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By P. Golledge, A. D. S. Gillies

An investigation has been carried on samples of three Queensland coal dusts to determine the potential explosibility of dust-gas mixtures. The explosion potential of the samples was classified by the lean and rich limits of explosibility and the limiting oxygen concentrations for each sample. Plotting of these points showed 2-dimensional flammability limit surfaces for coal dust/oxygen, methane/oxygen and coal dust/methane mixtures. From these plots the 3-dimensional flammability envelopes defining the explosibility of the mixtures were defined. The explosion limits of the coal dust/methane/oxygen system were seen to be influenced most by the explosibility characteristics of coal dust. Methane exerted a stronger influence over the explosion limits when the coal had a low volatile content

Jun 19, 1905

By J. A. Finch, D. Lin

The robustness of the large-sections correction procedure, Hill's fast approximation, Barbery's correction and the PARGEN correction was examined by comparing their ability to reconstruct the true liberation distribution using sectioning data from computer-generated spheres. The results indicate that the flexibility of a correction procedure is related to the assumptions it makes about the continuity of the liberation distribution, locked-particle characteristics and ore texture. Overall, the large-sections procedure appeared to be the most generally applicable. The Hill fast approximation performed well, but this was probably because it partially incorporates the sphere model; the performance of the PARGEN and Barbery corrections varied from case to case.

Dec 1, 1995

By K. D. Russ, A. J. Beer

Non-contact systems for measuring underground voids have used theodolites, reflective or non-reflective laser methods and sonar techniques. An effective but cheaper alternative is based on use of a Wild T1000 electronic theodolite coupled to a Leica Data DISTO and a Wild GRE3 data logger. The software used to process the theodolite data is a spreadsheet and macro combination, while Surpac, Datamine and AutoCAD modelling packages have been investigated for viewing the tunnel profiles. The main limitations were found to be blinding, when irregularities in the stope obstructed the line of sight, and the 30 m range of the Data DISTO model used in the study, although more powerful models are available. All three modelling packages proved suitable, with Surpac providing the best-quality printed images of the voids surveyed and AutoCad by far the cheapest alternative

Jun 21, 1905

By J Parnell, B Manson

Bitumen occurs in the basins in reservoir sandstones, in veinlets close to hydrocarbon source rocks, in veins through lava beds and in sulphide-mineralised veins where it is closely associated with, but predates, the sulphides. The role of organic matter was probably in enhancing metal reduction by creating a low-Eh environment rather than in metal transport. Coeval euhedral quartz crystals or albite in sulphide-bearing carbonate veins provide evidence of an aqueous component to the hydrocarbon fluid

Aug 1, 1995

By I. L. Bell

The ironmasters of America had asked the Iron and Steel Institute to visit the USA. The Council decided it was not possible to accept, but Mr. Bell visited; this is an account of his trip. Topics covered include transport, charcoal, coal measures, coal, anthracite, bituminous coal, flux, magnetic iron ore, specular iron ore, limonite, red hematite, clay ironstone, black band ironstone, smelting works, blast furnaces of Pennsylvania, Lake Champlain furnaces, Lake Superior furnaces, Cleveland furnaces, Pittsburg furnaces, Missouri furnaces, and those of the southern states. He goes on to describe Catalan hearths, malleable iron works, Bessemer works, the Blair steel process, and labour.

Jan 12, 1875

By S. P. Singh

The purpose of the cut is to provide a free face to which the remainder of a development or breasting round can break. The results of field testing in drifts and at a quarry face were used as a basis for a description of the rock breakage and flushing mechanism in the cut. It was concluded that the important features of a cut design are proper hole spacing, sufficient relief volume, drilling accuracy and relief holes slightly longer than the planned length of the round. The void space provided by the relief holes should be about 15% of the cut volume, with more required in weak, highly fissured rocks. The importance of drilling accuracy increases with round length, an error being magnified by the small blasthole spacing. The first hole pulls only about 20% of the round length, 4-6 holes having to be fired before the cut is pulled close to its design depth. The first four blastholes should be fired with a minimum inter-hole delay of 100 ms to provide progressive relief of burden and avoid the superimposition of ground vibrations. The earliest-firing charge should be closest to the relief area and act laterally, while the first of the vertically-fired charges to be detonated should be the uppermost. Problems during cut-pulling include sympathetic detonation, dynamic pressure desensitisation, charge disruption and freezing of the cut

Dec 1, 1995

By R. D. Stewart

Paper presented at the conference: Risk assessment in the extractive industries, held in Exeter, UK, 23-24 March 1994, and first published London: IMM, 1994, preprint volume, 18pp., 5 refs. A seismic risk assessment method has been developed for application to rockburst prone deep-level mining sites which have sufficient seismic coverage. The technique utilises several seismic hazard parameters simultaneously and assesses the seismic risk on a daily basis according to the individual levels of these parameters. Critical levels are determined from investigation of the long-term behaviour of the parameters in relation to recorded potentially damaging seismic events. The method has been applied to a data set comprising 15 months' worth of seismic data, with encouraging results

Aug 1, 1995

By S. P. Mishra, G. R. Chaudhury

The adsorption of Cu2+ ions by Penicillium sp. displayed a dual rate, with an initial faster phase followed by a slower one. The adsorption rate increased with increasing pH due to chemical and biochemical reactions. The Cu-loading capacity of the biomass increased at higher initial Cu2+ concentrations. Above 40 degrees C the adsorption rate decreased which may be due to partial hydrolysis of biopolymers which are essential constituents of the cell wall. Adsorption kinetics followed the Freundlich isotherm and the equilibrium concentration that was calculated on the basis of the isotherm matched the observed value well. A series of theoretical adsorption curves were produced using mathematical correlations between the mass transfer coefficient, the Cu2+ ion concentration at equilibrium and at time t. The correlation between the theoretical and observed adsorption rates for different experimental conditions was good. It was concluded that the results from the study were best explained using a mass-transfer adsorption model

Aug 1, 1995

By B. J. Breen, C. S. Mogg

Considerable borehole investigation work has been completed at a proposed site at Sellafield in Cumbria, supplemented by seismic surveys, other geophysical sensing and geological mapping. The focussing of investigation on the rock mass itself will be achieved by means of the planned underground rock characterisation facility, giving access to depths of about 800 m in the strong, low-permeability basement rocks of the Borrowdale Volcanic Group. Characterisation work undertaken during the sinking phase and interaction with continuing surface-based exploration and monitoring should permit a firmer assessment of the long-term safety of a repository. Key considerations in the choice of a design for the repository include the waste handling method, underground inlet cell, underground vaults, vault environment and environmental effects

Aug 1, 1994

By I. R. Hanby

A simple solution to the problem of whether to round the calculated number of trucks up or down to the nearest whole number is to adopt as criterion the minimum cost per unit volume/mass moved, assuming all trucks in the fleet are of the same type. When the effects on journey time of varying haul-road slope are calculated for several rolling resistances, it is shown that the optimum angle of 7.5 degrees is moderately independent of both rolling resistance and height climbed; the lower the resistance, the lower the sensitivity to ramp angle, but if haul-road gradients do not exceed 1 in 10 (5.7 degrees) for safety reasons then travelling time will never be more than 7% greater than its theoretical minimum. Further calculations result in a graph of the maximum payload values to incur the minimum cost, for different values of total effective resistance

Jan 1, 1991

By O. R. Eckstrand, M. Asif, P. L. Schwann, A. J. Naldrett, R. J. F. Scoates

Paper presented at the IAGOD international symposium on mineralisation related to mafic and ultramafic rocks, held in Orleans, France, 1-3 September 1993. PGE-bearing sulphide mineralisation is contained in the lower 600 m of the Upper Central Layered Zone of the intrusion. There are four regimes with distinctive crystallisation characteristics. PGE content is low, both in bulk rock and in terms of metal in 100% sulphides, in the sulphide-rich cumulates but increases sharply in the sulphide-poor cumulates at the base of regime 1. Increases in regime 2 have no such clear relationship with incoming cumulus sulphides. PGE contents are low throughout regime 3, but regime 4 has sulphides with high PGE content, decreasing rapidly upwards, at the base of many of its cyclic units. The observations are interpreted as indicating that sulphide saturation occurred in the middle of a cyclic unit in regime 1, after which fractional segregation of sulphide caused a systematic decrease in PGE content. The resulting contrast between 40 000 ppb PGE in sulphides below the mineralised zone and less than 1 000 ppb above is of practical importance in exploration for such zones. In regime 2 the magma chamber was open to fresh influxes and PGE content was not so sensitive to sulphide saturation. In many regime 4 units influxes of new magma caused immediate sulphide saturation and PGE depletion, so that PGE-rich cumulates do not underlie PGE-bearing sulphide zones. Theoretical analysis indicates that regime 1-type behaviour is likely to characterise intrusions below the level at which plagioclase has entered as a cumulus phase and regime 4-type behaviour above

Apr 1, 1994

By L. J. Cabri

Although no complete mineralogical balances have been published, the background knowledge and proven, highly sensitive analytical techniques to produce them already exist. For PGE-Cu-Ni sulphide ores a combination of ore microscopy, image analysis and electron microprobe analysis with proton microprobe analysis of sulphides for Pd, Rh and Ru and ion microprobe analysis for Pt, Ir and Rh (in some minerals) should provide the necessary data when combined with reliable assays. Other sulphide ores, such as the Cu-Ni-(PGE) ores of Sudbury, Ontario, require a similar approach except that the ion microprobe would be more suitable for the analysis of Pd, Pt and Rh because of its greater sensitivity. Oxide-silicate ores may be harder to deal with quantitatively, although the potential to confirm the presence of trace PGE within silicates and oxides may be greater than in PGE sulphide and Cu-Ni-(PGE) sulphide ores. However, solid solution of PGE in oxides and silicates still requires thorough documentation and evaluation in terms of their significance for the overall metallurgical balance

Apr 1, 1994

By G. S. Camm

Gwynfynydd is a small, high-grade black shale-hosted vein-gold deposit. The Chidlaw Link Zone is the only area being mined and contains 24 000 t ore grading 15.2 g/t gold. Within the Link Zone a complex vein structure occurs consisting of a mother vein up to 5 m thick and narrow (less than 0.5 m) leader veins. The former shows minor variations in dip, strike and thickness, whereas the latter show marked changes in all three. The leader veins are hosted within the footwall zone of the mother vein and both are composed of quartz with galena, sphalerite, chalcopyrite, pyrite and minor arsenopyrite. The vein system is transected by a series of cross-vein and intra-vein dip-slip faults. Pockets of gold occur at vein intersections or branches and within the complex footwall zone and are often related to variations in vein attitude and/or geometry. The Chidlaw Link Zone displays a complex, erratic distribution of gold mineralisation and a multi-stage history of structural activity, fluid flow and mineral deposition

Jun 18, 1905

By P. P. Jenkins, T. G. Ball

Paper presented at the Drillex '90 conference held in London, 5 April 1990. Two drilling techniques are employed - guided longhole drilling and reverse circulation coring - for underground longhole exploration of the coal reserves and the fault structures that affect them. These are complementary to, or replacements for, surface boreholes, underground development drivages and seismic techniques. The developments of the drilling techniques and some case histories are presented in detail.

Jan 1, 1991

By F. M. Vokes, P. M. Ihlen

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. Ore deposition was related to three major stages: continental rifting and separation (Vendian-Late Cambrian), convergence (Late Cambrian-Early Silurian) and collision (Early Silurian-Devonian). The first stage included deposition of volcanogenic massive sulphide Zn-Cu and stratabound or stratiform Fe and Zn-Pb(-Cu) on continental margins, as well as less economic Nb and Fe in carbonatites, U, Mo, Ni and V in Alum Shales and orthomagmatic Cr, Fe-Ti and Ni(-Cu). The numerous volcanogenic massive sulphides formed during convergence included Early Ordovician Cu-Zn, mature-arc Cu, Zn, Pb and Fe-oxide deposits, Besshi-type deposits dominated by Cu or Zn in gabbro-intruded sediments and minor Cu-Ni(-PGE), Cu-Mo and skarn deposits. The collisional stage is represented by epigenetic deposits including sandstone Pb deposits (Pb, Zn, Ba, F and Cu) and minor vein deposits with variable Au, Ag, Pb, Cu, Zn, Fe, As, Sb, W and Mo

Jun 19, 1905

By F. Tailoka

Bi was electrorefined from alloys containing 10-90 wt% Pb, together with Cu and Ag as minor impurities, in a basic cell and in a recessed-channel cell with 27.5:72.5 NaCl-PbCl electrolyte at 450-470 degrees C and 10 000-20 000 A/m2. The voltage in the basic cell was as high as 9 V, with some carryover of Bi to the cathode observed, whereas in the recessed-channel cell it was as low as 285-635 mV. Flow patterns observed in a room-temperature model indicated that the recesses provide both static liquid hold-up and good mixing of the alloy, enhancing cell performance in combination with the reduced anode-cathode distance of 0.90 mm. The purity of the resulting anode product is as high as 99.9%

Aug 1, 1995

By M. K. Abd El-Rahman

A complete chemical analysis of the waste showed that it contains 15.64% P2O5; X-ray diffraction analysis revealed that it is composed mainly of francolite, calcite, pyrite, quartz and dolomite. The phosphate values were recovered and the settling rate of the wastes enhanced by the use of hydrocyclone and flocculation techniques. The hydrocyclone produced an underflow enriched in phosphate and an overflow enriched in clays. The former represented 39.8% by weight of the phosphatic clay waste and assayed 26% P2O5 at a recovery of 66.36%. The results of flocculation of the phosphatic clay waste showed that both the degree and rate of settling were increased and that the process water could be recycled. The settling rate was 37 times greater when anionic polyacrylamide A130 was used

Jun 21, 1905

By J. A. Hudson, D. L. Millar

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: Rock engineering system performance monitoring using neural networks.) Synthetic and analytical approaches to objective-based design of rock engineering projects are discussed. Rock masses are considered as complex dynamic systems with components that concurrently interact with each other and their environment. The existence of a rock engineering system canon (i.e. a set of systems governing rules) is proposed. Its possible components are highlighted and an application is demonstrated using a "rock mass automaton" designed to simulate dynamic heat distribution in rock. In the example given, the canon implements the basic result from probability theory applied to the thermodynamics of solids. Rock engineering system performance is reduced to the mapping of the output of a rockmass to varying input (design) options, within the state space of the systems model. The Kohonen Self-Organising Map provides an extremely useful analytical tool to reduce the hyper-dimensionality of rock engineering system behaviour. Further, the hyper-dimensional state vector is mapped "quasiconformally" such that the neural map tends to spatially organise similar input state vectors, facilitating interpretation of rock engineering system behaviour (performance monitoring). Work is reported on the development and validation of the automation as a basis for an internal representation of the rock mass bahaviour. The results are reported of simulations compensating for the uncertainty of the exact mechanisms operating within the rock mass, using additive noise with the input state vector in the training stages of the self-organising map implementation. Initial work on adopting Grossberg's Adaptive Resonance Theory neural network architecture for classification of rock engineering systems behaviour is also presented

Apr 1, 1994

By D. M. A. Flight, G. E. M Hall, P. R. Simpson

theoretical viewpoints.

Apr 1, 1994

Carbon anode cells were studied by two-dimensional computer simulation to evaluate their suitability for alumina electrolysis at high superficial current densities. The most efficient anode arrangement was needed to overcome the electrochemical disadvantages of alumina's low solubility in chlorides. Cells with packed-bed anodes might provide practical superficial current densities greater than 0.67 A/cm2 when the granule size was less than 1 cm, but in the process of electrolysis the granules within the active zone would be consumed and become smaller, affecting alumina concentration transport. For zones of very small granules a concentration-dependent model should be considered; for more complete consideration a time-dependent model can be introduced to describe the variation of granule size and its influence on mass transfer and polarisation

Jun 19, 1905