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By B. E. Blair

Accelerometers of various types, velocity gages, and a displacement meter are shown to give reliable date when measuring seismic pulses generated in rock by the detonation of explosive charges. Displacement and velocity records are differentiated and shown to compare with velocity and acceleration records. Velocity and acceleration records are integrated and shown to compare with displacement and velocity records, respectively. The experimental data are shown to satisfy the scaling laws developed by dimensional analysis. Propagation laws are developed for peak amplitudes of the first pulse of displacement, velocity, and acceleration. These propagation laws are shown to be independent of the gage used to obtain the data. As a result, the usefulness of the various gage types can be extended. For example, accelerometers, because of their high frequency and amplitude limits, can be employed near the shot to measure acceleration and/or velocity (by integration), Velocity gages, because of their higher sensitivity, can be employed at relatively larger distances from the shot to measure velocity and displacement or acceleration (by integration or differentiation).

Jan 1, 1954

By Harry R. Nicholls

As part of the pre- and post - shot mine examination at Project GNOME , acceleration data were recorded underground from a series of chemical explosive shots . The cube root of the charge weight was used to scale acceleration and distance because charge weight was not constant . Regression analysis of particle acceleration - distance data gave the following propagation equation : A W1 /3 = 5.10 x 105 ( R / W¹ / 3 ) −2 .43 The quantity A W1 /3 is scaled particle acceleration expressed in g's - lbs¹ / 3 , and R/W1 /3 is scaled distance expressed in ft / lbs¹ /3 Data obtained from the nuclear explosion were scaled and fall within one standard deviation of the calculated propagation law for the smaller shots . Cube root scaling laws were adequate to group acceleration data from explosive charges varying by a factor of more than 1 x 10 in charge weight and over shot - to - gage distances varying from 100 to 46,000 feet . Data obtained from a series of small tests provided sufficient data from which reliable predictions of acceleration could be made for the large nuclear explosion .

Jan 1, 1964

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 A. J. Barry

Two methods of testing anchorages of headed expansion-type mine roof bolts were investigated by the Federal Bureau of Mines to determine whether they are acceptable for general use. In both methods a load was applied to a tightened bolt with a hydraulic jack. A total of 80 tests, 40 using each method, was conducted in 4 test areas in 3 commercial coal mines. Electric resistance strain gages were used in all tests to indicate true bolt load as the bolt was tightened and when an additional load was applied with the hydraulic jack. The results indicate that: 1. The relationship between the true bolt load and the jack load will vary according to the test method until the two loads become equal. The bolt load-jack load relationship below this point can be determined only with strain gages. 2. The point at which the two loads become equal can be estimated by noting the load when the hardened washer becomes loose in one method, and when the bearing plate becomes loose from the roof in the other. It also can be approximated for either method of testing by noting the load when the first abrupt change in the slope of the jack load-bolt displacement curve occurs. 3. The anchorage characteristics of the test bolt can be determined from the data obtained from either method by examining the slope of the jack load-bolt displacement curve above the point at which the true bolt load is equal to the jack load.

Jan 1, 1960

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 Fred N. Kissell, R. J. Bielicki

In this report the importance of diffusion in controlling the emission of methane in mines is examined. An in-situ diffusion parameter is defined and calculated for a hypothetical unfractured lump of coal in the Pittsburgh and Pocahontas No. 3 coalbeds. The values obtained are similar to those obtained with lump coal in laboratory experiments.

Jan 1, 1972

By Wm. C. Dean

The location of trapped miners from their seismic signals will be in- accurate if we assume the P-wave propagation velocity is a constant. P- wave velocities are anything but constant in regions about mines, so some calibration is necessary to obtain more accurate seismic locations. The reference event method compares the time arrivals of signals generated by the miners with those previously recorded from a reference or calibration event in the vicinity of the miners. This method locates the miners' position relative to the calibration source. Hence, the location of the miners is absolute if the reference event position is known absolutely, usually from surveys and mine maps. Advantages resulting from the system, besides greater accuracy, are locations independent of the velocity model assumed, the same solution from the full array and from any subset of four or more seismometers in the array (three if the miners' depth is known), fewer seismometers required, and no complex computers required for analysis. VELA Uniform experience shows that the accuracy of locations of teleseismic explosions and earthquakes is improved by an order of magnitude over locations computed from average travel time curves. Each calibration event is applicable only over a limited range. We recommend a field test of the method at a mine to measure its location accuracy, the range of effectiveness for each calibration event, the number of seismometers needed, and the number of reference events required per mine. From these experiments we could decide whether the reference event method was useful and, if so, what form a practical rescue system would take.

Jan 1, 1974

By Martin Hertzberg

In this Bureau of Mines report, the optical detection of fires and explosions is considered fundamentally. The measured spectral radiances from methane-air ignitions are compared with the background irradiances from stray and ambient sources, and with the spectral sensitivites of various sensors. The comparison naturally suggests the optimum spectral ranges and signal processing logic that can uniquely characterize the ignition event. Both ultraviolet (UV) and infrared (IR) are considered. Several alternate sensing methods are proposed and discussed. The development and testing of an IR system designed for use in ignition suppression devices in mines is described.

Jan 1, 1975

By E. O. Bennett

Various methods of making leakage tests have been tried during a study of losses in the transmission of natural gas. This work has been carried on by the Bureau of Mines in cooperation with the Natural Gas Association of America. Results of tests show that the "shut-in pressure-drop" method described by Rawlins2 is the most accurate and reliable; therefore its use is recommended. This paper describes a graphic method for computing the rate of leakage from the fall in pressure and change in temperature determined by the "shut-in pressure-drop" method of testing. METHOD OF MEASURING PRESSURE DROP The gas is "shut in" the line to be tested and is not allowed to escape except through existing leaks. The leakage causes the pressure in the line to fall. The change in pressure is obtained with a dead weight gage. Approximate results may also be obtained from readings on a good spring test gage. Numerous tests show that the dead weight gage is more sensitive to small changes in pressure than spring gages.

Jan 1, 1926

By Hendrik Gerritsen

The research to be described is directed to the construction of an instrument that detects methane in air. The principle on which it is based is that methane gas absorbs infrared radiation in the wavelength range of about 3.2 to 3.4 micron. Solid state p-n junctions of composition In, .97Ca.03As emitting radiation in a band centered at 3.3 micron were grown by liquid epitaxy on InAs. Fight separate growth cycles and a total of 200 diodes were measured to determine total power, wavelength peak, spectral. half width and reproducibility of the method. In order to compensate for temperature changes, dual emitter systems (one InGaAs, and one InAs diode) mounted on the same TO-5 header were made. These devices were imaged, using a folded optical path cell, on large area InAs detectors, grown by a planar diffusion technique. In the 0-50°C range the primary temperature sensitivity is in the InAs detector rather than in the emitters. Several methods to reduce the overall temperature sensitivity to within acceptable limits were demonstrated. Humidity was shown to have a negligible effect on the measurements.

Jan 1, 1976

A revolutionary development in blasting materials has occurred in the past 5 years. Ammonium nitrate, sensitized by the addition of a few percent of No. (class) 2 diesel fuel or other suitable petroleum product, has been adopted as a low-cost, efficient blasting agent2/ by a wide variety of mining and heavy construction operations. Moreover, ready availability of the component supplies throughout the Nation and ease of their formulation into effective blasting agents have made it possible for the blaster himself to pre-pare the mixes at the site of use. Although these field-mixed products have partly or wholly displaced explosives such as dynamites in some applications, there are other blasting operations where the fuel-sensitized ammonium nitrate agents do not appear to be well adapted. Important safety characteristics are inherent in ammonium nitrate-based blasting agents prepared under competent factory control, or when field mixed under equivalent close control--as long as the hazards they present are clearly understood and respected. This publication attempts to summarize knowledge of those hazards and to incorporate practical ways to cope with them. A series of safety recommendations thus is presented. These recommendations cover the preparation, storage, transportation, and use of field-mixed ammonium nitrate blasting agents.

Jan 1, 1960

By R. Hogg, T. F. Dumm

"It is generally agreed that dust characteristics play a role in the development of Coal Workers' Pneumoconiosis (CWP). Unfortunately, there is a serious lack of information on what the characteristics of mine dust actually are and how they vary among different mining regions, coal seams, etc. This paucity of data can generally be attributed to the serious problems encountered in collecting sufficiently large quantities of dust for conventional analytical procedures.Personal samplers are widely used in coal mines for regulatory and enforcement purposes. Generally, these provide information only on the total (respirable) dust loading in the mine atmosphere and on the mineral matter (primarily quartz) content of the respirable dust. A procedure has been developed by which samples collected with a slightly modified personal sampler can be analyzed for particle size distribution, total mineral matter content and elemental composition, in addition to the standard mass and quartz measurements. These analyses could readily be performed on a routine basis. Shape analysis by Scanning Electron Microscope (SEM) could easily be included if appropriate shape criteria are established. Extension of the procedure to include the determination of complete size/specific gravity (composition) distributions is quite straightforward provided sufficiently large samples (at least 10 mg) can be collected. Typical sample sizes for a personal sampler carried by a miner for one shift range from about 0.5 to 2 mg.The basic procedure was developed and evaluated using synthetic mine dust prepared in the laboratory. Field tests in three working mines in Pennsylvania and West Virginia have confirmed the applicability of the approach to the real world. Particle size distribution measurements on mine dust collected in the modified personal sampler were found to agree closely with the results of simultaneous in situ measurements obtained using cascade impactors."

Mar 1, 1989

By Samuel A. Goldberg

The Federal Coal Mine Health and Safety Act of 1969 delegated to the Bureau of Mines a yearly program of health inspections. Respirable coal mine dust concentrations are measured by Bureau inspectors. Samples of respirable coal mine dust are weighed to determine dust concentration and then analyzed for ash and quartz content. This paper describes the laboratory procedure for determining the percent quartz in the respirable coal mine dust samples.

Jan 1, 1972

By H. J. Van der Veer, F. E. Griffith

"Reflector button signs similar to those used to attract the attention of motorists on the public highways at night are now being used to good advantage by a few mining companies in underground workings for danger, warning, direction, and safety signs and signals. Most safety signs and signals used in underground mining are of the electric light painted-board, or enameled or porcelain metal-plate,type, all of which have good features as well as some disadvantages; among the disadvantages are: The filament of electric incandescent lamps is prone to ""burn out"" occasionally anti usually the lamps are not replaced promptly; painted-board and enameled or porcelain metal-plate signs can be seen only a short distance and often are ""passed up"" unintentionally by employees, consequently these signs do not always serve the purposes intended and may be the cause of injury or death through failure to warn the men of danger.The advantage of using reflector button signs in mines or underground workings is that the cap lamps or headlights with which employees and locomotives generally are equipped, if directed at these buttons will reflect the light back to its source, and if they are arranged to spell words of warning or direction, or if suitable symbols are used, they are discernible and can be read at a distance of several hundred feet. The distance the light is reflected depends largely on the color of the buttons used. The reflector buttons also in many instances can be used to good advantage in conjunction with other methods previously mentioned.Several types of reflector buttons are available, among them the flat-lens type with mirrored metallic foil or plate back, the facet-cut-lens type with a mirrored metallic foil or plate back, and a type with a hemispherical smooth lens with a parabolic mirrored metal back. Lenses for the different types are available in several colors. Crystal, amber, red, and green are the colors of the buttons used to the greatest extent in underground signs up to the present time. These buttons may be had in different sizes, also.It has been observed that crystal-colored buttons reflect light the greatest distance (about 1,000 feet) and red-colored buttons the least (about 500 feet); reflection from green and amber colors ranges somewhere between the red and crystal colors in distance.Reflector buttons for underground use should be designed to reflect light a maximum distance; they should be made of materials that resist oxidation and corrosion, especially of the mirrored backs, and should be relatively free of protruding parts or projections that will collect dust.Reflector buttons approximately 3/14 inch in diameter seem best suited for underground use in general because fewer reflector units are required for a signal of given size."

Dec 1, 1937

By L. W. Brandt

Studies of liquid-vapor equilibria of gas mixtures at the Bureau of Mines Amarillo Helium Plant Laboratory require that the equilibrium cell be maintained uniformly at any desired temperature from approximately room temperature to -320° F. The temperature-control system must also tolerate a substantial heat input, in the form of warm gas flowing into the cell, without loss of control. Temperatures between the sublimation temperature of carbon dioxide (-109° F.) and the boiling point of liquid nitrogen (320° F.) are usually obtained by methods utilizing a hydrocarbon liquid bath cooled by liquid nitrogen.4/5/6/7/ Owing to the fire hazard attending such baths, a safer method of temperature control was desirable.

Jan 1, 1955

By L. C. IlsLey

One of the details which the engineers observe closely in conducting tests on explosion-proof type equipment at the Pittsburgh experiment Station of the Bureau of Mines is the construction of covers and their means of fastening. These covers are of particular concern from a safety standpoint, because they are very liable to be frequently disturbed for the purpose of making inspection or repairs to internal parts of motors, controllers, etc. When depended upon to permit frequent inspections it is desirable from a practical operating standpoint that the cover be easily and quickly removed and replaced. The position that been taken by the Bureau of Mines is that the questio of ease with which covers will permit inspection should be determined by the mamu- facturer and the user. If the scheme used requires considerable effort, as in the removal of several bolts, it has been assumed that the one going to all this trouble to get the covers off could be trusted to put the cover back in place properly, especially as the approval plate generally calls specific attention to this point. Where a cover is simply screwed in place, fastened by a single bolt, or secured by a hing in or other similar arrangement, the bureau has not been willing to assume that the, cover would in all cases be properly fastened and has required further security by means of a lock or seal. In the course of its investigations the bureau has had occasion to inspect and test five types of covers as follows: (1) Covers having two plane surfaces bolted together. (2) Covers having two plane surfaces held together by lugs, clamps, or other means besides bolts. (3) Covers which have screw thread and fit a similar thread in the compartment. (4). Covers having plane surfaces with the addition of a tongue-and-groove joint at about the center of the plane surface and in general secured by hinge pins or similar means of fastening. (5) Covers in the form of an annular ring accurately fitted to a motor shell which can be rotated around the shell, and thus make easy access to inspection openings in the shell and rotated back again to effectively seal these openings. Tests. have also been made of large bolted covers having a smaller and more accessible cover within the large one, which could be opened for inspection purposes.

May 1, 1930

By Henry M. Harris, George J. Carter, Karle G. Strandberg

Field and laboratory data were used to evaluate sand from 13 dune locali­ties along the Oregon coast between Fort Stevens and Coos Bay. Chemical and glass button analyses were used to classify the 65 samples into two geographic zones of decreasing iron concentration. These data and data from preliminary magnetic beneficiation tests indicated that the sands between the Umpqua River and Coos Bay contained fewer impurities and were easier to beneficiate than those from areas between Fort Stevens and the Umpqua River, In addition, the dunes in the Umpqua River-Coos Bay area are the largest along the Oregon coast and are most favorably located with respect to existing transportation facilities, A composite sample from the Rogers area on the west bank of the North Slough of Coos Bay was selected for detailed mineral dressing studies. Splits from this sample were treated by various processes including magnetic separa­tion, electrostatic separation, flotation, and acid leaching, Concentrates were evaluated in glass melting tests. Test results indicated that high intensity magnetic separation followed by acid leaching would produce a prod­uct that could be used in amber and clear container glass batches. Good glass sand concentrates were also prepared by froth flotation; however, recovery was low and reagent costs excessive.

Jan 1, 1964

By Marc T. Filigenzi

Two of the major ground control safety issues confronting underground mine operations today are shaft pillar stability and the failure of rock around active mine openings. Failure of a mine shaft can lead to the entrapment of workers. Failure of rock around active underground mine openings can lead to roof falls, which in turn can result in worker injuries and fatalities. Finite-element analysis has proven to be a reliable method for predicting stresses and displacements around underground mine openings. However, this is a complex and time-consuming technique and is not used as often as it could be in mine planning. The purpose of this paper is to demonstrate one technique developed at the Spokane Research Center that allows the user to create a finite-element model of a two-dimensional section of an underground mine in a relatively straightforward manner. This model is then used to calculate stresses, displacements, and safety factors around mine openings. With this information, mine planers can evaluate the stability of mine openings as well as the stability of pillars and mine shafts. This analysis will help develop mining sequences and layouts that minimize stresses in that section of the mine. This, in turn, should minimize the occurrence of shaft failure, roof falls, and other hazards associated with underground mining.

By Richard L. Lewis

This is a discussion of the application of the zonal harmonic series to problems involving dipole sources in the vicinity of spherical boundaries. The application of a formal zonal-harmonic series solution to directly obtain numerical results involves two distinct problems: namely, the convergence of the series solution and the accurate calculation of the special functions involved in the series solution. Some interesting techniques will be introduced which help to improve the convergence properties of the series solution.

Jan 1, 1973

By Victor E. Kral

"INTRODUCTION The Segerstorm-Heizer property was examined by engineers 3/ of the Bureau of Mines in May and June 1942 and Mach 1943. As a result of these examination, the Nevada State Department of Highways,constructed 9.3 miles of graveled road under the mine access-road program. A magnetometer survey was made by the Geophysical Division 4/ in October 1943, and as a result the Mining Branch set up and conducted a core-drilling,project. Work on the deposit started May 24, 1944, and was suspended on July 31, 1944, but was resumed on December 4, 1944 and continued until completion on March 27, 1945.ACKNOWLEDGMENTSIn its program of exploration of mineral deposits, the Bureau of Mines has as it, primary objective the more effective resource to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploration work, and prepares the final report. The Metallurgical Branch, R. G. Kinickerbocker, chief analyses samples and performs beneficiation tests."

Mar 1, 1947