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By Sathit Tandanand

Geological differences among various coalfields restrain the applicability of subsidence prediction using empirical approaches previously developed. The Bureau of Mines assessed data collected from 16 longwall panels in the Northern Appalachian basin. Attention was focused on the effects of rock lithology, excavation width, and panel depth on the subsidence factor. The results show that the subsidence factor can be expressed in terms of the width-to-depth ratio by a simple exponential equation, which has a coefficient tentatively considered as the subsidence index. This index varies with the lithology of a particular site, and can be expressed in terms of percent distribution of weak and strong rocks in the overburden.

Jan 1, 1982

Compare the dust control efficiency and bit life of surface coal mine drills using standard water injection and water injection with water separation. Approach A research study was conducted to determine if a water separation technique affects wet suppression dust control. Dust control efficiency and bit life of surface coal mine drills were compared during tests using both standard water injection (wet drill bit cutting) and water injection with water separation (dry drill bit cutting). Background Surface coal mine blast hole drills typically generate a substantial amount of dust during the drilling cycle. One method used to control this dust is the injection of water into the bailing air. This is known as wet suppression.

Jan 1, 1988

By C. M. Mason

Mechanical mining produces large quantities of very fine coal dust called float dust. The associated increase in hazard requires a reexamination of the Bureau of Mines method of evaluating the incendivity of explosives in coal dust-gas-air mixtures. A technique recently developed by Bureau of Mines laboratories for evaluating the incendivity of explosives in coal dust-air mixtures was applied, with modifications, to coal dust-air-natural gas mixtures. A series of permissible explosives were evaluated by this modified technique. Results indicate that the modified technique could be the basis of a more discriminatory procedure than that presently in use.

Jan 1, 1968

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 Zachary J. Fink

A continuous-monitoring system has been developed for analyses of mine gas concentrations associated with spontaneous combustion, mine fires, and explosive and toxic levels. The analysis center, which is linked to sample locations by polyethylene tubes in bundles, has been successfully field tested by the Federal Bureau of Mines for analyzing carbon monoxide and oxygen; a computational scheme has been developed to process the data at the site. This report contains information on the design, purchase, installation, and maintenance of the tube-bundle system. A brief comparison of the tube-bundle system with the underground-analysis system and plans for future research are also included.

Jan 1, 1975

By Manuel Gomez

Prediction models were constructed for seam elevation, overburden, and sodium concentration for a lignite deposit in Ward County; N. Dak. These models were developed by mathematical-statistical techniques using surface coordinates as independent variables to permit interpolation between drill holes. The results suggest that sodium concentration in lignite may be predicted in advance of mining. This information is helpful to mine planning, specifically, in scheduling production to deliver a uniform product to existing powerplants.

Jan 1, 1970

By W. P. Rumancik, C. P. Lazzara, A. C. Smith

The United States Bureau of Mines (USBM) developed SPONCOM to aid in the assessment of the spontaneous combustion risk of an underground mining operation. A prior knowledge of the spontaneous combustion risk of the coal and factors that increase that risk can be useful in the planning and development of proactive monitoring, ventilation, and prevention plans for the mining operation. Interactive data input screens prompt the user for information about the coal's chemical and physical properties, the geologic and mining conditions encountered in the mining of the coal, and the mining practices employed. During the input process, 'expand' screens provide the user with specific information on each input parameter. This information includes a description of the parameter and its effect on the overall spontaneous combustion risk. The program logic determines the coal's relative spontaneous combustion potential, based on the coal's proximate and ultimate analyses, and heating value. The program then evaluates the impact of the coal properties, geologic and mining conditions, and mining practices on the spontaneous combustion risk of the mining operation. The program output provides details on each factor that increases the risk of spontaneous combustion.

By L. C. Marchant

Results of detailed analyses of four cores from the Threemile Canyon area in the P. R. Spring tar sand deposit in Utah are reported by the Bureau of Mines. The cores were obtained by the Utah Geological and Mineralogical Sur-vey as part of a l7-corehole evaluation program in the P. R. Spring, Hill Creek, and Rim Rock tar sand deposits. Average properties of the oil zone in the Threemile Canyon area as deter-mined from these cores are as follows: Oil saturation, 67.4 pet of pore volume; porosity, 29.2 pct; permeability before oil extraction, 133 millidarcies; and permeability after oil extraction, 2,855 millidarcies. Average net thickness of the oil zone is 23.8 ft and average depth to the top of the oil zone is 189 ft.

Jan 1, 1974

By Harry Dobroski, Larry G. Stolarczyk

Medium-frequency (MF) techniques have been successfully .[pplied] to the problem of radio voice communications in both coal and metal and nonmental mines. Long range is achieved by taking advantage of existing mine conductors that carry and propagate the signal over vast areas. It is very likely that in the near future such systems will become the referred method for general mine communications. MF techniques can also be applied to the areas of in-mine control and monitoring. Preliminary work in this area is described. In a western mine, locomotives are being operated under MF remote control in a loading operation. In several eastern mines, MF has been evaluated as a method for monitoring the status of devices in remote areas of the mines. All control and monitor information uses existing mine conductors.

By R. V. Ramani, C. B. Manula, A. Owili-Eger

MINE PROTOTYPE The prototype chosen for application demonstration is from Kingery (1960). The mine and the ventilation plan is presented in Figure 11. A new coal mine is projected with entrance by slope 1,500 feet long. Nine train entries will be standard for development, five as intake and four as return. One return shaft is planned near the slope bottom. The slope will have an area of 150 square feet and a perimeter of 55 feet. The return shaft will be circular with a diameter of 18 feet and will be 500 feet deep. Two hundred feet of the shaft and 500 feet of the slope will be concrete lined. Will it be possible to operate five units per shift with amount of air at each unit not less than 25,000 cfm? Additionally, a shop at the slope bottom will require 10,000 cfm. The problem is completely worked out using standard ventilation formulas and simple manual calculations in the above reference and is reproduced here in Appendix II for ready reference. APPLICATION In this manual, four different applications of the PSU/MVS are outlined. An article by Stefanko et al (1972), outlines how one can move from a mine map to a network for the generation of computer input. Attention is drawn to Figure 12, which is the network line diagram of the mine ventilation system in Figure 11. Note that every roadway junction has been numbered. The dotted lines represent leakage paths and the letter 'R' on a branch denotes that the split is regulated for the quantity shown. For example, there is a leakage

Jan 1, 1975

By Fun-Den Wang

A new approach for evaluating pit slope stability by the limiting equilibrium method has been developed by the Bureau of Mines. The finite element method of plane strain analysis is used to find the stress field of the pit slope structure. This stress field is then used to find the normal and shear stresses along a potential failure surface. The normal stresses are used with the Coulomb equation to calculate the shear resistance. The shear stresses are integrated to determine the total driving force. The factor of safety is evaluated from the ratio of the resisting force to the driving force along a failure surface, and is found to be affected by the elastic material properties, modulus of elasticity, and Poisson's ratio.

Jan 1, 1970

By B. E. Davis

As part of its program to increase the domestic availability of critical minerals, the Bureau of Mines conducted characterization and beneficiation studies on a St. Johns County, Fla., phosphate ore that was mined by borehole mining. Results revealed that the ore from this test mine was mostly sand-size carbonate-fluorapatite and quartz and contained 24.6 percent P205. Concentration by various flotation techniques produced phosphate concentrates that ranged, in percent, from 30.0 to 31.4 P205, 0.73 to 0.80 MgO, and 2.8 to 7.2 acid insoluble. Recovery of the phosphate from the ore ranged from 89.4 to 96.3 percent.

Jan 1, 1982

By Jeffrey Johnson, Thomas Brady, Radford Langston, Mary MacLaughlin, Hendrik Kirsten

The magnitudes and directions of in situ stresses affect the stability of mine openings, as well as the type and amount of ground support needed to maintain a safe working environment for miners. Using hollow inclusion stress cells, researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health obtained two in situ stress measurements from the face of two footwall lateral drifts at the Stillwater Mine near Nye, MT. The first measurement, obtained in 1997, was collected under the valley beneath the Stillwater River. The second measurement was obtained in 2002 under the main frontal massif of the Bear tooth Mountains in the western sector of the mine. Although few data are available, the major principal stress under the valley has been recorded as nearly horizontal in a north-south direction perpendicular to the ore body, while beneath the mountains, stress runs east-west parallel to the ore body. This paper documents the measurements, describes the in situ stress state, and discusses a finite-difference analysis of the biaxial test.

By Stephen Krickovic

A methane emission rate study was conducted in 1969 on a longwall section of a Lower Kittanning coalbed mine in central Pennsylvania. The longwall face was mined with a drum shearer between developed headings on the head end and headings on the tail end that were driven with a ripper-type continuous miner as needed. The study was conducted over 22 consecutive shifts (7-1/3 days). The average methane emission rate from the Lower Kittanning coalbed during mining at the face and developing the headings at the tail end of the face was 34 Am. Caving of the gassy overlying strata as the result of mining at the face increased the methane emission to rates ranging from 702 to 1,049 cfm.

Jan 1, 1971

Provide blasting-resistant, quickly reusable stoppings for large mine openings. Approach Stoppings are assembled using roof-to-bottom panels of brattice held together by Velcro seams that peel open when struck by a strong air blast. How It Works The Velcro seam is designed to open when exposed to forces lower than would normally damage the brattice. When the seams partially open, they relieve the blast air overpressure to prevent damage to the brattice panels and their anchoring devices. A stopping is returned to service by reclosing the Velcro seams. To hang a brattice panel, its top is stapled to a board, and wrapped once or twice around it. That assembly is then attached to the roof with bolts. The length of the board should be a foot less than the width of the panel to allow for the sealing seam on each side of the panel. The boards are installed end-to-end in an approximately straight line across the roof of the mine opening.

Jan 1, 1979

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

Mine ventilation can be broadly defined as the branch of mining engineering primarily concerned with the controlled flow of air through mine airways to maintain an acceptable atmospheric environment wherever men work or travel underground. Martinson (1976) has defined three elements of mine ventilation, 1) an engineering element concerned with establishing quality control (removal of dust and gases), quantity control (regula¬tion of air direction and magnitude) and climatic conditioning (temperature-humidity control), 2) a biological element in which an understanding of biological response is used in assessing the mine environment, and 3) a philosophical element requiring judgements as to the degree of risk or worker discomfort that is socially acceptable. Most texts on ventilation, such as Hartman (1961), limit themselves to a discussion of the engineering element. Although also limiting his text to engineering control, Weeks (1928) thoughtfully addresses the other elements in the preface of his book where he states: "Life is brief and happiness elusive under the best of conditions; so beside the commercial aspect must be placed the humanitarian. Is it not reasonable that the operator should give his men a chance to spend their working hours in a comfortable environment, with the danger of sudden death or disability reduced as much as possible?" The statutory requirements of ventilation are, in most countries, established on the basis of biological response as determined by basic research or are dictated by social awareness, often touched off by major disasters, resulting in demands on regulatory bodies for more stringent requirements. To a limited extent, the philosophical and biological elements of ventilation are intertwined in that social awareness may

Jan 1, 1977

Design a high-production coal mining machine with inherent low dust generation and low frictional ignition potential. Approach Constant depth linear cutting (CDLC) provides a longterm solution to excessive dust generation from shearers and continuous mining machines through new design of the rotary drum culling system. Problems with rotary drum systems, which must be eliminated to control the dust generation at the source, include the effect of a con¬stantly varying depth of cut using fixed bit spacing, secondary fragmentation of already broken coal and, frictional heating of bits and entrainment of dust by fanning action due to high drum rotational speed, Each bit on a rotary drum enters the coal face at zero depth of cut, goes to some maximum depth at the horizontal centerline during sump, and exits at zero depth.

Jan 1, 1989

Protect rescue workers fighting fires or mine personnel temporarily working in hot environments from heat stress. Approach A specially designed ice-cooled vest is worn while working in hot environments where cooling the mine air is not possible. How It Works The vest holds a total of 44 individual ice cells in packets that are firmly held near the wearer's skin. These ice cells remove heat from the wearer, reducing heat stress and increasing comfort. The locations of the ice cells and packets are shown in the diagram. The vest is constructed in three layers with the outer layer being aluminzed fiberglass cloth. Its aluminized surface reflects radiated heat, and its fiberglass cloth provides fire resistance and strength.

Jan 1, 1979

Reduce fire warning time and avoid activation of false alarms in underground mines. Approach A heat activated stench/tracer gas system was developed which automatically releases the gas mixture into the mine ventilation air. How It Works A canister approximately 12 inches long and 3 inches in diameter is charged with 50 grams of ethyl mercaptan or other appropriate stench gas and 500 grams of instrument detectable Freon. The canister is then pressurized to 100 psi with nitrogen. A disc is used to seal the contents of the canister. A low-temperature alloy designed to melt at a predetermined temperature is used to restrain a spring loaded plunger. Upon exposure to heat, the alloy melts and the plunger is released. The plunger ruptures the disc and the mixture of stench and tracer gas is released from the canister. Canisters are mounted in areas of a mine which are susceptible to fire such as near

Jan 1, 1983

By W. L. Staker

The Bureau of Mines investigated methods for selectively eluting mercury, silver, and gold from strong-base anion-exchange resins, including Rohm and Haas resins lRA-430 and 900 and Dow Chemical resins 2lK, SMA-I, and SBR. Resins were typically loaded to 145 oz/st of each metal. Loaded resins were eluted with H2S04, NaCl-H Cl, NaOCl, and NaCl04 solutions. The resins tested had similar elution characteristics for mercury and precious metals. The best selective elution scheme was achieved by eluting in a column with 2N H2S04 to recover 99 to 100 pct Hg, with 200 giL NaCl in IN HCI to rec;ver 99 to 100 pct Ag, and with 2M NaCl04 to recover 79 to 89 pct Au.

Jan 1, 1987