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By R. P. Vinson, D. P. Tuchman

The personal dust monitor (PDM) is a sampling device developed for measuring the personal exposure to coal mine dust of mine workers. The device is based on proprietary technology known as the tapered element oscillating microbalance (TEOM) originally developed as a fixed- site environmental particulate mass monitor by Rupprecht and Patashnick Co., Inc., Albany, NY. Currently, the monitoring of exposure to coal mine dust relies on periodic samples taken by traditional coal mine dust sampling units that use a cyclone, filter, pump, and laboratory measurement of the filter mass. Better measurement of mine dust levels has been the goal of industry and labor for nearly two decades. PDM technology offers accurate, end-of-shift and near real time assessment of worker dust exposure. Laboratory and underground tests compared measurements taken by a prototype PDM-2 (a two-piece TEOM) to the average of multiple personal dust samplers monitoring the same space. In the range of mass loadings P between 0.5 and 4.0 mg/m the PDM met a 25% accuracy criterion 95% of the time with 95% confidence. However, some questions still exist about potential bias between types of coal. The prototype two-piece device is in the process of being combined into a single unit that also contains the miners' cap lamp creating a more ergonomic dust sampling system.

"There mines are located in out of the way places, where timber is scarce and its price high, the problem of protecting it from fire risk is of considerable practical importance. Scarcity of timber for mining purposes is commonly met with in the more arid parts of the country, where, so, mine timbers are most likely to become dry, and inflammable, and where, therefore, the risk from fire is accentuated. Any effective and cheap method of securing adequate protection of such timber at the lowest possible cost is worthy of careful investigation. The use of magnesite cement has been suggested in this connection.The necessary qualities for any substance for the use suggested above may be summarized as follows: It should be resistant to abrasion, and to impact and structural stresses. It should be durable when subjected to the action of the elements, and stable to any minor derangements of the base on which it is placed. It must be relatively unaffected by changes in temperature, by the action of water, and should adhere to the material on which it is placed, and it should also be free from shrinkage cracks due to setting up the material, Magnesite cement appears to fulfill the various conditions outlined above.The elasticity of such cement is the outstanding quality which makes it desirable for exterior work. It also possesses the ability to adhere to all materials in a marked degree. Its freedom from expansion and contraction after setting is one of the principal reasons for its adhesive quality. It may be applied to old brick or stone walls, even tho they have been repeatedly covered with paint, and the quality of adhearing to wood makes it possible to secure a weather-proof protection to the wooden casings and trim of exterior openings. The quality of adhesion and elasticity is easily proved by applying a 1/2"" layer to a 1"" board which has been first covered with metal lath. Such a board, about 8 feet long, may be repeatedly deflected about 3"" in the center without breaking the bond to the board, or causing any cracks to appear in the magnesia cement. The ability to resist fire as well as the possession of insulating qualities are also desirable characteristics of magnesia cement stucco.Magnesite cement stucco should be applied in two coats, each 1/4"" thick on various surfaces such as wood lath, metal lath, sheathing board, brick, hollow tile, or stone; care being taken as regards the presence of lime, unless the same has been rendered, or become inert as with very old, walls. The first coat made up to a consistency that works easily under the trowel is applied in the usual manner. No water should be added to the liquid chloride as it would alter its density, and injure the work. The second or finishing coat is then applied. The aggregates are different in each, and no other dry material should be added to them as they come to the trade. The cement may be applied in zero weather without damage. Setting is quite slow under such conditions, but the cement ultimately becomes hard. It should always be applied to a dry surface excepting that under certain conditions it is desirable to apply a solution of magnesium chloride before using the stucco."

Dec 1, 1919

By P. R. Bremner

The United States is more than 90 pct dependent on imported bauxite a source for aluminum, but it has vast nonbauxitic aluminum resources, such as kaolinite, anorthosite, alunite, etc. As part of a program to devise processes for treating these resources, the Bureau of Mines investigated a bench-scale leaching process using hydrochloric acid (HC1) and fluoride to extract aluminum from Wyoming anorthosite. HC1 and fluoride-to-aluminum (F/Al) mole ratios were studied with respect to aluminum extraction for single-stage, cocurrent, and countercurrent leaching modes. Using 95 pct stoichiometric HC1 and a F/Al mole ratio of 0.27, 90 pct of the aluminum was extracted by countercurrent leaching. Single-stage leaching with the same amount of acid and fluoride extracted 48 pct of the aluminum. Three fluoride sources, CaF2, Na2SiF6, and H2SiF6, were used and gave similar results on aluminum extractions.

Jan 1, 1982

By J. Gautam, T. Ong, W. E. Wallace, M. Keane, S. Xing, J. Harrison

"INTRODUCTIONOrganics extractable from respirable diesel exhaust soot particles by organic solvents have been known for some time to be direct acting frameshift mutagens in the Ames Salmonella typhimurium histidine reversion assay (Huisingh, et al). Upon deposition in a pulmonary alveolus or respiratory bronchiole, respirable diesel soot particles will contact first the hypophase which is coated by and laden with surfactants. To model interactions of soot and pulmonary surfactant, we dispersed soots in vitro in the primary phospholipid pulmonary surfactant dipalmitoyl glycerophosphorylcholine (lecithin) (DPL) in physiological saline. We have shown that diesel soots dispersed in lecithin surfactant can express mutagenic activity, in the Ames assay system using S. typhimurium TA98, comparable to that expressed by equal amounts of soot extracted by dichloromethane/ dimethylsulfoxide (DCM/DMSO)(Wallace, et al, 1987). Here we report additional data on the same system using additional exhaust soots and also using two other phospholipids, dipalmitoyl glycerophosphoryl ethanolamine (DPPE), and dipalmitoyl phosphatidic acid (DPPA), with different ionic character hydrophilic moieties. A preliminary study of the surfactant dispersed soot in an eucaryotic cell test system also is reported.MATERIALS AND METHODSSoots D4 and D6 were collected at two different times as scrapings from the exhaust pipe of a diesel tractor-trailer immediately after the engine was stopped. Surfactant dispersions were made by ultrasonic probe sonicating 25 mg of commercially obtained DPL, DPPE, or DPPA into 1O ml of O.85% physiological sterile saline (PSS) for 10 min at 40 watts power. For surfactant dispersions, 2.5 mg soot was mixed into 2.5 ml of the appropriate phospholipid dispersion. Mixtures were sonicated by 40 watts sonicator probe for one min, then incubated in the sonicator water bath for 30 min at room temperature; the mixture was then incubated for one hour at 37C while being rotated continuously. Dilution series were made with saline. For solvent extraction, 2.5 mg soot was mixed into 2.5 ml of DCM and incubated in a sonicator water bath for 30 min at room temperature. The sample was then mixed with 2.7 ml DMSO, placed in a dry bath at 45C, and the DCM evaporated under a stream of nitrogen gas until 2.5 ml of liquid remained. Ames salmonella/microsome assay utilizing TA98 for frameshift mutation was used for mutagenicity testing, with and without S9 activation, as described by Ames et al (1975). Unfiltered sample extractions or dispersions were preincubated with tester cells for 90 min at 37C : 0.1 ml of sample was mixed with 0.5 ml of PSS, or of S9 mixture, and 0.1 ml of an overnight TA98 culture incubated samples were then added to 2 ml of top agar supplemented with biotin and a trace amount of histidine, and overlayed onto Vogel-Bonner minimal media plates. After 48 hours incubation at 37C, revertant colonies were counted. Solvent controls were DMSO, DPL, DPPE, DPPA, and saline. Positive controls were trinitrofluorenone (1 ug/plate), for samples not treated with S9, and 2-aminoanthracene for S9 treated samples (2.5 ug/plate). All samples were assayed in duplicate. Sister chromatid exchange (SCE) assay was performed, following Lett, et al (1981), using V79 cells, of Chinese hamster pulmonary fibroblast origin. Stock diesel sample suspensions were made as 10 mg soot/ml DPL suspension, or 20 mg soot/ml in DMSO. Aliquots of these soot preparations were added to 15 ml of culture medium per sample flask to result in concentrations of 25, 50, and 75 ug soot/ml medium. After 12 hours incubation, 200 ul of 25 uM 5-bromodeoxyuridine (BrdU) was added to each flask. After another 35 hours incubation, 200 ul of 10 ug/ml colcemid were added; and the cells were harvested three hours later. Cells were swollen by hypotonic saline, and fixed twice with methanol/acetic acid, and burst on microscope slides. Cells on the slide were stained with Hoechst 33258, exp"

Jan 1, 1990

By F. E. Brantley

Optimum autoclaving conditions were determined for separation of iron and manganese values from pregnant leach liquor produced in extracting manganese from low-grade umber are. The umber was leached with a synthetic anolyte similar to a recycle solution, used in manganese electrolysis cell operations, that had been renewed with ferrous sulfate and sulfuric acid. The equipment used and results obtained are presented for the several conditions employed. The kinetics of the separation were studied. Rate equations were derived for the formation of solid ammonium-manganese sulfate, (NH4)2 Mn2 (S04)3.

Jan 1, 1968

Estimate costs for projected uranium in-situ mining operations. Approach Develop a computer model and an associated data base which will allow users to supply data applicable to a specific mining site in order to estimate total capital and operating costs for a potential in-situ mining operation at the site. How the Model Works The model requires a minimal amount of input from the user. The data input must be known or estimated information about a potential in-situ mining operation. The user can also supply any additional project specifications. The computer model uses a process-engineering approach and determines through a discounted cash flow analysis the total capital and operating costs for the life of the project. This time-span measures from the start of the pilot-scale operation through to the site's restoration and reclamation. The model will determine the production cost per pound of material mined subject to the rate of return identified by the user. Conversely, it will also solve for the rate of return realized for the specific sales price per pound. [ ] Currently the model's data base can tai ns costs, rates, and specifications for Texas and Wyoming, the only states where commercial uranium in-situ mining is being conducted. However, this model can be used by anyone who is conducting in-situ leaching or who plans to leach uranium in-situ. At least part of any uranium deposit has a potential for in-situ mining.

Jan 1, 1982

By Edward D. Thimons

The Bureau of Mines conducted in-mine tests to determine correction factors applicable to low-velocity airflows (below 150 fpm) measured by the smoke cloud, vane anemometer, and oil of wintergreen tracer gas techniques 0 The average correction factors found for these methods of measurement were lower than those reported in the literature for use with higher velocity measurements. All tests measured airflows with controlled average velocities ranging from 50 to 100 fpm. Correction factors averaged about 0.75 for readings taken by the centerline smoke cloud method, remotely controlled and stickheld center" line anemometer, and split traverse stick-held anemometer. For hand-held centerline anemometer and oil of wintergreen tracer gas readings, correction factors averaged about 0.67. Since special anemometers are needed to measure airflows in this low-velocity range, and since proper calibration of these anemometers is difficult and expensive, the use of anemometers for low-velocity measurement is imprac-tical. On the other hand, smoke and oil of wintergreen give results as con-sistent as those obtained with specially calibrated, low-velocity anemometers. Furthermore, they are easy to use and inexpensive.

Jan 1, 1979

By P. G. Barnard

The Nation's steel industry is largely dependent on shipments of manganese from foreign sources for steel production. An adequate substitute for the manganese requirements of our present steel technology would improve our national self-sufficiency and also contribute substantially to the conservation of our manganese resources. As each of these objectives is a major interest of the Bureau of Mines, possible substitutes for manganese in steel were investigated. Titanium was selected as the most promising substitute because the published results of several investigations indicate that titanium would perform the most obvious function of the manganese in steel: The elimination of iron sulfide and its deleterious effects. The investigation involved extending the published data on titanium additions in steel to provide enough information for an accurate evaluation of the practical value of the substitute. Therefore, quantitative data were obtained on the partition of sulfur and carbon between iron and relatively small titanium additions.

Jan 1, 1962

By Katherine Harding

This Bureau of Mines publication describes a practical approach to sampling that does not require elaborate statistical techniques. Simple steps are given for finding a cutoff point in the response from a repetitive survey. This procedure can be used to estimate the aggregate value of the characteristic being measured without waiting for a complete count from the survey. This is a useful technique when the reference periods are repeated at frequent intervals, such as monthly and quarterly, and when the statistical collecting agency is engaged in publishing timely data which must be accurate economic indicators.

Jan 1, 1971

By M. R. Geer, H. F. Yancey

"INTRODUCTION The increased use of coal as pulverized fuel has focused attention on the grindability of coal and on the necessity of evaluating this property by a method suitable for use in the usual coal-testing laboratory. Without some knowledge of how various coals behave in the grinding operation, that is, how their use affects mill capacity and power requirements, the selection of coals for pulverized-fuel plants cannot be made on the same critical basis used in selecting coals for other types of burning equipment. The grindability of a coal, serves principally as an indication of the mill capacity attainable in grinding it - not as a direct index of the total cost of grinding. Although the grindability of coal may play a minor role at some plants, it is a decidedly important factor where pulverizer capacity limits the ability to carry high loads.Purpose Standardized tests for determining the grindability of coal are relatively new, so that the information now available on the grindability of various coals is limited in comparison, for example, with that available on proximate analyses. Published information is restricted to determinations on many important Eastern coals by the Fuel Engineering Co. of New York, 4/ a bulletin giving the results of numerous tests by the Babcock and Wilcox Co. 5/, and a comprehensive report on. Alabama coals by the Bureau of Mines. 6/This report presents the results of grindability tests of 34 samples of coals from Illinois, Kentucky, Pennsylvania, Utah, Virginia, Washington, West Virginia, and British Columbia at the Northwest Experiment Station of the Bureau of Mines, Seattle, Wash., in cooperation with the College of Mines of the University of Washington. In the future, as the laboratories of the Bureau make grindalility tests of other coals, additional reports will be issued."

Jul 1, 1938

By Linda L. Chasko, Ronald S. Conti, John D. Cool

Mine operators often rely on mine rescue teams to save lives during an underground emergency such as an underground fire, explosion, roof fall or water innundation. It is extremely important that team members are provided with adequate exploration equipment and that training simulations are conducted in a realistic manner. A series of mine rescue training exercises was developed, conducted, and evaluated by the National Institute for Occupational Safety and Health (NIOSH) in cooperation with the Pennsylvania Department of Environmental Protection, Bureau of Deep Mine Safety and several mining companies. The exercises were conducted at NIOSH’s Lake Lynn Laboratory and operating mines during 1995 to 1999 and resulted in improved technology and training for mine rescue teams. For example, existing technologies were identified to help rescue teams during exploration. These included various chemical light shapes and laser pointers to identify team members and mark crosscuts and mine materials, strobe lights for mapping out escapeways and marking crosscuts, and thermal imaging systems to see through smoke. A hands-free communication system showed potential for enhanced communications between team members and the fresh air base. Anew team lifeline that allows for flexibility of movement between team members was developed. A positive-pressure inflatable escape device (IED) was used to isolate the “hazardous” environment from fresh air and allow rescue team members to traverse through. An inflatable feed-tube partition that can rapidly block large openings such as underground passageways and simultaneously provide a feed-tube for high-expansion foam generators was also deployed for several simulations. During the simulations, mine rescue team members donned self-contained breathing apparatuses (SCBA) and traversed more than 400-m of mine passageways filled with nontoxic smoke. Visibility ranged from 0.3 to 0.9-m. In one area of the mine, a kerosene heater was used to simulate a fire and reduce the oxygen concentration. In another area, a 1.5 pct methane zone was established. The team members searched for "victims,” administered first aid, mapped the passageways, built temporary stoppings, and ventilated the smoke-filled entries. Advanced training included the extinguishment of a conveyor belt fire in a surface fire gallery. Two teams, each carrying charged waterlines, were escorted into the fire gallery through both doors. These teams controlled the rollback smoke and extinguished 7 to 9-m of burning conveyor belt. Team members indicated that the exercises were extremely beneficial due to the realism of thetraining simulations.

By Robert M. Becker

A thick-wall cylinder solution applicable to the evaluation of anisotropic elastic parameters is derived for the interpretation of stress relief data. For a restricted class of problems, a special relationship among certain orthotropic moduli yields stress distributions for the plane orthotropic problem that are identical to the corresponding isotropic case. A ring or hollow cylinder with these specialized anisotropic properties subjected to uniform radial loads is one of the problems in this class. Consequently, known stress solutions are used to develop the strains and displacements for a specialized orthotropic thick-wall cylinder under uniform pressures. The results are consistent with anisotropic equations used in the evaluation of in situ rock stresses.

Jan 1, 1968

By D. Harrington

"The recent discovery and exploitation of petroleum territory have resulted in the enactment of new petroleum laws in most of the South American Republics. The activities in the discovery of these new fields were engendered by the knowledge of the fact that present producing fields must within well defined periods be exhausted. Oil operators were willing to take the initial steps in exploitation in the absence of legislation that applied strictly to petroleum operations. The enactment of modern legislation in many of these Republics encouraging and protecting exploitations may cause tremendous oil activities in these countries, and the results may be comparable with the magnitude of the undertakings and the prestige of the companies now entering this territory.These, oil fields are admirably located for convenient distribution of petroleum by water to all the Nations using oil as fuel for shipping and industrial concerns. The oil markets of the western coast of South America will derive immense benefits from the Panama Canal. This navigation route brings these markets into direct ocean shipment with the Atlantic coasts of the Western and Eastern Hemispheres.One deterrent to oil production in the Republics of South America is the want of inland. transportation facilities, but the recent laws of these Republics without exception provide for acquiring rights of way for pipe lines and other modes of transportation; and doubtless the great interests and. syndicates already operating in these regions will, as production increases, provide ample pipe line transportation sufficient to convey to the coast the oil produced. It way be assumed, from the legal guarantees afforded, and from operating equipment and machinery that are now being concentrated that refineries will be erected at shipping points for the purpose of making these petroleum products accessible to the world."

Jun 1, 1921

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 Joseph P. Flick, Kathleen M. Kowalski, Lynn L. Rethi, Roberta A. Calhoun

Many miners are involved in tasks at the mine site that are similar to those sub-tasks performed in general construction, maintenance and repair (CMR) type work activities. As a result, many of the injuries in the mining industry today can be traced to employees performing these CMR type work activities. Indeed, a recent analysis of a major aggregate company revealed that 65% of all injuries documented originated from performing such CMR activities. It is hypothesized that the number of injuries to miners performing construction, maintenance and repair (CMR) work activities on mine property may be reduced through improved training that focuses on better hazard recognition using the numerous visual and other cues that are available for evaluating workplace health and safety hazards. To this end, researchers at NIOSH’s Pittsburgh Research Laboratory have merged two proven methods of training miners to recognize hazards, stereoscopic (3-D) slides and the concept of degraded images, into this training program. Stereoscopic (3-D) slides have been shown in earlier NIOSH and U.S. Bureau of Mines research to be an effective training aid for improving the ability of miners to recognize various geologic and mining-induced irregularities that can cause groundfalls.3 They realistically portray the natural mine environment, and thus are an excellent training aid for teaching miners to recognize such visual cues. The degraded image concept, originally developed by the military and used for target detection training, describes scenes where the target is partially hidden by cloud cover, dust, rain, natural barriers, buildings, or other obstructions that can camouflage or confuse the target. Research had shown that flight observers who were trained with less than ideal (or degraded) pictures were more successful in subsequent identification of targets than those trained using ideal (or highlighted) pictures of targets. In order to investigate this concept for training miners to recognize hazards, NIOSH researchers developed a prototype hazard recognition training program using such mining scenes. A control program based on traditional highlighted mining scenes was also developed. Both programs were applied to subjects in a field experiment. Results indicated that miners trained with the degraded images did significantly better on a follow-up test of hazard recognition.4 This hazard recognition program teaches trainees to look for hazards in a more realistic manner than that of the control program. This specific training program for CMR activities involves using the degraded image concept and 3-D slides. The module is designed to educate workers on hazard identification techniques and safe work practices. It focuses on teaching miners techniques for recognizing visual (sight) cues, and then uses these cues to evaluate mining conditions. It should be stressed that other senses, such as sound can also play an important role in hazard detection.

Jan 1, 1999

This Volume documents the Phase 111 effort on the Seismic Detection and Location of Isolated Miners on Contract H0122026 undertaken during the fall of 1972 by a task team composed of ADL staff and several seismic consultants. The team was assembled specifically to work together on complementary tasks, at an accelerated level of effort for four months, to meet the Bureau of Mines' time schedule for obtaining independent, objective, technical judgments regarding seismic methods and systems for detecting and locating isolated miners. The impetus for this work resulted from a compilation and analysis, during the first half of 1972, of new experimental data obtained from a series of in-mine field tests conducted by Westinghouse Corp .+ using the CMRSS* interim seismic location system. The Bureau of Mines took advantage of the availability of these new data to reassess the potential and limitations of various seismic methods and systems, and to direct its seismic system improvement program accordingly. ADL assisted the Bureau in this reassessment by drawing on the skills of seismic consultants from industry, universities and government, to supplement the skills of the ADL project team. The consultants were principal resources of broadly-based and detailed technical expertise in the areas of seismic signal-source and signal-propagation characteristics, natural and cultural seismic noise, seismic sensors and field instrumentation, seismic signal and data processing for detection and location, and overall seismic system utilization in the field under operational emergency conditions. Specifically, the participating consultants were: F. Crowley, Air Force Cambridge Research Laboratories ; W. Dean, Teledyne Geotech, Alexandria Laboratories; R. Greenfield, Pennsylvania State University; J. Kuo, Columbia University; D. Peters and R. Crosson, University of Washington; and F. Pilotte, U.S. VELA Seismological Center. The principal ADL participants were J. Ginty, R. Lagace, M. Roetter, and R. Spencer.

Jan 1, 1974

By Michael D. Fenton

Bauxite resources were primarily in Africa, Asia, Oceania, and South America. Only five countries combined, Australia, Brazil, Guinea, India, and Jamaica, contained most of the total world reserves available for extraction under current economic conditions and accounted for nearly 80 % of world production of bauxite. World bauxite and alumina production declined and prices for smelter-grade alumina remained below the $200/mt level during 1993 because of growing aluminum inventories on international markets and declining worldwide demand. The United States imported bauxite primarily from Australia, Brazil, Guinea, and Jamaica. U.S. alumina plant capacity remained essentially unchanged throughout 1993, but apparent capacity utilization decreased by the close of 1993. Chromium Most of the world's known resources and reserves of chromite are located in India, Kazakhstan, South Africa, and Zimbabwe. India, Kazakhstan, and South Africa accounted for 73 % of world production of chromite. The two largest producers of chromite, Kazakhstan and South Africa, were in the process of major economic and political change during 1993. South Africa's production and exports of chromite continued to fall during 1993, because of weak international demand and a flood of cheap metal from the former U.S.S.R. and China into world markets. Despite a significant increase in production, South Africa's ferrochrome producers continued to operate below capacity in 1993. Prior o the dissolution of the U.S.S.R., Kazakhstan was a major internal supplier of chromite ore to the U.S.S.R. consumer, but subsequent decline in demand led to a downward trend of chromite production in Kazakhstan and increasing exports to Europe during 1992 and 1993. The United States consumed, about 10% of world chromite ore production in various forms of imported materials. The United States imported nearly one-half of its required chromium contained in chromite ore and chromium ferroalloys and metal from South Africa; the remainder was from the minor producers Turkey, Yugoslavia, Zimbabwe, and others.

Jan 1, 1995

By William C. McBee

Prompted by forecasts of a sulfur oversupply, the Bureau of Mines, U.S. Department of the Interior, is conducting research on potentially large-scale uses of this commodity to extend or replace such construction materials as asphalt, cement, and mineral aggregates. Through these efforts, paving materials have been developed in which sulfur replaces up to 50 pct of the asphalt normally present and which can be prepared and placed with existing mixing and paving equipment. Laboratory properties and design methods for this direct mixing process are described along with properties obtained on small-and large-scale field demonstration projects. These properties are compared with those obtained from control materials prepared without sulfur additions. Monitoring for toxic gases during laboratory and commercial mixing and paving operations is discussed also.

Jan 1, 1978

By Robert R. Stein, Roy C. Bartholomae, William W. Aljoe

This Bureau of Mines report describes in detail the design and operation of a test apparatus for measuring the sound power levels of drills used by the mining industry. The two major components of the test apparatus are a computer-controlled automated drill test fixture (ADTF) and a large (45,000-ft3) reverberation chamber that houses the ADTF. Design specifications and performance capabilities of the ADTF and the reverberation room are given. Initial test results for three types of drills--a pneumatic percussion drill, a hydraulic percussion drill, and a pneumatic rotary drill--are given to illustrate the types of experiments that can be conducted with the test appartus.

By C. H. Elder, Fred N. Kissell, S. D. Maksimovic

The Bureau of Mines evaluated the hydraulic stimulation of a gob-degasification borehole to determine if this procedure would aid in degasifying a longwall panel. The stimulated borehole did not degasify the longwall panel as expected either before or after mining of the panel started. It reduced the underground methane emission only 11 pct, considerably less than the reductions effected by two unstimulated boreholes in the same panel. Some probable reasons for the reduced methane flow from the hydraulically stimulated borehole are very low reservoir gas pressure, location of hydraulically stimulated zones within the grouted casing, a casing break caused by lateral shifting, possible vertical movement of rock strata during caving, grouting of a 4-inch pipe blocking three stimulated zones, plasticity of shales, and possible hole damage by swelling of water-sensitive minerals. The borehole was also located between two second-mined areas, which may have allowed partial degasification of the overburden and the coalbed in advance of mining. Finally, a period of 3 months is probably not long enough for the borehole to degasify the overburden before mining.

Jan 1, 1977