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By James J. Olson

The Bureau of Mines used micro fracture density analysis of quartz grains in thin sections and diametric pulse velocity measurements along preblast and postblast cores to determine the nature and extent of rock damage produced by small (0.25-,0.50-,1.0-, and 2.0-kg) charges of high intensity explosive (C-4) in granite. Pulse velocities from the postblast cores were significantly lower than velocities from the preblast cores and, with the core logs, provided clear identification of the upper and sometimes the lower limits of most severe damage. These zones ranged from about 1.68 ft for the 0.25-kg blast to 4.16 ft for the 2.0-kg blast. Microfracture densities from postblast cores were significantly higher and more variable than densities measured from preblast cores. The microfracture density measurements showed that microscopic damage was present far past the zones of most severe damage as delineated by the pulse velocity logs and core logs. An exponential relation-ship was observed between the micro fracture density levels and the charge weight.

Jan 1, 1973

By Gene Asai

Properties obtained for columbium carbide-carbon castings ranging in car-bon content from 12 to 17 weight-percent were compared with those of hot-pressed composites of similar composition. The properties were oxidation resistance in static air between 500° and 700° C, linear thermal expansion between 20° and 2,400° C, electrical resistivity between 20° and 1,500° C; microhardness between 20° and 1,500° C, and modulus of rupture between 1,300° and 1,800° C. CbC-C castings differed markedly from hot-pressed material with respect to microstructure, electrical resistivity, and modulus of rupture, but behaved quite similarly with respect to oxidation resistance, thermal expansion, and hot hardness. In oxidation resistance, thermal expansion, and hot hardness both materials were independent of carbon content. Both castings and hot-pressed composites oxidize rapidly in air above 600° C, have thermal expansion coefficients very similar to columbium metal, and the logarithm of the hardness decreases linearly with increasing temperature. The microstructures of hot-pressed composites contained varying amounts of graphite in a CbC matrix but did not contain significant amounts of a eutectic structure present in all castings, nor did they contain graphite needles which were present in the hypereutectic castings. The higher electrical resistivity of hypereutectic castings over hypereutectic hot pressings was attributed to the presence of highly oriented graphite needles in the castings. The modulus of rupture of castings was 1-1/2 to 2 times that of hot-pressed composites. Both materials displayed bend ductility above 1,800° C.

Jan 1, 1971

Reduce longwall shearer operator's dust exposure by selecting the best drum water spray sys-tem for minimizing dust generated durinq cutting. Approach Three of the most commonly-used drum water spray systems were installed on the same set of shearer drums and compared to determine which system best suppresses dust. The spray systems studied were: ? pick-point flushing ? cavity filling ? water-through-the-it Instantaneous and gravimetric sampling instruments were used to measure the respirable dust exposures of the shearer operators and dust concentrations downwind of the shearer. The Three Systems: Longwall shearer drums are routinely equipped with internal drum spray systems since these systems have been shown to be more efficient than external systems in terms of dust suppression per gallon of water applied. All U.S. longwall shearer faces utilize some type of internal water delivery spray system. The two most common systems are bit-or pick-point flushing and cavity filling. Pick-point flushing uses nozzles mounted in the bit blocks or in special blocks immediately in front of the bits. Cavity filling utilizes spray nozzles installed in a pipe manifold mounted on the drum hub between the scrolls or along the edge of the vane scrolls; water is sprayed radially from the manifold towards the adjacent vane scroll.

Jan 1, 1986

Promote safer and more efficient mine operations by providing communications between personnel located anywhere in the mine. Approach A radio communications system was designed which takes advantage of existing mine wiring such as telephone lines or electric power cables. The existing wiring distributes radio signals throughout the mine, making communications possible between roving miners, vehicle operators, dispatchers, and other personnel. How It Works Research has shown that medium frequency (MF) signals (300 KHZ-3 MHZ) can couple onto and re-radiate from nearby conductors. This effect is known as parasitic coupling and re-radiation. In a mine, these conductors include electric power cables, control lines, telephone lines, trolley lines, as well as metal water and air pipes Since all underground mines require these conductors for normal operations, the necessary network already exists and expands automatically as the mine is developed. A radio communication system has been developed that uses the parasitic coupling and re-radiation characteristic of MF. Using this system, whole mine radio coverage can be achieved without the need to install or maintain communication lines. The system consists of mobile transceivers for roving personnel and vehicles, and fixed-location base radio stations and repeaters.

Jan 1, 1982

By D. A. Paice, A. B. Shimp

Illegitimate loads on a mine dc power distribution system can be detected by measuring a superimposed ac current. To implement such a scheme, a 10-volt, 3-kHz voltage is applied at each dc power substation. By this means, the mine dc power distribution network, consisting of a feeder and trolley wires with a grounded rail return, is caused to serve also as a 3-kHz ac distribution network.

Jan 1, 1975

By Richard J. Mainiero, Marcia L. Harris, James H. Rowland

In the past several years, there have been a number of blasting-related carbon monoxide migration incidents. In each case, there have been some common factors that appear to be related to carbon monoxide migration. Geology, heavy confinement of the blast, close proximity to the affected structure, and open pathways into the affected structure are just a few. Prince William County, VA is an area undergoing a boom in suburban development. In the year 2001, more than 4,050 new homes were constructed within the county.1 In the new housing development located in Bristow,VA, trench blasting was utilized to excavate proposed sewage and utility lines. On November 8, 2002, a trench blast was conducted for the installation of utility lines. Later that evening a carbon monoxide detector alarmed in a nearby house. The gas company and fire department sampled for carbon monoxide and measured 100 ppm and more than 200 ppm on the first floor and in the basement respectively. Subsequent efforts to prevent migration of CO into the nearby homes met with mixed results. The only reliable technique for protecting neighbors from CO appears to be the placement of CO monitors in the homes. The events are presented and discussed.

By Thomas A. Gray, Lynn M. Crayne, Michael A. Trevits, Phil Glogowski

Mine seals can be remotely constructed in underground coal mines, through vertical boreholes, when direct access to a fire is impossible or considered to be too dangerous. This method has great merit because boreholes can be drilled to specific mine areas and seals can be positioned close to a fire zone. The technology however, can be largely ineffective if the constructed seals do not provide effective barriers to airflow or cannot be used to impound water and other inert materials. Unfortunately, no viable alternatives exist to sealing the entire mine at the ground surface. Full-scale remote mine seal construction research is being conducted at the National Institute for Occupational Safety and Health’s (NIOSH) Lake Lynn Laboratory (LLL). Under this effort, Howard Concrete Pumping Company and GAI Consultants, Inc. have joined forces to evaluate a potentially significant improvement to the current state-of-the-art. This paper will cover development of novel technology for remote mine seal construction, evaluation of the materials used, construction practice, and follow-up testing.

By Bruce K. Cantrell, Stephen W. Stein, Kenneth L. Williams, David Hassel, Harvey Patashnick

In June 1992, the Mine Safety and Health Administration (MSHA) published the "Report of the Coal Mine Respirable Dust Task Group, Review of the Program to Control Respirable Coal Mine Dust in the United States." As one of its recommendations, the report called for the accelerated development of two mine dust monitors: (1) a fixed-site monitor capable of providing continuous information on dust levels to the miner, mine operator, and to MSHA, if necessary, and (2) a personal sampling device capable of providing both a short-term personal exposure measurement as well as a full-shift measurement. In response to this recommendation, the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Center, initiated the development of a fixed-site machine-mounted continuous respirable dust monitor. The technology chosen for monitor development is the Rupprecht and Patashnick Co., Inc. tapered element oscillating microbalance. Laboratory and in-mine tests have indicated that, with modification, this sensor can meet the humidity and vibration requirements for underground coal mine use. NIOSH is continuing that effort by developing prototypes of a continuous dust monitor based on this technology. These prototypes are being evaluated in underground coal mines as they become available. This effort, conducted as a joint venture with MSHA, is nearing completion with every promise of success. The immediate benefit of this effort will be to researchers, regulatory personnel, and mine personnel, by permitting evaluation of specific mining practices to see which expose mine workers to excessive dust levels. Using this information, mine personnel can optimize mining procedures to reduce dust exposure. MSHA and the operators will also be able to use the dust concentration data to judge whether dust plan parameters are adequate to continuously maintaining environmental dust levels below the applicable standard. The second development recommended by the Dust Task Group was a person-wearable version of the continuous dust monitor. It will be a monitoring system designed to provide a measurement of worker exposure to respirable dust, both during and at the end of the shift.

Eliminate the need for roof bolter operators and their helpers to work under unsupported roof while setting or removing temporary supports before or during the roof bolting cycle-a task that annually accounts for approximately 20 percent of all roof fall fatalities. Approach The Bureau of Mines designed, built, and field tested an auto-mated temporary roof support (ATRS) that can be carried from place to place on the drill head of a single, fixed-head roof bolting machine (squirmer) used in low coal seams (less than 42 inches thick). How It Works The ATRS is designed for installation on any streamlined squirmer. It consists of a ten? foot-long, steel, wide-flange beam supported by two double-acting, telescoping hydraulic cylinders. A steel sleeve, mounted on the bottom center of the beam, is designed to fit over top of the

Jan 1, 1983

By GEORGE S. POPE

The purchase of coal by the Government under specifications depending on the heating value of the coal, its content of ash and of moisture, and other considerations, rather than upon the reputation or trade name of the coal, was based on the fuel investigations begun by the Technologic Branch of the United States Geological Survey in 1904. The plan was first adopted by the Treasury Department in 1906. Since then the plan, variously modified in form but the same in principle, has been gradually adopted by other departments until at present of the coal used by the Government, the total value of which approximates $8,000,000 annually, more than half is purchased under specifications. The Government publications dealing with the adoption by the Government of the specification plan, the number of contracts awarded on that basis, and the quality of the coal delivered under such contracts in the several fiscal years covered by the reports are given in publications listed at the end of this bulletin. Under the authority of acts of Congress making appropriations for analyzing and testing fuels belonging to or for the use of the United States Government, a laboratory is maintained at the headquarters of the Bureau of Mines, Washington, D. C., where samples represent- ing deliveries of coal purchased under specifications for Government use are analyzed and tested. At this laboratory more than 1,200 samples have been analyzed and tested in one month. With the complete equipment and the efficient force employed, the analytical work has been so perfected that the analyses and heating-value tests of the samples received are as accurate as may be reasonably expected in laboratory work of this nature. One of the serious drawbacks to the general adoption of the speci- fication method for the purchase of coal is the difficulty of obtaining at reasonable cost samples of coal that can be considered fairly repre- sentative of the commercial product delivered in wagons, railroad

Jan 1, 1913

By E. C. Lane

This report on properties of commercial motor fuels is the twelfth in a series made in accordance with a cooperative agreement between the Cooperative Fuel Research (C.F.R.) Committee and the Bureau of Mines of the United States Department of the Interior. The first report contained data on motor gasolines sold during the winter of 1935-36.V The -present report, covering the summer of 1941, presents analytical data for 1,857 samples, representing the products of approximately 135 companies. As in previous surveys, these companies include both large and small suppliers. In addition, the Pacific coast is represented by data averaged by the Pacific Coast Technical Group before being submitted, and these data are published exactly as they were received. Conforming to previous surveys, the data cover three groups of samples -- regular-price, premium-price, and third-grade gasolines -- and each group has been aver aged separately. The number of samples, items, and brands comprising each group, exclusive of those of the Pacific coast, are as follows: Regular price, 1,010 samples, 291 items, and 86 brands; premium price, 577 samples, 263 items, and 78 brands; third-grade gasoline, 270 samples 159 items, and 74 brands. The meanings of these terms as used in the surveys are as follows: Sample: The individual supply of gasoline obtained at the filling station and analyzed in the laboratory.

Jan 1, 1942

Develop an alternative to water bath exhaust conditioners (water scrubbers) for permissible diesel equipment used in gassy mines. Background Water scrubbers are a safety device used on diesel-powered vehicles in gassy mines. Exhaust from the engine passes through the scrubber, where it is cooled, and any flames or sparks present in the exhaust are extinguished. This prevents the ignition of combustible mine dust or methane that may be present. Unfortunately, water scrubbers consume large amounts of water and require frequent maintenance. Approach Methods that do not require water replenishment and frequent maintenance were investigated. The dry exhaust conditioning system was selected for investigation because no water is consumed and existing heat exchanger technology can be adapted to underground mine vehicles. In accordance with U.S. Mine Safety and Health Administration (MSHA) requirements, the system was designed to cool exhaust and trap flames and sparks. The U.S. Bureau of Mines (USBM) developed and evaluated a system for large engines and evaluated a second system for smaller engines. Both systems were evaluated on an engine test bed; if warranted, the system was then tested underground.

Jan 1, 1993

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

8. Refuge Chambers 8.1 Refuge Chambers - Technical Discussion 8.1.1 Introduction As a part of the overall escape system, refuge chambers can provide a last resort when existing escapeways are blocked. These chambers are intended to provide both protection from toxic gases and a life supporting environment for a period of time before external rescue or further escape efforts can be carried out Escapeways may be blocked physically (due to cave-ins, etc), by fire, or by the presence of a toxic or oxygen deficient atmosphere. In the first two cases, the trapped miners would most likely await external rescue efforts, and hence the design of the chamber will have to consider the time durations that such efforts may take, It is also possible, in the second case, for fire fighting and fire protective equipment to be stored in the chamber so that miners may attempt their own escape. In the third case, it should be recognized that a compact, beltmounted 1-hour self-contained breathing apparatus has been developed(9), and that other, less compact equipment is available for up to 4 hours of self-contained breathing supply. If such equipment were stored in the chambers, then miners could escape by travelling from chamber to chamber, taking temporary refuge in each before proceeding to the next. 8.1.2 Background The concept of "barricading" has long been recommended for those emergencies where miners are trapped inby a fire. Barricading, which is the construction of a makeshift shelter in a crosscut or deadend, protects the entrapped miners from toxic gases and enables them to conserve a supply of air. In this manner, they can survive two or three days--hopefully enough time for them to be reached by rescue teams. In the past, many lives have been saved with this technique.

Jan 1, 1976

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Jan 1, 2012

Improve the safety and comfort of operators of large mining equipment. Approach Develop an improved driver restraint system that is easy to use, reliable, and cost-effective, while providing increased protection in the event of a collision or rollover. The Novel Restraint System There are several problems associated with conventional lap-belt type restraint systems. Among these are: restriction of movement, lack of comfort, and fear of entrapment. Standard seatbelts become dirty and oily from lying on the vehicle cab floor and can ruin a driver's clothes. Some haulage equipment may not even have seatbelts available to drivers since they are sometimes removed during maintenance activities or as a result of vandalism. Recognizing a need to address such problems by providing a more acceptable means of driver restraint, the Bureau of Mines designed and fabricated a novel vest-type restraint system. The vest is designed to be worn during a driver's 8-hour shift and would be issued much like safety glasses, hard hats and safety shoes, thus becoming part of the operator's individual protective equipment and assuring that each vehicle has a restraint system when in operation. The vest-

Jan 1, 1985

By Gerrit V. R. Goodman, Charles D. Taylor, Edward D. Thimons

Future coal mining systems will be able to cut from crosscut to crosscut where advances could exceed 100 ft. However, limitations arise when ventilating such mining systems. In deep advance mining, there would be no workers at the face to advance ventilation tubing or curtain manually. Traditional methods also provide no means for maintaining face ventilation after the miner backs away from the face. U.S. Bureau of Mines research is studying means to provide effective ventilation at cut depths beyond the current limit of 40 ft. Several innovative ventilation schemes are currently being considered. One such method is the use of a jet fan to ventilate a deep cut. A jet fan is simply a freestanding fan using little or no ducting to direct the ventilation flow. Jet fan testing in a 90-ft entry revealed that higher exit velocities and greater penetration depth occurred when various configurations were used to confine and direct the air flow. Additional testing also indicated that 2,200 cfm of fresh air was delivered to the face 90 ft distant when a check curtain was used to limit entrainment around the fan. Without this curtain, this quantity dropped to only 1,000 cfm This testing indicated that a jet fan was capable of providing ventilation to a distant face area. It also highlighted potential problems, such as recirculation at the fan and reentrainment in the jet flow. Despite these potential problems, jet fans may be adequate for ventilating cuts exceeding 40 ft.

Jan 1, 1992

Surface mining of coal involves removing soil and rock that overlay coal beds in order to expose the coal. Compared to underground coal mining, surface mining generally costs less, is safer for miners, and usually results in more complete recovery of the coal. However, it also results in much more extensive, though temporary, disturbance of the land surface, which can cause serious environmental problems unless the mined land is carefully reclaimed. The earliest commercial U.S. coal production was in the anthracite region of Pennsylvania. Beginning in 1807, mining became important enough for the federal government to begin keeping statistics on annual production. During those early years of coal mining, reclamation of mine sites and Support facilities was not required by law; however, in the 1930's, as surface mining became more widespread, the idea of mandatory environmental protection and reclamation started to grow. In 1939 West Virginia enacted the first law to regulate the coal mining industry. Similar laws were enacted by Indiana in 1941, Illinois in 1943, and Pennsylvania in 1945. During that period, coal production accelerated greatly and the surface mining of coal became much more prevalent. During World War 11, the demand for coal took priority over environmental concerns, with little consideration for reclaiming the land after mining. Mining pits were not backfilled. Dangerous highwalls were left exposed. Trees and other vegetation were buried by waste material that was simply dumped down the slopes below mines. Topsoil was buried or allowed to wash away. Landslides formed on unstable hillsides. Slopes eroded rapidly because of the lack of vegetation. Polluted water collected in mine pits. Streams became clogged with sediment. Streams and rivers were frequently polluted by acid mine drainage. This vivid image of surface coal mining remains indelible in the minds of most Americans, who remain unfamiliar with modem surface coal mining methods and the changes brought about by the Surface Mining Control and Reclamation Act. After 1945, more coal-producing states instituted regulatory pro- grams. Many required permits for mining. Some included inspections. A few made operators post performance bonds to guarantee reclamation when mining was completed. However, due to the variations in those individual programs, it cost less to produce coal in states with less stringent reclamation requirements, giving operators in those states an economic advantage, generally at the expense of environmental quality. With the 1970's came a surge in the demand for coal resulting from the nation's need for increasing electric power generation and the uncertain supply and increased cost of imported petroleum-based fuels. The resulting increased coal production prompted a series of state laws, primarily in the West, aimed at controlling the environ- mental effects of surface mining. During the late 1960's and early 1970's, North Dakota, Wyoming, Colorado, and Montana passed laws to regulate mining and reclamation. The continuing lack of uniformity among the state surface mining programs and the increase in unreclaimed land and associated pollution of water and other resources caused a growing demand for nationwide regulation of surface coal mining, both to remove the economic inequities and to is sure an acceptable standard of reclamation. After many years of debate, Congress passed the Surface Mining Control and Reclamation Act (SMCRA), which was signed into law August 3, 1977. The Act established a coordinated effort between the states and the federal government to prevent the abuses that had characterized surface coal mining in the past. The law also applied to surface disturbances created by underground coal mining.

Jan 1, 1992

By T. G. Carnahan

The Federal Bureau of Mines investigated, on a laboratory scale, a technique for recovery of silver from pregnant solutions generated in the hydro-metallurgical treatment of complex base-metal sulfide concentrates with oxidizing chloride media. This technique provides a means for recovery and simplified reduction of accessory silver to metal from chloride solutions. The method consists of adding NaI or KI to the solution to precipitate AgI, which is then contacted with Na2S to produce Ag2S and to regenerate the iodide salt solution. Silver recoveries range from 99 pct with 20 pct excess iodide precipitant, to 92 pct when the theoretical stoichiometric amount of precipitant is employed. The Ag2S product can be reduced to silver metal by contact with aluminum chips in NaOH solution followed by purification with conventional fire refining techniques.

Jan 1, 1980

By Launa G. Mallett, Dana Reinke, Charles Vaught, Michael J. Brnich

As mines become safer and major disasters fewer, the number of experienced emergency responders is decreasing. This decrease will create a gap in response expertise which could have serious ramifications during future mine disasters. While working toward safety goals which may make emergency response obsolete, it would be reckless not to acknowledge that the potential for disaster still exists and that the protection of miners in such circumstances must remain a priority. The Mine Emergency Response Interactive Training Simulation (MERITS) is a computerized mine emergency simulation that meets a variety of needs. It allows personnel in leadership positions to test their knowledge and skill. Groups of individuals composed of representatives from mining companies, labor, and government agencies can practice working together during the simulated mine emergency much in the same way an actual emergency would require. An individual could also run the program to enhance his or her response skills. With this training tool, responders will be able to learn from their mistakes before facing situations with potentially catastrophic consequences. This paper discusses MERITS and its use in providing command center training.

By James E. Hill

The Bureau of Mines has been carrying on an extensive diamond- drilling program during the past 7 years on deposits of strategic and critical minerals . Often the project reports and the drill-hole logs describe the findings only in terms of the mineral being sought at the time . Then , too , results may not always be interpreted alike by several mining engineers , and the cores therefore provide a permanent tangible record to complement the project reports . The cores from projects in the eastern divisions are being stored at the Mount Weather Testing Adit . Core from a representative hole ( or skeletonized sections from several holes , if these are more representative ) is selected at each project and shipped to Mount Weather for permanent storage . At the Testing Adit an underground room was prepared and storage racks were installed . Wooden core trays designed to accommodate cores of various sizes were purchased .

Apr 1, 1947