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By Syd S. Peng

Coal mine ground control is the science of the application of rock mechanics principles to coal mining operations. More acceptance of ground control techniques by the US coal mining industry has been seen in the 1980s. It has been demonstrated many times that a proper ground control design is key to a successful coal mining operation. However, numerous in-mine applications of various ground control techniques by the author indicate that cur¬rent techniques need improvement. The biggest problem in coal mine ground control is that miners are dealing with materials of rapidly varying properties and occurrence. And only the exposed surface can be identified positively. Thus, in attempting to solve the ground control problems, many unknown factors are assumed. Some of these problems deriving from such assumptions are discussed here. Coal pillars There are two types of coal pillars - barrier and chain pillars - depending on the purpose. Barrier pillars are those located between panels or sections or mines. Their objective is to isolate the mined-out effects of one from the other. Chain pillars are characteristic of room-and-pillar mining. They are designed to support the overburden load and protect the surrounding entries and crosscuts. Pillar design is the most popular and, frequently, the only ground control technique employed by coal operators for mine design. There are many pillar design formulae available (Bieniawski, 1983; Peng, 1986). Nearly all consider both size and width/height effects. Specifically, pillar strength decreases with increases in pillar size and increases with increase in the ratio of width to height. However, the manner of those changes varies with investigators. Consequently, the pillar size determined varies considerably from investigator to investigator. And the variation grows much more pronounced as the seam depth increases (Fig. 1). The question, then, is which one should be used? One may say each formula is developed for a particular coalfield. A particular formula may have been used to design a pillar, which has not failed. Does that mean it was over designed? Not necessarily, because no one can confirm its stated "safety factor." Recent case studies (Peng, 1986; Tang and Peng, 1988) show that all pillar formulae are too conservative for chain pillar design in room-and-pillar mines due to the following two problems: • Uncertainty about in situ pillar strength. All formulae employ uniaxial compressive strength of selected samples tested in the laboratory and scaled to that for underground pillars. The scaling factors are not well proven. In situ testings by Bieniawski (1969) suggested that 1.5 m (5 ft) pillars are representative of in situ pillars that, after being tested in various US coal mines, are not universally applicable. • Uncertainty about the actual loading on the pillar. The most frequently used tributary loading theory defines the loading as total overburden weight tributary to each pillar (from roofline to surface). This is too conservative when it applies to coal measure rocks. The overburden consists of layered strata of different stiffness. Many stiffer strata will self-support over small roof spans. Depending on the location of these strata above the coal seam, it will reduce pillar loading in various proportions. It follows that total structural analysis using, for instance, finite element method is more appropriate. It can take into account the interaction of roof and floor strata with coal. This has been demonstrated by Peng et al. (1986,1988) on several case studies. However, the validity of the finite element structural analysis depends on the accuracy of in

Jan 1, 1989

By Hennessy F. L

It is generally recognised that slags are active participants in pyrometallurgical processes, and not merely inert liquids which must be produced. to effect separation of gangue material in smelting, or of impurities in refining. The importance attached to slag-metal reactions in steelmaking is shown by the numerous investigations in this field. However, there are still many important reactions of slags which require explanation. In this paper some new aspects of the reactions of slags will be discussed, as far as possible quantitatively.FREE AND COMBINED OXIDESMetallurgical experience indicates that variations in the composition of slags produce changes in the chemical behaviour of the various components. These variations have been generally ascribed to changes in the proportions of free and combined oxides, i.e., compounds have been assumed to be present in the liquid slag.Considerable support for this view has been adduced from the existence of compounds such as metallic silicates, phosphates, etc., in the solIdified slag. However, this does not imply that such compounds necessarily exist in the molten slag.The most direct evidence as to the nature of molten slag is to be obtained from a study of the liquid state. In...

Jan 1, 1950

Three methods of gold analysis are briefly described highlighting some of the problems and advantages of each. The variation of results between samples and splits and due to method of preparation is illustrated. The mean per cent difference of the fire assay values from the means of sample split values for three cases is 15 per cent.Finally, a comparison of the aqua regia leach atomic absorption spectroscopy (AAS) and fire assay fusion AAS techniques is made.This shows that the mean precision, the ability to obtain the same value, of the methods at 98 per cent confidence is ± 30 per cent and ± 15 per cent respectively. The fire assay fusion AAS method is relatively more accurate than the aqua regia one.

Jan 1, 1984

By I. J. Barker

Keywords: Submerged-arc furnace, plasma furnace, d.c. furnace, scale up, Søderberg electrodes, smart grid, demand side management, load shedding This paper argues that the scale up of furnaces and the supply of electricity are going to be two major issues that will affect the ferro-alloy industry in the near future, and that economic factors will drive this development. The most common type of furnace for producing ferro-alloys at present is the submerged-arc furnace with three electrodes, fed from a three-phase a.c. electrical supply. The scale up of this technology has now reached a fundamental constraint, which is caused by the electrical reactance of the secondary circuit. If the economy of any further scale up is to be achieved in the future then a different technology will have to be used. The supply of electrical power in future is likely to become a more complex issue than it is at present. Existing submerged-arc furnaces tend to run at fairly steady loads, but the ability to swing the load under demand-side management may offer advantages, and may allow a furnace to get cheaper power from the organisations that supply this power. This will have to be counterbalanced against the nuisance factors incurred by having a varying load in the operation of the furnace. Various options are therefore discussed in this paper. The possibility of scale up of Søderberg electrodes is discussed, as well as the use of d.c. power and multiple electrodes. Some of the issues with load swinging are also examined. A particular scenario is also briefly presented to show that considerable further scale up of ferro-alloy furnaces is still possible.

Jan 1, 2011

By A. L. Garassino

Dans cet article on parle sortout de l'approche de calcule pour les pieux charges horizontalement avec particuliere reference aux curbes p-y et è une solution semi-empirique qui prende en consideration les variations typiques du module du sol avec la deformation obtenue par les données expérimentales. 1. INTRODUCTION The analysis of the piles under lateral loads depends very strictly from the pile stiffness and geometry, from the soil type and from the strain field. Different approaches were adopted in solving the problem. Some Authors developed methods for estimating the ultimate lateral resistance of piles and pile groups by conventional static approaches, as the Brom's widely known (1964) or by the plane strain solution developed by Davis (1961) or by empirical engineering con­siderations l

Jan 1, 1994

Results of flotation tests on lead-zinc ore from Broken Hill, N.S.W., confirmed that flotation at pH 9 in the presence of cement gave poorer metallurgical results than flotation at pH 7. Additions of 2 kg/tonne wood raspings [e.g. blackbutt (Eucalyptus pilularis), blue gum (E. saligna), brushbox (Tristania conferta), or turpentine gum (Syncarpia laurifolia)l had little effect at pH 7 but greatly accentuated the deleterious effect of cement at pH 9. This was shown to be caused by e:xtractives (e.g. polyphenols and carbohydrate materials) derived from woods at pH 9. The proportion of extractives, as shown by DV absorbance spectra, increased with increase of pH and was affected by various salts.Additions of 1 kg/tonne Al2(S04)3.16H20 when cement or cement and wood were present showed that metallurgical results obtained by flotation were then very simHar to those in the absence of cement or wood or both. This was ascribed to lower pH values in the presence of aluminium sulphate and possibly to specific chemical effects.Additions of aluminium sulphate appear to offer an economic solution to the problem of treatment of ores contaminated with cemented fill at Broken Hill.

Jan 1, 1974

By I. H. Wong

The large diameter caisson foundations and their construction methods for three 50 to 60 storey high buildings in Singapore are described. The caissons are 5 m to 8 m in diameter and 40 m to 100 m deep, excavated either by hand or mechanised excavators or by drilling and blasting. Performance of the 50 storey DBS Building is described.

Jan 1, 2010

In common with general experience in the iron-making industry overseas, Australia has in recent years suffered a deterioration in the physical quality of her iron ores in their suitability as a direct blast furnace feed. The increasing amounts of fines and the more friable nature of lump ore, especially in the ore from the Cockatoo Island deposits in Yampi Sound, Western Australia, have focused attention on problems of ore preparation and agglomeration, particularly sintering.Although very small pilot scale Dwight-Lloyd type sinter machines were operated at the steel-making centres at Newcastle and Port Kembla during World War II, no sizeable capacity was installed, so that ore was charged to the blast furnaces almost entirely unscreened, and the resultant flue dust was stockpiled.Towards the close of the war, the pilot plant at Newcastle was replaced by a small machine, adjacent to the flue dust stockpile, with a rated capacity of some 20 tons per hour. After approximately five months of part-time operation, this plant was closed down in January, 1945. Production was not resumed until December, 1950, when, due to a temporary ore shortage, it was decided to supplement available ore with sinter produced from the large flue dust stocks of about 300,000 tons. In spite of mechanical and process difficulties, inherent to the design of the plant, operation was continued on a two-shift basis, with several shutdowns for extensive overhaul and plant alterations, until September, 1954, when production was put on a three-shift basis. Addition of Yampi ore fines to the sinter machine burden was not commenced...

Jan 1, 1957

During the course of the major research in the Metallurgy Department of the University of Melbourne into the creep characteristics of lead and .its dilute alloys, it has been the practice to prepare the majority of test specimens from rolled strip. From time to time during the progress of the work, certain variables involved in. the rolling of the experimental ingots have been investigated. It is proposed to collect together in this paper the results of these experiments. Some general features relating to the type of deformation produced have been discussed in a previous paper.While it is admitted that the conditions prevailing through this work differ' in some respects from those of industrial rolling practice, it is felt that many of the factors investigated have an important practical significance. Some of the work described forms a continuation of the researches of R. S. Russell (2) , (3) , (4), into the recrystallization of various pure leads after deformation by rolling.MATERIALS USEDIn this work, a variety of "pure" leads and certain dilute alloys made from the purest of the basis leads have been studied. The compositions of the basis leads and the corres...

Jan 1, 1940

By Driver R. C, Moelle K. H R

This paper is dedicated to the memory of our friend Peter McKenzie who contributed much to the knowledge of the New South Wales Coalfields.ABSTRACTA fossil river system was recently mapped over parts of the Southern Coalfield, N.S.W. This river system occurs in the roof strata of the Bulli Seam. Sandstone of a fluvial nature was deposited in its course. The sandstone exhibits strong sedimentary vectorial properties and has a marked influence on strata-control in colliery workings.The sedimentary features analysed indicate an approximate S200W flow direction. Petrological studies reveal a clastic, well-cemented sedimentologically and structurally anistropic rock type. Washouts have been found and isopach maps of both sandstone and underlying roof-strata have been compiled. Relevant measurements were carried out in existing colliery workings and on bore cores.Optical determinations of feldspars revealed the presence of plagiocIase feldspars with few exceptions. Most of the feldspars are altered to clay minerals. It was found that a geographical trend exists in the distribution of feldspars, with more basic plagioclase in the northern part of the field.The source area of the fluvial sandstone lies to the north of the Southern Coalfield.Petrofabric analyses were done on several specimens of the fluvial sandstone. In the vicinity of major disturbances, penetrative fabrics were discovered.Calcites (e, 0112), micas (001), and quartz (crystalIo graphic c) show preferred orientations.

Jan 1, 1967

By L. H. DeWald

During the examination of various commercial brands of copper wire bars, which had exhibited different degrees of adaptability for being drawn into fine gages of wire by the present-day high speed machine, it was found that each brand had a more or less characteristic crystal macrostructure. The extremes of these macrostructures are similar FIG. 1.-EFFECT OF METAL TEMPERATURE IN CASTING ON CRYSTAL MACROSTRUCTURE OF BAR. Reading from left to right, metal temperatures were 1166" C., 1149" C., 1132" C.. 1121" C., 1093" C. to the maximum variation shown in the photomacrographs reproduced in Fig. 1. As the various brands did not differ materially in chemical composition, it was concluded that the differences in structure were the result of variations in casting technique.

Jan 1, 1931

By S. Mostaghel, S. Nicol, M. Y. Solar

Once upon a time, the process engineer developing the design criteria for a new saprolite ferronickel smelter had it easy: most ores were around 2.5% Ni, with a Fe/Ni ratio of 4 to 5 and a SiO2/MgO ratio of about 1.6; to use the French word: garnierites. The ferronickel grade selected was the conventional 20 to 25% Ni and the impurity levels could be predicted from well established [C], [Cr] and [Si] vs (FeO) graphs. However the process engineer can no longer depend on statistics to design smelters: Ni grades are decreasing while the goethite contents are increasing; SiO2/MgO ratios vary from 1 to 3; and Al2O3 concentrations are reaching levels that cannot be ignored. Mechanistic models must be developed to select or predict essential parameters such as kiln and furnace reductions, ferronickel grade, slag losses, metal and slag liquidus, operating temperatures, etc. But these models must be simplified so that they can be used on a routine basis; and they must be calibrated against a wide range of commercial operations in order to yield the most realistic predictions possible. The present paper proposes one possible approach, using FactSage as a basic source of thermodynamic data. The predictions thus obtained are compared to actual performance for two well documented operations, as well as to the predictions made with other tools that might be more accessible.

Jan 1, 2014

The Rosebery and Hercules mines, situated in the Rosebery-Williamsford district in western Tasmania, have a history of production dating back to 1896-7, although full scale production did not commence until 1936, following the development of a satisfactory process of selective flotation (Hall, Cottle, Rosenhain and McGhie, 1953). The mineral composition of the Rosebery zinc-lead ores was first described in detail by Stillwell (1934). The Hercules ore is generally similar, but as yet no descriptions of it have beenpublished.Since Dr. Stillwell's paper appeared, the management of the Rosebery and Hercules mines has from time to time submitted a number of interesting mineral specimens to C.S.I.R.O. Mineragraphie Investigations. Examination of these specimens brought to light eight minerals, some relatively uncommon, not previously recognized in these ores.They are cassiterite, molybdenite, stannite, electrum, meneghinite, boulangerite, pyrargyrite and pyrrhotite. Some of the specimens are also rich in tetrahedrite and gold. In addition each of the other ore minerals described by Stillwell, viz. pyrite, sphalerite, galena, bournonite, chaleopyrite and arsenopyrite, was detected in one or more of the specimens examined during the present study. The principal gangue minerals were found to be quartz, manganiferous carbonate, sericite and barite, agreeing closely with the observations of Stillwell.The present study was based on the examination of the following eight specimens.

Jan 1, 1960

By Albert Zima

ACCORDING to recently published statistics, it is predicted that as much oil must be produced during the next 16 years as has been produced during the past 75, in order to satisfy the high rate of consumption of petroleum products. During 1934, over 17,000 oil wells were completed in the United States, and it is expected that over 20,000 additional wells will be drilled during the current year. Were it not for the remarkable progress made during recent years in the improvement of drilling technique and in the development of equipment used in the production phase of the oil industry, it is doubtful whether sufficient oil could be produced to meet present requirements. A few years ago, wells seldom were deeper than 3500 to 4000 ft., owing to the limitations of the drilling methods and equipment employed. Today, however, through the application of scientific drilling methods and the adaptation of modern equipment and improved materials, many wells range from 6000 to 8000 ft, in depth, and a few recent completions exceed 10,000 feet.

Jan 1, 1935

Bortech’s BoreClad corrosion protection system will be displayed at MINExpo. BoreClad is an innovative system for inside diameter cladding of nozzles, tubes and other circumferential devices. Pressure vessels, mud pumps and other mining equipment must be protected from corrosive caustic chemicals. Usually manufactured from mild steel, they can be clad with a protective material, such as stainless steel, to provide corrosion resistance. However, most welding processes leave voids where corrosion can damage the base metal. BoreClad provides void-free welds by combining gas metal arc welding with automated feed and rotation of chuckable parts. Workpieces of up to 915-mm- (36-in.-) long with a 460-mm- (18-in.-)swing can be clad with stainless steel, Iconel or other exotic metals. In addition to eliminating the voids associated with hand welds, BoreCladcan lay more than 2.2 kg/h (5 lbs/hour) of metal. That is a significant reduction in weld time. Web sitewww.bortech.com.

Jan 1, 2004

By L. You

Theoretical and analytical analyses of three mitigative measures- plane fitting method, trenching, and tension cable led to the development of a total protection plan to eliminate or reduce damages to the residential structures subjected to surface movements caused by underground longwall mining. The protection plan was applied to twelve residential houses and two external garages. The success rate is overwhelming. This paper describes the methods employed for protection and results of those case studies.

Jan 1, 1986

The greater part of this paper comprises the material used in a lecture delivered to the South Queensland Branch of the Australasian Institute of Mining and Metallurgy in September, 1949. It contains little in the way of original matter, its main purpose being to call attention to the need for research into the properties of Queensland coals and to indicate some of the lines such investigations might profitably follow.Since the lecture was given the Powell Duffryn (1949) 1 report, which has made an excellent start along these lines, has been printed. This report is, however, only a beginning, though a big one, and there is ample room for many years of work along similar lines.The paper is based largely on the work of de Jersey (1946, 1949)2,3,4,5 and Jones and de Jersey (1947)6, but these workers in turn owe a debt to the work of many British and American investigators, too many to enumerate. The subject is a very large one-to deal with it fully would require not a paper but a book; all the author can hope to do is to discuss very briefly some of the main lines of investigation and indicate some of their applications.The reason for selecting Queensland coals in particular is the widespread ignorance of the extent of the coal resources of that State and the almost complete ignorance, to within the last year, of the modern industrial purposes to...

Jan 1, 1950

By R. T. Jones

Keywords: Pyrometallurgy, DC arc furnace, myths, history, hollow electrode, radiation, resistance, flicker, AC DC arc furnaces are widely used for steel scrap melting as well as for reductive smelting of ore fines. Industrial smelting applications include the smelting of chromite to produce ferrochromium, the smelting of ilmenite to produce titania slag and pig iron, and the recovery of cobalt from non-ferrous smelter slags. A number of myths and misconceptions are widely held, especially regarding: the age of the technology, the use of a hollow electrode, arc stability and shape, arc and bath radiation, interaction between the arc and molten slag, electrical behaviour of arcs and slags, a comparison between AC and DC furnaces, DC reactors, the lifespan of bottom electrodes, and the applicability of DC arc furnaces to various metallurgical systems.

Jan 1, 2011

By R. T. Jones

DC arc furnaces are widely used for steel scrap melting as well as for reductive smelting of ore fines. Industrial smelting applications include the smelting of chromite to produce ferrochromium, the smelting of ilmenite to produce titania slag and pig iron, and the recovery of cobalt from nonferrous smelter slags. A number of myths and misconceptions are widely held, especially regarding: the age of the technology, the use of a hollow electrode, arc stability and shape, arc and bath radiation, interaction between the arc and molten slag, electrical behaviour of arcs and slags, a comparison between AC and DC furnaces, DC reactors, the lifespan of bottom electrodes, and the applicability of DC arc furnaces to various metallurgical systems.

Jan 1, 2011

Close spatial relationships between the deposits of the Etheridge Goldfield (23 000 kg of bullion) and various regional geological and geophysical features suggest that genesis of the ore deposits was a multi-stage process that started with magmatic and metamorphic stages in the mid-Proterozoic, climaxed with structural and hydrothermal stages in the late Palaeozoic and terminated with an oxidation enrichment stage in the Cainozoic. Acceptance of this hypothesis permits classification of the Georgetown region into areas likely to contain deposits of the Etheridge type and those unlikely to do so. Consequently there is little scope for the discovery of extensions of this field. However, the stratigraphic interval between the source rocks of the Etheridge field and stratigraphically bigger host rocks of the Croydon field may contain disseminated replacement gold deposits of the Carlin type. The potential host (pyritic carbonaceous and locally dolomitic siltstone of the Candlow Formation) is locally faulted and cut by granitoids and the extension of a mineralised, long-standing zone of structural weakness.

Jan 1, 1980