Search Documents

By K. Kar, A. Sreeoath, M. Gautam

"This paper presents results of an experimental investigation of the sampling efficiency of a blunt cylindrical sampler oriented with respect to the oncoming flow. The number of particles sampled by the cylindrical blunt sampler and an isokinetic sampler is measured using the TSI Aerodynamic Particle Sizer. A technique is described to conven the ratio of the particles sampled into the sampling efficiency. The experimental data thus obtained is then compared with the impaction model of Vincent and Mark (1982) with the empirical constant determined from our experiment.. The comparison shows excellent agreement for 0° and 90° orientation.1.0 IntroductionCylindrical dust samplers are widely used in practice to determine the concentration of the airborne particulate matter. The sampler is simply a means to collect particles from the ambient, whose concentration is subsequently measured by some size selective techniques. Gravimetric and optical techniques are the two most commonly used methods to measure the particle sizes. While impactors are used in gravimetric analysis, Aerodynamic Particle Sizer, Aerosizer. Electron microscope, Coulter Counter etc. use the optical method to measure the particle sizes. The Aerodynamic Particle Sizer (APS) and the Aerosizer are the new generation devices which employ the time of flight of particles within intersecting laser beams to determine the particle size.The introduction of the sampler in the free stream disturbs the flow pattern due to two distinct actions of the sampler on the fluid stream: one of them results due to the conformity of the flow to the geometry of the circular cylinder and the second one is caused by the flow into the suction orifice. If the sampler performance is determined by the number of particles entering into the sampler inlet relative to the number of particles present in the free stream, then the particle trajectory outside the sampler and into the inlet is the deterministic factor for the sampling efficiency. The particle trajectory inside the sampler is not important in this case."

Nov 1, 1995

By Paul W. Johnson, Ralph C. Kirby, Frank A. Peters

An evaluation is presented for a process designed , on the basis of published work , to extract alumina as potassium alum from clay using sulfuric acid and potassium sulfate . The silica residue is separated by filtration . Ferric iron is reduced to ferrous iron , and the alum is crystallized from the solution , leaving the ferrous iron in solution . The alum crystals are separated from the solution and redissolved for feed to autoclave decomposition . In an autoclave the alum is partly decomposed to a basic alum , recovering five - ninths of the sulfuric acid and two - thirds of the potassium sulfate without using an acid plant . The basic alum is decomposed by calcining , and the potassium sulfate is then removed by washing with water . Operating costs for a plant producing 1,000 tons of alumina a day are estimated at $ 96.15 per ton of alumina . The fixed capital cost is estimated at $ 155 million . This process is not competitive under current economic conditions with the production of alumina from bauxite by the Bayer process . Improvement in leaching , basic alum decomposition , and washing could reduce the costs and improve the product which contains some potassium .

Jan 1, 1963

This summary of State laws on explosives was compiled primarily to ascertain what subjects relating to their control have been acted upon by each State legislature and, in general, how they have been treated. It does not include any legislation passed after 1942, or any proclamations, regulations, or administrative orders. It does not purport or attempt to be authoritative. If any problem arises involving interpretation of the statutes of any particular State, the original source must be consulted for the exact words used by the legislature. This summary, however, will be useful in determining whether relevant statutes exist, and in locating them quickly with a minimum of effort. It will be of value also in comparing statutes in one State with similar statutes in other States to determine what construction has been placed upon them by the courts of these jurisdictions or to contrast the varying provisions of many States upon a similar subject. To make these comparisons easier, the statutory provisions for each State have been grouped under several major topics in outline form. Although this sometimes has resulted in disruption of the continuity of individual acts, the increased general clarity and availability of comparable sections have more than justified the procedure followed.

Jan 1, 1943

By Frederick K. Allgaier

This report presents the final data from a 5-yr Bureau of Mines study designed to determine the surface subsidence characteristics resulting from longwall coal mining in a geologic environment common to the Western United States, It includes a description of the geologic setting of the study site, the mine plan, measurement techniques, and results of the monitoring program. Measured subsidence values were obtained over four adjacent longwall panels- Major subsidence characteristics such as longitudinal and transverse profiles, angles of draw, time-related subsidence development, and critical width are discussed. The maxima subsidence value of 5.8 ft was 68 pct of the mining thickness. The average angle of draw was 30°, Subsidence at the center of the first panel continued for 46 months following undermining. The lengths of the longwall panels precluded a definitive determination of the critical width and maximum possible subsidence.

Jan 1, 1988

By G. A. Smyres

The Bureau of Mines investigated a HCI-02 leaching procedure to recover Cu, Ni, and Co from a low-grade bulk sulfide flotation concentrate prepared from the Duluth gabbro complex. Since the Duluth gabbro complex is the largest known and unexploited Ni resource in the United States, the development of options for extracting the metal values from the flotation concentrate of this domestic resource is necessary. Conditions were determined for producing a pregnant solution low in Fe to facilitate recovery of the metal values. Leaching experiments were conducted at 15 pct solids, 1000 to 1200 C, 0.2 to 0.3 g HCI per gram concentrate in a 50-gal reactor pressurized to 50 pSig with 02. Base metal extractions from the concentrate were, in percent, 90 to 92 Cu, 99 Ni, 97 to 99 Co, and 0.1 .Fe. Precious metals extractions were erratic and unpredictable; at best their extractions were, in percent, 55 Au, 90 Ag, 40 Pt, and 45 Pd. The reaction time at 1200 C was 0.5 h. The use of compressed air instead of 02 as the oxidant was also investigated. Solvent extraction using LIX 622 was used to remove Cu from the pregnant solution. Cementation on Cu was tested for precious metals recovery, while sulfide precipitation was used to produce a Ni-Co product. A conceptual flowsheet for treating the Duluth gabbro concentrate is proposed.

Jan 1, 1985

By L. J. E. Hofer

This Bureau of Mines study, part of a broad program of research in air pollution related to minerals, was conducted to determine the nature and extent of the poisoning of catalysts when used to remove certain air pollutants from exhaust gases. The poisoning examined in this investigation occurs when leaded gasoline is used as a fuel for automotive engines. This research was conducted in cooperation with the Public Health Service. The smog in the Los Angeles area is attributed to the effect of radiant energy on the mixture of hydrocarbons and nitrogen oxides found in the atmosphere there. A large portion of the hydrocarbons is believed to originate in the exhaust gases of automobiles. To prevent the escape of these hydrocarbons into the atmosphere catalytic mufflers have been proposed. In principle, these are simple and nonmechanical, consisting of a vessel charged with a catalyst capable of destroying the exhaust hydrocarbons by catalyzing their oxidation. However, these catalysts are severely affected by the particulate matter, mainly in the form of lead sulfate (PbS04), lead oxysulfate (PbS04.Pb0), and Lead chlorobromide (Pb(Cl,Br)2), contained in the exhaust gas. Deposition of lead on the catalyst as PbS04, PbS04, PbS0, and Pb(Cl,Br)2 restricts catalytic activity. As a result,after 20,000 miles of operation the temperature necessary to achieve 50-percent conversion of isopentane in a mixture of 0.2 percent isopentane, 2 percent carbon monoxide and 4 percent oxygen, and the balance nitrogen at 10,000 hourly space velocity has risen from 400° C. to 500° C. even with a catalyst taken from the exit portion of the catalyst bed. The rest of the catalyst was more severely affected. Therefore, it would appear that operation for 20,000 miles is near the limit for a catalyst.

Jan 1, 1963

By Jay F. Colinet

Longwall mining in lower seam heights may necessitate the use of single-drum shearers to overcome size constraints associated with standard double-drum shearers. To avoid the operational problem of clearance in the tailgate entry with one single-drum shearer, two single-drum machines can be operated on the same face, with each shearer responsible for mining a predefined portion of the face. However, utilization of two shearers on the same face necessitates the positioning of one shearer operator and a jacksetter in the return air of the upwind shearer, thus complicating respirable dust control on the longwall. In an effort to evaluate the unique dust control problems associated with this type of mining, the U.S. Bureau of Mines conducted dust surveys on two multiple-machine longwall operations. Sampling was done to quantify major sources of respirable dust and to identify potential solutions to problem areas. Sampling results indicate that the cutting sequences utilized on multiple-machine faces may have to be designed to minimize dust exposure, as opposed to optimizing productivity or facilitating operational requirements. Also, state-of-the-art dust control techniques typically found on double-drum shearer longwalls must be employed to help minimize the exposure of all face personnel to traditional dust sources.

Jan 1, 2010

Watershed Jll in Jefferson County, Ohio we instrumented in 1977 as one of three watersheds established for the purpose of investigating surface mining and reclamation effects upon local hydrology, sediment discharge, and sediment and water quality. Each watershed was less than 50-acres in size, and was in a different geologic setting within southeastern Ohio. Surface runoff and ground¬water levels were monitored. Samples were taken for sediment determination and chemical analysis prior to mining. Monitoring and sampling continued through the period of watershed disturbance caused by mining and reclamation activities, which began in May 1980 at Watershed Jll. A psuedo-postreclamation period followed the initial cessation of man-machine activity on the watershed. A second reclamation effort occurred in the fall of 1981 and was to be followed by a third in 1982 after observations ceased. A true final postreclamation period was not monitored at this site, because the erosion control practice (terrace diversions) failed after each reclamation. Watershed Jll was a small pasture and wooded watershed with sandstone and shale above the mined coal seam prior to mining. A clay layer under the coal supported a perched saturated zone, termed the top aquifer for convenience. A lower underclay supported a second saturated zone called the middle aquifer. A lower perched aquifer had been dewatered by previous deep mining. After about three years of premine data and about two and one-half years of mining reclamation and psuedo-postreclamation data, the following general observations may be made: 1. The mining-reclamation phase was very short, and the postmining period was characterized by erosion failures and remedial disturbances that kept the watershed condition and size in a state of change. It was impossible to collect sufficient data to confidently characterize the hydrologic-sediment-chemical aspects of the mining period or of a postreclamation period and, most importantly, of the future watershed after its various properties and characteristics have ceased adjusting to its severe disturbance and reconstitution. 2. A seeding of wheat followed by grasses and legumes was not a particularly successful reclamation practice in terms of stabilizing the new soil. Numerous rills and small gullies developed in spite of installed diversions. 3. Storm runoff rates and yields at the watershed outlet increased from the premine, (phase 1) to the mining-reclamation (Phase 2) periods, and remained at or near the Phase 2 level through the postreclamation (Phase 3a) period. 4. The top aquifer changed in physical and chemical character as a result of mining and was becoming reestablished as the project drew to a close; but it is impossible to predict its final configuration or character. 5. Dewatering of the top aquifer resulted in a complete cessation of baseflow because the middle aquifer water table lay below the elevation of the watershed outlet. 6. The top and middle aquifers were merged in one area of the watershed where the upper coal underclay was disturbed. 7. Failure of the diversion terraces and their outlet obscured the effects of the reclamation practice upon sediment concentration and yields. There was little difference in sediment concentrations between Phases 2 and 3a. 8. Drinking water standards were met by surface waters throughout the period of observation except for two samples that exceeded the nitrate-N allowable level of 10 mg/l. 9. In all Phase 3 surface-water samples, iron concentrations were within the limits established by OSM, and manganese concentrations exceeded the regulation level only once. pH fell below the lower regulation level of 6.0 between 10% and 20% of the time. 10. The chemical quality of sediments was generally about the same after reclamation as before mining, with the exception of organic carbon, which decreased.

Jan 1, 1983

By Paul T. Allsman

This paper describes metal- mining practices at the Harrington -Hickory lead - silver - zinc mine at Milford , Beaver County , Utah . The operations of the Harrington-Hickory incorporate a number of features that should prove of interest and value to other operators of small mines . These features include employee participation in profits , a well- laid -out electrical system, adequate financing , a well - balanced equipment and supply inventory , a well - organized system of bookkeeping , adequate roads , and good management . As crude ore is shipped directly to smelters and mills in the Salt Lake Valley , close attention is paid to see that the ore is segregated by classes and treated where it can bring the greatest not return . A combination of these features has resulted in maintaining relatively low costs, considering the grade and size of ore shoots at a time , during and following the war , when equipment , supplies , and labor were costly and difficult to obtain . The period covered in this report includes two war years and two years following , from April 1, 1944 to June 30 , 1947 .

Apr 1, 1949

1. A total of 14,413 mining operations reported employment to the Mine Safety and Health Administration (MSHA). Nearly half (48.9%) were sand and gravel operations, followed by stone (28.5%), coal (14.7%), nonmetal (5.7%), and metal mines (2.1%). 2. Mine operators reported 240,000 full-time equivalent workers1 (down 3.9% from 1999). Independent contractors reported 42,000 full-time equivalent workers working on mine property (up 8.6% from 1999). Coal operators accounted for 26.8% of reported employee hours, followed by stone operators (25.9%) and sand and gravel operators (12.1%). 3. Eighty-four (84) work-related mine fatalities occurred in 2000 compared to 90 the year before. •The mine fatality rate was 29.8 per 100,000 full-time equivalent workers compared to a fatality rate of4.6 per 100,000 employees for all private industry. •Thirty-one percent (31%) of the fatalities occurred in underground work areas, which account for only17% of total employment. •Although the largest number of fatalities (28) occurred among miners who work for coal operators, coal contractor employees had the highest fatality rate (61.1 per 100,000 full-time equivalent workers). 4.There were 10,839 nonfatal lost-time injuries reported to MSHA, occurring at a rate of 3.8 injuries per 100full-time equivalent workers, and resulting in a total of 417,918 lost workdays.2 •Among all employees,3 the highest injury rate occurred among coal operator employees (5.6 nonfatal injuries per 100 full-time equivalent workers). •The highest percentage (34.7%) of nonfatal lost-time injuries were due to handling materials (e.g., over-exertion in lifting, pulling, or pushing objects), which also accounted for the greatest percentage of lost workdays (29.3%). •Among the most frequently occurring injuries, the most severe (as measured by the median number of days lost) were associated with accidents involving falls of ground, the use of powered haulage, and slips or falls. •The most frequently reported part of the body injured was the back (22.9% of all injuries). Back injuries accounted for the highest percentage of lost workdays (21.6%). 5.Seven hundred sixty-seven (767) cases of occupational illness were reported to MSHA. •The most frequently reported illness was repetitive trauma, resulting in joint, tendon, or muscle inflammation or irritation (37.3%). •There were 155 (20.2%) illnesses reported as hearing loss. The majority (68.4%) of hearing loss cases occurred among surface workers. •Coal workers' pneumoconiosis accounted for 14.5% of reported illnesses.

May 15, 2002

By T. L. Johnston

A review of technical literature of the last quarter century discloses that much experimental work has been carried on in an effort to develop commercial processes for making sponge iron. In addition to the work that has been recorded, other work has been done the results of which have not been published. The degree of success or failure of these investigators does not detract from the fact that the problem has its challenging aspects and practical possibilities that encourage further investigation. The purpose of this report is to record information derived from recent experimental work that .had its 'objective the development and demonstration of one method of producing sponge iron. Work of other investigators was studied and applied wherever possible.

Jan 1, 1948

By Robert J. Evans

The monorail bridge conveyor (MBC) is a prototype continuous face haulage system that was surface tested and evaluated by the Bureau of Mines. The MBC consists of a series of cascading belt bridge conveyors suspended from roof-supported monorail track. Tests were conducted to determine MBC haulage capability, maneuverability, power consumption, and reliability using rigid and chain-suspended monorail track installations. Subsequent modifications to improve operation and reliability made during surface testing are described. Mining plans were devised to show potential MBC installations for room-and-pillar, longwall development, and shortwall mining sections. Compatibility tests were conducted with the Bureau's prototype hopper-feeder, to provide additional surge capacity and lump-breaking capability. Results from the surface test program, along with modifications to improve system operation and reliability, indicate that the MBC has the potential to perform success- fully in an in-mine trial.

Jan 1, 1987

By W. W. Adams

Lower accident rates were the outstanding feature. of the second annual sand and gravel safety competition conducted in 1930 by the United States Bureau of Mines in cooperation with the National Sand and Gravel Association. Both the frequency and, severity rates for accidents were greatly reduced as compared with those shown by the first year's contest, that for 1929. Three times as many plants were enrolled, and the number of man-hours of work represented wad more than doubled. Seventy-six sand-and-gravel plants, situated in 20 States, participated in the competition, as compared with 26 plants, located in 13 States, in the year before. The number of man-hours of employment, which indicated the amount of exposure to occupational hazards, was 4,915,592 an increase of more than 100 per cent over, the previous year's total of 2.259,572 hours. The frequents of accidents declined from 74.4 per million hours for all plants enrolled in the first year's contest to 42.7 per million man-hours for all plants enrolled in 1930. The accident-severity rate was reduced from 9.7 days of disability per thousand man-hours of exposure in 1929 to 5.9 days of disability per thousand man-hours of exposure in 1930.

Jan 1, 1931

By F. E. Block, T. T. Campbell, D. Z. Hobbs

Several methods were investigated for the preparation of high- purity elemental boron in an attempt to develop a feasible process for producing boron on a large scale . In the work described in this report , the metal was prepared by metering boron trichloride gas into a crucible containing molten metal reductants . It was necessary to remove reaction byproducts by acid and aqueous leaching . Magnesium and sodium were tested as reductants , but best results were achieved using lithium or zinc as reductants . Contaminants originating from the materials of construction were the chief impurities in boron made by this method . Impurities ranged from 0.5 to 5.0 percent . Impure boron ( 85 to 90 percent ) was also prepared by the magnesium reduction of boron trioxide in a thermite - type reaction . This product contained magnesium as the chief contaminant . Impure boron made in this way could be upgraded by fusing with potassium fluoborate or potassium acid fluoride . After acid leaching the fusion cake , a product containing 95 to 97 percent boron was obtained . Analytical techniques for accurate determination of impurities in elemental boron are a major problem , requiring solution before a valid comparison can be made of the quality of boron prepared by these various methods .

Jan 1, 1964

By G. H. West, R. L. Sebastian, W. A. Darror

"This bibliography was compiled in the course of research work by the Bureau of Mines on the utilization of magnesites in the West. The results of the research will appear as a bulletin of the Bureau.1. ANALYTICAL METHODS. 11 Knight, X. and Wheeler, W.H. Proc. Iowa Acad. Sci., 13, 1907, 167 (C.A.1, 1370). Describes experience in analysing calcite and dolomite. Reports great excess of oxalate unnecessary and separation of sulphates by alcohol is best.2 Meyerhofer, J. Zeit, Angew. Chem., 21, 1908, 592. Direct determination of Mg as phosphate after removal of SiC2, by keeping R203 in solution with ammonium citrate.3 Merckschen Guano Phosphat Werke. Chem. Ztg., 33, 1909, 545 (C.A. 3, 2281). volumetric analytical methods.4 Popel, M. Zeit. Angew. Chem., 21, 1908. 2082 (C.A, 6, 412). Determination of CaO in presence of CaC03.5 Blasdale, W.C. Jour. Am. Chem. Soc., 31, 1909, 91? (C.A. 3, 2658). Studies of separation of Ca from Mg.6 Hundeshrgen, F. Zeit. Offent. Chem., 15, 1909, 85 (C.A. 3, 1853). Valua¬tion of caustic magnesia by analysis. Volumetric methods.7 Frerichs, H. and Krosberg, W. Apoth. Zeit., 24, 1909. 679 (C.A. 3, 2996). Tecting magnesia alba for Fe.8 Schoorl, N. Zeit. Anal, Chem., 48, 1009, 593 (C.A. 4, 5E9). Microchemical tests for Mg, Li, K. and Na.9 Heyer. Chew. 2Ag., 33, 1009, 1157 (C.A. 4, 1588). Determination of CaO in presence of CaCO3. CaCO3 in soluble in cold neutral solution of NH3 salts. Solubility Is diminished by free NH4OH."

Oct 1, 1923

By R. Hogg

"The basic population balance models for agglomeration processes are reviewed and procedures are described for extending their applicability to systems with size-dependent rate constants and to the formation and growth of porous agglomerates from rigid, solid particles. Simplified procedures for the further extension of the models to include simultaneous agglomerate growth and breakage arc also described. IntroductionThe association of small particles into clusters or agglomerates is a significant factor in many facets of particle processing. Agglomeration processes are widely used to facilitate handling, storage and utilization of fine powders. Processes such as coagulation or flocculation are used to aid solid-fluid separation in dispersed particulate systems. Agglomeration also occurs as an accompaniment, often unwanted, to other particulate processing operations such as fine grinding, mixing and blending, transport and flow.Reliable agglomeration models are needed for improved understanding of the processes in general and of the complex role of numerous, interacting variables as well as for direct application to the design and control of industrial processes such as flocculation, granulation and pelletization. Ideally, the models should account for the primary forces responsible for agglomerate ·formation and growth, the effects of external forces on process dynamics, the development of agglomerate structure and its role in the process itself, and the effects of concurrent processes such as structure modification (e.g. compaction) and agglomerate breakage or degradation.In its most general form, the process of agglomeration involves taking discrete, independent particles, bringing them into contact with one another, promoting (or allowing) interparticle adhesion to occur and then causing structure rearrangement, usually under the action of external forces. The relative importance of these steps varies with the nature of the particulate system being agglomerated and with the kinds of agglomerates being produced. Coagulation or flocculation of particles dispersed in fluids is generally dominated by the contact and adhesion steps. In the granulation of powders, on the other hand, particles are already in contact so that structure rearrangement is the principal step."

Mar 1, 1992

By J. Roger Loebenstein

This report presents a U.S. Bureau of Mines study of the flow of arsenic-containing materials in the United States, based on the best data available in 1991, includes a consideration of arsenic as a byproduct of the processing of nonferrous metals, the fate of arsenic in manufacturing wastes, the quantity of arsenic used in products, tile fate of arsenic in dissipative uses, and the useful life of discarded products. Where possible, estimates are given of the amounts of arsenic lost from the materials flow. Arsenic byproduct of mining nonferrous metals. Historically, most U.S. production has been from the states of Montana, Washington, and Utah. The smelters in these states are believed to be the areas of the country where arsenic is most concentrated in the soil, tailings ponds, and waste dumps. Since the closure of the last domestic producer of arsenic in 1985, all arsenic has been derived from imported sources. Historically, arsenic was important in agricultural applications as an insecticide, herbicide, and cotton desiccant. As the environmental movement gained momentum and the toxicity of arsenic became better understood, most of the agricultural uses for arsenic were banned. Beginning about 1975, the use of arsenic as a wood preservative began to grow. After 1980, wood preservative uses became more important than agricultural applications. By 1990, 70% of the arsenic consumed in the United States was used by the wood preservative industry and 20% by the agricultural industry. The major source of domestic arsenic emissions in 1989 was from the U.S. copper processing indus¬try. About 7,800 mt/yr of arsenic was discarded in leach dumps, tailings, and slag. Another 800 mt/yr was liberated to the atmosphere and 1/100 mt/yr was exported in copper concentrates. On the consumption side, 9,200 mt/yr was lost, mostly from dissipative agricultural uses and the disposal of obsolete arsenical products.

Jan 1, 1994

By W. A. Dunkley

During the past year and a half the Western United Corporation of Aurora , Illinois , has been distributing carburetted water ges from its Lockport , Ill . , plant , to an extensive territory , under an initial pressure ranging up to 90 lb.. per sq. in . The most distant distributing point on the system is at Harvard , Ill . , about 35 miles from the plant.. The territory supplied is approximately 85 miles long and 35 miles wide , the total mileage of rains being 1223 , or approximately 24 per cent of all the gas trains in Illinois outside the city of Chicago .

Feb 1, 1923

By B. H. Eccleston, R. F. Kendall, D. E. Hirsch, Norman G. Foster

The mass spectra of 23 alkylthiophenes are presented , including 21 that have not been previously reported . Correlations between mass spectra and the structure of the thiophene homologs are discussed . Comparisons with , and corroboration of , earlier workers ' correlations and predictions are made . Several additional correlations are reported to enable the spectroscopist to identify the substituents on alkyl - substituted thiophenes , and the relationship of the mono - substituted and 2,5 - disubstituted alkylthiophenes is discussed in detail .

Jan 1, 1964

By Maureen M. Foss

Underground coal mining is hazardous due to changing geological conditions. One geophysical method showing promise for in-seam hazard detection is ground-penetrating radar (GPR). The Bureau of Mines recently completed preliminary studies to demonstrate the feasibility of using GPR for in-seam hazard detection. Investigations included air and coal tests for the purpose of checking equipment accuracy, coal penetration, and other factors such as the effects of receiver orientation. Further investigations involved using both a short pulse and a new prototype synthetic-pulse system to locate a clay vein in a coal seam using trans-illumination. Data were gathered on multiple travel paths, and a back projection processing technique was then used to create a tomographic image using the calculated velocities. A computer model of the same coal seam was subsequently processed using the same tomographic tech-nique, and the results were compared with those of the actual data. Analysis of the tomographic images shows the presence of the clay vein, although its boundaries are unclear due to the tomography method used. Results of these preliminary studies show that GPR is feasible for use in in-seam hazard detection and point the direction that future research should take. A need has been shown for research involving more sophisticated tomography techniques, transmission studies on thicker coal seams, and reflection studies using the synthetic-pulse system.

Jan 1, 1987