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By David C. Peters, Robert S. Crosson

A method of error analysis has been applied to the location technique of non-linear least squares iterative inversion in order to evaluate the resolving power of several seismic array configurations with various assumed earth models and errors and inaccuracies in arrival times. The results obtained demonstrate that lateral accuracies of location are improved significantly when the depth of the miner is known. Lateral location to within 100 feet appears achievable in many instances. If it is possible to refine earth models significantly beyond what has normally been assumed in this work by the use of on-site data, or if the mine is shallow (300 feet or less), accuracies of-about 30 feet or so may be attainable. Inaccuracies in earth models of about 5% are found to contribute much more heavily to these location inaccuracies than errors of a few milliseconds in picking arrival times; however, arrival time errors of 15-20 ms or above will dominate these model inaccuracies. The expected accuracy of location is found to fall off very rapidly as the miner moves outside the array. The strength of this effect depends markedly upon the geometry of the array configuration and can be reduced by careful design. Also, as the size of the array is increased, expected location errors within the array are not altered much, but continue to match the error associated with the smaller array over a larger area (assuming that all stations can still pick up the miner's signals). Better location accuracy, especially with respect to depth control is achievable in an earth where the velocity is depth-dependent (increasing with depth) than in one which is homogeneous. This is an advantage since the

Jan 1, 1974

By J. Burlin Johnson

In small-scale blasting experiments conducted in the Bureau of Mines laboratory, small charges were used to produce craters in blocks of concrete mortar. The results are compared with larger scale experiments of other research workers, and the comparison demonstrates the similarity of the results obtained and indicates that small-scale blasting should be a useful tool for predicting large-scale blasting effects. INTRODUCTION The purpose at this investigation was to conduct blasting experiments in mortar in the laboratory and then, by comparing the results with those from larger scale field blasts in rock to determine to what extent, if any, the laboratory results resemble those in the field. The work described herein was the initial phase of a project aimed at evaluating small-scale blasting as a tool for use in improving blasting techniques. It is evident from the stand-point of control and cost that small-scale blasting would be valuable in the study of rock fragmentation by blasting in mines and quarries, if the extrapolation is valid.

Jan 1, 1962

By Robert C. Steckley

The Bureau of Mines performed a fragmentation experiment in cooperation with Duval Corporation in a porphyry copper-molybdenum deposit near the Sierrita pit south of Tucson, Ariz. This experiment evaluated the fragmentation created in a 10-hole test blast having blasthole spacings of 25, 20, and 15 feet. The 10 blastholes were 9 inches in diameter and contained a total of 17,400 pounds of aluminized slurry blasting agent in 50-foot columns with 60 feet of stemming. Diamond drill core examination was the primary method used to determine the condition of the rock before and after blasting. These core examinations included study of length recovery, rock quality designation (RQD), weight recovery, and size distribution. Topographic surveys were used to measure the rock swell produced by the blast and a fragment size distribution was obtained for the broken material on the surface. Fragmentation to depths of 110 feet was excellent from the 15-to 20-foot blasthole spacing patterns. Good breakage was also produced by the 25-foot pattern although the effects of the blast were not so obvious. In situ leaching tests were not conducted. However, based only on size consideration, all three blasting patterns produced adequate breakage for successful leaching.

Jan 1, 1975

By A. J. Miscoe, W. M. McKewan

A unique machine for inducing bending fatigue in wire ropes was built at the U.S. Bureau of Mimes' Pittsburgh Research Center. This machine can produce nine levels of degradation through repetitive cycling of long samples of wire ropes of the types used in the mining industry. This report provides an analysis of the results of the first wire rope to be fatigued on this machine. These results have indicated that as a wire rope accumulates bending cycles, its strength first decreases because of wear and then in- creases due to cold working of the wires. As the amount of cold working increases, more and more of the embrittled wires break and the strength of the rope decreases rapidly. In this test, application of several of the regulatory retirement criteria to various sections of the rope suggests that there may be some inconsistency among them.

Jan 1, 1993

By L. A. Neumeier

The Bureau of Mines evaluated creep and other properties of extruded Zn-30 pct-AI alloys containing 0 to 0.7 pct Mg. The alloys were extruded both above and below the Zn-Al eutectoid temperature of 275° C. Creep behavior is defined for the alloys as extruded and after various heat treatments. Tensile properties, hardness, thermal expansivity, impact resistance, and microstructures are given. The alloys, either with or without magnesium, required substantially less pressure for extrusion near 275° C than at higher or lower temperatures. The alloys containing magnesium exhibited significantly greater hardness, tensile strength, and creep resistance, but much lower ductility than the 2n-30 pct Al alloy. The properties were very sensitive to the processing conditions.

Jan 1, 1971

By Larry G. Stolarczyk

This report deals with information regarding a new Medium Frequency (MF) Wireless Communication System for underground mines. This new telecommunication system works on low loss electromagnetic wave propagation modes which allow it to provide quality radio communications almost anywhere in a mine. Tests show the MF system can provide improved safety and managerial control, increased productivity, better organizational team-work and reduced maintenance cost; furthermore, MF's unique design allows for easy installation at a minimum cost. This paper covers the following: 1) MF design plan, 2) Overview of mine radio communications systems, 3) Preparations needed for designing an MF system, 4) MF equipment, 5) MF installation, 6) MF design considerations, 7) MF design specifica¬tions, and 8) Recommendations dealing with MF system. Experiments in four mines are illustrated to demonstrate the success and via¬bility of the MF system. The mines range from small (500 tons/day) to large (67,000 tons/day) capacity and represent several different mining methods. The MF Wireless Communication System represents an advancement in mining communication and the groundwork for other advanced mine systems.

Jan 9, 1984

By Ivan F. Avery

DOMEST1C production of carbon black in 1963, remained at about the same level as in 1962. Carbon black produced by the furnace process increased 2 percent to 1,880 million pounds in 1963 and accounted for 91 percent of the total output. Channel black production continued to decline and was 14 percent less than a year ago. Shipments during 1963 totaled 2,098 million pounds, a 1 percent increase for the year. An increase of 88 million pounds in domestic sales was partially offset by a decrease of 72 million pounds in carbon black exports. Total value of carbon black production in 1963 was $148 million. The average value per pound was 7.18 cents or 0.12 cent per pound more than in 1962.

Jan 1, 1964

By Leon W. Dupuy

"INTRODUCTION Scheelite occurring in tactite at the Black Rock tungsten mine, near Benton in Mono County, Calif., was investigated by the Bureau of Mines in cooperation with the Geological Survey as part of their search for additional sources of supply of strategic minerals authorized under the Strategic Materials Act. 3/4/The work accomplished by the Bureau, and the assays of samples taken are described in this manuscript. The ore found aided materially in prolonging the operating life of the mine during the recent national emergency, supplying much-needed tungsten for war use. ACKNOWLEDGMENTSIn its program of investigations of mineral deposits, the Bureau of Mines has as its primary objective the more efficient utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. The Mining Division, under the direction of Lowell B. Moon, chief, conducts preliminary examinations, performs the actual development work, and prepares the final report. The Metallurgical Division, under the direction of C. C. Ralston, chief, analyzes samples and performs beneficiatibn tests."

Mar 1, 1948

By David C. Byrne

From an engineering perspective an ideal industrial noise control solution focuses directly on the actual source of the poise. Eliminating the noise-generating mechanism altogether obviates the need for other noise contra l treatments or hearing protection devices. However, in cases where attenuating the source is not feasible engineering controls must be oriented toward blocking the path that the sound waves travel toward employees. Acoustical enclosures are commonly used as sound path treatments to contain the noise from a machine: alternatively a control room/booth or equipment operator's cab may be used to isolate the worker from the noise. Anyone who has successfully used acoustical enclosures knows that the design procurement, and installation process is deceptively simple. Alt too often First-time efforts fait to account for many of the constraints that can render the enclosure essentially useless. Things that cannot be overlooked include: providing convenient worker access (physical and visual): allowing for proper machine operation/product flow; and supplying fresh air or preventing undue heat or contaminate build-up inside the enclosure. All of these factors must be given careful consideration, otherwise the enclosure will not perform adequately.

By Carl Rampacek

Recent research by the Bureau of Mines has demonstrated that the segregation process has merit for treating oxidized and mixed oxide-sulfide copper ores. The process comprises heating the crushed ore with salt and coke or other carbonaceous materials at about 700° C. to produce fine flake copper, which then is recovered by conventional copper-flotation methods. Bench-scale laboratory tests of a number of oxidized and mixed copper ores assaying 0.78 to 5 percent Cu gave copper recoveries of 73 to 96 percent. The flotation concentrates assayed 21 to 76 percent Cu, depending on the ore being treated.

Jan 1, 1959

By P. Coleman, J. C. Kerkering, S. Iverson

Fault tree analysis is a systematic safety analysis tool that proceeds deductively from the occurrence of an undesired event (accident) to the identification of the root causes of that event. One recurring mine safety problem—a dozer falling into a void over a drawpoint on a coal surge pile—was analyzed using available, inexpensive fault tree programs on a personal computer. The analysis identified basic and intermediate events that led to the burial of the dozer and graphically depicted the interrelationship between these various subordinate events as well as the various chain of events leading up to the primary event. A sensitivity analysis on these probabilities showed which events had the greatest influence on dozer burial in a coal surge pile.

By R. Craig Smith

The Bureau of Mines conducted a study of production costs for the secondary lead industry and determined costs for present, pending, and proposed environmental legislation. Operating costs for smelters by capacity groups range from 16.8 to 19.6 ¢!lb of refined lead. Present regulatory compliance costs for these groups range from 2.2 to 2.4 ¢!lb. Pending compliance costs could add 3.5 ¢!lb of refined lead, and proposed regulations could add another 1.3 ¢!lb. The individual capital costs necessary to comply with pending environmental regulations are estimated to be $1.8 million for small smelters and $10.4 million for large smelters. Proposed regulations could require additional expenditures from $1.9 million for small smelters to $4.9 million for large smelters. These cost estimates, based on average 1985 dollars, indicate that pending and proposed legislation could add significantly to capital and operating costs of the secondary lead industry. These regulatory compliance costs may result in a loss of up to 40 pet of secondary lead production capacity.

Jan 1, 1987

By J. H. Weber

This Bureau of Mines publication describes the hardware system and software package for the semiautomatic acquisition and automatic processing of high-resolution mass spectrographic plates. The semiautomatic data acquisition allows a tenfold saving of time compared with manual data acquisition. Automatic processing of the high-resolution data to yield exact masses, intensity, and the corresponding empirical formulas is accomplished by efficient programming on a small, inexpensive, programmable calculator system.

Jan 1, 1974

By Joseph A. Perry

One goal of the Bureau of Mines is to develop technology tp insure a dependable supply of minerals to the United States. To support this goal, the Bureau's Albany Research Center has modified a commercial atomic absorption spectrophotometer to rapidly determine trace levels of mercury by cold-vapor atomic absorption spectrophotometry. Such diverse materials as ores, mill products, stream water, sediments, and flue dust have been analyzed. A very high dynamic range of 0.2 ng/ml to 1 µg/ml of mercury in solutions is routinely analyzed by this instrument.

Jan 1, 1981

By D. S. Kimmel

The Bureau of Mines sponsored development of a system to remotely energize and de-energize the trolley wire in a section in response to demands from vehicles as they enter and leave the controlled section. The system developed utilizes a detector/actuator that controls a dc contactor at the outby end, and a 3 kHz oscillator at the inby end. A prototype system has been built and installed at the Bureau's trolley test site at Bruceton, Pennsylvania which has demonstrated the ability to also provide load discrimination for faults of 300 amperes or more. The system could readily be modified by locating the oscillator on the vehicle to provide automatic de-energizing of the trolley wire when the vehicle's pole is removed or the vehicle leaves the section.

Jan 1, 1978

By W. E. Wallace, B. L. Razzaboni, P. Bolsaitis, M. J. Keane

"Therma1 and chemical treatment of respirable size silica dusts samples is shown to induce marked changes in their hemolytic activity. The cytotoxicity of crystalline a-quartz (Min-U-Sil), and fumed silica (Cab-0- Sil) particles, as measured by a hemolytic activity protocol, is decreased by calcination and can be related to the dehydroxylation of the surface. The hemolytic activity of P-cristobalite particles of respirable dust si7.e was also determined and found to be lower than that of a-quartz. The change in the surface structure resulting from thermal treatment is detectable by photo-acoustic infrared spectroscopy and zeta-potential measurements. The absorption band in the 3200-4000 cm-1 frequency region of both Cab-0-Sil and MinU- Sil disappears upon heat treatment while a sharp band, identified with single silanol groups, at 3750 cm-1 increases in intensity. The zeta potential-pH profile, in the pH range of 4.0-7 .0, of the calcined, siloxane surfaced particles is more negative than that of material with a silanol surface.The cytotoxicity of the crystalline and fumed silica dusts was also found to be strongly dependent on particle size. Fumed silica of large surface area (small particle size) exhibits an initial increase in hemolytic activity upon calcination. This result confirms other experimental observations pointing to a particle size of maximum toxicity. INTRODOCTIONThe toxicity of silica and other mineral particles, as manifested by their role in inducing pneumoconiosis, fibrosis, silicosis and other pulmonary disorders is largely traceable to the characteristics of particle surfaces and to particle morphology. The great wealth of data on the physical and chemical properties of silica is still insufficient for a comprehensive understanding of the specific parameters to be associated with fibrogenic activity and, correspondingly, with the optimum means for characterizing and quantifying the toxicity of dusts, and the design of possible preventive or therapeutic methods.The great diversity of parameters that have been proposed and tested for correlation with cytotoxicity suggest that more than one mechanism may be involved in the fibrotic activity of silica particles. The crystalline structure of the material (more active tridymite versus less active crisobalite and passive stishovite), freshly formed surfaces and free radicals associated therewith, silicic acid adsorbed onto silica surfaces, the concentration of hydroxyl groups at silica surfaces, particle size and morphology, among other properties, have been investigated and found to conelate in tests of cytotoxicity."

Jan 1, 1990

By L. J. Douglas, A. G. Kim

Methane and other hydrocarbon gases, byproducts of coalification, are emitted from coal at widely varying rates and often present ventilation problems during mining. The air in some coal mines apparently contains no methane. To determine if coals from mines which had no history of detectable gas emission contained adsorbed methane, samples of coal at the shaft bottom and at an active face were obtained and placed in sealed metal cylinders. The atmosphere around the coal was sampled and analysed by gas chromatography. Methane, ethane, ethylene, propane, propylene, and butane were found to have been desorbed from these coals. Hydrogen and helium were also detected. An estimate of the amount of residual gas per ton of coal indicated that coal samples from the active face generally contained more adsorbed gas than coal samples obtained from the shaft bottom, although in both instances the total amount of gas was relatively small.

Jan 1, 1973

By R. S. James, E. J. Gleim

Not long after electrically driven equipment was introduced into coal mines it became apparent that the spark-producing parts, such as controllers and motors, required safeguards to prevent the ignition of mine gas that might come into their vicinity. Many of the early designs attempted to provide protective enclosures having ventila¬tion and relief for pressures if ignition should occur within. The principal feature of the Davy safety lamp, namely, the wire gauze, was employed widely for this purpose. Other devices were developed to reduce the temperature of products of combustion escaping through the protected openings to a value below that which would cause ignition of surrounding explosive atmospheres. Although many such devices performed their intended function satisfactorily under laboratory conditions they were not so satisfac¬tory when subjected to the rigorous conditions encountered under¬ground. Corrosion, mishandling, and accumulations of grease and dirt reduced or destroyed their protective qualities after a period of service in the mines. In the United States this has led to abandon¬ment of special devices in favor of what is called " total enclosure " which means that no regular provision is made for ventilation and release of pressure but rather that the housings or enclosures are built strong enough to withstand the explosion pressures without rupture. As a further protection the joints usually are made of broad, closely fitting surfaces. It is impractical to make such joints absolutely gastight in ordinary machine practice when provision must be made for partial or complete disassembly to facilitate ad¬justments and repairs. Therefore, when an explosion occurs within such enclosures flames may escape through the joints. If the latter are broad enough and not separated too widely, however, the flames will be cooled by contact with the metal surfaces (flanges) of the joints, by rapid expansion, or by both cooling and expansion, with the result that an explosive atmosphere surrounding the enclosure will not be ignited. This is termed " flange protection." In testing parts of cutting machines and other equipment for coal mines, with the ultimate object of approving the equipment for use

Jan 1, 1935

By L. A. Neumeier

The Bureau of Mines evaluated the properties and anisotropy in properties of rolled Zn-Ti and Zn-1.0 wt pct Cu-Ti alloys containing up to 0.36 wt pct Ti. Finish rolling was at varied temperatures to total reductions as high as 92 pct. Alloy properties are very sensitive to various combinations of composition, rolling temperature, and reduction. Properly rolled Zn-1.0 Cu-Ti alloys are superior in strength to Zn-Ti alloys. Conditions are described that lead to best tensile properties. Creep resistance for Zn-Ti alloys decreases with increased rolling temperature when finish rolled to 92-pct total reduction: but not when finish rolled to 33- or 67-pct reduction. Creep resistance for 7n-1.0 Cu-Ti alloys improves with increased rolling temperature to about 480° F. Heavily cold-rolled Zn-1.0 Cu-Ti alloys have fine grain sizes and poor hardness, tensile, and creep properties, but high ductility. Thermal expansivity is markedly affected by the copper addition. Data show the anisotropy of tensile, creep, and thermal expansivity properties. Large idiomorphic crystallites of TiZn15 appear in both Zn-Ti and Zn-Cu-Ti alloys when more than about 0.2 pct Ti is present. A new Zn-Cu-Ti intermediate phase was also identified. Empirical equations are presented relating creep rates with major process variables.

Jan 1, 1971

By Raymond B. Ladoo

"The increasing realization of the fire hazards involved in the use of wooden shingles caused the National Lumber Manufacturers' Association to beginsome five years ago a search for a suitable fire-resistant paint. The problem was submitted to the Educational Bureau of the Paint Manufacturers' Association of the United States and work was started by Mr. Henry L. Gardner at the Institute of Industrial Research, Washington D.C. in collaboration with Dr. Herman von Schrenk, a timber expert of St. Louis.The results of this,work have been described by Heckel, in ""Asbestos"", (Heckel G.B., Asbestos in the Paint Industry, Asbestos, Vol. 2, July, 1920,pp.- 5-10).,,who gives the following formula for one of the colors as typical: It will be noted from this formula that ""asbestine"" forms 33% of the total liquid pigment by weight or 31.8% of the solid constituents. Hockel in the article referred to describes this paint,as ""asbestiform"" and assumes since ""asbestine"" is magnesium silicate it must be the chrysetile variety of ""Asbestine"", however, is not asbestos but is a trade name for a fibrous variety of talc mined in the Gouverneur district, St. Lawrence County, New York. This rather natural error persists through the article and credits asbestos with many desirable properties which are characteristics of talc."

Aug 1, 1920