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By D. R. Tesarik

As part of its research program to investigate ways of improving resource recovery and reducing subsidence, researchers from the U.S. Bureau of Mines placed instruments in the B-North ore body of the Cannon Mine, Wenatchee, WA, to monitor cemented backfill and rock deformation during mining. The vibrating-wire gauges proved to be reliable and versatile, and approximately half of the instruments are providing data after 2 years of use. A two-dimensional, finite-element model was used to analyze the Cannon Mine's multilevel bench cut-and-fill mining method and predict rock and backfill displacements. The model accurately predicted rock displacements, but the predicted and measured displacements in cemented backfill had a correlation coefficient near zero, indicating that the model should only be used to predict rock displacements and not backfill displacements. A finite-difference model was also used to evaluate the stability of a cemented backfill pillar. Results can be used to conservatively predict backfill stresses, but on-site observation of pillar failures coupled with in situ measurements are needed to make more accurate predictions. An ongoing evaluation of the mining system has indicated that filling the primary stopes tight to the back with cemented backfill allowed these pillars to carry overburden loads soon after the cemented backfill was placed.

Jan 1, 2010

By P. J. Remington

Field measurements utilizing a seat pad accelerometer were made on 61 surface coal mining machines in order to quantify the vibration levels experienced by the operators. Those data were combined with information on the statistics of the operating times of those machines in order to compare the operator's vibration exposure to the criteria in ISO 2631, ?A Guide for the Evaluation of Human Exposure to Whole Body Vibration.? The comparison showed that about ha]f of all surface coal mining machine operators can be expected to be exposed to vibration exceeding the fatigue decreased proficiency criterion, whereas only on the order of 15% would be expected to experience vibration exceeding the exposure limit. Detailed exposure statistics are presented and the implications of the results are discussed.

Jan 1, 1983

By J. L. Reuss

The Bureau of Mines derived information on the softening characteristics of both unfired and indurated iron ore pellets as measured by hot compression strength in a laboratory study. A surprisingly high hot strength (240 1b per ½ -inch spheroid) was developed by unfired magnetite pellets near 900° C; lesser maxima were developed by pellets made from hematite and specularite concentrates near 1,000° C. Those from goethite remained weak throughout the pre induration heating. Fully indurated commercial pellets retain a high resistance to softening when heated in air. On the contrary, in a hot reduing atmosphere their high cold crushing strength dissipates rapidly. At 1,000° C, for example, the average compression strength of seven different commercial pellets was 110 lb; at 1,100° C, the hot strength was only 60 lb. After a rather sharp initial drop, the loss of strength with increase of temperature was gradual. There was no sudden collapse, nor any significant difference, in behavior of commercial pellets whether made from magnetite or hematite concentrates.

Jan 1, 1968

By James S. Browning

The Bureau of Mines conducted laboratory batch and small-scale continuous selective flotation tests of barite-fluorspar ores from two deposits near Marion, Ky., to determine the technical feasibility of recovering commercial grade fluorspar and barite concentrates. The lignin sulfonate-sodium fluoride method of floating the fluorspar successfully produced acid-grade fluorspar concentrates. Flotation of the barite from the fluorspar tailing using petroleum sulfonate collector yielded concentrates suitable for use in compounding oil-well drilling mud. The fluorspar and barite recoveries were about 82 and 85 percent, respectively.

Jan 1, 1963

By N. H. Snyder

THE Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the com-position as shown by proximate analyses. To these, when required, are added the fusing temperature of ash, Hardgrove grindability index, and the free-swelling index. Under most of these specification contracts the bidders guarantee the quality of coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instructions 4 issued by the Bureau; the samples are analyzed in the Bureau's laboratory to determine whether the coal is of the quality guaranteed by the contractor and, if it is not, a price adjustment is made. Analyses of delivered coal and "tipple" samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) are valuable data for use in evaluating future bids. Moreover, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal.

Jan 1, 1953

By E. L. Garton

Analyses of samples of crude oil from fields in West Texas have been published from time to time in Bureau of Mines reports.3/ Analyses of 100 samples of crude oil from West Texas) collected during 1946 to 1952) are presented in this report. The production of crude oil from the fields in this portion of Texas totaled 381,129,000 barrels4/ during 1951 - an amount greater than that of any previous year. Total cumulative production of this area through 1951 was 2,792,692,000 barrels.5/ Table 1 gives monthly production figures for 1951 and yearly totals for the preceding 10 years (1942-1951) [ ]

Jan 1, 1953

By Craig S. Compton

The failure of the immediate roof or "roof skin" between installed primary and secundary roof supports causes hundreds of injuries and, on average one or two fatalities each year in U.S. underground coal mines. Conventional roof supports cannot cover enough roof area to adequately control these relatively small, but very dangerous rock falls. The 2006 Mine Safety and Health Administration (MSHA) accident database lists a total of 542 ground fall injuries, including 10 fatalities. An analysis of the database suggests that 434 of the injuries and three of the fatali­ties can be attributed to roof skin falls (See Figure 2). The key to controlling falls of the immediate roof or roof skin is maximizing the area of roof coverage ilnd confining these relatively small loose rocks. Roof screen offers maximum coverage of the immediate roof. Depending on the size and configuration of the screen panels, coverage of up to 100% of the roof area is possi­ble. Screen also offers a first line of defense for machine operators working in the face area by confining or deflecting small rocks that can come loose during mining or roof bolt installation. Figure 1 shows an example of the protection screen provides dur­ing bolt installation. Although the benefits of screen are well-known, mining com­panies in some areas of the U.S., mainly Northern Appalachia and the Illinois basin, are not convinced that roof screen is the best tool for dealing with roof skin control issues. The logistics of material handling, possible ergonomic injuries to workers, and the costs associated with installation are delaying the acceptance of screen as an on-cycle roof support tool. Other mines however, have concluded that installing roof screen can be cost-effective when compared to the cost of lost time accidents, training of replacement workers, or returning to already developed entries for the cleaning and rebolting process.

Jan 1, 2009

Electrical trailing cable used to power coal mining machinery is frequently damaged in usage because of tensile strain or crushing effect of mining machines running over the cable. One of the repair problems is finding the exact location of a short or open in this cable so it may be spliced or otherwise repaired. The U.S. Bureau of Mines and FMC corporation signed Contract No. H0 122011 in August, 1971, to develop instrumentation for finding faults in coal mine trailing cable. This report describes performance of several existing instruments as trailing cable fault locators and also construction details and performance records of several cable fault location instruments that FMC designed, built and tested as part of this project.

Jan 1, 1973

By Jim F. Lemons

The Bureau of Mines Minerals Availability System collected and analyzed data for 34 nonlaterite and 9 nickeliferous laterite domestic chromite deposits in order to assess their viability as sources of chromium under present technologic and economic conditions. These 43 deposits, none currently in production, contain approximately 6.3 and 22.3 million metric tons of Cr203 at the demonstrated and identified resource levels, respectively. Approximately 4.6 and 15.6 million metric tons of Cr203 are recoverable at the demonstrated and identified levels, respectively, for the 34 nonlaterite deposits. None of these resources are economically recoverable at January 1981 market prices. Production of metallurgical-grade chromite (market price $128 to $144) would require a minimum chromite market price of $237 per metric ton. Chemical-grade chromite production (market price $74 to $85) would require a chromite market price in excess of $188 per metric ton. From the 34 nonlaterite deposits, roughly 5.4 and 17.6 million metric tons of ferrochrome could be produced at the demonstrated and identified resource levels, respectively; however, a minimum market price of $770 per metric ton of ferrochrome would be required to stimulate production. The nine nickeliferous laterite deposits were not evaluated through production stages because of uncertainties in process technology and cost.

Jan 1, 1982

By Amitava Ghosh

A new analytical formula for predicting ground vibrations induced by blasting is proposed. One factor accounts for geometrical spreading. One factor corresponds to inelastic attenuation. The geometrical spreading function is based on likely source geometries, idealized as either square-root, cube-root or site-specific scaling, and on the propagation characteristics of predominant wave types. The inelastic attenuation is approximated by an exponential function. The empirical constants in these functions are backcalculated from field measurements. Regression analysis has been performed on twenty-three sets of measured data in order to determine the validity and the effectiveness of the proposed method. In many cases, the proposed method gives better correlation than the conventional method. In most of the remaining cases, there was no difference between the two methods. Best-fit lines given by the proposed method fit the data trend very well, especially at large scaled distances. At large distances the proposed method gives a prediction much closer to the actual values than the conventional methods. The statistical analysis shows not much difference between square-root, cube-root or site-specific scalings.

Jan 1, 1983

By J. M. Stuve

Low-temperature heat capacities of chiolite (Na5Al3F14) were determined by adiabatic calorimetry in the temperature range 5.8 to 300 K. The derived standard entropy (S°, 298.15) was 115.6 ± 0.2 cal/deg-mole. High temperature enthalpies relative to 298.15 K were obtained by precision drop calorimetry up to 1,000 K. Tables of experimental data and related thermodynamic functions are given for the temperature range of experimental observations.

Jan 1, 1980

By Thomas M. Nasiatka

This report briefly describes the present state of the art and the technological highlights of tunneling from its inception to the present. The discussion is concerned primarily with tunnels driven through relatively competent rock for mine development and various civil purposes. In addition to pinpointing the major technological breakthroughs in tunneling, this report indicates their general effect on the speed of tunneling. The tunneling speeds are based upon data from approximately 80 tunnels listed in the appendix. These data include length; cross section shape and dimension; type of rock; tunneling method; method of breaking, loading, and transporting the rock; average linear progress rate; and cost in values during the period of construction. Most of the tunnels described have diameters of 15 to 30 feet.

Jan 1, 1968

By A. L. Engel

This report describes results of laboratory-scale experimental treatment of nine ores containing gold and silver, including samples of products of previous plant treatment, from ore deposits in California and Nevada. The samples treated were taken by engineers of the Bureau of Mines during investigations of these ore deposits. The information reported is of interest for development of the mining districts represented or in future Investigations of similar ores from other sources. The treatment methods were as simple as possible. More complicated treatments were tried when required, The applicability of the methods and their limitations in treating the ores are shown by the data in this report. The following treatment methods were employed in the experiments described: Screen analyses were made to determine distribution of values in various screened-sized portions of crushed ore, or to determine optimum size to which a particular ore should be crushed or ground to liberate values, and some-times to determine residual values in various-sized portions of treated material.

Jan 1, 1961

By Thomas J. Blalock

The volumetric determination of uranium according to the method of Sill and Peterson (6),3/ which uses cerate oxidimetry after the separation of interferences such as sulfides and cupferrates, has been used for some time by the Bureau of Mines and gives satisfactory results for many of the samples tested. However, in those instances where the uranium content did not exceed a few tenths of 1 percent and iron was present in the range of 10 to 40 percent (as Fe203),4/ the method was cumbersome and unreliable. The need for a more accurate procedure for the determination of small amounts of uranium in the presence of large amounts of iron, such as in shale or black sands, prompted this investigation. The Bureau desired that materials containing as little as 60 p.p.m. of uranium be assayed within reasonable limits of accuracy. One of the primary aims of this work has been to eliminate, as far as possible, the necessity for repeated cup ferron extractions.

Jan 1, 1960

By J. M. Mutmansky

"The objective of this study was to produce coal dusts for laboratory research that are similar to mine airborne dusts in chemical, mineral, and physical characteristics. In this investigation, dusts produced in laboratory comminution equipment were compared with continuous miner- generated dust for similarity in physical characteristics. Mining-generated dust (MGD) and bulk coal samples were first collected from an underground mining operation. The bulk samples were then processed in the laboratory for size reduction in various comminution devices. These laboratory- generated dust (LGD) samples were subjected to size and microscopic analyses. Physical properties of the dust particles were studied on a scanning electron microscope (SEM ). A numerical shape coordinate system (SCS) was also developed and applied to 300 particles from each sample. Statistical analysis was then performed on the collected data and characteristics of the MGD and LGD samples were compared. IntroductionIn many biomedical studies, researchers routinely introduce a dust mass into an experimental environment to assess the response of a biological entity, usually lung macrophages in vitro or a live laboratory animal, to the dust mass. To provide data of maximum usefulness, it is highly desirable to use dust with characteristics of actual mine airborne dust. The primary objective of this research was to produce dusts in the laboratory similar in chemical, mineralogical, and physical characteristics to mine airborne dusts. This paper outlines the evaluation of the physical characteristics of the lab-generated dusts.Particle shape analysis is perhaps the least-developed area in mineral-related particle science and technology. There are still no standard methods or instruments to scientifically quantify particle shapes. To date, many attempts have been made to characterize particle shapes. These procedures can be roughly classified into three categories:"

Dec 1, 1995

By D. J. Singleton

Erosion corrosion of 12 alloys in phosphoric acid waste water was studied by the Bureau of Mines. Tests were conducted on oblate spheroids or cylindrical specimens in 12-and 60-cm-diam ball mills by grinding phosphate rock in gypsum pond water with a starting pH of 1.6. For comparison, tests were conducted while grinding phosphate rock in plain water. Static corrosion tests in gypsum pond water also were conducted. For all alloys, the wear by erosion-corrosion (milling with gypsum pond water) was greater than the sum of erosion (milling with water) plus static corrosion. Erosion-corrosion wear was about 1,500 to 3,000 mpy for the alloyed white cast irons, 1,000 to 1,400 mpy for commercial steel ball material and type 316 stainless steel, and 600 to 900 mpy for nickel-base alloys and a high-manganese, nitrided stainless steel. Alloy costs per unit of phosphate rock 'processed favor a low-alloy, high-carbon steel or a high-manganese, nitrided stainless steel.

Jan 1, 1985

By J. M. Stuve

In this Bureau of Mines investigation, the low-temperature heat capacities of polycrystalline phases corresponding to the sulfide compounds CoSO?89' CoS1?33, and CoS2 were measured by adiabatic calorimetry within the nominal temperature range 5 to 300 K. The derived absolute entropies S298 were 10.36±O.02, 12.96±O.03, and 16.31±O.03 cal?mol-1?K-l, respectively, assuming third-law behavior. In addition, the standard enthalpy of formation 8Hf298 of CoSO?89 was determined by bromine solution calorimetry. The derived value of 8Hf298 was -50.63±2.1 kcal?mol-1, based on the 8Hf298 of Co0. This result is considerably more negative than previously published formation values based on high-temperature gas equilibrium studies.

Jan 1, 1985

By J. Koster

[In 1178 thn S-00n of thr !~Viluralcal Divicion, pur--'11 cf Mines, bcran an o. 't iv in': n-t!Y_Vnn of vothod; for recoverin'-1, Achol, copp~r, nK precioun notnin Zycn o;. -z of tic Bunkcrvillo KOH& in Clark County, Tcv. Tho Bunkcrvillo ran arc of t,-j)(,e of -iincrilization similar to that of 02 SWbury, Ontario, CannO, nichvl dc-?o?-:.t,. At prcoont, only n anall tonnes? p of ore has loan cxDr)scd in t*ic' :hui:er7ilIp rc: inn, ann. there is decided nce! for orjn: izod OrospectiAg ina drvclo-nnnt "crk there. It wann believod, howevar, t4it the dc,cuits varo 3ilficUntly siSnIficant to warrant an investigation iito their]

Jan 1, 1939

By Thomas M. Barczak

This U.S. Bureau of Mines report examines the causes and consequences of longwall face sloughage. Theoretical relationships were developed to evaluate mechanisms that produce slough age. From these relationships, contributory factors were identified for further analysis in field efforts. A survey identified 12 mine sites with sloughage problems, and these were investigated. From these studies, it was determined that the depth of cover and mining height are the two most significant factors causing sloughage on longwall faces. Coalbed friability and cleat orientation also were found to be significant factors in promoting sloughage. It was concluded that sloughage is primarily a problem in thicker seams or seams with friable coalbeds, and that the problem is more severe as the depth of cover increases. Sloughage also was found to increase as the rate of mining decreased. Observations indicated that face slough age can increase dust generation significantly on longwall faces. Current efforts to control dust generation from longwall sloughage are described.

Jan 1, 2010

By William L. Crentz

In a Nation-wide appraisal of coking-coal reserves and of the practicability of upgrading marginal deposits to metallurgical standards, this study of the preparation characteristics of the coals in Cambria County, Pa. , was undertaken. Over 90 percent of the coal remaining in Cambria Comity is found in the Upper Freeport, Lower Freeport, Upper Kittanning, and Lower Kittanning beds. The Middle Kittanning bed, although mined on a commercial scale in the past, is not an important bed now, as most of the remaining reserves are too thin to be mined over wide areas. For many years, Cambria County has been an important source of coal for industrial and metallurgical purposes. The) principal production comes from the Lower Kittanning bed, which accounts for almost .60 percent of the Cambria County coal output. Table 1 shows the county's coal production, by beds, during 1948.

Jan 1, 1950