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Alcoa of Australia's Western Australian bauxite mining operations in the Darling Ranges, southeast of Perth, present major challenges in the control of air blast. The close proximity of rural communities and the face profile make the traditional methods of air blast control difficult.An extensive blast noise monitoring programme has been established. The development of a computerised blast noise prediction model and the establishment of a radiosonde weather balloon facility have reduced blast induced complaints by a factor of ten.The meteorological factors affecting blast noise transmission are discussed and examples are given of adverse weather conditions for the southwest region of Western Australia.

Jan 1, 1983

By H. S. Drinker

THE first discovery of zinc 011 the property now worked by this company was made by the celebrated mineralogist, Prof. William Theodore Rapper, in 1845. Different claimants kept the property in continual litigation till 1861, when everything was satisfactorily settled by the purchase of the land by the company, who have worked it ever since. The mines are situated in a valley, four miles south of Bethlehem, Pa., in Lehigh County. The valley is from two to three miles broad, and is bounded 011 the north and south by syenitic hills. Syenite underlies the valley, and upon this is deposited the Potsdam sandstone, then a layer of slate, and, finally, a dolomitic limestone, belonging to the Chazy or Black River formation, in which the zinc deposits are inclosed. The rocks occur in folds, and have evidently been subjected to tremendous pressure from below, the zinc deposit being found in an anticlinal axis, in nearly vertical veins. I t is supposed that the zinc was originally disseminated through the

By Jorge Soto

Las plantas de tratamiento ubicadas en Nazca-Ica y Chala-Caravelí, Arequipa en el sur del Perú, utilizan sistemas de almacenamiento de relaves convencional donde los riesgos de ruptura y contaminación están latentes en la operación. Estas plantas están bajo la fiscalización de los entes reguladores (OEFA, OSINERGMIN, ALA), comunidades, población, ambientalistas, accionistas y gerentes de compañías quienes se ven con necesidades inmediatas de invertir altos presupuestos con la finalidad de mitigar los riesgos físicos, químicos y ambientales derivados de dichas soluciones convencionales.

Sep 1, 2017

In Mount Isa voltage and frequency fluctuations caused. by haulage shaft operation gave considerable difficulties with the initial application of Atomic Absorption Spectro-photometry.The methods used to stabilise the various units ' have been described.- Some other difficulties and the means used to eliminate or reduce them together with a-modified burner design are also discussed.

Jan 1, 1963

By Thomas W. Healy

Particles present in mineral processing systems that are termed ultrafine are those that are small enough to be unaffected by gravity or the flow conditions imposed on the pulp. As such, their interaction with one another and with other larger particles are controlled by specific attractive and repulsive colloidal or surface interactions. Electrostatic repulsion between ultrafines is dominated by surface potential, double layer thickness and specific adsorption potential effects - controlled by pH, salt and complexing ion concentrations. Attraction due to van der Waals interactions must be assessed in terms of bulk and surface coating effects and of particle size and shape. The net effect of attraction and repulsion must finally be related to the average kinetic energy of particles in the real system.

Jan 1, 1979

By John R. Wynnyckyj

Results of correlations between strength-development and sintering shrinkage occurring during induration are presented. A mathematical treatment of the shrinkage kinetics is, next, given and is based on the use of semi-empirical equations. The discussion stresses the significance of kinetic constants and activation energies in the assessment of iron ore concentrates for pelletizing and induration. Next, starting with the assumption that there is a need for parameters to characterize the iron-ore concentrates and relate these parameters to shrinkage-kinetic constants and balling behaviour, results of compaction measurements and pore structure characterization (mercury porosimetry) are presented and discussed.

Jan 1, 1977

By Kristiansen J

A series of laboratory blasting and ball mill grinding tests have been done on four different types of hard and competent rocks. The results show that exposing these rock types to a higher level of explosive energy will enhance their grindability. True blasting optimisation should therefore look at the whole comminution process from solid rock to a marketable product.

Jan 1, 1995

By J. J. Friel, E. S. Erickson

Dolomite-fluxed pellets of various compositions were made from magnetite concentrate, hematite concentrate and a concentrate containing a natural mixture of both. Physical properties and reduction test results were used to ascertain proper compositions and firing temperatures. These pellets were subjected to physical tests and to reduction tests. Petrographic and electron microprobe examinations were made to evaluate the effect of composition and fining on the phase assemblage. We interpreted our test results in terms of chemistry and microstructure and related these to properties. This approach enabled w to determine the composition best suited to each of the three concentrates. Compared with acid pellets, dolomite- fluxed pellets of the optimum compositions had similar physical properties but swelled less, softened at a higher temperature, and reduced faster and more completely.

Jan 1, 1983

By W. Jack Wilkes, Gilbert L. Butler

TRANSPORTATION TUNNELING The use of tunnels for transportation, namely rapid rail transit systems and highways is on the increase. How much that increase might be through the 1980's is the question that is discussed in this paper. In 1975, there were 218 route miles of subway tunnels for rapid rail transit and 154 lane-miles of highway tunnel. From the viewpoint of many transportation planners and designers, the tunnel is one of the tools which may be used to by-pass many types of obstacles: a mountain, a body of water, or a Central Business District (CBD). Therefore, the transportation tunnel is a rural as well as an urban solution with major emphasis on the latter because of the current transportation needs of our cities. In the case of rural locations, tunnels are usually constructed through mountains in order to eliminate miles of steep grades and dangerous curves, such as the Eisenhower Tunnel which cuts through the Continental Divide in Colorado along 1-70 and saves 10 miles and 40 minutes of driving time. Tunnels also provide an excellent transportation link across bodies of water in order not to interfere with shipping lanes. The Chesapeake Bay Tunnel and Bay Tubes of the BART system are excellent examples of this type of tunnel.

Jan 1, 1976

By M. S. Miller, R. H. Mullennex

The growing need for development of thinner, more erratic, or less easily-mined coals in the Appalachian region requires more detailed analysis of conditions and factors controlling or influencing deposition of these seams. The value of depositional modeling in evaluation of such coals has been demonstrated in many recent studies and publications. Such modeling may be applied to allow prediction of factors varying from regional coal occurrence trends to very local areas of seam discontinuities but requires thorough we of all available types of data. Mapping of general depositional energies, as derived from basic geophysical and driller's logs, can be applied to specific prediction of coal occurrence, and projection of particular facies as representative of unique depositional features or conditions may prove more applicable to coal character delineation than mapping of the coal itself. Depositional modeling and trend projection may also serve as a guideline in reserve classification and confidence levels in reserve estimations.

Jan 1, 1983

By Denni Hoffmann

"Banded iron formation rocks associated with massive sulfide lenses in the Broken Hill Pb-Zn-Cu-Ag deposit in the Namaqualand Metamorphic Complex, South Africa, were investigated with respect to the geochemistry of manganiferous silicate-rich bands. Two common varieties of these are: amphibole- and garnet-rich iron formation bands. The results reveal that the former are enriched in Fe, Mg, Cu, Co and S. The garnet-rich bands are enriched in Mn, Ca, P, Pb and Ba with significant detrital contamination of Ti, AI, Zr, Cr, Y, V, Ni and Nd.The silicate-rich bands have compositions, in terms of, Si/AI, SilFe, FelMn, LalCe and Co/Zn, comparable to submarine chemical sediments which precipitated from hydrothermal fluids. The garnetand amphibole-rich bands are interpreted as ""evolved"" and ""immature"" hydrothermal sediments, respectively. The latter resulted from rapid precipitation after exhalation, whereas the former had a longer residence within sea water. The silicate-rich bands both exhibit increasing Mn/(Mn+Fe) fractions, which are consistent with a variation expected from proximal to distal depositional settings. The prevalence of garnet-rich bands over amphibole-rich bands is interpreted as the result of injection of hydrothermal fluids from a single vent situated along the northwest margin of the Broken Hill deposit."

Jan 1, 1994

By Richard H. Sprute, Dennis J. Kelsh

Slow-settling, fine-grained suspensions can often be dewatered and densified by applying direct current between buried electrodes. Although water removal rates and power expenditures depend on physical and chemical properties of the treated slurries, metal mine tailings from Idaho, Colorado, and Mexico have responded well in laboratory testing, as have 29 samples of ultrafine coal waste from mines in nine states. This Bureau of Mines report reviews field tests at two Idaho metal mines and describes the recent installation at the Henderson molybdenum mine near Empire, Colorado, and the treatment of coal sludge at a Clinchfield Coal Co. preparation plant near Dante, Virginia.

Jan 1, 1980

By A. H. Tousley

The cement industry is on the horns of an economic dilemma. Within the last ten years, its over- capacity in the United States has varied from 139- 127% of demand (Fig. 1). The most direct effect of this is seen in cement prices, which reached a peak in 1960, retreated steadily through 1966 and only recently climbed back to the 1960 level again. With prices in a slump and production costs estimated to be up almost 30%, there has been a steady drain on cement profits. Since 1960, labor costs have increased 86% while fuel costs have risen 18%. Meanwhile, customer service costs have also soared owing to the competition for cement customers and the wider variety of available cement products. This search for sales advantage has in turn led to a higher Blaine number, which means more grinding and hence bigger mills, more power, and, once again, higher costs. New plants as well as expansions and revisions to existing plants are also costing more owing to higher

Jan 1, 1971

By C. G. Brehm

THE anthracite-producing region is in the northeastern section of Pennsylvania, and has an area of approximately 484 square miles. It is divided geographically into three separate fields, known as the Northern, Middle and Southern. The Northern field, with Wilkes-Barre approximately at its center, is a basin about 60 miles long and almost 6 miles wide at its greatest distance across. Generally speaking, it may be said that the coal meas-ures in this field lie horizontally, or on slight pitches, and consist of from 11 to 19 veins of coal, varying in thickness from several inches to several feet. The intervening strata between veins may be composed of slate, clay, rock or shale, or a combination of several, and are sometimes very thin. This condition often causes a treacherous roof, therefore roof sup-port and the attending hazard of mining are problems of concern. The Middle field is made up of a number of small basins of not very great depth, and the measures, which are in like number to those of the Northern field, are varying inclinations running from nearly flat to steep pitches.

Jan 1, 1938

By Thomas J. Regan

The first stage of the Massachusetts Bay Transportation Authority's Red Line Extension Northwest, is a two-track rapid transit extension from Harvard Square in Cambridge, through three stations, to the Alewife Station/Garage complex in North Cambridge. The extension, about 5.0 km. (3.1 miles) in length, is entirely in tunnel, with the Alewife Station/Garage complex and adjacent line sections of tunnel constructed by cut-and-cover methods. The Station/Garage complex, just west of Alewife Brook Parkway, is in an area underlain by deep deposits of very soft highly sensitive clays. It is proposed to construct the station and adjacent tunnel sections by the slurry trench method, using the slurry wall as the permanent structural wall of the station and tunnel. The unusual nature of the underlying clay and its very high sensitivity raised questions concerning the feasibility of the proposed construction. Since research failed to reveal any construction precedent for the specific conditions encountered, a test section was undertaken to determine construction problems, resolve uncertainties, and to establish acceptable parameters for the construction of the slurry walls. PROJECT ORGANIZATION Sverdrup & Parcel as tunnel and transit systems consultant for the Red Line Extension-Davis Square to Alewife had overall responsibility for determining program objectives, project management and test implementation.

Jan 1, 1979

By D. J. Shields

The U.S. Bureau of Mines has developed a microcomputer-based mineral modelling system that enhances analytical capabilities of the agency. It draws upon the extensive data base previously developed for the Bureau's Availability studies. The model is first formulated as a generalized network flow optimization problem, the optimal flows from which are fed into a transportation algorithm. The goal of the modelling system is first to fulfill prespecified demand at the minimum opportunity cost and second to identify feasible, optimal trade patterns. The system facilitates the analysis of policy issues on a real-time basis and supports the Bureau's mission to assess mineral resources.

Jan 1, 1987

The high maintenance of load-haul-dumps (LHDs) and front end loaders in hard rock affects mine planning with reduced availability and productivity. Intensive study of maintenance costs and availability of machines related to machine age and life provide the basis for planning from available operational alternatives.Derived programmes and experiences have led to the beginnings of unmanned operation and automation through reduction of manual diesel units and spreading electrification and use of radio. But electrification has obvious layout limitations. This approach to the present has resulted in better utilisation, costs and safety and the computerised monitoring and control provides continuous awareness of machine and work conditions with the promise of future improvements.

Jan 1, 1991

By C. H. Rawlins

The total amount of ferrous slag generated in the U.S. is about one-third the amount of iron ore mined, thus ferrous slag can be considered a significant mineral body for processing. Steelmaking slag contains up to 30 wt.% metal of which only the >25mm fraction is commonly recovered. A grinding study was conducted of BOF, EAF, and LMF slags using the Bond Work Index method to determine grindability to 106µm. Work Index values obtained were 13.8-24.9 kWh/ST, depending upon the slag type and composition. Steel particles were magnetically recovered from the crushed and ground samples for size-by-size analysis, yielding up to 18 wt.% of the slag weight recovered as magnetic. The recovered material, as characterized by inert gas melting, was found to be 61-96 wt.% metallic.

Jan 1, 2008

A new watersoluble binder for mineral ore pellets has been developed by the sulfonation of bituminous materials. A highly effective binder for iron ore pellet making is obtainable from bituminous materials produced in the hightemperature cracking of crude oils. This paper deals with production process and basic properties of this binder as well as new applications in the field of iron ore pelletizing.

Jan 1, 1974

By Stanley J. LeFond

Jan 1, 1985