slopes; hence, they are inferred to be more stable.

Jan 1, 1970

By David C. Byrne

From an engineering perspective an ideal industrial noise control solution focuses directly on the actual source of the poise. Eliminating the noise-generating mechanism altogether obviates the need for other noise contra l treatments or hearing protection devices. However, in cases where attenuating the source is not feasible engineering controls must be oriented toward blocking the path that the sound waves travel toward employees. Acoustical enclosures are commonly used as sound path treatments to contain the noise from a machine: alternatively a control room/booth or equipment operator's cab may be used to isolate the worker from the noise. Anyone who has successfully used acoustical enclosures knows that the design procurement, and installation process is deceptively simple. Alt too often First-time efforts fait to account for many of the constraints that can render the enclosure essentially useless. Things that cannot be overlooked include: providing convenient worker access (physical and visual): allowing for proper machine operation/product flow; and supplying fresh air or preventing undue heat or contaminate build-up inside the enclosure. All of these factors must be given careful consideration, otherwise the enclosure will not perform adequately.

1. PURPOSE The Temporary Face Support System (TFSS) consisting of beams, posts and carrying-emplacing equipment was developed to provide temporary supports between the working face and the permanent roof supports. 2. GENERAL DESCRIPTION The system consists of: ? A Beam And Post Carrier And Deployer (BAPCAD), a self-propelled machine that carries as well as emplaces the beam-and-post sets. ? Lightweight mechanically self-deploying posts designed to safely support a load of 10,000 pounds each. ? Lightweight constant strength beams (bars) capable of sustaining an approximate equally distributed load of 8500 pounds. Note. All referenced figures and drawings are found at the back of this manual.

Jan 1, 1980

By Howard E. Parkinson

The mine pager phone to public telephone interconnect system permits mine paging telephones to be interconnected with the public phone system, thereby providing emergency and off-hours communications. The system, a push-to-talk, push-to-listen system, is compatible with any mine paging system utilizing dc voltage on the line to enable paging. A tone generator of the proper frequency enables an outside caller to page over mine pager system loudspeakers. A caller inside the mine can make an outgoing call to a preselected, preprogramed number with the use of a proper frequency tone generator. The system includes an automatic hangup timer that restricts the time off-line due to a wrong number or incorrect hangup to 20 seconds and 6 minutes, respectively.

Jan 1, 1974

By J. D. Dixon

The Bureau of Mines investigated the principles of support-rock interaction, based on structural matrix methods which permit mathematical formulation of the problem and computer solution. The principles are given under two main sections: the first discusses the idealization of the tunnel support structural system for matrix analysis; the latter discusses the analysis procedures necessary for carrying out the solution. A general frame matrix computer program and a medium-size computer should be sufficient for carrying out the procedures involved. The example problem consists of a circular tunnel support which is subjected to a uniformly distributed vertical load, Three wall thickness-radius ratios are studied in combination with four support-rock modulus ratios. This problem illustrates the main procedures of the support-rock interaction analysis involved, and examination of the results reveals the influence of the relative rigidities of the support and the rock.

Jan 1, 1971

By R. J. Shanley

This report presents a computer code that has been developed by the Bureau of Mines for isolating naturally occurring clusters of data plotted on the unit hemisphere and testing these clusters against a probability distribution which admits elliptical symmetry about its mean. A listing of the computer code is provided along with an example output illustrating the delineation and analysis of clusters in fracture orientations measured in a porphyry copper deposit.

Jan 1, 1975

By Yael Miron

Coal mines that undergo self-heatings, and specifically mines that sustain both floor heave and self-heatings, would benefit from the use of sealants to minimize air ingress to susceptible areas. The U.S. Bureau of Mines(USBM) evaluated three sealant systems for this purpose, bentonite-water mixtures, silicate gel, and guar gum gel. The guar gum-based gel was the only sealant that possessed the desired properties of elasticity, ease of preparation, adaptability to the mine, and a long life. In addition, since the gel consists mostly of water, it could quench or cool nearby heatings. Optimal formulations were determined in laboratory tests, and then tested in the USBM Safety Research Coal Mine. Two formulations resulted in stable gels that lasted for at least 12 months in the mine. Semi continuous preparation of gel using an eductor was evaluated and appears feasible. Although guar gum gel is expensive, selective use to prevent heatings in specific areas would be cost-effective, both interms of productivity and enhanced mine safety.

Jan 1, 1995

By Harry G. Dosh

Sillimanite, kyanite, and andalusite are aluminum silicates having the same chemical composition (Al2SiO5) and are used in the ceramics industry for the manufacture of high-grade refractories. Natural sillimanite with added corundum or other alumina to just short of mullite (3Al2O3 -2SiO2) proportions is unequalled for jobs wherein strength at high temperatures, resistance to spalling, and resistance to slagging by acid slags are desired. High-grade porcelain ware also requires these minerals. At the same cost, sillimanite would be preferred for most uses, but the lack of any large source of sillimanite bas given economic preference to kyanite or andalusite for special refractories and high-grade porcelain wares. Sillimanite-bearing schists were observed in Spartanburg County, S. C.; as early as 1937 by D. Hoye Eargle, geologist with the U. S. Soil Conservation Service. The mineral was not identified until 1942, when Miss Jewell Glass, of the U. S. Geological Survey, examined several of the deposits. This identification was confirmed in 1943 by Dr. Laurence L. Smith, of the University of South Carolina, when he examined the Spartanburg County deposits and found numerous additional occurrences of sillimanite schist in Greenville County. Subsequent work by the Bureau of Mines and the South Carolina Geological Survey has been responsible for the location of additional sillimanite-rich schist deposits in Spartanburg County. Between October 1, 1948, and November 21, 1948, the Bureau of Mines conducted an exploratory diamond-drilling project on the John Gideon property in the southeastern section of Spartanburg County (fig. 1) and drilled a total of 681.7 feet in six holes. Drilling indicated that the deposit is relatively shallow, as no ore was cut below the zone of weathering.

Jan 1, 1950

By Guy A. Johnson

This Bureau of Mines report summarizes the results of efforts to develop reasonably priced, reliable mine shaft fire and smoke protection hardware for metal and nonmetal mines. The hardware was incorporated into a viable prototype system that would minimize fire and smoke hazards. The design of the system had to be sufficiently flexible to be utilized in a wide variety of metal and nonmetal mine shaft and shaft station configurations. As a result of long-term, rugged field tests, an improved (second generation) system was developed. The hardware is now commercially available.

Jan 1, 1978

By John Owens, Hamid Maleki

Efficient and safe use of mobile roof supports (MRS) depends on the interaction between the MRS and coal strata. Of particular interest to this study are the mechanics of strata deformation as influenced by geologic conditions, pillar extraction methods, and MRS load-bearing capabilities. To provide a better understanding of the mechanics of strata deformation, the authors have collected and reviewed measurements of convergence and stress in one western U.S. mine and have completed pseudo-three-dimensional, boundary-element modeling for two typical pillar-pulling plans. Stress distribution in the mine roof above pairs of MRS’s was calculated to demonstrate how MRS’s contributed to the control of roof block movements. It was shown that overall stress and roof-floor convergence patterns were most influenced by the stiffness of coal-measure rocks and by pillar-pulling sequences and layouts. MRS’s and other support systems play a critical role in controlling the stability of both the immediate roof and the middle roof for a distance of up to 18 m (60ft) above the seam. MRS’s provide unique ground control advantages over other types of secondary support by significantly reducing the time between mining and installation of secondary support. Although MRS’s are similar to posts in stiffness and capacity, they are more effective than posts under static loads because they can yield and still maintain loads at near-peak capacity, whereas posts fail and loose their ability to limit mine roof deformation.

By Manuel Gomez

The mean and the standard deviation were used to describe general sulfur and ash populations as well as specific populations of these variables from one coal seam. Both the mean and the standard deviation were incorporated in the exploration process to determine the number of drill cores necessary for seam evaluation and to guide the sequential drilling plan. Probability regions were computed to establish a basis for predicting probable ranges of average sulfur and ash concentrations that may be expected upon continued or future drilling. A computerized plot program was utilized to interpolate sulfur and ash concentrations between grid points. The plot program, which is essentially a moving average technique, permits a rapid evaluation of sulfur, sulfur forms, and ash spatial distributions as a drilling program progresses sequentially. This information, in the form of contour plots, can be made available to both the mining engineer and the fuel technologist in advance of mining to outline reserves, to improve selective mining, and to anticipate preparation facilities.

Jan 1, 1972

By Fred Garcia, William P. Diamond

As part of its mine safety and health research program, the National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, has been investigating the geologic and mining factors influencing methane gas emissions associated with longwall mining. A primary focus of this research has been the consequences of increasing longwall panel dimensions, particularly face width, in gassy coalbeds. Continuous longwall face emission monitoring studies were conducted at two adjacent mines operating in the Pocahontas No. 3 Coalbed, where longwall faces were to be extended from 229 to 305 m (750 to 1,000 ft). Average longwall pass methane emission rates for 229-m (750-ft) wide faces were 61 % (0.072 m31sec (153 cfm)) higher at the VP-3 Mine than at the VP-1 Mine. It was predicted by regression analysis of methane emissions data from 229-m (750-ft) wide faces that extending faces to 305 m (1,000 ft) would increase methane emission rates by only 7%, or 0.009 m3/sec (20 cfm), to 0.144 mysec (304 cfm) at the VP-1 Mine. In contrast, it was predicted that extending faces to 305 m (1,000 ft) at the VP-3 Mine would increase methane emissions by as much as 13%, or 0.029 mysec (65 cfm), to 0.268 dlsec (567 cfm).

Jan 10, 1999

By E. A. Johnson

As part of its effort to reduce the environmental impact associated with mining and metallurgical operations, the Bureau of Mines used a modified form of the Environmental Protection Agency's Extraction Procedure toxicity test on copper reverberatory slags that contained low, medium, and high levels of the impurity elements As, Pb, Sb, Bi, and Zn. All tests resulted in extracts that did not exceed those limits published in the May 19, 1980, Federal Register; there-fore, these solid wastes were designated as nonhazardous for most landfill disposal situations. However, arsenic and lead levels disturbingly close to the allowable limits--and even higher levels of copper and zinc, for which there are no established limits--leached from the high-impurity-element granulated slags. These slags should be handled in such a way so as to minimize the possibility of water contamination. One baghouse dust was tested according to the EPA procedure and found to exceed the extract limits by a factor of 10. This solid waste may be considered hazardous.

Jan 1, 1982

By Clete R. Stephan, Mark J. Schultz, William A. Slivensky, Eric S. Weiss, Kenneth W. Jackson

he Pittsburgh Research Center (PRC)~ and the Mine Safety and Health Administration (MSHA) are participating in a research program to evaluate the strength characteristics and air leakage resistance of seals and water trap designs for use in underground coal mines. This program is being conducted at PRC's Lake Lynn Laboratory near Fairchance, Fayette County, PA. Seals designed with a 40-cm-thick polymer (polyurethane) and aggregate core between two dry-stacked (no mortar) concrete block walls (coated on out by sides) withstood a 138-kPa pressure pulse while maintaining acceptable air leakage rates. Similar seal designs utilizing a 97-cm-thick, 91-kg/m7-density, polymer-only core did not survive; however, a 5 1 -cm-thick, 203-kg/mi-density, polymer-only core seal successfully withstood the explosion pressures. Evaluations of cellular concrete seal designs have shown that a two-pour slurry injection technique did not adversely affect the strength of the 1.2-m-thick seals when subjected to a 138-kPa pressure pulse. Two seal designs utilizing low-density cementitious block have also been evaluated with successful results. In addition to seal strength tests, various 15- and 30-cm-diam U-shaped water trap pipes and a water trough design were evaluated under explosion conditions and were shown to be inadequate when evaluated under worst-case conditions. Simple modifications to the various water trap designs were successfu1 in preventing the passage of explosion flame through the trap.

Jan 4, 1996

By R. V. Ramani, V. T. Burgos, J. A. McClay

Introduction The Cost program was developed to provide the planning engineer with a tool to evaluate the cost implications of the technical mine design decisions. Direct costing methods are employed, where feasible, to provide greater detail and accuracy in the primary cost centers. Options have been provided in the cost computation, economic analysis, and output data subsystems to increase the flexibility of the system. Computer Program The program is written in Fortran IV for use in the IBM System 360/370 computers. i. Main - The main routine reads and stores input data from three sources, user input, Cost Data Library, and data transfer from the Master Design Simulator. Data is trans¬ferred to the appropriate subroutines, as they are called, by means of labeled common blocks. ii. Subroutine CSTCOM - is a data modification routine which computes the peripheral charges related to labor and supervisory costs. iii. Subroutine MANPWR - interrogates section data to determine the total labor and supervisory costs for each cost center. iv. Subroutine CAPCST - computes the total capital investment for each cost center, including the economic life and salvage value of each element. Capital costs are determined by user selection of quantities and models of equipment. Equipment costs are stored in the Cost Data Library for retriev-

Jan 1, 1975

By F. P. Miknis

Previous studies at the Bureau of Mines have shown that broad-line nuclear magnetic resonance (NMR) techniques have potential applications for rapid evaluation of oil-shale deposits. In a continuation of this study the techniques of pulsed NMR have been applied in a similar manner. The basis for the pulsed NMR oil-shale assay method lies in the assumption that the free induction decay (FID) amplitude following a 90° pulse is proportional to the potential oil yield. This assumption was tested on two groups of oil-shale samples, numbering 141 and 263 samples, from two different oil-shale cores. For both groups of samples a small number were selected as calibration samples. Free induction decay amplitude measurements were made on the 141 and 263 samples. The best least-squares regression line was obtained for the calibration samples, and the oil yields of the remaining samples were calculated using the slopes and intercepts obtained in the regression analyses. The agreement between measured and calculated oil yields was good, the indexes of determination being 0.93 and 0.89 for the groups of 141 and 263 samples, respectively.

Jan 1, 1974

By J. H. Jansky, P. W. Jeran, G. L. Hassett, M. C. Irani

This Bureau of Mines report tabulates methane emissions from U.S. bituminous coal mines with daily emission rates of at least 100,000 cfd according to States, counties, and coalbeds. Most of the methane emitted is from mines in the Appalachian States. Total daily emissionin 1975 was 216.3 MMcfd, compared with 227.0 MMcfd in 1971 and 214.5 MMcfd in 1973. Thirty counties in nine States had daily methane emissions of 1 MMcfd or more, These emitted 93 percent of the total methane. The highest emissions were from Monongalia County, W. Va,, which accounted for 18.9 percent of the total. This was followed by Marion County, W. Va., 9.6 percent; Buchanan County, Va., 8.5 percent; Jefferson County, Ala., 6.1 percent; and Washington County, Pa., 5.9 percent. The Pittsburgh coalbed emitted 45.7 percent of the total methane, followed by the Pocahontas No. 3 coalbed with 12.9 percent. The report lists 196 mines, of which 60 had daily methane emissions of 1 MMcfd or more. Included in this compilation are the identification and thickness of the coalbed, methane emission, coal production and ventilation rates, number of drifts, shafts, and slopes used for ventilation purposes, shaft depth, age of mine, and gas-to-coal ratio.

Jan 1, 1975

By Byron A. Baker

The Bureau of Mines used a windowed cell to measure the phase-boundary pressures of two related series of gas-condensate fluid mixtures. Normal butane was added to the mixtures incrementally to determine its effectiveness for lowering phase-boundary pressure. All the experimental data were correlated, so that the pressure required to maintain light oils mixed with natural gas in the single phase may be computed for secondary recovery applications. The heavy hydrocarbon parts of the mixtures were distillation fractions of a Gulf Coast condensate. Intermediate normal hydrocarbons in the butane-heptane range and natural gas were added to the fractions in selected proportions, so that phase-diagram pressures of 26 fluids were actually studied. The experimental range of temperatures was 50° to 280° F. Two correlations were developed to represent phase-boundary pressures by means of a polynomial. Independent variables represent natural gas content, disparity of properties of components comprising the mixtures, and temperature. A fourth variable, for one correlation only, was the quantity of normal butane added to the original mixtures. The latter correlation with four independent variables contains 15 coefficients and is estimated to be accurate to 135 psi.

Jan 1, 1973

By W. W. Adams

"The third annual safety contest for plants producing sand and gravel, which was conducted in 1911 by the United States Bureau of Mines in cooperation with the National Sand and Gravel Association, registered further progress in safety as compared with the two previous annual contests. Both the accident-frequency rate and the accident-severity rate were reduced.The period covered was the calendar year 1931; sixty plants participated, and 17 States were represented by the participating companies.The contest covered accidents and man-hours worked by all men at the participating plant who were employed by the same company; and it included work up to the point of delivery of the material directly to the consumer or to an independent agency of transportation--in other words, to the point of relinquishment of control of the material by the producer.The purpose of the yearly contests for producers of sand and gravel is to aid in the promotion of safety among the employees and in the reduction of accident costs to the companies. The contests develop friendly rivalry among the various plants and among the employees of individual plant in a concerted effort to prevent accidents.Two safety trophies are awarded annually, both of which are provided by Rock Products magazine. One of the trophies is for the host safety record among plants that were in operation the contest year 100,000 or more man-hours; the other trophy is for the best among plants that were in operation lees than 100,000 man-hours. Awards and the relative standing of the various plants are based upon statistical compilation by the Bureau of Mines of accident reports and employment reports furnished by the enrolled companies. are summarized at the close of each year, and the summaries are submitted to each company concerned for certification as to the accuracy of the summary and the completeness of the company's reports from which the summary was prepared. When the summery is returned signed by an official of the company, the records are considered to be a trustworthy basis for determining the relative standing of the various plants. The position of each plant is determined by its accident-severity rate; that is, the number of days of disability resulting from accidents for each 1,000 men-hours of work done by all employees at the plant."

Aug 1, 1932

By L. C. IlsLey

Coal mining is more widely distributed throughout the United States than is generally known, as 30 States are credited with having coal mines. In 1919 twenty-three of these States each produced at least a million tons of bituminous coal, and all the States produced about 560,000,000 tons. In addition, Pennsylvania produced about 85,000,000 tons of anthracite. Twenty-eight States have regulations prepared by commissions or have enacted laws governing the operation of coal mines. Pennsyl¬vania has separate codes for the anthracite and bituminous fields. The codes may be classified as follows: Twelve distinctly coal¬mining codes; eight codes that are essentially coal mining, but also apply to other mines; five codes that are subdivided, referring partly to coal mines and partly to other mines; and four codes that are essentially metal mining, but apply in part or in whole to coal mining. The first State to have a coal-mining law was Pennsylvania, which enacted a law, for Schuylkill County only, in 1869. The first State to enact a coal-mining law governing all the coal mines in the State was Illinois in 1872, followed by Ohio in 1873. Pennsylvania in 1879 enacted a law for anthracite mines only, but did not enact similar laws for bituminous mines until 1577. At least 10 other States enacted coal-mining laws between the years 1870 and 1890. Before 1890 electricity was little used in coal-ruining operations and therefore practically no provisions governing the installation, inspection, or maintenance of electrical equipment were made in any of the laws enacted up to 1890. In the law of Colorado, approved April 8, 1885, there is a reference to the use of telephones, probably the first reference to electrical equipment of any kind in a State-mining code. Most of the mining codes have been changed from their original form by amendment or by complete revision. In some of the early changes a casual reference is made to the use of electricity or to the handling of electrical equipment. In 1911 Pennsylvania added

Jan 1, 1920