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Aid mine workers in detecting hazardous roof conditions in underground mines by developing a method of roof sounding which supplements or replaces the traditional roof sounding technique where the miner relies on experience to determine whether or not the rock is sound. Approach The Bureau of Mines developed an electronic roof sounding de-vice that acoustically determines the integrity of mine roof rock by "listening" to the variation in frequency vibrations within the rock. How It Works n previous research, the Bureau of Mines found that loose rock in a mine, when impacted, vibrates at a much lower frequency and for a lower time period than does a solid slab. By quantifying the enhancement of low frequency vibrations in loose rock over solid rock, a repeatable, objective measure of the rock's soundness can be obtained. This approach was used in developing the rock stability tester.

Jan 1, 1986

By Rex D. Thomas

Concentration of the kerogen (organic material) in oil shale was accomplished by centrifuging after pretreating the oil shale with carbonic acid to remove the carbonates and pretreatment with sodium hydroxide (pH 11.5) to remove the claylike minerals. Analysis of the materials obtained showed that the concentrations of organic sulfur and organic nitrogen compounds were not affected by centrifuging. These compounds are evenly distributed in the kerogen and are not strongly bound to the mineral constituents. Organic oxygen compounds, however, were concentrated in the light fraction. These compounds are more closely associated with the kerogen and are not bound to the mineral constituents. Iron compounds other than pyrite apparently are closely associated with the organic material.

Jan 1, 1970

Provide reasonably priced, reliable fire protection for loading shovels. Approach An automatic fire, sensing and suppression system using both dry chemical and Halon 1301 was developed. It is more rugged than similar industrial-type fire protection systems. How It Works Temperature sensors detect heat from a fire, and trigger the system. These sensors are located inside the machinery house and under the house and shovel frame where it rotates around the crawler chassis ring gear. An alarm is sounded, and extinguishing agents are released either in the machinery house or in the ring gear area. The system can also be triggered by a manual control. If the fire Is detected in the machinery house, all power is shut down to the motor-generator sets, ventilation fan, and all electrical controls. Doors are automatically closed. After a delay to allow time for the ventilation fan to stop, Halon 1301, a gaseous fire extinguishing agent, is released inside the machinery house until it reaches a concentration of about 7 percent. This concentration is sufficient to extinguish a fire, but isn't toxic to personnel

Jan 1, 1980

By Wesley A. Grosh

The Sutherland copper prospect is situated in Floyd County, Va. The immediate area was prospected around 1850, and one of the adits possibly dates from that time. Little or no ore has been mined from the deposit. The deposit is a mineralized sulfide zone occurring in mica schist and consisting mostly of pyrrhotite with minor amount of copper. A magnetometer survey of the deposit by the American Metal Co. in 1939 showed an anomaly that was thought to indicate a zone: of secondary enrichment. The Bureau of Mines diamond-drilled 14 holes, totaling 913 feet, and opened an adit during February and March 1943. No appreciable copper values or indications of secondary enrichment were found.

Jan 1, 1948

By H. H. Dewing

The Bureau of Mines conducted a laboratory-scale investigation of a technique that produces zinc sulfate and elemental sulfur from sphalerite concentrates by reaction with sulfuric acid at 175° to 200° C and ambient pressure. The objective of the investigation was to develop a hydrometallurgical method of producing zinc from sulfide concentrates that does not generate sulfur dioxide pollutants. Reaction with 80-to 85-pct sulfuric acid produced 4 moles of sulfur for every 3 moles of sphalerite reacted, with minimal production of sulfur gases under optimum conditions. More than 98 pct of the zinc was recovered as zinc sulfate after 3 hours at 175° C. The reaction mixture was leached with simulated spent zinc electrolyte containing 13-pct sulfuric acid to recover zinc sulfate from the insoluble, high-sulfur residue. Neutral zinc sulfate, which is required for electrolysis, was separated from the sulfuric acid solution by crystallization as ZnS04?7H20 at -10° C. Up to 80 pct of the water in the recycled electrolysis solution was removed by the crystallization process; evaporation was used to further concentrate the sulfuric acid for reuse in leaching sphalerite. Advantages of the proposed method over conven-tional roasting and leaching include virtual elimination of sulfur dioxide, production of a solid sulfur byproduct, and higher zinc recoveries due to elimination of zinc ferrite losses.

Jan 1, 1978

A construction material based on plasticized sulfur and mineral aggregate, that is superior in corrosion resistance and strength to portland cement concrete. The material can be used in the chemical, metallurgical, and fertilizer industries, and will also provide an attractive market for by-product sulfur resulting from compliance with pollution regulations. How It Is Made Sulfur concrete is thermoplastic material. Plasticized sulfur is mixed with sand and gravel aggregate heated to 375-400° F. The sulfur melts and acts as the binder or cement. The sulfur concrete is poured hot and sets at a temperature of 200° F. Full strength is attained in a few hours, compared to several days for portland cement concretes. Sulfur concrete even pours and sets in freezing weather. Although unmodified sulfur with aggregate will produce a sulfur concrete with good initial properties, it undergoes crystallographic modifications, and deteriorates with time, particularly when exposed to moisture or freeze-thaw conditions. The Bureau of Mines has developed plasticizers which, when reacted with the sulfur, give sulfur concretes with excellent moisture and freeze-thaw resistance. The plasticizers are based on mixtures of dicyclopentadlene (DCPD) and ollgomers of cyclopentadiene. About 5 percent by weight of the plasticizers is reacted with molten sui fur for several hours. The sulfur cement can be used directly or allowed to solidify for easier handling and storage.

Jan 1, 1981

By Leon E. Esparza

The Bureau of Mines studied 780 acres of the 24,130-acre Sheldon Contiguous Wilderness Study Area (CA-020-1012) in 1985. The study was done at the request of the Bureau of Land Management and authorized under the Federal Land Policy and Management Act (Public Law 94-579, October 21, 1 976) in order to evaluate the mineral resources. The study area is located in Washoe County, NV, about 35 miles northeast of Cedarville, CA. A search of county courthouse records and an examination by foot traverses through and adjacent to the study area did not reveal evidence of any mining or mining exploration activity past or present. In addition, evidence of any form of rock alteration was not observed. Evidence of mineral resources is not apparent. Although basalt, the only rock-type present in the study area, can have some limited industrial applications, sources closer to potential markets probably would preclude rock from this area being economically competitive. INTRODUCTION This report describes the USBM (U.S. Bureau of Mines) portion of a cooperative study with the USGS (U.S. Geological Survey) to evaluate mineral resources and potential of the Sheldon Contiguous study area at the request of the BLM (U.S. Bureau of Land Management). The USBM examines individual mines, prospects, claims, and mineralized zones, and evaluates identified mineral and energy resources. The USGS evaluates potential for undiscovered resources based on areal geological, geochemical, and geophysical surveys. Results of the investigations will be used to help determine the suitability of the study area for inclusion into the National Wilderness Preservation System. Although the immediate goal of this and other USBM mineral surveys ;s to provide data for President, Congress, government agencies, and the public for land-use decisions, the long-term objective is to ensure the Nation has an adequate and dependable supply of minerals at a reasonable cost.

Jan 1, 1986

By M. L. Fenger, S. F. Mauser

This 1s a report on an Investigation performed during Contract No. H0166069 "High and Medium Voltage Trailing Cable Splices and Connections," which presents a summary of the requirements formulated. The requirements are presented in the form of considerations for medium-voltage splices, and medium- and high-voltage couplers used in underground coal mines.

Jan 1, 1979

By J. Litsenberger, T. E. Marshall, P. R. Coyle, L. J. Prosser, A. T. Iannacchione

For the first time in an underground stone mine, the relationship between roof movement and microseismic emissions was examined in conjunction with two distinct roof fall areas. As roof monitoring increases in acceptance and monitoring technology advances, the goal of providing reliable roof fall detection systems to enhance the safety of underground mine workers moves closer to reality. Instrumental to reaching that goal is the ability to interpret accurately and completely roof movement and microseismic emissions, which can serve as precursors to roof falls. This paper examines the capabilities of convergence and microseismic monitoring systems to better understand roof rock failure mechanics and to anticipate roof falls. An understanding of how these techniques are used and how they interact with each other is critical in developing the most effective ground control strategy for our nation’s mines.

By Jon C. Volkwein

The industrial sand industry has been exploring new techniques to reduce dust. One company was experimenting with adding water during bagging operations to the surface of the hag, and into the product as it flowed into the bag. The Bureau of Mines, using instantaneous dust sampling instruments, measured the effectiveness of three methods of adding water. Results indicated that various types of water sprays applied in carefully controlled amounts could reduce dust up to 50% at worker locations at the bagging machine and inside a railroad boxcar. This report also discusses constraints such as product handling, customer acceptance, cold weather problems, dust collector performance, and other areas.

Jan 1, 1981

By Lloyd A. Morley, Alan M. Christman

General A review of the literature has revealed important areas which should be investigated during the field work. Of the utmost importance is the safety of mine personnel. Should a phase-to-ground fault occur on a shovel or other piece of equipment, current may return to the substation through the machine's contact surface with the mine floor, thereby raising the frame above ground potential and posing a shock hazard to anyone who touches the equipment. If the frame-to-earth resistance is very low, then no dangerous potentials will be developed, and a basis for elimination of the ground conductors from trailing cables could be postulated. However, should the contact resistance be high, then lethal voltages could be present on the machine frame. In this instance, low-resistance ground conductors in the trailing cable would be a necessity. Therefore, field tests should include measurements of the earth resistance of electrically operated portable or mobile mining equipment such as shovels, draglines, and drills. When the electrical distribution system is subject to lightning discharges, the grounding grid must safely carry to earth and dissipate enormous current surges. It is essential that the grounding grid have a low value of earth resistance, because any potential developed across the grounding grid as a result of current flow will appear on the frames of all machinery connected to the grid. Thus, an earth resistance

Jan 1, 1976

By E. Morrice

The effect of the temperature of SmF3-LiF electrolyte on the electrolytic preparation of samarium-cobalt alloy by the consumable cathode technique was investigated. The temperatures of the cathode zone, alloy collection zone, and samarium oxide (Sm203) feed zone had to be controlled carefully to obtain a satisfactory samarium-cobalt alloy product. Any appreciable deviation from certain temperature values adversely affected yield and product quality.

Jan 1, 1971

By R. J. Matetic, D. Elsworth

The objective of this U.S. Bureau of Mines hydrologic-subsidence investigation was to evaluate the effects of longwall mining on the local ground water regime through field monitoring and numerical modeling. Field data were obtained from multiple-position borehole extensometers (MPBX's) that were used to measure subsurface displacements. Survey monuments were installed to measure mining-induced surface deformations. Numerous drawdown and recovery tests were performed to characterize hydrologic properties of the overburden strata. Coreholes were drilled above the study area to determine lithologic and strength characteristics of the overburden strata using the rock samples collected. Electronic recorders were installed on all monitoring wells to continuously monitor ground water levels in coordination with mining of the longwall panels. A combined finite element model of the deformation of overlying strata, and it's influence on ground water flow was used to define the change in local and regional water budgets. The predicted effects of the postmining ground water system determined by the model correlated well with field data collected from the field site. Without an infiltration rate added to the model, a static decrease of 3.0 m (10 ft) in water level would occur due to mining of both longwall panels and if an infiltration rate was inputted in the model, no predicted long-term effects would occur to the ground water system.

Jan 1, 1995

By Vladimir Adamek

This paper describes the Bureau of Mines development of a novel subsidence prediction methodology suitable to the mining and geologic conditions in the Northern Appalachian Coal Region. It describes the computation of vertical and horizontal movements, inclination, curvature, and horizontal strains. The substance of this method is the separation of the effects of lithology by introducing a correlation between hypothetically homogeneous overburden and existing lithologic conditions, while providing for different mining conditions, i.e., underground geometry and overburden thickness. The effects of lithology have been expressed in the form of a variable subsidence coefficient within the subsidence trough. The subsidence coefficient is considered a constant for other predictive methods. Field data from 16 test sites at 11 Bureau longwall panel studies were used in the analysis. For each panel, the characteristics of the variability of the subsidence coefficient were defined. Regression analysis of the subsidence coefficients from all test sites on their locations relative to the edges of their respective panels yielded a third-degree polynomial equation. The results from additional longwall panel studies, not included in the regression analysis, were used to prove the validity of this method. To facilitate the use of this precalculation methodology, a computer program was written in BASIC for use on a personal computer.

Jan 1, 1987

Reduce the time, complexity and expense of dissolving metal and mineral samples in solution in preparation for chemical analysis. Approach In earlier research, the Bureau of Mines developed a rapid and inexpensive method for the dissolution of mineral and metal samples in plastic pressure bottles heated in a boiling water bath. Using this technique, samples could be prepared for chemical analysis in less than one hour compared with several hours by traditional dissolution methods (see Technology News No. 85, December 1980 for further details). By heating in a microwave oven, sample dissolution time can be reduced to approximately 5 minutes.

Jan 1, 1983

By A. Mayton, A. Brien, W. Porter, O&apos

In 2004, management at Unimin's Gleason, TN operation began implementing ergonomic interventions specifically targeted to reduce risk of musculoskeletal injuries (MSIs). Together with corporate and site management, Unimin identified work site hazards and began to modify work practices/equipment. Some interventions were relatively simple and were implemented immediately. Others, like improvements to a mobile shredder, were more complex but were eventually resolved through a participatory approach with employees, management, manufacturers and NIOSH. This paper discusses ergonomic interventions that were successfully implemented using a bottom-up approach to reducing the risk of injury.

By Anthony Iannacchione

One of the more pressing engineering problems for deep longwall mines in the Southern Appalachian Basin is to design longwall systems that will eliminate catastrophic coal pillar failure from the working environment. The purpose of this study is to quantify the behavior of a particular size abutment pillar prone to burst or bump. Because the 24.4-111 (80-ft) square abutment study pillar is within the pillar size commonly used in this region, understanding the behavior of this pillar should aid in future efforts to design optimum mining strategies. This research has attempted to construct the pillar stress and roof-to-floor convergence profiles in order to evaluate the ultimate strength, deformation modulus, visco-elastic deformation, and violent failure characteristics of the pillar during longwall mining. This information reflects the overriding influence of the local geologic characteristics on bursts, provides the field measurements needed to verify concurrent modeling studies, and suggest some basic mechanisms associated with the coal pillar bursts discussed in this paper.

By Howard E. Parkinson

An environment monitoring and communication system has been installed in the Bruceton Mine, and research is under way to improve mine safety. Standard day-to-day mine communications are available, along with additional systems installed to permit experimentation with wireless radio, through-the-earth phones, along-the-roof paging, and mine face machinery communications. Research is continuing and the essential concepts for a dependable whole mine communication system, providing simple environment monitoring, improved day-to-day communications and post-disaster communications, will be demonstrated in a larger mine with about 900 feet of overburden.

By Wilbur I. Duvall

The borehole deformation gage and overcoring techniques developed by the Bureau of Mines form one of the primary methods of determining in situ rock stress. This report describes a least squares method of calculating the average rock stress components in the horizontal plane from more than three diametral deformation measurements in a vertical borehole. This least squares analysis provides a means of determining the multiple correlation coefficient, the variance, and the scatter for a set of deformation measurements. From this information, confidence limits can be calculated for the secondary horizontal principal stresses and their directions. The material presented in this report can be used as a guide to the development of least squares solutions for stress measurement techniques other than the borehole deformation method. Since the statistical information that results from the least squares method is extremely useful in the interpretation of results, it is recommended that a least squares analysis be used on stress measurement data whenever possible.

Jan 1, 1979

By M. K. Larson, J. K. Whyatt, R. B. Langston, J. C. Johnson, H. Kirsten, T. M. Brady

An experiment is described in which hollow inclusion cells (HICells) were used to measure stress in a jointed rock mass during drift development at the Stillwater Mine, Nye, MT, USA. Two HICells were installed in the footwall approximately two drift widths ahead of the face. One HICell was over cored and then immediately tested in a biaxial chamber. The other HICell was left in place and monitored as the drift was excavated in three advances, each one-half the width of the drift. Strains were recorded hourly by a datalogger. Results show that there was little stress change during the first and second drift advances, but that a large stress change occurred after the third advance. The measurements also showed that the in situ principal stress directions lined up with regional geologic structures. Stress changes during face advance were likely caused by deformation along localized joint sets and inelastic deformation near the face.