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By W. H. Eddy

The Bureau of Mines conducted laboratory batch and continuous flotation processing tests on waste granite fines from South Carolina to determine the possibility of recovering high-quality feldspar and glass sand. Three flotation systems were used for removal of the iron-bearing biotite: Two employed an alkaline anionic-cationic circuit and the third employed an acid cationic circuit. Commercial-grade products were obtained when the remaining biotite was magnetically removed from the feldspar and quartz concentrates. Continuous flotation processing yielded a feldspar concentrate containing, in percent, 3.60 Na20, 5.60 K20, and 2.25 Ca0, with recoveries of 75.3, 66.6, and 72.6 percent, respectively. The feldspar tailing was high quality glass sand containing 98.0 percent Si02 and 0.025 percent Fe203; about 60 percent of the quartz was recovered.

Jan 1, 1972

By Stephen C. Tadolini, Thomas M. Barczak

Roof support systems, longwall shields in particular, have persistently grown in size and capacity for the past 25 years. Why is this? Is it a good thing or is it unnecessary? What are the consequences of this “bigger-the-better” design philosophy? Rarely do we see a “one size fits all” approach to roof support except when it comes to longwall shields, where the historical trend for new procurements is to simply purchase the highest capacity support you can buy. Does high capacity ensure failures will not occur? The answer is no! The highest capacity tailgate supports are typically the ones that fail the most often. What does this tell us? It tells us that there are fundamental aspects of support design and ground control that we still do not understand or recognize when designing a support system. This paper provides an interesting evaluation of these issues and proposes a different approach to support design that attempts to match the support performance characteristics to the ground behavior. Along the way, some of the old premises of support design will be discarded, and new “controversial” ideas developed. Thinking outside the box never hurt any industry. Mining has made it a common practice.

By Thys B. Johnson

A three-dimensional dynamic programing method is presented for determining the optimal ultimate open pit limit. The method given is based on the block concept and is an extention of the two-dimensional Lerchs-Grossmann approach. The three-dimensional technique presented herein is fast and simple and may be used for an initial open pit evaluation when only limited data are available or as a more refined model when the entire deposit is well delineated. The method is illustrated by simple numerical examples and is also presented in algorithmic form. A computer program was written in Fortran IV which implements the three-dimensional algorithm and some computational aspects are discussed.

Jan 1, 1971

By Stephen W. Lambert, Michael A. Trevits

The Bureau of Mines examined the wellbore of a vertical gas drainage well in the Mary Lee coalbed to determine the results of specific completion procedures in coal. A jet-slotting tool was used to cut four vertical slots through the casing about 1 ft below the coalbed. Even though stimulation treatment pressure was excessive, hydraulically induced channels were contained entirely within the target coal zone. Sand-filled, induced channels were horizontal, inclined, and vertical, and were propagated in directions similar to bedding planes, rock joint, and coal cleat directions measured in the mine. Variable gas flow rates, recorded during the productive life of the well, were attributed to chronic downhole pump malfunction and the slotted casing below the production zone.

Jan 1, 1978

"Correlatina Lung Crackle Usina Holographic lnterf erometryAli Afshari, MS, West Virginia University, 1989The Effect or Surfactants on Suppression of Non-Wettable ParticlesAli Alaboyun, MS, Mineral Engineering, The Pennsylvania State University, 1989Geochemical Characterization of Kerogem, ShaJes, and Coal .Refme ~ted with Allegheny Fonnationof Cases of Northern West VirginiaDick Andre, MS, West Virginia University, 1987Particle Concentrations in a Hazelton Inhalation ChamberShahram Bavani, MS, West Virginia University, 1985Use and Potential of Luer Holographic Interferometry and Subsidence Model Study of an Underground.Room and Pillar MineRichard Begley, MS, West Virginia University, 1984Development of a Mechanistic Model for Prediction of Subsidence in a Longwall MineRichard Begley, PhD, West Virginia University, 1990.Redesign of Micro-Orifice Unifonn Deposit ImpactorSteve Behm, MS, University of Minnesota, 1991A Fracture Mechanics Study of Crack Propagation Mechanism in Coal: The Mechanics of Fine FragmentFonnationZ. T. Bieniawski and R. Karl Zipf, Jr., Mining Engineering Department, The Pennsylvania State University,University Park, PA. Final Report, October 1, 1988A Mathematical Model for the Prediction of Ambient Dust Concentrations in Mine AtmospheresR. Bhaskar, MS, Mining Engineering and Operations Research, The Pennsylvania State University, 1984Spatial and Temporal Behavior of Dust in Mines-Theoretical and Experimental StudiesR. Bhaskar, PhD, Mining Engineering, The Pennsylvania State University, 1987Experimental Studies of Dispersion and Deposition of Fane Particles in a Wind Tunnel and Mine AirwayKlaus Bode, MS, Mining Engineering, The Pennsylvania State University, 1991Perf'onnance of the High Yield Technology PM - 100 - Particle 11ux MonitorRobert Caldow, MS, University of Minnesota, 1987Development of Improved Methods for Monitoring and Control of Diesel Particulate in an Underground CoalMineD. H. Carlson, B. C. Cornilsen, P. L. Loyselk, X. Shan and J. H. Johnson, Michigan Technological University,Houghton, Ml. Final Report, June 15, 1991"

Mar 1, 1992

By BUREAU OF MINES

The Bureau of Mines in its investigations of respiratory apparatus for use in mines and allied industries, tests equipment that is voluntarily submitted by manufacturers in accordance with published schedules of tests. These tests are designed to insure that the equipment has the minimum require- ments for safety in use. Approval certificates are issued for apparatus that meets the bureau's specifications, and the memfacturer is permitted to mark his equipment with a seal showing that it has been approved as "Permissible." A complete list of permissible self-contained oxygen breathing apparatus, gas masks, and hose masks tested before July 1, 1930, was published in Bureau of Mines Information Circular 6362.1 The present list includes all equipment tested and approved up to and including April 1, 1931.

Sep 1, 1931

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 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

Pillars with width-to-height ratios of less than 1.0 are frequently created in underground hard rock mines. The strength of slender pillars can be estimated using empirically developed equations. However, the equations can provide variable results when the width-to-height ratios approach 0.5. This paper investigates some of the issues affecting pillar strength at low width-to-height ratios in hard brittle rock. The investigation includes an evaluation of empirical pillar strength data presented in the literature and observations of pillar performance in underground limestone mines in the eastern United States, supplemented by numerical modeling in which failure processes and sensitivity of slender pillars to variations in rock mass properties are evaluated. The results showed that the strength of slender pillars is more variable than that of wider pillars. The numerical model results demonstrated the increasing role of brittle rock failure in slender pillar strength. The absence of confinement in slender pillars can result in a fully brittle failure process, while wider pillars, fail in a combined brittle and shearing mode. The onset of spalling in slender pillars occurs at or near the ultimate strength, while this is not the case for wider pillars. Slender pillars are shown to be more sensitive to the presence of discontinuities than wider pillars, which can partly explain the increased variability of slender pillar strength. Two examples are presented that illustrate failure initiation by brittle spalling and the sensitivity of slender pillars to the presence of discontinuities.

By Charlie Wyche

Principal mineral products in the Dominion of Fiji were gold, silver, pit and quarry construction materials, and cement. In 1981, the combined value of these commodities accounted for about $11.6 million,2 over 85% of the total value of mineral output. Production of cement, sand and gravel, and quarry products increased substantially above the 1980 level. Mining bated on gold production was decreasing, and employment in the industry was declining. The better grade deposits in the one active mine were worked out, and only another 10 years' production at current rates was estimated to remain. While the high world gold price of 1979-80 led to intensive exploration, there has been little sum.

Jan 1, 1983

Provide an effective method for "soft" soldering aluminum and aluminum alloys using conventional tin-lead solder alloys and flukes. The Problem In the past, it was virtually impossible to solder aluminum and aluminum alloys using standard tin-lead soldering systems (solder and flux) due to the presence of an aluminum oxide surface film which forms instantly on aluminum and aluminum alloys when these are exposed to air. The tenacious and stable oxide film enables aluminum-base materials to maintain their bright luster. But the film also prevents the required wetting and spreading of solder on the substrate, causing the loss of adhesion between the solder and the substrate. In addition, the heat produced during soldering increases

Jan 1, 1983

Use water-jet-assisted cut-ting technology to reduce the exposure of mi ne workers' to respirable dust. Approach Install water-jet-assist on mining machines and evaluate its impact on respirable dust. How It Works Water-jet-assisted cutting involves a mechanical cutting bit working in combination with a moderate pressure (generally up to 10,000 psi) water jet directed just in front of, or through, the bit tip. One of its advantages is reduced dust generation because the jet wets the face of the material being cut more efficiently than a conventional low-pressure water spray, thus capturing much of the dust before it ever becomes airborne. It also removes loose cuttings ahead of the bit before they are pulverized by the bit into respirable dust. Total water consumption is about the same as for conventional low pressure dust control water spray systems. However, there is some increase in power consumption because of the energy needed to provide the high pressure water.

Jan 1, 1987

Reduce spillage hazards and contamination when adding hydraulic nil to mining machine reservoirs. Approach An easily transported module, that delivers hydraulic oil directly into mining machines, was built and tested. How It Works The Hydraulic Oil Delivery Module is carried, from the oil storage area to the equipment needing oil, in the bucket of a scoop or other utility vehicle. Oil is pumped into the module reservoir from storage, or out of the module reservoir into the machine being serviced, through a long hydraulic hose. During long-term testing, the 115 foot long delivery hose made it possible to replenish the hydraulic oil in mining machines at the face with only limited interruption to the mining operation. (Figure 1 shows one! version of the module.) The compact Hydraulic, Oil Delivery Module consists of: an oil reservoir: a pump driven by a hydraulic motor; two high pressure, low volume oil lines, filters; and a low pressure, larger capacity delivery hose equipped with quick-connect-couplers. The high pressure oil lines are connected to the scoop's hydraulic power takeoff, which supplies the power to pump oil in or out of the module reservoir.

Jan 1, 1977

By Noel N. Moebs

The Bureau of Mines measured surface subsidence above four small coal mine room-and-pillar sections in southwestern Pennsylvania, to obtain preliminary information on the magnitude and character of selected parameters, such as angle of draw and maximum subsidence, which are essential to the development of subsidence prediction methods. Data varied widely at the four sites; this is attributed to local geologic and mining conditions. Surface deformation at each site was of a magnitude normally associated with severe structural damage.

Jan 1, 1982

Provide an accurate, simple, alternative means of evaluating the safety of mine electrical ground systems which has little or no negative impact on mine productivity. The Traditional Evaluation Method The Code of Federal Regulations requires all mines to safely ground their power systems to earth. Effective earth grounding reduces shock hazards to mine workers operating electrical equipment, protects equipment from damage by voltage transients, and provides a means of detecting and locating ground faults. Once an earth ground bed has been constructed, its level of resistance has traditionally been used to gauge the safety of the entire grounding system. Bed resistance measurements are normally performed using a ?fall of potential? technique with a current return electrode placed at a remote location, If the resistance measured is acceptably low, then the bed is assumed safe.

Jan 1, 1985

The REL of 1 mg/m3 for respirable coal mine dust does not assure a zero risk for the development of occupational respiratory diseases among all miners exposed during a full working lifetime. Consequently, a medical screening and surveillance program that includes initial and periodic chest X-rays and spirometric examinations is important for the early detection of disease and the prevention of "material impairment of health or functional capacity" [30 USC 8 11(a)(6)(A)]. The medical screening and surveillance program is also useful for disease surveillance, which includes the tracking trends, the setting of prevention and intervention priorities, and the assessment of prevention and intervention efforts. NIOSH encourages both underground and surface coal miners to participate in the medical screening and surveillance program.

Jan 1, 1997

Provide an economic alternative to drill-blast excavation with the same ability to excavate openings of varied orientation, shape, and size. Approach Develop an efficient, adaptable, mechanical excavation machine that produces unconfined tensile failure in rock. How It Works A drill-split fragmentation machine that combines a drill and a unique splitter has been developed. The drill and splitter are mounted on a carriage that positions the splitter in a hole immediately after it is made by the drill. The splitter creates force loads that cause the rock to fragment, and the process is repeated for excavation. The unique splitter applies both radial and axial loads to the rock mass, which produces an excavation action comparable to pulling a plug. This excavation action distinguishes the radial-axial splitter from typical demolition splitters, which require a free surface parallel to the axis of the splitter toward which to break rock.

Jan 1, 1989

Provide a coalbed methane data source for industry use in mine planning. Approach Coalbed methane data have keen collected and formatted into a computer implemented data base with software developed for storage, retrieval, and generating files of selected data in response to information requests and for statistical analysis of relationships among various coal parameters. How It Works Coalbed methane data is obtained by the Bureau's direct method test on exploration coal cores. The test involves sealing fresh coal cores in desorption canisters and periodically bleeding the gas into a water-filled, graduated cylinder to measure the volume of gas released. Coalbed methane data collected over the past 9 years have been entered into a computer-implemented data base for efficient retrieval and statistical analysis. Data base processing is accomplished with a commercially available storage, sorting, retrieval, and report writing software package (Datatrieve 11). Information requests from the coal industry are processed with the system, and the data in the desired output format am printed and forwarded to the requestor. Information such as coalbed name, location (state and county), depth of sample, gas content, and coal rank are available from the system. The data can be used for

Jan 1, 1982

By J. A. Organiscak

Two types of airflow splitting methods for improving longwall dust control were investigated by NIOSH's Pittsburgh Research Laboratory. These methods included a translucent mesh barrier and a staged spray barrier system to confine the shearer-generated dust to the coal extraction side of the longwall face while maintaining a cleaner split of airflow on the opposing worker walkway side of the longwall face. The translucent mesh barrier was shown to provide notable dust control effectiveness up to 60 m downstream of the shearer in both the laboratory experiments and a longwall field evaluation, provided the mesh barrier remains relatively parallel to the airflow. The staged spray barrier system showed marginal dust control effectiveness in the laboratory and subsequently was not field tested.

By C. B. Manula, R. L. Sanford, R. A. Rivell

A central requirement for using simulation models is the need for retrospect testing to validate experimental conclusions. Acceptance of a model by managers and safety practitioners is more likely to depend on its tested performance in-the field rather than on the underlying logic or the validity aspects of the model itself. It is here that simulation bridges the gap between theory and useful design procedures. The original version of the rail haulage sub-assembly was success¬fully tested in the field (Sanford, 1969). However, the case studies that were described here involved single-stage haulage and restricted jobtypes from UGMHS. Since this report together with Volume VI (Production Subsystem) describes extensive changes and modifications to the rail haulage sub-assembly and UGMHS, field tests were necessary to verify both the rail model and the linking concepts to the Produc¬tion Sub-system. Mine Description The candidate mine selected for model verification works the 6 1/2 foot Pittsburgh seam. Shaft openings are used for manways and ventilation and a dual compartment slope for materials handling. In the bottom half of the slope, a hoist with track handles supplies and equipment. In the upper half, a 42 inch belt conveyor travelling at 450 fpm moves coal from a rotary dump to the surface. The immediate roof is shale with the first 12 inches taken during development mining. About 4500 raw tons are produced daily from seven face units and one spare working three shifts. At seven of the sections,

Jan 1, 1974