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A case-study is presented of the tailings dam of Nairne Pyrites Pty. Ltd., at Brukunga, South Australia. The methods of-construction and operation of the dam are outlined over the whole working life of the mine. Procedures of soil mechanics used to estimate the stability 'of the face of the dam are described, and seepage problems are dis- cussed. It is concluded that the dam is basically stable, and enabled Nairne Pyrites Pty. Ltd. to dispose of tailings economically, although more attention to seepage control may have been ad- vantageous. Suggestions are made on the construction and operation of tailings dams elsewhere.

Jan 1, 1975

By R. V. Ramani, V. T. Burgos, J. A. McClay

This report was prepared by The Pennsylvania State University under USBM Contract No. G0111808. The contract was initiated under the Coal Mine Health and Safety Program. It was administered under the technical direction of DMSE, with Mr. G. R. Schottler acting as the technical project officer. Mr. J. A. Herlckes was the contract administrator for the Bureau of Mines. This report is a summary of the work recently completed as part of this contract during the period June, 1971 to September, 1974. Thls report was submitted by the authors on February 13, 1975.

Jan 1, 1975

By S. L. Crouch, C. Fairhurst

The general term "coal mine bump" refers to the sudden and violent failure of in-situ coal. Coal bumps occur in most countries where coal is worked by underground methods. They are related to geological factors and mining techniques. Coal bumps can be characterized as unstable releases of energy associated with yielding that occurs with progressive mining. Unstable releases of energy occur when the coal is able to absorb less energy than is released by the surrounding rock mass during the yielding process. At any stage of mining, the amount of excess energy so released is governed by the mining geometry, the overburden stress, the elastic properties of the rock mass, and the stress-strain characteristics of the seam material. If the coal in the vicinity of the working face is crushed, the peak abutment pressure occurs at some distance into the intact portions of the seam, and mining takes place in essentially destressed coal. With subsequent mining, additional yielding occurs, excess energy may be released, and the peak stress is again shifted into the solid. This process continues until the mining geometry is such that the zone of peak stress is effectively surrounded by yielding coal, at which point it can be anticipated that further mining will produce dramatic redistributions of stress and be accom¬panied by large releases of energy. On this basis, the differences between several alternatives for mining a given block of coal may be pronounced.

Jan 1, 1975

By S. Rajan

Familiarity with NEMA standards and the influence of the power supply on the motor-load system permits the user to make the necessary decision as to whether a standard or special motor is needed for his particular application. This paper highlights the more important aspects of NEMA standards for ac induction motors from the application engineer's standpoint and the effect of the power supply on motor characteristics.

Jan 1, 1975

By Golledge P

Safety legislation has a long history and widespread application, but how can one test its effectiveness? One way is to examine safety statistics. Another way is to compare the legislation with principles of good safety practice. Mine safety legislation contains many features that are widely accepted, and these should be examined critically to determine their importance. Uniform legislation and revision of legislation should be considered. INTRODUCTION

Jan 1, 1975

By G Alan Foster

This paper discusses the cause of air blast and modern techniques to reduce this at the source. In addition it raises the problem of their marked variability due to prevailing weather conditions and how weather data can be obtained and used in the control of air blast.

Jan 1, 1975

By R. V. Ramani

This report is volume 1 of an eleven-volume final report for a Grant completed by The Pennsylvania State University for the Bureau of Mines to develop a dynamic general purpose computer simulation model for underground coal mining. The simulator developed under the Grant has a wide range of possible applications in the design and evaluation of underground coal mining systems from the standpoints of health and safety, productivity, and mine environment. The Master Design Simulator consists of nine free-standing function-oriented subsystem models linked together into an integrated, comprehensive model of an entire mining system. The subsystems comprising the Master Design Simulator include geology and reserves, methane generation, roof support, subsidence, production, rail haulage, cost, water generation, and ventilation. This volume of the final report contains a statement of the purpose and scope of work of the Grant, and provides an overview of the Master Design Simulator with a brief description of each subsystem. Also included is a discussion of several areas of application for the simulator.

Jan 1, 1975

By G. B. Sonneman

This final report summarizes the work done by The Bendix Corporation, Environmental Science Division, under contract to the Bureau of Mines to design, develop and test two improved systems for remote sampling the air at the working face of a coal mine in conjunction with approved portable methane detectors and machine-mounted methane monitors respectively. The work was started in May 1973 with preliminary design studies and was completed in May 1975. Five portable and two machine-mounted sampling systems were delivered. Contract "add-on" requirements for (1) modification of the machine-mounted system to accommodate a flame safety lamp and (2) a study of sensor response time improvement for the machine-mounted system were also completed.

Jan 1, 1975

By P. W. Jeran, C. D. Sullivan, C. M. McCulloch

A series of geological surveys were completed in six coal mines in connection with a Bureau of Mines research program on methane control. The aim of these surveys was twofold: First, to study the overall geology of the coalbed, and second to use the resulting data to evaluate the influence of the geological characteristics of the coalbed on safe and efficient coal extraction. This report explains the advantages of geologic maps and fence diagrams in coal mining, and how the knowledge gained from such geologic investigations of mines can help control many underground problems.

Jan 1, 1975

By Omnes G

Sixty Schlumberger electrical soundings were carried out in the Depot Springs area, near Agnew, Western Australia as part of an investigation into the availability of groundwater for the Agnew nickel project. The object of the survey was to locate calcrete aquifers related to Tertiary drainage channels on the Pre- Cambrian surface. The electrical soundings were initially interpreted using sets of master curves and auxiliary point methods. Electrical sections were produced and contour maps prepared of apparent resistivity for AB=80m, total conductance of the overburden and transverse resistance.

Jan 1, 1975

By Donald Towse

Geothermal heat might become an important fuel for several reasons: (1) To substitute for other scarce and critical fuels. (2) Because it may be less costly to the user than alternate fuels. (3) Because its production may be more profitable than production of other fuels. (4) Or for a number of other more or less non-economic reasons such as convenience or because of less environmental impact. In competition with conventional and other non-conventional fuels, geothermal heat must score well on one or more of those points. This study first considers projections of energy needs in several United States economic sectors and the technical possibility of geothermal heat substituting for other fuels in those sectors. Then, reported and projected costs of energy from geothermal heat are compared with costs of other fuels to show the relative costs of fuels in several economic sectors. Relative costs are reported from a sample of real and hypothetical geothermal projects. The actual cost of energy will vary with each application and the particular circumstances of each geographic location.

Jan 1, 1975

By Neil B. Young

Carbonate minerals constitute a major fraction of the oil shale in Colorado's Green River Formation. Quantification of carbonate minerals is important for the characterization of oil shale, particularly because of their thermal activity in production of oil from shale. The carbonate minerals found in this oil shale are nahcolite (NaHCO3), dawsonite [NaA1(OH)2CO3], dolomite [(Mg1-xFx)Ca(CO3)2], calcite (CaCO3), and ferroan [(Mg1-xFex)CO3]. Although carbonate minerals can be removed by acid extraction from the balance of the oil shale, direct determination of carbonate minerals is complicated by the occurrence of the same cations in more than one mineral. A method for assigning the acid-soluble cations to the individual carbonate minerals was developed from two assumptions based on oil shale geochemistry: (1) Calcite and ferroan do not occur together, and (2) the ratio of iron and magnesium is the same in dolomite and ferroan. These assumptions were tested by the Bureau of Mines by applying the technique for assigning cations to 219 samples from the saline section of the formation. The reported carbonate mineral amounts were compared statistically with X-ray diffraction peak heights, verifying the cation assignment method.

Jan 1, 1975

By Warner RE

SINCE 1952, when Elliott et a/ first applied the Sherwood correlation for flooding in chemical absorption towers to blast furnaces numerous investigators throughout the world have followed their example and much research effort has been spent to tighten the correlation and recently to extend investigation of flooding to side gas entry conditions. The widespread use of the Sherwood concept of flooding has been such that even the word itself has become an integral part of blast furnace nomenclature. The evidence for the applicability of Sherwood's relationship has been that the flooding limits calculated from blast furnace parameters lie approximately on the Sherwood line. However, the values of many of the variables for the blast furnace calculation are only estimates and at first sight one may wonder at such 'close' coincidence when some of the estimated parameters entering the Sherwood correlation are raised to the power of three or more, as for the bed porosity and the liquid surface tension. It is felt that the explanation of this result lies in the logarithmic: nature of the plot and/or the fortuitous can- cellation of the errors of the estimates in the calculations coupled with the fact that blast furnace fluid ratios lie within a very narrow range of values. The foregoing considerations should in their own right place doubt on the correctness of the Sherwood type flooding correlation applied to the blast furnace. Additional doubt regarding the existence of the Sherwood type flooding in the furnace has been cast by the results obtained in the Tokyo University experimental blast furnace. From the reasoning of both Standish and Colquhoun (p. 20) and Warner (p. 23) it is deduced that flooding in the traditional sense will only normally occur in the upper bosh (somewhere near the mantle), following softening as discussed by Palella et a/ on p. 75, and flooding in that zone is likely to result in furnace irregularity. On the other hand, the concept developed by Warner of slag hold-up above the raceways as a stable phenomenon not affecting furnace regularity is a process unique to the blast furnace and is not described by the Sherwood flooding theory. Recognising the considerable practical implications of slag hold-up above the raceways, this note further explores the physical process of slag hold-up. We envisage that bed of coke above the raceways in almost all blast furnaces would contain some slag held up by the gas pressure gradient. In general the slag would be contained in a ring and gas would bubble through in its ascent through the furnace. The force supporting this slag is the pressure gradient and obviously -much of the blast pressure is dissipated in supporting this structure.

Jan 1, 1975

By Oleg Terichow

Electrophoretic mobility measurements were made by the Bureau of Mines on samples of a Florida phosphate slime to determine the optimum conditions of coagulation and settling in an aluminum sulfate solution. Addition of anthracite to promote mutual coagulation demonstrated the practicability of heterocoagulation by reduction of the repulsive effect of double layers. By proper selection of the electrolyte and its concentration, the reduction of the double layers to a net zero point of charge causes the predominance of Van der Waals' forces of attraction leading to the coagulation and rapid settling of both particle systems, as is predicted by the Derjaguin-Landau-Verwey-Overbeek theory of colloidal stability. Confirmation was found in the microfiltration tests where a modified Carman equation was applied to evaluate the specific filter bed resistance.

Jan 1, 1975

By J. E. Tress

The Bureau of Mines has developed a process to utilize waste heat from electric arc steelmaking furnace gases to preheat the ferrous material charged to the furnace. Four heat exchangers were designed, tested, and operated successfully on 1-ton electric arc furnaces. Briquets and pellets were charged continuously, both countercurrent to the hot furnace offgasses and at ambient temperatures. A comparison of the electrical energy consumed in each situation showed that preheating can lower energy requirements as much as 15.6 percent.

Jan 1, 1975

By Firkin GR, Allen RJ

Sulphide Corporation Pty. Limited has roasted a number of different zinc sulphide concentrates on its sinter machine which pro- duces zinc-lead sinter for an Imperial Smelting Furnace, and results have varied widely. The differences are considered to be functions of !concentrate particle size and reactivity. Amdel have used differential thermal analysis to examine these concentrates and two major effects have been found. Firstly, in concentrates 1containing small quantities of pyrite and chal- L [copyrite, heat is liberated at 400¦C to 650¦C [by oxidation of these two sulphides. Secondly, as particle size decreases, heat release from the oxidation of zinc sulphide commences at flower temperatures and rate of heat release In a sinter bed, the presence of some rite and chalcopyrite would help to heat the cc sulphide to ignition temperature in a orter time, while a finer concentrate would sult in roasting being completed more ickly. Both of these effects result in a arper flame front and minimise the chance heat and combustion fronts being mismatched. is theory is supported by sintering results tained by Sulphide Corporation. As a result

Jan 1, 1975

By M. Stuart, R. F. Down

The Copper flotation concentrate produced at Gortdrum mines contains about 1% Hg. This article deals with the treatment used to produce a substantially mercury-free copper concentrate. Metallic mercury is a byproduct. Nearly all the mercury in the Gortdrum concentrate is present in the copper mineral tennantite-tetrahedrite. This mineral is variably distributed throughout the ore body so that by selective mining it was possible to produce salable concentrate relatively low in mercury while the treatment plant was being built. Roasting was the only feasible method found for removing the mercury from the concentrate, and it was decided that this should be done in an atmosphere with limited oxygen. A multiple hearth furnace is used. Mercury soot is condensed from the gas stream and treated to produce prime virgin mercury. Problems were experienced at first with materials handling, oxygen control, cooling of the calcined concentrate, treatment of the mercury soot, and in the metallurgical accounting. Precautions were necessary to avoid health problems. The plant is now operating reasonably well. The value of the mercury produced does not warrant the cost of the plant but without it, the copper concentrate could not be sold.

Jan 1, 1975

By E. G. Valdez

The Federal Bureau of Mines, in cooperation with Ford Motor Co., investigated the recovery of polyurethane foam and other assorted plastics from the nonmagnetic reject of automobile shredders. Preliminary studies were con-ducted on a 1957 hulk augmented with additional foam and assorted plastics. The proposed flowsheet developed by the Bureau from the preliminary studies consists of a combination of screening, water classification, and gravity separation. The process was then tested on reject from two shredded 1972 cars. All of the foam and between 52 and 70 pct of the assorted plastics were recovered. The composition of the reclaimed foam concentrates ranged from 46 to 66 pct foam; the concentrates were hydrolyzed in laboratory tests by Ford Motor Co. to produce a reusable liquid mixture of polyether glycol monomers and toluene diamine.

Jan 1, 1975

By Jack C. White

The purpose of this Bureau of Mines research was to determine the technical feasibility of direct sulfuric acid digestion of Florida land-pebble phosphate matrix. Preliminary tests in a continuous digestion circuit showed that 92 to 96 percent of the P2O5 contained in the matrix was extracted, while the P.05 concentration in the product acid ranged from 21 to 30 percent. The waste filter cake contained about 1 percent P205 and up to 18 percent water. These sandy compact filter cakes, comprised mostly of quartz and gypsum, appeared to be suitable for backfilling and reclamation of mined lands.

Jan 1, 1975

By Haydn H. Murray, Sam H. Patterson

The term "clay" is somewhat ambiguous un¬less specifically defined, because it is used in three ways: (1) as a diverse group of fine-¬grained minerals, (2) as a rock term, and (3) as a particle-size term. Actually, most persons using the term "clay" realize that it has several meanings, and in most instances they define it. As a rock term, clay is difficult to define be¬cause of the wide variety of materials that com¬pose it; therefore, the definition must be gen¬eral. Clay is a natural earthy, fine-grained ma¬terial composed largely of a group of crystalline minerals known as the clay minerals. These minerals are hydrous silicates composed mainly of silica, alumina, and water. Several of these minerals also contain appreciable quantities of iron, alkalies, and alkaline earths. Many defini¬tions state that a clay is plastic when wet. Most clay materials do have this property, but some clays are not plastic; for example, halloysite and flint clay. As a particle-size term, clay is used for the category that includes the smallest particles. The maximum-size particles in the clay-size grade are defined differently on various grade scales, Soil investigators and mineralogists gen¬erally use 2 micrometers as the maximum size, whereas the widely used scale by Wentworth (1922) defines clay as material finer than ap¬proximately 4 micrometers. Some authorities find it convenient to use the term "clay" for any fine-grained, natural, earthy, argillaceous material (Grim, 1968). When used this way, the term includes clay, shale, or ar¬gillite, and some argillaceous soils. Even though no standard definition of the term clay is accepted by geologists, agronomists, engineers, and others, the term is generally un¬derstood by those who use it. Clay is an abun¬dant natural raw material, and it has an amaz¬ing variety of uses and properties which will be discussed in this chapter. Clays rank among the leading industrial min¬erals in both tonnages produced and total value. Their importance is indicated in Table 1, which lists the 1970, 1971, and 1972 production and values according to the U.S. Bureau of Mines (Ampian, 1972). Adequate reliable statistical data on which to summarize world production of clay are un¬available; this paragraph outlines the world re¬quirements for clay only in a very general way. According to one estimate, the world bentonite production in 1972 was 3.5 million tons (Anon., 1973a), but in the authors' opinion it was prob¬ably at least 5 million tons. The total fuller's earth produced was at least 1.5 million tons and may have been as much as 2 million tons. The total world kaolin production in 1972 was more than 10 million tons. Approximately 7 million tons of this total was produced in only two regions-the Georgia-South Carolina kaolin belt in the United States and the Cornwall re¬gion, United Kingdom. The world's 1972 out¬put of ball clay, which is also produced pri¬marily in the United States and the United Kingdom, was approximately 1.5 million tons or perhaps a little more. The total world fire clay production in 1972 was probably about one and one-half to two times and the miscellaneous clay production three times the United States production. As industrial minerals, clays are a complex group that consists of several mineral commodi¬ties, each having somewhat different mineral¬ogy, geologic occurrence, technology, and uses. In this chapter these commodities are organized

Jan 1, 1975