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By Y K. Leong

Iron ore tailings typically containing 40 to 50 per cent Fe can be beneficiated to iron ore products containing 54 to 60 per cent Fe. The impurities are comprised of clay, quartz, cristabolite and TiO2. Goethite and hematite are also present. At high concentrations of 55–60 wt% solids, the tailings displayed high yield stress and viscosity and cannot be pumped over long distances. Composite additives comprising of NaOH, phosphate-based additives and sodium metasilicate are found to reduce the viscosity and yield stress very significantly by a few orders of magnitude. The yield stress of 100 Pa can be reduced to almost zero. At this state, dilution of the tailings with its process water to 40 per cent solids causes the coarse and high-density iron ore particles to separate from the colloidal fractions located in the supernatant after a few minutes of sedimentation. Separation by decantation produces a sediment with an Fe content of 54 per cent from tailings with 47 per cent Fe. Another tailings sample with 48 per cent Fe was beneficiated to greater than 57 per cent Fe using NaOH-metasilicate-polyphosphate additives and employing an additional washing step. The use of other composite additives, NaOH and polyphosphates, increased beneficiated product Fe content to greater than 60 per cent from the same tailings. With the current iron ore spot price of more than US$180 per tonne, the cost of this treatment process even including a desalination step, if necessary, is relatively insignificant. This study has given tailings an economic value that should be exploited as soon as possible.

Nov 8, 2021

By M Ujihira, M Komazaki, K Higuchi, D F

A diesel engine with a misfiring cylinder is likely to break down in a short time when the engine is used without maintenance. The authors have developed a method of detecting the occurrence of cylinder misfiring and specifying the misfiring cylinder by using wavelet analysis and statistical analysis on the root mean square (r.m.s.) values of two kinds of acceleration waveforms. This detection method is considered superior to traditional methods, which require several accelerometers, especially in terms of simplicity. Since the development of the method, research has been conducted on semi-automatic processing of measured signals and signal transmission from the worksite to a remote office. Field tests confirmed that 1 + 105 points of dynamic data could be transmitted through the mobile multimedia network within 15 minutes, and the time for signal processing was within 15 minutes. Final determination on the condition of a diesel engine in heavy machinery could be achieved within 30 minutes. Shortened processing time is expected by improvement of the processing software.

Jan 1, 2003

By L J. Reynolds

Gold mineralisation at the Globe Progress deposit is hosted by a geologically complex zone of shearing and brecciation, within a package of deformed metasediments. Mineralisation styles range from quartz breccias and lodes to sheared clay pug zones and disseminated sulfides. A review of the diamond drill core intersections through the deposit indicates that critical hanging wall and footwall contacts can be a combination of sharp or gradational; visual or non-visual boundaries. Approximately 60 per cent of mineralised contacts can be confidently identified visually, particularly where associated with veining, distinct brecciation or shearing, and high sulfide content. However, the gold grade and distribution of disseminated mineralisation can be extremely difficult to estimate visually, with implications for resource estimation and grade control when mining. Using observed drill hole geology and assays, a new geologically based model for the gold mineralisation has been constructed for the deposit to reflect the expected variability of the mineralisation contacts. This new model will constrain resource estimation and also serve to act as a predictive model when open pit mining commences. Nevertheless, careful grade control practices such as drilling, trenching and supervised extraction of ore will be required to maximise ore recovery and minimise dilution during open cut mining.

Jan 1, 2006

By Smith JW

Studies of 13C/12C ratios of carbon dioxide in seam gases and in secondary calcites show that 1. In mines prone to carbon dioxide outbursting, the source of this gas is external to the coal. 2. Faults draining reservoirs of magmatic or primary carbon dioxide, rather than intrusives, are the most likely points of entry of carbon dioxide into mines. 3. The higher the concentration of carbon dioxide in seam gas and the wetter the mine, the lower the likelihood of secondary calcite occurring as a filling in cleats, fractures etc. 4. A -role played by carbon dioxide in promoting outbursting may be the conversion of calcite to soluble bicarbonate, the removal of this in mine water and the subsequent weakening of the resistance of the bulk coal to stress.

Jan 1, 1980

Builders have been very familiar with iron since ancient times, but because of its weathering characteristics it was relegated to use as a fastening material in unexposed places and bronze became the popular metal for exposed applications. It is of interest that iron nails buried deeply about A.D. 87 at a Roman fortress and carefully covered with clean beaten earth under conditions practically excluding oxygen were found to be almost unrusted 1870 years later. (1) Today, weathering steels, which contain less than 2% of alloying additions, can be used in exposed situations without protection and without experiencing continuous wastage. As we all know the steady access of atmospheric oxygen to the surface of plain steel causes continuous corrosion. Weathering steels, on the other hand, due to their alloying additions develop their own impervious surface layer which limits the access of atmospheric oxygen and effectively limits corrosion. Table 1 shows the chemical composition of a plain carbon steel and a typical weathering steel. Fig. 1 shows what we refer to as direct corrosion - time curves in which corrosion loss is plotted against time of exposure in an strial environment. The weathering steel has a high rate initially which then decreases steadily for about three years, as the stable rust film builds up. This is followed by a practically linear relation where the very low corrosion rate, according to one school (2), is due to a blocking of the rust pores by insoluble complex salts formed from interaction of the oxidation products of the separate alloying elements. The start of the linear region represents a total corrosion loss of only about 2 thousandths of an inch.

Jan 1, 1970

By Bolton G. C

Experiments were conducted to access the feasibility of removing zinc from lead slag by sulfation or chlorination or both. Gaseous sulfation with sulfur dioxide and oxygen released only 50 per cent of zinc even under the most severe conditions. Sulfation with concentrated sulfuric acid by a fast-leach process released 95 per cent of zinc while pug-roasting released a maximum of 78 per cent of zinc. Chloridization with NaCi in the presence of sulfating gas released 50 per cent of zinc, while direct chlorination with chlorine gas and oxygen released 85 per cent of zinc and 100 per cent of lead in a chloride condensate containing little impurities.

Jan 1, 1980

A number of suggestions have been made to improve the design of cells used for electro winning and electro refining of metals. Most of these designs have been aimed at increasing the current density used in order to improve cell capacity, although the purpose of some has been to produce electro deposited metals in a continuous manner. Improvements in the electrolyte flow pattern in conventional cells have resulted in an increase in the rate of mass transport of metal ions to the electrode surface; giving rise to lower concentrat- ion polarization and an improvement in the nature of the product obtained, Other cell designs are based on a moving electrode, usually a rotating disk, and these may include provision for removal of the product in a continuous manner, The maximum current density which can be used in an electro- lytic deposition process is determined by the limiting diffusion current, the physical nature of the, product, the purity of the product required and by the increase in power costs which result from the higher cell voltages, This paper examines the properties of an agitated bed of particles as an electrode system when used for a metal deposition Process,

Jan 1, 1969

By M Pizey, P Lindsay

Coal mining has been occurring on the Stockton Plateau for over 100 years. As a result of both natural conditions and mining activities, surface water on the plateau is known to have low pH and elevated metals concentrations, a condition known as acid rock drainage (ARD). Solid Energy New Zealand Ltd (SENZ), as owners of the current mining operations at Stockton desire to understand the nature and causes of ARD at Stockton to determine whether commercially viable options can be developed to improve the water quality to levels acceptable to the local community and regulators. A series of integrated water quality investigations have been performed towards developing a characterisation of the water quality on the Stockton Plateau and receiving waters. The investigations performed include: design and implementation of a water quality monitoring program to collect a satisfactory base of water quality data from which to develop an understanding of the water quality and its variability, and to collect data regarding the range of flow rates that occur in the principal streams; development of a hydrological model for the Plateau with the ability to predict flow rates at key locations on the plateau and on the Ngakawau River; field investigations of the bio-diversity of the plateau and surrounding areas, to develop a snapshot of the health of aquatic communities and whether streams draining mine workings are æadversely impactedÆ; eco-toxicology; waste dump seepage water quality monitoring at selected basal springs, drilling, investigations and permeability and geochemical testing; data processing of a range of historical data and the newly acquired data for the development of empirical relationships that describe the water chemistry system and its relationship in turn to flow rates in the streams; simulation of the long term water quality record for the measured parameters (pH, acidity and metals concentrations), based on the hydrological model and the empirical relationships developed from the new database; and preliminary development and examination of mitigation options for the ARD issues at the mine. The study has progressed towards design of pilot studies of options for mitigation of the generation of the ARD as well as treatment of the discharges. It is the integrated approach adopted by SENZ from an early time in the investigations, that has enabled fast-tracking of the pilot engineering trials. This paper presents the results of the field investigations and eco-toxicology studies and demonstrates the value of predictive modelling of water quality in the study area, even at a very early stage in the remedial engineering design process.

Jan 1, 2003

By Hematian J

A high horizontal stress field has significant effect on the stability of underground roadways and influences the design of a support system in this environment. The high horizontal stresses at E1lalong Colliery, NSW, Australia provided the environment for this study. Samples of coal measures 'rock were collected and tested to determine their mechanical properties. The lithology, stress state, geometry and conditions prevailing in particular areas of the mine were obtained from geotechnical reports available at the mine and by field observation. The results of a series of finite element models constructed and tested under various conditions provided a basis for comparison with field observations. Analysis of the results indicated sufficient correspondence to provide a basis for the proposed design of an optimum support system. It is not suggested that finite analysis provides 'exact answers', but it does show the relative importance and interaction of various parameters.

Jan 1, 1995

By T GRAHAM-TAYLOR

A trend towards mining more complex and economically marginal orebodies, often combined with increasingly tight product specifications, increases the number of variables which need to be considered in production scheduling. Linear programming incorporating integer constraints can be used to create production schedules which are practical as well as mathematically optimum. Factors which can be taken into account include variability in product stockpiles, targets for head or product grades, production of different material types, production from different areas, production targets for loaders, and dependencies between mining blocks. For each schedule an appropriate objective for optimisation must be chosen. Examples of objectives are: to minimise or maximise grade variation; to minimise waste movement; and to minimise movement by front end loaders. A staged approach to the implementation of computer systems based on linear programming optimisation is Proposed.

Jan 1, 1992

The prevention of silicosis by metallic aluminium has been reported by Denny, Robson, and Irwin in two papers. The first was published in 1937; the second, in 1939. The results definitely established that silicosis was prevented in animals by the inhalation of small quantities of aluminium. The present communication records subsequent progress in this field of research.

Jan 1, 1944

By Linying W

Entropy is an important concept both in natural and social sciences.Considering the preparatory process of the earthquakes as an open system, in view of basic ideas of the Theory of the Dissipative Structure, the seis-mological Entropy is introduced as an order parame-ter, describing the scale of order associated with the earthquake distribution in time, space and mag-nitude. The features of evolution of seismic acti-vities before and after the large earthquakes have been studied by using the seismological entropy.The preliminary results show that the seismological entropy in certain region decreases as the large earthquake is approaching, it means that the distri-bution of earthquakes has turned gradually in order from disorder.It is expectation that the application of the Principle of Entropy in seismological research will deepen the understanding of the physical process of earthquake preparation. Meanwhile, it will also offer some enlightements in studying mitigation of seismic hazard as well as earthquake prediction.

Jan 1, 1990

By Musa MA

Tunnel excavation for sewer construction long remained a labour intensive, hazardous and costly operation. Even with the of mechanical and semi-mechanical shields for tunnel excavation, many problems remained until recently. In the past decade, however, the technology has changed dramatically which has made possible the use of advanced tunnelling methods for sewer construction.

Jan 1, 1993

Techniques and results achieved during the excavation of the Melbourne Underground Rail Loop (HURL) are summarised and discussed in the context of the various restraints present in a typical urban construction project. Mechanical methods (as distinct from those utilising blasting)accounted for the bulk of the excavation. Ground support was critical in this particular geological excavation setting, but is not discussed in detail except insofar as it constitutes a restraint to excavation progress.

Jan 1, 1978

In those days no one worried - there were plenty of other things to do. But in'these days it is different. Everyone worries- and. because there is so much worry, emotion has entered the picture. And, worse than that, capital is being made in political circles. People who were quite unaware, five years ago, that any problem existed, have now become experts on the subject, and shout to high heaven that something should be done - and yet they go on using the leaded high octane petrol they deplore so much. And even scientists, who should know better, adduce only such evidence as fits the argument in hand. And the Press is not without blame - some of its reportings is open to serious question, whatever may be the excellence of its motives. The point is made that one should know what one is talking about. And make sure that the evidence quoted is fact - and make sure too, that all the evidence is used, not only that which suita the argument.

Jan 1, 1971

By Xizhen J

Point load testing for irregular rock specimens was studied to determine the relationship between tensile and compressive strengths, drill penetration rate and other rotary drilling parameters. The DH-l type point load tester was developed and more than 2 000 irregular specimens of over 60 kinds of rock from 16 mines and quarries were tested. The effects of size, shape and number of samples on the point load strength index were investigated, using regression analysis. Experiments were carried out to investigate the relationship between point load strength index and uniaxial compressive strength on 29 kinds of rock. The relationship between these values and the drill penetration rate for rotary and percussion drills is discussed.

Jan 1, 1986

By Ohga K, Isobe T

Basing upon many and long practical experiences of gas drainage from coal seam and results investigations on the gas flow through in si-tu coal seam using tracer gases,it became clear that solid coal itself is hardly gas permeable or has extremely low gas permeability. Almost all of gas flows from a coal seam into boreholes through fracture net- works intersecting with them.Primary and secondary fractures in coal seams differ in their size and continuity from place to place according to differences of the coal strength and the stress conditions. A lot of gas can be drained through boreholes which intersect with many and/or wide fractures. A mathematical model for gas flow from a coal seam to a borehole through a discoidal fracture is proposed. From the numerical analyses,the apparent radius of the discoidal fracture in this model is shown to be a good indication of the gas drainage ratio. In addition to this,an atempt to make fractures around a borehole using high velocity water jet(ca.lmm dia.,300-700atm., 100-200 1/min.) is introduced.

Jan 1, 1982

By Wang S

Fragmentation is the basic concern in rock blasting and serves as the main measure of blasting effectiveness. A good estimation of fragment size distribution before blasting is very useful and helpful for selecting the proper equipment for loading, transporting, and crushing rocks. A fragmentation model is presented that is based on a hole by hole analysis and correlates the rock properties, burden, spacing, and explosive column with the blasted volume and fragmentation obtained. The drill bench is divided into three separate areas corresponding to different breakage mechanisms. They are: 1) a main breakage or casting area, 2) a secondary breaking area, and 3) an overbreak area. The boundary of the main breakage area is found from the magnitudes of strains in the stress waves and the tensile strength of the rock. The secondary breaking area is determined by stress wave reflections at discontinuities and interactions between colliding stress waves from adjacent boreholes. The overbreak area is that beyond the main breakage area "where the reflected tensile waves no longer break the rock. This analysis is applied on a hole by hole basis to locate the breaking points. Then connecting the breaking points on each side of a borehole forms the triangle of the main breakage area. This is repeated for the next hole and the remaining area is the secondary breakage area. After the angle and area for each hole are found the Kuz-Ram model is used to predict the fragmentation size distribution for each hole. Then summing up the size distribution for each hole gives the total fragmentation distribution. This analysis has been successfully applied to field tests performed in a limestone bench where the entire spoil pile was screened to determine the fragment size distribution. Knowing the explosive and rock properties the breaking area was found for each hole, the strain and stress values, the breaking point, and angle of breakage (104 degrees). The fragmentation size distribution was then calculated and compared to the field data with excellent agreement.

Jan 1, 1990

In the geologically prospective nations which rim the Pacific Ocean, mineral deposits offer great potential to create wealth for social and economic development. The paper first examines the geological and economic attributes of potential mineral wealth based on current outlook assessment of all significant base metal deposits discovered to 1988 in two Pacific Rim nations - Australia and Canada. The variability of mineral wealth among the economic deposits evaluated and the major contribution of the few world-class discoveries to total mineral wealth are highlighted. Then, the essential but too often neglected linkage between the makeup of potential wealth and its actual realization is analyzed. The impact of taxation and the role of exploration are crucial in this regard. Finally, the ingredients of exploration success, prerequisites for realizing the mineral wealth of nations, are examined.

Jan 1, 1995

By Wilson A. F

The use of stable isotopic measurements as a technique for elucidating the origin and history of the water in hydrothermal fluids is relatively new. Recent studies have emphasized the importance of meteoric water in the formation of many hydrothermal ore deposits including many epithermal gold-base metal deposits which occur in faulted volcanic terrane. Other vein-type gold ores are be- lieved to have formed from fluids of magmatic or metamorphic origin and exhibit characteri stic 6180 values. These values also give information regarding temperatures and the degree of equilibrium. Preliminary oxygen data for some important gold deposits of eastern Australia are evaluated in the con- text of styles of mineralization.

Jan 1, 1980