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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 R. K. Dunham, D. J. Reddish, X. L. Yao

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, 10pp., 10 refs. The integrated approach combines a powerful ground movement prediction program with a knowledge-based expert system. ESDAS (Expert Structural Damage Assessment System) was developed to evaluate mining subsidence damage in the form of risk and in terms of the three vital contributing components (mining factors, site factors and structural factors). Using a certainty factor risk assessment technique, the system can be used to predict the likely damage to a particular structure subjected to mining subsidence. A previously developed powerful ground movement prediction program, SWIFT (Subsidence With Influence Function Techniques), has been combined with the expert system to allow the mining factor to be more accurately determined in a broader range of mining layout. Since SWIFT can be calibrated to any particular coal field using local subsidence data, it is believed that the integrated system could be used in any coal field worldwide for the assessment and control of mining subsidence damage risks

Dec 1, 1995

The Council of the Institution of Mining and Metallurgy submitted the report of the affairs of the Institution for the session 1970-71, and the Statement of Accounts for the year ended 31 December, 1970. The statistics given in the report refer to the calendar year 1970. Details are included of membership, officers, representation on other bodies, honours and distinctions, awards, meetings, publications, library, overseas activities, fellowships and grants, the revenue and expenditure account, the balance sheet, trust fund balances, contributing companies, and schedule of investments

Dec 1, 1971

By P. G. Flood

A simplified conceptual model shows how the arc flank to arc fringe areas adjacent to ignimbritic centres form a prospective zone for natural zeolites. Large alkaline lakes that serve as the repository of voluminous ash-fall tuffaceous material provide the ideal chemical setting for pervasive alteration of silicic glass to zeolites. The unusually old age of the Escott deposit demonstrates that any silicic volcanic province that contains low-temperature, unmetamorphosed sequences is a potential zeolite exploration target and that age should not be used as a criterion to exclude potential areas. It has also been demonstrated that heulandite and mordenite, formed by diagenetic alteration of silicic glass, do not always change to analcite and albite through the ageing process

Jan 1, 1991

By Qing Wang

In this method the state of an open-pit mine is represented by the number of benches that are mined in each predesigned mining phase (or pushback). Consequently, a specific mining schedule can be represented by a sequence of states which starts with the topography of the mine site and ends with the ultimate pit. For a given set of mining phases all feasible states are first generated and sequences of states are then evaluated for technical and economical feasibility. The best sequence, which gives the maximum net present value (NPV), is found by applying a dynamic programming optimisation algorithm. The algorithm also optimises the cut-off grade which satisfies the mill feed requirement for each planning period. It was found that the algorithm can be used not only for scheduling but also as an effective tool for analysing the effects of mining and milling capacities and cut-off constraints on the mining schedule and the total NPV. The algorithm, which was programmed in C, was successfully applied to a large Au-Cu deposit

Jul 1, 1996

By L. Villa, O. Suarez, D. Arias, L. G. Corretge

The deposit comprises two vertical, lenticular bodies emplaced in the allochthonous block of a Variscan thrust. Epigenetic mineralisation occurs as replacement of carbonated volcaniclastic rocks of Cambro-Ordovician age. The dominant sulphide minerals are sphalerite and galena with minor chalcopyrite; the main non-metallic mineral is quartz and there is hydrothermal silicification, chloritisation and sericitisation. Sulphur isotope values for sphalerite and galena are heavy and reflect the fundamental relationship between delta-34S in ZnS and in PbS, suggesting isotopic equilibrium. Four sphalerite-galena pairs yield temperatures between 163 and 218 degrees C, in good agreement with the 187-207 degrees C estimated by the Ga/Ge-sphalerite geothermometer. The ore sulphide was leached by the hydrothermal solution from diagenetic pyrite in the host rocks and disseminated sphalerite and galena in Cambrian carbonates

Jun 19, 1905

By B. Tiryaki, O. Z. Hekimoglu

Shearer drums are a critical component in the overall performance of coal shearers, with the cutting performance depending very much on the disposition of cutter tools on the drums (the tool-lacing arrangement). A series of practical and theoretical studies has been undertaken to investigate aspects of shearer drum vibration in terms of circumferential pick spacing. A number of commercially available drums were redesigned and the lacing patterns compared with those of the original drums under near-uniform conditions. Mine trials were carried out at the Middle Anatolian lignite mine in Turkey with drums fitted on Eickhoff type EDW-230 double-ranging drum shearers. It was found that the performance of drums could be improved if the concept of circumferential pick spacing was taken into account in CAD packages along with the existing design parameters such as cutting rate, reduced dust, low pick consumption and low down-time

Jun 19, 1905

By M. Bustillo, S. Ordonez

"Paper presented at the conference Economic geology in Europe and beyond II, models for mineral deposits in sedimentary basins, held in Keyworth, UK, 13-14 April 1994. The Mississippi Valley-type deposits occur in massive, homogeneous dolostones from which diagenesis has obliterated all primary sedimentary structures. The mineralisation forms irregular, lens-shaped stratabound bodies, mostly in the lower part of the dolostones. They are composed exclusively of sphalerite, galena, pyrite, marcasite and barite, with white sparry dolomite a common cementing phase. Mineral zoning can be recognised from pyrite and marcasite in the east to barite in the west. Sphalerite, the most common sulphide, occurs basically as colloform and banded crusts and galena as isolated cubic or skeletal crystals, mainly in the centre of the banded botryoidal sphalerite. The combined observations of the deposits' geology, geochemistry and ore petrology suggest a three-stage genetic model: carbonate sedimentation in a shallow-water environment; dolomitisation, probably after compaction, by fluids of connate origin and lateral evolution; and mineralisation by migrating solutions, perhaps related to oil-field brines, that originated in deep zones of the basin during diagenesis of the basinal mudrocks in the NE"

Apr 1, 1995

By Xuejing Xie, Tianxiang Ren

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Standardised stream-sediment sampling procedures have been used in mountainous and hilly terrains. Special sampling procedures were developed for application in remote environments, such as high mountains, desert, semi-desert, karst and loess-covered regions. The diversified analytical methods used in more than 20 analytical laboratories participating in the project have been unified into two multi-element, multi-method analytical systems. A unified data monitoring procedure was developed based on primary and secondary standard samples. To date the project has covered about 4 000 000 km2 and the aim is to complete the coverage within the present decade

May 1, 1991

By M. Moinpour, Y. K. Rao

The catalysed direct reduction of copper sulphide with carbon and lime was investigated in the range 850-1000 degrees C using Cu2S-CaO-C and Cu2S-4CaO-4C reaction mixtures. The effects of the catalytic additives K2CO3, Li2CO3, Na2CO3, NaF, Na2SO3 and the ternary eutectic (K,Li,Na)2CO3 were determined. Potassium carbonate, sodium fluoride and the ternary appear to be the most effective catalysts for the direct reduction process. The rate enhancement of the catalysed carbothermic reduction of copper sulphide in the presence of lime was explained in terms of the catalysis of the Boudouard reaction

Jul 1, 1991

By R. G. Garrett, A. J. S. Geddes

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). The 1986 geochemical survey was successful in recognising all the previously known mineral occurrences of significance in Jamaica, in outlining areas not previously believed to have mineral potential and in stimulating fresh appraisals of old occurrences in terms of their potential for new commodities. This has resulted in a very significant increase in mineral exploration activity in Jamaica

Jul 1, 1991

By M. J. Scoble, L. M. Daneshmend, C. Hendricks

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993. An attempt is made to relate emerging technologies to education and training requirements by examining the nature of the Canadian mining industry's human resources. Particular attention is given to the trends evident in mine automation and their likely impact on instructional needs. The characteristics of "computer-aided instruction" systems are reviewed and related to the implementation and support of mine-wide monitoring and communication networks, which are seen as fundamental to the eventual automation of underground hardrock mines

Apr 1, 1994

By P. S. Heyns, M. Heyns

A computer model has been developed of mine hoisting systems in deep South African gold mines. Particular attention was paid to the contribution of different modelling assumptions for the guides and guide-roller assemblies. Objective functions indicative of guide-roller tyre endurance, slipper-plate forces and perceived vibration levels were introduced to quantify dynamic performance. These objective functions were used to compare models. It was found that the choice of guide and guide-roller models did not influence the forces on the guide rollers significantly for typical shaft and conveyance characteristics at typical levels of viscous damping coefficients. The rigid and finite-element guide models gave the same results as those of the effective-stiffness guide model, and while the latter is suitable for simulation for design purposes, the finite-element model should be used for unusual guide geometries

Jun 19, 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 T. Lenarcic, R. Svrkota, J. M. McNeal, E. Prohic, S. Pirc

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Surface drainage samples, the usual media employed in mapping national territories, cannot be used for the geochemical mapping of carbonate terrains because there is no regular surface-drainage pattern on karst. Suitable sampling media have been studied in Yugoslavia, one-third of which consists of karst terrain. Sampling designs for the work were based on analysis of variance techniques. During initial investigations of various sampling materials in NW Yugoslavia sediment and aquatic moss from karst springs, along with soil, were established as the most appropriate media. Modified sampling procedures were then carefully applied along the entire Yugoslav karst belt, which includes terrains of contrasting topography, climate, pedology and vegetation. The studies indicate that climate and relief do not systematically influence the geochemical composition of soil. Regional and local variability was assessed for 21 chemical elements and the feasibility of producing stable regional geochemical maps was determined for a number of elements on the basis of sampling aquatic moss and sediment from karst springs and soil

Jul 1, 1991

By O. Dojcar

The results of a laboratory investigation of rock fragmentation conducted with a model material were partially verified under field conditions. The object of the investigation was to study the qualitative and quantitative relations between the parameters of the primary blast and fragmentation to enable the planning of an economically efficient degree of disintegration with optimum utilisation of the blast energy. The three blast parameters that were considered were burden, specific charge and the ratio of spacing to burden

Jan 1, 1991

By W. D. Maier, H. V. Eales

Paper presented at the IAGOD international symposium on mineralization related to mafic and ultramafic rocks held in Orleans, France, 1-3 September 1993. A lithological and geochemical study revealed significant lateral variation of the interval over 170 km of strike, from about 30 m at the Union Section to 220 m near Brits. The cumulates also become more evolved and leucocratic with distance from the Union Section both towards the NE (Amandelbult) and SE (Impala, Rustenburg and Brits). It is inferred that the persistent heat flux from a putative major feeder zone near the Union Section impaired deposition of felsic cumulates in the vicinity, delaying crystallisation of successive phases in parts of the chamber near the feeder. New influxes were therefore deposited on a footwall of varying thickness and lithology in response to different degrees of crystallisation and accumulation along strike. The development of cyclic units of chromitite, harzburgite, pyroxenite, norite and anorthosite was interrupted at different stages in different parts of the chamber

Apr 1, 1994

By S. A. Sayed, M. N. M. Ahmed, M. A. Doheim

The performance of a 12.7 cm hydrocyclone was investigated by considering the effect of design variables (diameters of the vortex finder and apex) and operating variables (pressure drop and solids content of the feed) at a medium feed solids concentration of mixed minerals. Cut-size was found to be the most important parameter in hydrocyclone design and operation. The effect of feed pressure in reducing hydrocyclone cut-size is less pronounced at medium feed solids concentration with a mixed mineral feed. The choice of vortex finder diameter and apex diameter becomes more sensitive at medium feed solids concentrations. The effect of feed solids concentration in increasing the cut-size becomes less marked at higher concentrations. Predictions of an empirical model were found to be in good agreement with experimental data. Comparison of results obtained from the model with those predicted by theoretically derived models showed the latter to be more promising, with the turbulent two-phase model giving closer agreement with the experimental data

Apr 1, 1995

By L Besra, A. R. Prasad, B. P. Singh

The role of surface-chemical phenomena and the physical processes that participate in the dewatering of a suspension of alumina trihydrate were subjected to a systematic investigation, which has increased understanding of the influence of surface tension, contact angle and adsorption in the process. The residual moisture content of the cake can be reduced significantly through the use of surface-active agents in slurry pretreatment or as wash-water additives. The effectiveness of a particular surfactant is hard to predict from any single parameter, but is dependent on its ability to reduce surface tension and possibly to modify the solid-liquid contact angle. If scaled up to industrial operation of the dewatering step of the Bayer process in India, the use of these chemical additives could substantially improve its process economics, reducing the fuel costs for thermal drying by a much as Rs 50/t

Jun 21, 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