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By Thomas M. Barczak, Ron Smith

Steel liner plates, which are bolted together to form a shell, are commonly used to provide temporary protective linings in the tunneling industry to ensure the stability of the tunnel and safety of the workers until more permanent ground reinforcement can be installed. As the ground deforms to try and close the opening, the liner plate is radially stressed, and by deforming redistributes these loads back to the surrounding insitu earth. Grouting behind the plates is done to fill any voids and ensure uniform contact to the strata around the back of the plates. Another function of the liner plate in some applications is to act as a platform or structure for the mining machine to react against in order to develop the necessary forward thrust to be able to excavate the face. In this case, the liner plates are loaded axially as a horizontal column of bolted liner plate rings, creating a jacking force against the liner plate assembly. In general, the buckling strength of the plate sections determines the jacking force capacity. Historically, the jacking force capacity of tunnel liner plates has been theoretically determined by some simplistic equations developed from tests of single liner plates. Recently, full-scale tests on a complete circular section of bolted liner plate ring segments have been conducted in the NIOSH Safety Structures Testing Laboratory using the unique Mine Roof Simulator to apply controlled loading in a manner that simulates the real world environment. Due to the unique size and capacity of the Mine Roof Simulator, these are believed to be the first full-scale tests conducted on the jacking force capability of tunnel liner plate rings. These tests indicate that the previously used theoretical equations tend to over predict the jacking force capacity of these tunnel liner plates. Unanticipated deformations in the field have been observed at loads below these theoretical design loads, therefore, a more accurate determination of the jacking force capability was needed. This report summarizes the full-scale test results, examines design parameters that impact the jacking force capability, and develops new mathematical models to improve the prediction of design loads.

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

Comprehensive ventilation surveys are made to review the adequacy of the mine system with regard to both statutory requirements and/or company policy, to evaluate improvements to the current ventilation system and to plan for £stun expansion. If computer simulation is to be used for these purposes, accurate quantity and pressure measurements become an absolute necessity since the validity of the computer generated output is heavily dependent on the accuracy of the input data. Consequently ventilation surveys that are run to generate input data for computer simu¬lation must use the best data collection procedures to guarantee as accurate results as are possible. These requirements have led to modifications in procedures that are used for routine ventilation surveying. McElroy and Kingery (1957) have recommended that pressures be measured independent of quantities since minor changes in mine conditions have a greater effect on absolute pressure measurements than on quantity measure¬ments. They estimate that, for large mines, a pressure survey may take only 1 to 3 days while the corresponding quantity survey would require 1 to 3 weeks. Although this procedure would undoubtedly lead to more ac¬curate pressure measurements, its use for the development of computer input data is not recommended for the following reasons. Atkinson's equation, H = RQ2, is used in computer oriented analysis to develop the airway resistance, R, based on quantity and pressure loss measure¬ments. It can easily be seen that since R a 1/Q2 and R a H, the effect of errors in quantity measurement is, in fact, more significant than those in pressure measurement. If the quantity and pressure measure¬ments are made at different times another problem results. Minor changes in quantity that may occur in the time between the pressure and quantity

Jan 1, 1977

By T. N. McVay

The Bureau of Mines has developed a field test for detecting the presence of columbium in a variety of minerals containing the clement. The test consists of fusing the mineral or rock powder with potassium pyrosulfate in a porcelain crucible, digesting the melt with hot dilute hydrochloric acid to release the columbium oxide (Cb205), and subsequently reducing the columbium oxide to a lower oxide by adding tin, which gives a blue color to the contents of the crucible. The method will detect 1 percent of contained columbium oxide (Cb205) in a mineral sample provided no tungsten is present. If a mineral containing appreciable titanium is test,-!d in the same manner, the solution in the crucible becomes violet. In the presence of columbium, titanium at first causes a violet coloration of the solution, which after a few minutes is masked by the stronger blue of the reduced columbium oxide. Although tantalum oxide (Ta205) does not interfere with the columbium test, tungsten gives a blue color that is indistinguishable from the color obtained with columbium. A simple method is available to detect the presence of columbium in the absence of tungsten, but when the presence of tungsten is suspected, the sample must be subjected to somewhat more elaborate chemical tests to determine the presence or absence of columbium. Although these latter tests can be made in the field, several steps are involved that arc best performed in the laboratory with simple equipment.

Jan 1, 1962

By Joseph S. Coffman

The Bureau of Mines investigated the availability of barite (BaSO4) from 35 U.S. and 41 non-U.S. mines and deposits in 17 market economy countries (MEC's). This evaluation assesses the availability of mud-grade barite, and concentrates consumed by the chemicals and fillers industries. The demonstrated resources defined in this analysis totaled 130 million metric tons (Mmt) of barite (contained BaSO4), yielding a potential 115 Mmt of recoverable barite concentrates. At the 1984 MEC production rate, the evaluated resources would last about 30 yr; however, this would include production costs of up to $100/mt concentrate. An average price needed to cover all costs of production over the life of each operation was determined for both mud-grade and chemical- and filler-grade barite products. Including a 0-pct discounted-cash-flow rate of return (DCFROR), regional weighted- average total production cost ranged from $38/mt for barite concentrates in Asia to $71/mt for U.S. operations. Transportation costs have the greatest impact, contributing up to 60 pct of the total cost of production. Rail transportation costs from the mines to U.S. markets are generally significantly higher than ocean shipping rates on imports.

Jan 1, 1986

By F. A. Rutledge

The Rainy Creek deposits lie at the western base of the Kilbuck Mountains, about So miles southeast of Bethel, in southwestern Alaska. The deposits were brought to the attention of the Bureau of Mines by placer miners on Rainy Creek after cinnabar concentrates were recovered by their gold-mining operations. In August 1947 the Bureau excavated 1,500 feet of dozer trenches totaling 2,547 cubic yards. Further hand trenching in the bottoms of the dozer trenches on the surface totaled 1,440 linear feet, or 40 cubic yards. Nineteen samples were taken for analyses.

Jan 1, 1948

By F. W. Wood

Ingots of zirconium and other highly reactive metals such as titanium and hafnium produced by the consumable-electrode arc-melting process require conditioning before forging or rolling. A nondestructive, arc-conditioning technique has been developed as a substitute for lathe conditioning. The technique employs en electric arc under an inert atmosphere to fuse surface metal on the sidewalls of ingots without seriously affecting the general quality of the ingots. Advantages of the practice are Increased yields, lower accumulation of inferior scrap, and actual cost savings. The work cited in this report was done on zirconium. INTRODUCTION The consumable-electrode arc-melting process as practiced at the Bureau of Mines3 4/ has proved to be a technique for producing sound, homogeneous, commercial-size ingots of zirconium and its alloys. Ingots produced by this process, however, have as a characteristic a layer of partly fused metal on the sidewall to a depth of 3/16 to 3/8 inch. To prevent extension of surface imperfections during forging, the ingots are ordinarily conditioned by removing defective material in a lathe. If the metal were less reactive or the requirements less severe, the machine chips could be recycled and remelted. However, zirconium, being so oxygen sensitive, is contaminated by merely being machined despite extensive cooling of the tool bit. Further, being contaminated with oxygen, the chip metal upon remelting is 10 to 25 Brinell-hardnese numbers harder than the ingot from which it was machined. For this reason, the ingot specifications for naval reactor use have prohibited remelting machine chips, except as required for starting pads. Again, were zirconium less costly or less in demand this ever-increasing pile could be burned to oxide and recycled through the Kroll sponge process. Economics do not favor this, as melting feed stock has an estimated increase In value over oxide of about $8.80 per pound of contained zirconium. The efforts of the Bureau to solve the problem have been directed along two lines: To reduce the contamination of the machine chips produced and to reduce the quantity of the chips produced. This paper presents the technique developed to reduce the quantity of chips produced by arc-conditioning the remelted ingot.

Jan 1, 1955

By M. M. Fine

This report describes a Bureau of Mines technical feasibility study of simultaneous reduction and induration of pelletized iron ore to make a product with superior qualities as blast-furnace feed. Highly reduced, physically competent pellets can be made from magnetite and specularite concentrates that contain small additions of bentonite as binder. In batch tests, pellets were dried, surrounded with solid fuel in crucibles, and heated to the reducing temperature. Total iron content of the best products was higher than 80 percent and crushing strength of 1/2-inch metallized pellets ranged up to 600 pounds or more. Comparative tests of several commercial oxide pellets showed a wide range in crushing strengths, but most values were less than 350 pounds. Continuous tests in a rotary kiln resulted in the same degree of reduction, but the pellets had lower crushing strengths because of the limitations in the maximum operating temperature of the small kiln.

Jan 1, 1962

By Oliver A. Dibble

This paper it one of a series being prepared for and published by the United States Bureau of Mines, describing mining methods and costs at clay pits throughout the United States. These papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating expenditures only and not total costs. It is recognized that publication of total costs might in many instances cause embarrassment to individual operators 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 open-pit recovery of clay for cement plants is a comparatively simple operation in comparison with underground mining of clays; nevertheless, it represents an appreciable factor in the cost of cement manufacture. The following report deals specifically with the methods employed by the Aetna Portland Cement Co., which operates cement mills at Fenton and Bay City, Mich., in recovering clay from their pit at Corunna, Mich., on the Grand Trunk Western Railway.

Jan 1, 1932

By August J. Kwitowski

This Bureau of Mines report describes how the reinforcement mechanisms of untensioned, full-column resin bolts were determined during one underground study. Both axial and transverse shear loadings were identified for two instrumented resin bolts that replaced standard resin bolts in an opera-ting room-and-pillar mining section. The strain responses of resin bolt steel cores to local axial and transverse shear loadings are described. This information was obtained from laboratory testing of resin bolts installations; it was also used to analyze the data from the underground test.

Jan 1, 1980

Develop a 22-ton capacity temporary mine roof support light enough to be easily lifted and transported manually from one place to another. Approach Several potential approaches were investigated in developing a new temporary support. An all-hydraulic, high-strength aluminum design was chosen as the best. The support was designed, fabricated, and tested in several mines. The first units, built for 6- to 8-foot seam heights, have a load- bearing capacity of 22 tons, and weigh only 55 pounds. How It Works The lightweight hydraulic support is designed for use in any temporary support situation in place of wood posts or steel mechanical or hydraulic supports. This includes use prior to roof bolting in room and pillar mining and in longwall development sections, use as head and tailgate supports for a longwall, and use as turn posts and breaker posts in retreat mining operations. The supports feature a release valve for quick manual extension to roof level, a lanyard

Jan 1, 1983

By M. M. Tilman

The Bureau of Mines conducted research to determine whether it is possible to substantially improve the fatigue resistance of lead sheet by means of surface coatings. Five types of coatings were applied to unalloyed chemical lead sheet. Flexural tests revealed that the best fatigue resistance was obtained with coatings of vacuum grease. Vacuum-grease coatings on unalloyed lead sheet resulted in fatigue resistance at least as good as that of the fatigue-resistant alloy Pb-0.04 Ca. Coated lead sheet was also tested in short-time tensile tests and in tensile creep tests. Tensile and yield strengths were increased by several of the coatings with only moderate loss of ductility. Creep resistance was also improved in varying degrees by most of the coatings. The Bureau also conducted research on the effectiveness of noise barriers by using sheet lead in combination with other materials. Noise barriers consisting of continuous-cast sheet lead with gypsum board were found to be effective and relatively inexpensive barriers.

Jan 1, 1978

By Robert P. Vinson

This report describes three coal mine ventilation studies by the Bureau of Mines in which sulfur hexafluoride (SF6) was used as a tracer gas. One of these studies was conducted to determine air movement and leakage in a sealed area. Another was run to determine the ventilation efficiency of a bleeder system. Finally, a study was made of air leakage across permanent stoppings of parallel intake airways. These studies proved sulfur hexafluoride to be a useful addition to the equipment commonly used in coal mine ventilation analysis.

Jan 1, 1976

By Paul Sands

Single- and two-stage tests were made with 6-inch, coal-cleaning hydrocyclones to determine the effect of hydrocyclone geometry, operating conditions, and feed composition on performance. Most of the testing was conducted in an open-circuit pilot plant that had a maximum capacity of about 9 tons per hour. The coals used in the investigation had top sizes of 1/4 inch and 28 mesh. Considerable latitude was found in the range of geometry variables that could be used without affecting performance adversely, although a certain minimum ratio of overflow to underflow openings had to be maintained for best operation. Two-stage cleaning proved distinctly better than operation with a single hydrocyclone, because clean coal lost in the refuse product of the primary unit can be partly recovered in the secondary. There is an unusually great difference in the specific gravities at which the individual sizes of the feed are separated in the hydrocyclone. This militates against high efficiency because maximum yield occurs when all sizes are cleaned at the same specific gravity. The size composition of the feed and, more particularly, the size composition of the impurity have a greater influence on the efficiency attainable in the hydrocyclone than in most other types of fine-coal cleaners.

Jan 1, 1968

By C. J. Thompson

In the course of the work currently conducted by the Bureau of Mines in cooperation with the American Petroleum Institute Research Project 48 on identifying sulfur compounds in petroleum, a micromethod was developed (12)5 for catalytically removing the sulfur atom from sulfur compounds. The product is the residual portion of the molecule; the structure otherwise was unaltered except for hydrogenation of any unsaturated bonds that were present in the original compound. Positive identification of sulfur compounds isolated from crude oils is a difficult problem. Direct comparison of properties of the unknown with those of reference compounds is often impossible because of the limited number of reference sulfur compounds available. However, a relatively large number of pure hydrocarbons is available, and the conversion of the sulfur compound to a hydrocarbon enhances the possibility of identification. The technique also can be used to prepare microquantities of scarce hydrocarbons by hydrogenating compounds that are readily available.

Jan 1, 1962

By Joseph W. Town

The Bureau of Mines conducted studies related to SO2 air pollution to determine attritioning rates, SO2 sorption rates, and sulfur loads that could be obtained on commercial alkalized alumina sorbent pellets. Fluidized-bed attritioning rates ranged from 0.025 pct/hr for alkalized alumina with a crushing strength of 4 kg to 0.075 pct/hr for 0.5 kg crushing strength mate¬rial. Airlift attritioning rates ranged from 0.50 pct/hr for 3 kg crushing strength alkalized alumina to about 3 pct/hr for 0.5 kg material. Attritioning rates for the commercial alkalized alumina were comparable to those obtained for sorbent pellets prepared in the Bureau of Mines laboratory. Sorption rates were related to S02 concentration in flue gas, temperature, and presence of nitrogen oxides in the gas stream. Sorption rates at 300° C were 0.35 X 10-6 gS/gp/sec (grams sulfur per gram pellet per second) in 0.045 pct so, gas, 5.1 x 10-5 gS/gp/sec in 0.34 pct SO2 gas, and 65 X 10-5 gS/gp/sec in 10 pct SO2 gas. For the 0.34 pct S02 gas, sulfur loads of 0.10 gS/gp (the projected load for regeneration) were obtained in 47 min at 130° C and in 116 min at 300° C. The presence of either NO or NO2 in the 0.34 pet S02 gas increased the SO2 sorption rates 2 to 3 times at 300° C, but had no effect at 130° C.

Jan 1, 1969

By James A. West

COUNTRIES of the Near East, with the world's largest and insist prolific petroleum resources, produced nearly 277 percent of the world's estimated total output of crude& oil in 1964 and accounted for about 60 percent of world exports of this commodity. Although petroleum largely dominated the mineral industry of tine area, production of antimony, chromium, copper, mercury, boron, potash, and phosphate rock was of world significance. Production of crude oil in Near East countries reached a record high of 7,520,000 barrels per day in 1964, an increase of nearly 11 percent over that of 1963. Kuwait maintained its position as the leading producer, accounting for almost 28 percent of the area's output. Saudi Arabia, Iran, and Iraq followed with 22.5, 22.2, and 16.5 percent of total area output, respectively. Despite record production, the Near East, proved crude oil reserve remained in excess of 211 billion barrels, or more than two-thirds of the estimated world proved crude oil reserve.

Jan 1, 1966

Pillars with width-to-height ratios of less than 1.0 are frequently created in underground hard rock mines. The strength of slender pillars can be estimated using empirically developed equations. However, the equations can provide variable results when the width-to-height ratios approach 0.5. This paper investigates some of the issues affecting pillar strength at low width-to-height ratios in hard brittle rock. The investigation includes an evaluation of empirical pillar strength data presented in the literature and observations of pillar performance in underground limestone mines in the eastern United States, supplemented by numerical modeling in which failure processes and sensitivity of slender pillars to variations in rock mass properties are evaluated. The results showed that the strength of slender pillars is more variable than that of wider pillars. The numerical model results demonstrated the increasing role of brittle rock failure in slender pillar strength. The absence of confinement in slender pillars can result in a fully brittle failure process, while wider pillars, fail in a combined brittle and shearing mode. The onset of spalling in slender pillars occurs at or near the ultimate strength, while this is not the case for wider pillars. Slender pillars are shown to be more sensitive to the presence of discontinuities than wider pillars, which can partly explain the increased variability of slender pillar strength. Two examples are presented that illustrate failure initiation by brittle spalling and the sensitivity of slender pillars to the presence of discontinuities.

By Andrew B. Cecala

The Bureau of Mines conducted laboratory and in-mine tests on the Racal airstream helmet (Model #AR21) to evaluate its protection efficiency. Laboratory tests indicated that as ambient air velocity increased, the protection offered by the helmet decreased. In tests conducted at several coal mine long-wall sections with face velocities under 400 fpm, the helmet was 84 pct effective at reducing respirable dust in the miner's breathing zone. However, at a high-velocity section, 1,200 fpm, the efficiency of the helmet was significantly reduced, confirming our laboratory results.

Jan 1, 1981

By Stephen Utter

This report summarizes the procedure and results of an investigation to determine the stresses in the rock around an underground opening in the Climax molybdenum mine, Climax, Colo. This study is part of an overall investigation conducted by the Bureau of Mines to determine the stresses induced by block-caving mining. The purpose of this study is to obtain estimates of the magnitudes and directions of the principal stresses, the location of the maximum stress concentrations, and the effect of topography on the stresses.

Jan 1, 1962

By J. D. Hadden, Albert Sainato

The Bureau of Mines conducted drilling studies in the Pocahontas No. 3, the Pittsburgh, and a western coalbed to establish the gas migration characteristics for each. Gas pressures in the Pittsburgh coalbed were about 260 lb/in2 and in excess of 550 lb/in2 in the Pocahontas No. 3. Caving in drill holes prevented pressure measurements in the western coalbed. The Pittsburgh coalbed contained intersecting "clay veins" which formed gas pres- sure cells. Although these geological features hamper mining, they can be used to control the flow of methane into a mine working. Methane control techniques are proposed for the Pittsburgh and Pocahontas No. 3 coalbeds.

May 1, 1969