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By C. P. Mangelsdorf

When the finely bedded shale frequently encountered over coal seams experiences a separation, the material below the separation must behave like a beam or plate in that it must resist both bending and shear. Be-cause of the weakness in interlaminar shear inherent in such strata, shear deflections that are usually ignored in isotropic beam theory may account for a significant part of the total roof sag. Similarly, when a roof truss is installed in such a roof the upward displacement reducing the sag will have components due to shear as well as bending. Questions asked by mine operators about the installation of roof trusses frequently deal with optimum position, slope, and initial tension of the inclined chords. This Bureau of Mines report examines the effects of those chord parameters on the strain energy of both shear and bending and offers optimum values that will minimize the total strain energy of the immediate roof. Design charts are provided, several design examples are included, and the results are compared with current practice. The effects of in situ stresses are investigated and are shown to be equivalent to an additional load on the beam.

Jan 1, 1988

By J. W. Miller

An investigation was begun by the Bureau of Mines in 1948 to determine the preparation characteristics of American coals. Results of the investigation were planned to be reported on a county basis and, from the data developed, to determine: (a) Which coals, either as mined or after beneficiation by conventional preparation, are suitable chemically under present standards for producing metallurgical coke. (b) Which coals require special and more intensive treatment in preparation than is now practiced. (c) Which coals cannot be considered potential sources of metallurgical coke, regardless of preparation. This report is one in a county series and describes the preparation characteristics of the coals of Logan County, W. Va. According to present-day standards for metallurgical coal, many believe that the sulfur content of the coal should not exceed 1.25 percent? Coal with more than this amount has been used for making metallurgical coke, especially when blended with coal containing less sulfur. In this series of reports 1.25 percent sulfur is used as a gage to determine whether or not a coal will be suited for metallurgical coke.

Jan 1, 1957

By Earl L. Phillips

The Bureau of Mines conducted laboratory tests on samples of pozzolanic-cement concrete to develop a low-strength backfill. Results show that support costs can be lowered by replacing a portion of the portland cement in mine backfill with pozzolan (fly ash) and lime. Unconfined compression tests on various ratios of fly ash to cement in 84 samples produced compressive-strength curves that can be used to estimate the best backfill mix for any mine.

Jan 1, 1981

By W. H. Tomlinson

This publication presents the basic text for a 20-hour accident-prevention training course developed for supervisors by the Federal Bureau of Mines. During the past 2 years, the course has been used by the Bureau in teaching more than 300 groups of coal-mine supervisors-men whose responsibility is twofold: To manage in production and maintenance phases of coal mining and to guide their men along paths of safety. This is a handbook for teaching teachers. In this handbook will be found references to safety practices followed by companies that consistently have low accident records. These companies credit their outstanding performance to the adoption and faithful observance of accident prevention by supervisors and workers alike on a wholesome, cooperative basis. Teaching safety to workers involves both on-the-job and classroom-type instruction. If such training is to be permanently effective, it must be reinforced consistently on the job by the immediate supervisor of the worker. This publication is intended to provide such a supervisor with the motivation to provide such follow-up and shows how he can accomplish it effectively.

Jan 1, 1962

By G. E. Rennick, F. E. Armstrong, J. Pasini, J. R. Abrams

An oil well penetrating the Pittsburgh bituminous coalbed in northern West Virginia was plugged and safely mined through 3 months later. A sensitive chemical tracer, introduced into the oil reservoir before the test, was not detected in the mine air following the plugging and during mining of the pillar and penetration of the well. Effectiveness of the plugging in preventing reservoir gas from entering the mine through the well hole was verified by continuous monitoring of the mine air for indications of sulfur hexafluoride, an inert gas detectable in amounts as minute as 112 part per billion. Expand- able cement and fly ash-gel-water slurry were utilized to seal the well above and below the coal seam. Three other wells were also plugged using various techniques.

Jul 1, 1972

By Peter G. Groer

The commonly used exact methods (1-2) to determine the WL measure the total a activity or the total number of a counts during three preselected time periods. Due to the half-lives involved (TRaB = 26.8 min, TRaC = 19.7) I these methods take 3S minutes to complete the a activity Ra measurements. Methods using the total a counts, obtained at times less than about one RaB half-life after the end of sampling run into statistical 214 problems. These methods are almost blind to RaB (Pb214) as a consequence of its relatively long half period (see above) and the fact that RaB is a ß emitter. The way out of this dilema is to measure RaB directly through its ß activity. Since RaB's daughter Rae (Bi214) is also a ß emitter, the two f3 spectra have to be separated to obtain RaB alone. How this is accomplished 1s described in subsequent sections describing the theory of the IWLM and its calibration. 2.0 THEORY The IWLM samples air for two minutes and counts this airs ample for two minutes starting 3 sec after the end of the sampling period. The instrument has three channels. The lower a channel, the upper a channel, and one ß channel. The total RaA counts observed are accumulated in the lower a channel, the total RaC? counts are stored in the upper a channel. The total ß counts from RaB and RaC are recorded in the ß channel. These three quantities are functions of NA, NB, and NC, the unknown concentrations

Jan 1, 1975

By Will H. Coghill, Fred D. DeVaney

"INTRODUCTION The Mesabi iron district of Minnesota has a potential production of over 50 million tons of iron ore annually. The large shipments of ore each year are gradually depleting the reserves, and if the present rate of production is to be maintained there must be a growth in the present available ore supply.Growth is a natural course. The growth of a city may be affected by the addition of city blocks or by the improvement of utilities necessary for its betterment, these may go on in the order named or concurrently. The city-block type of growth of the Mesabi has been tremendous, and the ""betterment"" type has followed in due course. Probably the former has reached its limit, and if so, more time will be allotted to the latter. It is not the intent of this paper to present either a eulogy of the wonderful mining methods or a history of the milling, but it is pertinent to say that if the lean-ore area continues to produce, the continuance will be more the result of further improvement of milling methods now well under way than of extension of boundaries by the city block plan of growth.In an examination of the western end of the Mesabi district one finds sludge basins containing millions of tons of millable ore rejected by washing plants which were built for economy in operating cost and with little thought of conservation, and rich tailings piles of jigging plant rejects. In addition, there is an appreciable tonnage of bawl rake pro-ducts so low-grade that it requires mixing with the best ore of the district to make it merchantable.Any of these three products is a source of additional reserves, but gangue must be removed before the products will comply with blast-furnace stipulations. All investigators are agreed that to effect this separation comminution must be fine enough for liberation, but beyond this point opinions diverge; some would seek new processes, while others adhere to methods and machines developed in other mining districts.In the investigation by the Mississippi Valley Experiment Station of the United States Bureau of Mines working in conjunction with the Missouri School of Mines and Metallurgy,Rolla, Mo., the latter course has been followed. Attention was first given to the sludge basins mentioned. From their contents good grades of concentrates were made and the results published 4 later commercial-scale tests were made in a pilot plant of 10 tables, and the laboratory results were confirmed, The tailings from jigging plants are high in iron, and a study of their possible retreatment showed that if they are recrushed, high recoveries of acceptable grade may be expected. The results will be published later."

Apr 1, 1932

By J. M. Singer

The objective of this investigation was to determine minimum air velocities and entrainment rates for coal and rock dust dispersion in wind tunnel experiments under conditions that simulate dispersion from surfaces in coal mines where airflows are induced by weak gas explosions. Dust deposits were bed-or ridge-shaped; particle sizes were 6 to 80 microns (cohesive deposits) or 100 to 150 microns (free-flowing deposits); and wind tunnels were 7.62 cm wide by 5.08 cm high by 300 cm long, and 2.4 m wide by 1.5 m high by 215 m long. The investigation showed that minimum air velocities (directed at mid-height) of separate, layered, or mixed piles of coal dust and rock dust were within the range 5 to 30 m/sec, independent of size of wind tunnel. This finding considerably facilitates scaling of data to mine-size passageways. Free-flowing deposits dispersed relatively slowly by single-particle detachment; cohesive dusts dispersed faster by the breaking and lifting of large clumps along weak failure flames; particle dispersion occurred in flight. Layered or mixed deposits of coal and rock dust did not disperse selectively. Semiempirical expressions were derived relating minimum air velocities and dispersion rates to dust-pile geometry, cohesion, porosity, and bulk density.

Jan 1, 1972

By Thomas F. Tomb

The penetration characteristics of a horizontal plate elutriator and of a 10-mm nylon cyclone were evaluated. The test aerosols were polydisperse coal-dust particles ranging from less than 0.3 to 15 micrometers in diameter. Particle densities ranged from 1.3 to 1.4 grams per cubic centimeter. Equivalent Stokes diameters were measured using Coulter counter analytical techniques. Experimental results indicate that the penetration characteristics of the horizontal plate elutriator closely approximate the sampling efficiency curve defining the respirable fraction of the dust cloud recommended and adopted by the Johannesburg Pneumoconiosis Conference in 1959. Penetration characteris-tics of the 10-mm cyclone were evaluated at flow rates of 1.4, 1.5, 2.0, 2.5, and 2.8 liters of air per minute. The data indicate that the penetration curve obtained at 2.0 liters per minute most closely approximates the sampling efficiency curve for respirable dust recommended at a meeting sponsored by the U.S. Atomic Energy Commission in 1961.

Jan 1, 1970

By N. H. Snyder

Coal analyses help to describe the character of coal as it lies in the ground of as it may he delivered to the user Analyses of samples of coal collected from the face of the bed in mines are plentiful, but available analyses of delivered coal are relatively few, and there is a distinct difference between "mine samples" and "delivered samples.” Mine samples are collected actor drag to a standard method. 13 The sampler cuts a channel. 2 by 6 or 3 by 4 inches from roof to, floor in the face of the bed, and excludes from the sample all partings more than 3/8 inch thick, and any lenses or concretions of sulphur or other impurities more than 2 inches in maximum diameter and 2 inch thick. Analyses of mine samples form a permanent and scientific record of the coal bed at the point sampled, they ale important in determining the character of the coal in any given mine or district These analyses, when the samples are taken by a standard method, are valuable to the operator When compared with analyses of delivered coal they show him whether his mine is being worked efficiently or whether the coal is being properly prepared, which involves the ques¬tion ii Nether he has suitable mechanical appliances for separating the impurities sties. In the purchase of coal, mine samples may serve as a sufficient guide for the experienced buyer who has knowledge of the impurities in the bed, and the degree to which these are eliminated in mining and preparing the coal To the average purchaser, however, unacquainted with these details, dependence on mine samples may be misleading The quality of coal indicated by the base samples call rarely, if ever, be attained in the delivered coal Certain impurities that are eliminated from the formally prepared mine sample may not be eliminated by the miner Some of the roof and floor may also be included if these are soft or flaky When coal prices are high and competition is lessened it is easy for the miner and the management to lower the standards of preparation, and a return to rigid stand¬ards is always difficult. In sampling delivered coal the Bureau of Mines follows a definite procedure. 14 A sample of not leas than 1000 pounds is systematically

Jan 1, 1928

By Jerry J. Gray

The utilization of secondary titanium was determined in a study by the Bureau of Mines, and a 10-year statistical table showing supply and distribution patterns is presented in this report. Over the total 10-year period, estimated scrap consumption is larger than estimated scrap supply. Trends from the estimated data indicate that titanium is in short supply and probably will continue to be in the future. Because of higher processing costs for recycle scrap, scrap will tend to migrate to the steel and aluminum industries and to ferrotitanium production and exports. Nonrecoverable losses of titanium metal during processing was determined to be a potential area for research.

Jan 1, 1971

By J. Shawn Peterson, David S. Yantek, Adam K. Smith

Occupational noise-induced hearing loss continues to be one of the most pervasive health problems in the mining industry, despite over 25 years of regulation. One of the loudest pieces of equipment used in underground mining is the continuous mining machine. Noise sample data collected by the Mine Safety and Health Administration indicate that 42% of noise overexposures between 2000 and 2005 involved continuous mining machine operators. Previously conducted field and laboratory tests have determined that the continuous mining machine conveyor system is a dominant noise source. Loud impacts occur as the conveyor chain flight bars, used to move the mined aggregate, traverse their path from the top to the underside of the conveyor deck. Various noise control treatments have been applied to abate noise caused by the conveyor system. A durable polyurethane coating has been developed for the conveyor flight bars, resulting in a time-weighted average reduction of 3 dB(A) for an eight-hour work shift. In an attempt to further reduce continuous mining machine operator overexposures, a similar urethane coating has been applied to the tail roller component of the conveyor system. Laboratory results showed a 2 dB(A) reduction in sound power levels, but the component failed during underground durability testing. An outer steel sleeve has been added to the urethane coating of the tail roller to enhance wear resistance during mining. The urethane jacketed tail roller is the latest effort, combined with previous noise treatments, to bring the continuous mining machine into compliance with federal noise regulations.

By Wils L. Cooley

This report analyzes electrical accident data in the metal/non-metal mining industry. Accidents are categorized to determine their root causes. Special attention is given to accidents associated with inadequate or defective grounding of mine power systems. Recommendations are made concerning proper grounding practice, especially for dredges and for quarries in hard rock or sand. The costs of instituting the recommended practices are estimated for model mine power systems which are based on field data obtained from 37 mines and several electrical contractors. The expected benefits of various suggested safety practices are also estimated.

Jan 1, 1981

By Henry C. Meeve

This report describes work done in the Creede Mining district, Mineral County, Colo., in 1965-66 as a part of a Bureau of Mines study of the silver production potential of the United States. The ruining history of the district is briefly covered, and representative former and current mining operations are described. Mining and milling costs of the Emperius Mining Company's operation are given in some detail as being representative of the cost of mining typical Creede ore bodies under current technology. An estimate of the silver reserves and resources of the district is presented, subject to many uncertainties stemming from inaccessibility of old workings, lack of mining records, and low level exploration activity, all of which limit the opportunity to accurately evaluate ore potential. The report concludes with an analysis of future silver production trends in the Creede district. An increase of silver production to as much as I million ounces yearly is projected, possibly starting in 1969. As long as ore bodies in the zone of enrichment, in which silver is a major constituent, contribute a substantial part of Creede production, silver price will affect overall production rates appreciably. As the richer are bodies become depleted, an increasing portion of production again will be coming from primary sulfide ores in which silver is a byproduct of lead and zinc. When this occurs, the level of silver production will be governed chiefly by lead and zinc production and prices and can be expected to decline to the 1960-66 level, which amounts to an average of 240,000 ounces per year.

Jan 1, 1968

By P. B. Altringer

The Federal Bureau of Mines conducted a study to determine if residues from fractional distillation represent a potential source of mineral values. A literature review and discussions with tar sand specialists failed to disclose the mineralogical nature of residues remaining after bitumen extraction. To develop this information, pilot plant tar sand residues or toluene-cleaned tar sands from 23 deposits were examined. The nature of the residues was determined by standard mineralogical methods and the chemical compositions were determined by X-ray and ICP (inductively-coupled plasma spectroscopy). None of the sands or concentrates examined contained sufficient valuable minerals to be economically important.

Jan 1, 1982

By Harry Perry

One of the most notable achievements of the iron and steel industry in the United States in this century has been the general increase in productivity of individual blast furnaces and the reduction in coke rate. Most of the improvement in furnace operations has occurred within the past decade. During this time the output of the average furnace increased about one-third, while fuel rates decreased from 15 to 20 percent. For example, in 1949, the iron and steel industry produced 811.2 short tons of pig iron per blast-furnace day with a coke rate of 1,870.4 pounds per ton of pig iron, By 1960, the average production of pig iron per blast-furnace day had risen to 1,182.4 tons, while the coke rate had decreased to 1,497 pounds per ton of pig iron. These figures are averages for the entire industry; many furnaces produced over 2,000 tons per day and one furnace, operating on pellets, reached 2,700 tons of pig iron per day, Coke rates of individual furnaces varied, but some furnaces operated on less than 1,200 pounds per ton of pig iron. The significance of this decrease in coke rate is shown clearly when data on pig-iron production and coke consumption in 1959 are compared with 1948. In 1948, 57.3 million short tons of coke was charged into blast furnaces to produce 60.1 million tons of pig iron; in 1959 only 47.6 million tons of coke was needed to produce 60.2 million tons of pig iron. Thus, in 1959, nearly 10 million tons less coke was required to produce about the same amount of pig iron as was produced in 1948.

Jan 1, 1962

By James L. Ash

This report contains the results of a technical and economic evaluation of conceptual systems for the underground mining, rubblization; and in situ retorting of deep oil shale deposits. Study efforts were first directed towards evaluation of the applicable geology, associated minerals, rock mechanics, in situ retorting, access mining, ventilation, rubblization, safety, and environmental impact factors. Conceptual systems were synthesized and then evaluated against these factors from both a technical and limited economic viewpoint. The results of these evaluations were then analyzed 'and, based upon this analysis, the following two systems were selected for further study: System II: Room and Pillar-Vertical Drill and Blast System IV: Tunnel Boring-Horizontal Ring Drill and Blast Due to the large number of variables to be considered, a computer program was developed and utilized to provide data for the cost trade-off studies and economic analysis. Results of the early computer runs indicated the value of the tool available in the computer program and led to an extension in the contract to determine the sensitivity of the systems to several of the more apparent significant variables. These results in turn led to a refinement in the design assumptions and a better understanding of the technical and economic options available to an owner-operator of a Vertical Modified In Situ Shale Oil Extraction System. This report is submitted in fulfillment of the requirements of Contract Number S0241073 by Fenix & Scisson, Inc. to the Denver Research Center, United States Department of the Interior, Bureau of Mines. Work was completed as of November, 1976.

Jan 1, 1976

By R. E. Tremoureux

This paper describing the methods and costs of quarrying limestone at Sloan, Nev., is one of a series of similar papers being prepared for and published by the Bureau of Mines on this industry in the United States. These papers are designed to disseminate information regarding the methods used. The cost tabulations represent local operating expenditures only and not total production costs. It is recognized that publication of total production costs might in many instances cause embarrassment to individual producers as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods Employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue. The quarrying operations at Sloan are interesting not only from a technical viewpoint and because of the magnitude of the deposit, but also because the quarry is located in a desert region far removed from the centers of population where lime is used. The quarry and plant are in Clark County, Nev., 20 miles west of Las Vegas, which is the nearest town to the site of the Boulder Canyon Dam. Sloan is on the main line of the Union Pacific Railroad connecting Salt Lke City and Los Angeles. The latter city is 280 miles from Sloan and it is the shipping, point for all supplies.

Jan 1, 1932

By John R. Reeves

The principal oil aha.le in Indiana ie known as the New Al'baZ\Y shale. It 11 ot Devonian age, and ia usually correlated with, although not certainly of the 1ame age a,, the Antrim shale of northern Michiga.. the Ohio shale of Ohio, and the Chattanooga shale ot Kentucky. Termescae • a."ld Georgia. The nqtmal thickneaa of the formation 1n Indiana 1e a.bout 100 faet, ltbough 1n the region of its out­ cro;l the tall th!::kne,111 io rarely exposed because cf the general d:.p of the strata, which is 11 about 30 feet per mile to the west. With the exception ot thin local pha1e1, the entire thickness is oil shale,

Aug 1, 1922

By J. M. Davidson

The potassium mineral polyhalite (K2SO4.MgSO4.2CaSO4.2H2O) found in large deposits in western Texas and southeastern New Mexico is associated with varying amounts of halite (sodium, chloride, NaCl) and anhydrite (calcium sulphate, CaSO4). Although the anhydrite, because of its low solubility and slow rate of solution, is relatively inert, the halite is dissolved immediately in any process solution with which the polyhalite comes in contact. Limited quantities of sodium chloride in the liquors used for the hot extraction of polyhalite materially improve the results obtained, but only a very small sodium chloride content may be desired in the entering polyhalite in other procedures, such as Bureau of Mines process. In all of the processes suggested for the recovery-of potassium sulphate from polyhalite the control of the sodium chloride content will be desirable, if not absolutely essential to efficient operation.

Jan 1, 1934