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By R. T. Grant, C. Bazin, D. Hodouin

It is shown that most of the variation in the results of semi-batch flotation tests is related to the unavoidably stochastic nature of the flotation process. The preparation and analysis of flotation samples and, to some extent, operator error in performing the flotation test procedure are responsible for a small proportion of the observed variability of the calculated flotation performance indices

Jun 17, 1905

By A. G. Waters, N. J. Bristow

A comparative study was made of an untreated and a heated haematite ore and a sinter produced from a feed consisting of 100% ore, to study the influence on reduction behaviour of sinter bonding phases such as SFCA (silico-ferrite of calcium and alumina). Under low-temperature reduction conditions the order of increasing reducibility followed that of increasing porosity and surface area but under similar conditions at 900 degrees C the sinter exhibited higher reducibility than the ores even though the total porosity and chemical reducibility of the individual phases were lower. This behaviour can be explained in terms of the higher total porosity of the natural ore at low temperatures and the higher level of fine pores in the sinter at high temperatures due to the presence of SFCA, which acts to support the fine (c.0.1 micrometre) pores created by the reduction process. This leads to the conclusion that the main role of SFCA in sinter during high-temperature reduction is to maintain a high level of fine porosity. Some implications of this work for granule design and sintering practice are discussed

Apr 1, 1991

By P A. Collier

The general view of the author is that all the good intentions of manufacturers can fail completely if the variations in circumstances in underground mining are not considered at all times. With a belief that it is the customer that has the experience and know ledge of problems which occur on long installations. Reilloc talk with customers in coal mines around the world, and have done so from their inception. With considerable experience in their home market, their technical approach was received with enthusiasm by coal companies in both Australia and South Africa, and whilst experience was obtained in other countries, it is the particularly close working relationship in these two areas that is covered in this paper. The refinement of manufacturing techniques and the fine tuning of the specification to which the chain is made was developed in conjunction with factual underground experience obtained by customers as they sought to improve their productivity and a reduction in working costs. With a reliable product the mines are able to concentrate on improved operational techniques to extend the useful working life and plan for multi-panel usage of the chain.

Jan 5, 1996

By C. H. J. Beaven, M. P. Jones

Since the various new techniques of automation and computing have enabled vast numbers of mineralogical observations of relatively small samples to be made cheaply and rapidly, the statistical assessment of these measurements has become of vital importance. Much of the theory and most of the procedures of sampling that are used in the mineral industry are based on Gaussian statistics, but modern measuring techniques show that many mineralogical parameters do not necessarily follow the Gaussian distribution function. Consequently, it has become necessary to examine the application of other, more suitable statistical methods in order to derive the maximum amount of useful information from the examination of mineralogical samples. Some of the errors that can be introduced by the use of incorrect distribution functions are discussed and the value of determining the function that is appropriate to the particular parameter that is being measured is shown. Examples are provided of non-Gaussian distribution functions in mineralogical materials that were encountered during prospecting and during mineral treatment operations: a Canadian uranium ore, a Thai tin ore, and gold ore tailings.

Dec 1, 1971

By L. Wade, R. Wang, M. A. Horton

Laboratory methods to find the mechanical properties of rock are inherently biased towards stronger strata, which best survive the sample preparation process. Geophysical techniques are not subject to such bias and may be used to predict mechanical properties rapidly and cheaply. Samples (151) were obtained from a borehole that had been comprehensively geophysically logged. The mechanical properties of the samples were established in the laboratory and correlated with the geophysical responses of the strata from which they came. The results indicate that, for homogeneous strata at least, it is possible to predict the unconfined compressive strength reasonably well from sonic travel time measurements made in the field. Predictions of static Young's modulus may also be made from this data source, but with a lesser degree of confidence. A multivariate regression equation is presented which relates down-hole sonic travel time to unconfined compressive strength, depth and the frequency of fractures in the rock mass. This equation may offer potential for the prediction of the mechanical rock properties of fractured and layered strata.

Jan 4, 1993

By A. D. Read

Selective flocculation was investigated as a possible method of recovering values from mineral slimes which are too finely divided to be treated by conventional mineral processing methods. It has proved possible to flocculate selectively either haematite or a silicate from a stably dispersed mixture by varying the anionic character of the high-molecular-weight, partially hydrolysed polyacrylamide employed. Different separation methods have been developed for hard and soft water media. Electrokinetic and infrared techniques have been employed to elucidate the mechanism whereby selectivity has been attained in the different cases. The following influences on the various selective flocculation parameters have been investigated: (a) the level of the different reagent additions and (b) the shear conditions during and after flocculant addition. A feature of the particular system studied was the high solids content at which it was possible to achieve good selectivity. Probable reasons for this are advanced, and the possibilities and potentialities of the process are discussed.

Dec 1, 1971

By R. J. Gochin, M. A. Diaz

A modified Hallimond tube is described which allows the determination of the ultimate recovery R and the flotation rate constant k in a single, continuous experiment. The range of fine particles which can be satisfactorily floated with the modified apparatus can be extended by increasing the length of the bottom part of the tube. Findings suggest that pyrite and arsenopyrite can be separated in alkaline suspension using the so-called F series of collectors. Lime was found to act as a depressant. The collectors operate under pH and dosage control and do not require other depressants. Collectors used in the study were thio-amine (a cationic surfactant) and alkyl propionamide (a non-ionic surfactant)

Apr 1, 1995

By R. D. Dukimo, M. V. Sevian

The nature of fracture and factors that control the extent of fracture in the tumble-drum and drop-tower tests have been identified. The product-size distribution, on which the standard strength indices for these tests are based, and the breakage rate constants depend on a number of factors other than the strength of the lumps. The standard indices and rate constants are meaningful only in a comparative context and for events whose loading mechanism is similar. The results of experiments on three Australian ores, from Yandi, Koolan and Mount Whaleback, are used in combination with fracture mechanics theory to explain why different tumble-drum standards have been found to be fully consistent. A more meaningful measure of strength could be the parameters of the Weibull function, scatter and average strength

Jun 19, 1905

By S. Babendererde

The twenty-ninth Sir Julius Wernher memorial lecture of the IMM, presented at Tunnelling '97, London, 2-4 September 1997. The tunnelling industry is well prepared to face the challenge from the population explosion in urban areas in the near future. Many well-established yet redundant concepts are still impeding progress, however, including the prediction of excessive surface ground settlements. The correct selection of TBM can minimise these, and ground deformations can be avoided completely if the appropriate techniques are applied. Advanced techniques have been used in the Tokyo Bay Crossing, where the tunnel lining was installed by robots. Other advanced techniques include the use of a sliding slip form to give temporary support to an extruded tunnel lining, the chemical processing of ground by polymers during earth-pressure balanced tunnelling and the use of electronic monitoring and steering devices in TBMs. There will be challenges to tunnelling in urban environments, as open cut techniques will no longer be tolerated. Two examples of mined stations are briefly discussed

Jun 19, 1905

By P. K. Kaiser, R. K. Brummer

Paper presented at the conference Risk assessment in the extractive industries, held in Exeter, 23-24 March 1994. A risk-based decision-making procedure has been developed for selecting rockburst-resistant tunnel support in burst-prone mines. The method is based on a risk-cost-benefit analysis and uses support cost data, costs associated with the risk of support failure or excavation loss, costs associated with accidents, injuries and deaths, and the benefits achieved by installing rockburst-resistant support. It takes into account the risk of damage to the support systems due to rockbursts, potential loss of production and the need to rehabilitate in the event of a damaging rockburst. A practical example is provided to illustrate the principles involved in the decision process

Jun 17, 1905

By H. S. Sichel, W. J. Kleingeld, C. E. Dohm

A model of ore value distributions is presented that is the culmination of a statistical approach rather than simply a model that has been successfully applied to the evaluation of ore reserves. Detailed geological and physical observations based on large sampling data sets have been used to support the statistical modelling. Fundamental to the modelling process is the concept that the occurrence of a given grade value in space is a function not only of the presence of the mineral but also of the fact that it is associated with a specific trapping mechanism. The concepts have been specifically applied to gold mineralisation

Aug 1, 1995

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 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 A. M. Tunstall, N. Djordjevic, H. A. Villalobos

The damage zone behind a typical smooth-wall blast in the open pit was assessed by visually examining diamond drill core to identify blast-induced cracking, mapping core rock quality designations to identify changes in fracture frequency and conducting uphole seismic testing to determine changes in rock mass characteristics. The results from the three techniques show reasonable correlation. They suggest that major damage, in the form of fracturing of intact rock, occurs at least 7 m behind the smooth-wall blast and significant damage, in the form of opening and extension of calcite-filled fractures, at least 12 m from the blast. At greater distances the dominant damage mechanism is the loosening of existent joints within the rock mass. In the trachytes at El Soldado these damage mechanisms correspond to peak particle velocities of 2 000, 900 and 500 mm/s respectively

Jun 19, 1905

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 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 J. A. Finch, Zhenghe Xu

The competitive adsorption of xanthates on sulphide minerals in a binary mineral system (pentlandite and pyrrhotite) was studied using the pseudo-in-situ technique of attenuated total-reflectance FTIR spectroscopy. The minerals were placed in the same collector solutions, either separated by a glass wall or in direct contact with each other before magnetic separation and separate analysis. The effect of mineral interaction on xanthate adsorption was clearly demonstrated spectroscopically for the first time. At low concentrations of xanthate, its adsorption on pentlandite was activated by physical contact with pyrrhotite; the effect may be attributed to the enhancement of electron transfer through electrical contact between the two minerals. The results emphasise the need for caution in extrapolating results obtained from single-mineral studies to flotation practice

Jun 18, 1905

By I. Garba

The Bin Yauri deposit in the Zuru schist belt of northwestern Nigeria is a vein-type quartz-sulphide-carbonate gold mineralisation hosted by a brittle fault zone. The occurrence of the mineralisation in a contact zone of a Pan-African granitoid was believed to be sufficient evidence of deposition from magmatic fluids. However, studies may now indicate a metamorphic source for the mineralising fluids. A study of rare earth element geochemsitry was used to investigate the nature of the fluid-rock processes involved and identify the sources of the auriferous mineralising fluids.

Jan 12, 1992

By D. A. White

A simple model for hydrocyclone classification based on the crowding theory first put forward by Fahlstrom is presented. This is a mechanistic theory that postulates that the behaviour of a hydrocyclone is the result of an ordered process that is independent of its dimensions. The main variables that describe the process are the fractions of feed solids and water that are ejected from the underflow. A simple model is developed from basic properties of the classification process and is compared with theory. Agreement is good but improves when the cyclone has a high solids content

Dec 1, 1991

By C R. Ferrari

Residual subsidence is generally accepted as being about 5% of the total subsidence occurring within 12 months of all mining finishing. This paper looks at five case studies from different parts of the country, in various mining settings within a depth range of 430m to 760m. From a single seam single panel working to working the eleventh seam, all are within the concealed coalfield, similar to today's mining. The monitoring of subsidence continued for many years once the mining had finished and the results obtained are at considerable variance from the accepted norm. Subsidence has been found to carry on for up to eleven years after mining has ended, within a range of 8% to 45% of total subsidence. A highly significant factor was that subsidence, as a whole, was generally much more than predicted. The residual subsidence aspect has to he viewed in this context and in order to debate the subject at length, the causes of residual subsidence have to be balanced against the apparent inability to accurately predict subsidence. The results from the case studies were similar, even though the mining settings differed considerably. Subsidence of around 10% to 20% continued for several years after mining had ceased.

Jan 7, 1997