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By Richard J. Mainiero, Eric S. Weiss

This project investigates the behavior of blast waves from the detonation of high explosives in an underground mine. A series of explosive tests was conducted in the underground and surface facilities at the Bureau of Mines' Lake Lynn Laboratory to evaluate the potentially dangerous effects of blast waves produced by open shooting, blown out holes, or accidental detonations of explosives. Shots of C4 and TNT were fired at the dead end of a 6 ft high by 20 ft wide entry, at the intersection of two entries, and on the surface. C4 and TNT were chosen for this research because they exhibit very consistent performance. Behavior of the blast wave was evaluated through recording of the pressure as a function of distance from the explosive detonation. For both explosives, C4 and TNT, peak pressure decay with travel down the entry was inversely proportional to distance to the 0.9 power. When comparing pressure measurements at 200 versus 100 feet from the detonation; at 200 feet the pressure would be 1/2 0.9 or 54 percent of that measured at 100 feet. By comparison, peak pressure for a surface shot exhibits a decay with distance to the -1.6 power, yielding a pressure at 200 feet 1/2 16 or 33 percent of that measured at 100 feet. This result confirms that the blast wave from detonation of an explosive in an underground mine maintains its force for a greater distance than would be the case on the surface. Table and figures follow the text.

By W. H. Young, R. L. Anderson

"Physical conditions, such as thickness and character of the coal seam, dip or pitch of the seam, depth of cover, character of roof and overlying strata, mine water, etc., affect the productivity in bituminous-coal mining. Thickness of the coal seam being mined is probably the most important single item that determines whether the output per man per day shall be low or high; however, in strip mining the depth of cover or overburden to be moved is of equal importance.Bituminous coal is mined today from seams of exceedingly variable thickness - less than 2 feet to more than 50 feet; however, a large majority of the mines are producing .coal from seams 3 to 6 feet thick. The average thickness of the coal seams mined in the United States has not changed materially in the past 25 years. The average seam thickness for all bituminous-coal mines was 63 inches in 1920 4/ and 65 inches in 19)45. As thick seams have been exhausted in the older fields, other thick seams, have been opened in the newer fields.Productivity increased from 4 net tons per man per day in 1920 to 5.78 in 1945. This 45 percent increase in productivity resulted from increased mechanization. The percentage of underground production represented by coal cut by machines increased from 61 in 1920 to 91 in 1945 Mechanical loading increased from less than 1 percent of underground production in 1920 to 56 percent in 1945, and strip mining increased from less than 2 percent to 19 percent of the total production during the same period."

Dec 1, 1947

By Thomas J. Peters

This report is part of the U.S. Bureau of Mines Idaho Land Assesment Program to study the mineral resources of priority roadless areas in Idaho. The results of these mineral inventories provide minerals information needed to make wise decisions regarding future land management practices, and to ensure a dependable supply of minerals at a reasonable cost. The 16,300-acre Lionhead area, studied in 1991, lies along the Montana border north of Henrys lake, 10 mi west of West Yellowstone, Montana. The study area includes much of the rugged Henrys Lake Mountains, and is largely covered with conifer forest. Several peaks are over 10,000 ft in elevation. The Lionhead area has been proposed for Wilderness. No mineral resources were identified within or near the Lionhead study area. Five prospects occur in, or within 1 mi of the area: these include 1) an intermittently used road gravel pit, 2) the Thimbleberry lateritic iron prospect, of geologic and historic interest only, 3) the Tick Heaven talc prospect, 4) the Dry Fork garnet prospect, and 5) the lynx prospect, which appears to be of historic interest only. Talc is seen only as float at the Tick Heaven prospect, but the geology is permissive of talc resources at depth. The garnet prospect, and nearby similar alluvial terrane, mainly outside the study area, appears to be the most likely setting to contain mineable resources. Examined workings include four trenches and pits in rock and one gravel pit.

Jan 1, 1992

By J. W. Adams

Measurements of surface magnetic field noise were made at various locations over the Geneva Coal Mine near Price, Utah, on June 12, 1973. The locations selected were on the surface over emergency locator beacons underground at depths between 3S0 meters (1150 ft.) and 488 meters (1600 ft.). The surface terrain where these measurements were made was mountainous, and access was difficult. There were no power lines within several miles, and the weather was clear; therefore, the magnetic noise levels were about as low as will normally occur. Results of measurements of distant sferics indicate rather sharp cutoff frequencies below which broadband, impulsive noise is attenuated. The mechanism of propagation for this noise above the daytime cutoff frequency of 3500 Hz and the nighttime cutoff frequency of 1700 Hz is deduced to be a waveguide formed by the D or F layers of ionosphere as an upper plane and the earth as a lower plane.

Jan 1, 1974

By A. Sainato, S. J. Kravits, G. L. Finfinger

This Bureau of Mines report describes and compares the procedures, capital investments, and operating costs of rotary and in-hole motor drilling techniques used to drain methane gas from the Pittsburgh Coal- bed in an underground mine located in southwestern Pennsylvania. A timestudy was conducted during the drilling of each of two boreholes, and the data were collated to serve as a base for comparing drilling procedures and operating costs. Findings indicate that drilling with an in-hole motor offers four advantages over rotary drilling; namely, an increase in drilling productivity, fewer worker-hours required, ease of maintaining vertical and horizontal bit trajectory, and less expensive drilling cost per foot of borehole.

Jan 1, 1985

By Robert L. Chufo, H. Kenneth Sacks

Medium-frequency (MF) waves can propagate in a coal seam, bounded above and below by conducting rock, in an approximate transverse electro-magnetic (TEM) transmission-line mode with the electric field vertical and the magnetic field horizontal. The theory of this coal seam mode is applied to recent MF data for a number of mines in order to classify the propagation characteristic of the mines in a simple way. When conductors such as rails, trolleylines, or power cables are present in the vicinity of the measurement path, it is found that the magnetic field versus range plots have two distinct regions with very different slopes. This effect is attributed to coupling of the cylindrically spreading coal seam mode to a low-attenuation conductor guided mode. As a result, voice communications range between mobile transmitters can extend several thousand meters. The use of MF for mine communications is discussed.

By Charles L. Kimbell

This study is intended to serve three roles. First, it is an extension of the previous works under the same title that have been the overview and summary chapter of the international volume of Minerals Yearbook since the inception of that volume. Following the traditional format of past chapters, the basic statistical presentations herein deal chiefly with 1989, and in some instances with 1988, the latter only because more recent, comprehensive global statistics for 1989 are simply not yet available owing to delayed data collection and processing in some countries and continued governmental suppression of data in others. The second role of this study is to provide an update to the coverage of events impacting on the world's mineral industry that have occurred between the end of 1989 and the preparation of this study. Inclusion of this update is almost essential because of the potential effect of some of these events on global mineral industry activities.

Jan 1, 1992

By David L. Bickel

The following instructions and descriptions are presented in two parts to assist an individual to make the borehole deformation gage transducer, and to assemble and test the three-component borehole deformation gage. This Bureau 8 of Mines three-component borehole deformation gage (4, 8, 11)2 fits in a 1-1/2-in-diameter borehole that is drilled in rock and then overcored to determine rock stress.

Jan 1, 1978

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 George J. Conroy

Techniques for locating trailing-cable faults are discussed, particularly those techniques suitable for use in underground coal mines, which have been the subjects of Bureau of Mines research. The discussion concerns precautions and suggestions for locating faults, rather than detailed descriptions of apparatus.

Jan 1, 1979

Case 1: A driller raised a drill rig mast into a 7200-volt overhead power line. Both he and his helper were killed. Case 2: A driller-helper was pulling a winch cable toward a stack of drill steel when the cable contacted a 12,000-volt power line. The helper was killed, and the driller at the rig controls was severely injured. [ ]

Jan 1, 2006

By Kray Luxbacher, Mario Karfakis, Erik Westman, Peter Swanson

Three-dimensional velocity tomograms were generated to image the stress redistribution around an underground coal longwall panel to produce a better understanding of the mechanisms that lead to ground failure, especially rockbursts. Mining-induced microseismic events provided passive sources for the three-dimensional velocity tomography. Surface-mounted geophones monitored microseismic activity for 18 days. Eighteen tomograms were generated and high-velocity regions correlated with high abutment stresses predicted by numerical modeling. Additionally, the high-velocity regions were observed to redistribute as the longwall face retreated, indicating that velocity tomography may be an appropriate technology for monitoring stress redistribution in underground mines.

By Larry A. Haas

The U.S. Bureau of Mines investigated the use of organic binders as substitutes for bentonite in agglomerating iron ore concentrate. Over 30 organic binders were evaluated at several dosage levels in laboratory tests. The binder groups producing the greatest green pellet strengths were natural gums (guars carboxyl methyl celluloses) and gelled starches. The nongelled and alkalized starches, starch acrylic copolymers) wood-related products, and dairy products were less effective but better than bentonite. The highest wet pellet drop numbers were obtained with binders that had a medium plate water absorption value (>500 and <10)000) in distilled water and a high slurry viscosity (>75 cP) at 6 pet solids. The highest dry compressive strengths were obtained with binders that gave the highest adhesive tensile strength (>4 kg/ cm2) on iron oxide lap-joint substrates. Pellets with 0.1 pct organic binder had lower compressive strengths and reduction disintegration indices than those with 1 pct bentonite, but higher reduction rates. Pellets with carboxyl methyl cellulose and gelled starch had higher softening temperatures than those with bentonite. Overall, the most promising binder is gelled starch. Its price makes it more cost effective than carboxyl methyl cellulose, and its pellets have metallurgical properties superior to those of bentonite pellets.

Jan 1, 1989

By J. P. Powell

Systematic waterflooding was first tried in Washington County, Okla., in 1937, when a 40-acre project was begun in secs. 24, 29, 32, and 33, T. 27 N., R. 13 E., jointly by the Keener Oil Co. and the Phillips Petroleum Co. The property later was sold to Lee Morrison. A second project was begun in 1941 in sec. 14, T. 6 N., R. 12 E., by the Oklahoma Oil Corp. Both projects were abandoned by the end of 1942. A third project was begun in 1945 and the fourth in 1948, but 1949 actually was the beginning of intensive waterflooding development in Washington County. The results of previous waterflooding projects are described in Bureau of Mines Reports of Investigations.2 3 4/ Oil production in the county followed a similar trend, dropping to a low of 990,000 barrels in 1945, then steadily increasing until 1956, when more than 4 mil-lion barrels of oil was produced. Most of the increase in oil production is directly attributable to water injection.

Jan 1, 1957

By Byron O. Pickard

With table of bibliography

Sep 1, 1922

By T. M. Barczak, S. C. Tadolini

Reduction in the recovery time required and improvements in safety during a longwall face move have compelled coal mine operators to examine and use pre-driven longwall recovery rooms. The recovery entry is developed at the longwall stop position and supported ahead of time so that the required combinations of standing and internal supports can be installed before the longwall face approaches. A calibrated three-dimensional finite element model, developed in conjunction with an underground test area, provided the critical components and design principals for a comprehensive parametric study. The study indicates that vertical, horizontal, and shear stresses concentrated on the outby abutment pillar corner of the recovery room resulting in deformations in the immediate roof above the primary roof support anchorage level. The results of the numerical model and field site observations indicated that the combination of the internal bolting system and the standing concrete supports are critical for the successful and safe extraction of the longwall equipment. Cable supports installed at and angle over the pillars can help stabilize the disturbed zone above the adjacent fender and outby pillars, however; standing supports are required in most sedimentary roof conditions to increase stability and assure a safe longwall extraction.

By Maria I. De Rosa, Charles D. Litton

The U.S. Bureau of Mines conducted experiments for predicting materials&apos; ease of combustion (smoldering onset, smoldering, flaming, and decomposition rates) by means of submicrometer smoke particle characteristics for the development of a simple test method. The experiments were carried out in an approximately 20-L furnace, with a 10-L/min airflow through the furnace for a 14-min duration, at set furnace temperatures of 150°, 250°, and 1,000°C. The variables studied as a function of time were the onset time of smoke particles, time and duration of maximum smoke particle generation, average concentration of smoke particles, and particles&apos; average diameter, mass weight loss, and furnace temperatures. Results show that the onset time of smoke particles is predictive of materials&apos; ease of smoldering, and the time of maximum smoke particle generation and its duration, coupled with mass weight loss, are predictive of materials&apos; ease of smoldering and flaming (depending on the experimental temperatures), and decomposition rates.

Jan 1, 1992

By Charles E. Munroe

On March 14, 1921, an explosion occurred at about 6:15 A.~. on the premises of an iron-mining concern throug:1 which two magazines, one containing upwards of 9,000 pounds ot a high explosive of the dynamite class, and a second, 60 feet distant, containing upwards of 10,000 No. 6 detonators, were completely destroyed, and a ncratertt,? f3et deep by 30 feet in diameter, was excavated in the gro~ at ~he place whare the mag~iine containing the high explosive had been lo~ated. As a rule any eye wit~esses to the circumstances im.~ediataly preceding and d(irectly concurrent with a.c.ci.:lental ex;losions ar.e victims of s11ch explosions, and, therefore, the conclusions reached as to the cauoa. of such explosions must, perf'orce, be based aln:ost completely on circumstantial evidetJ.ce. In this iii.stance, b:ecause both the explosive and detonators were of -orov{:;d: character; because of the time of the day and the state of operations iit the·· time of the e:.q,losion; because the rerroteness of the location of the n:-1agazi::1es 1 0::1 the side of a ravine, easily admittfi of unobserved approach; beca:iise differencas existed, and because no obvious cause was at once apparent, there arose suspicfon that the explosion was not accidental.

Sep 1, 1921

By Clayton M. Rumsey

The U.S. Bureau of Mines investigated prospects and mineralized areas in and adjacent to the Indian Pass and Picacho Peak study areas in 1983 and 1984. The Indian Pass study area contains 33,640 acres and the Picacho Peak study area contains 5,450 acres. The study areas are located in the southeast corner of California and are underlain by Precambrian gneiss, Pre-Tertiary metavolcanic and metasedimentary rocks, and Tertiary volcanic and non-marine clastic rocks. Low-grade gold-silver resources may be present in hydrothermally altered gneiss in the upper plate and altered schist in the lower plate of the Chocolate Mountain thrust fault. The thrust fault is exposed in the study areas for about 3.5 miles west and 5 miles east of Indian Pass. Mineralized zones in the thrust plates were not discovered until 1983. Earlier prospecting explored areas containing minor copper carbonate occurrences in schist and sedimentary and volcanic rocks that are younger than the thrust. Twenty-three mines, prospects, and mineral occurrences inside the study areas and fourteen outs; de were examined for this study. These surficial copper occurrences have been prospected extensively in the study areas; large areas have been scraped, pitted, and trenched by bulldozers. However, they appear to be of limited economic significance. Slightly mineralized zones are in the northwest part of the Indian Pass study area where granite contacts sedimentary and volcanic rocks.

Jan 1, 1986

By David F. Gearhart, Thomas M. Barczak

This U.S. Bureau of Mines report examines the roof and floor contact pressure provided by the interaction of a shield with the surrounding strata. Controlled forces were applied to an 800-ton two-leg shield in the Bureau&apos;s mine roof simulator; the distribution of forces acting on the canopy and base of the shield were measured with 24 hydraulic pressure cells. Several influential factors that affect the load distribution were investigated: (1) the magnitude of loading (leg pressure); (2) the profile of the canopy, principally the upward-sloping tip; (3) the base-lifting device; (4) horizontal load acting on the shield; and (9 compliancy of the immediate roof and floor. It was concluded that the shield does not develop full canopy or base contact without deformation of the strata. Maximum contact pressures are developed at the rear of the canopy and on the toes of the base. Less than 10 pct of the available shield capacity is developed at the canopy tip despite the design intention to ensure tip contact. Horizontal loading reduced the toe pressure acting on the base by as much as 75 pct. The base-lifting device exaggerated the inherently high toe loading, increasing the contact pressure by more than 200 pct.

Jan 1, 1992