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By E. H. R. Schümann, H. Wagner

SYNOPSIS The paper gives a detailed overview of the history of subsidence engineering on South African collieries. Surface displacements resulting from total-seam extraction are discussed, and the important role of local geology is highlighted. It is shown that the differences in subsidence behaviour between South African and European collieries can be attributed to the presence of competent strata in the overburden of South African coal seams. Criteria are given for the prediction of the most important subsidence parameters, and a new model for the simulation of surface subsidence above total-extraction panels is introduced. The final section of the paper deals with the damage to surface structures caused by total-seam extraction. A brief summary of the most important undermining experiments on South African collieries is given, and it is concluded that local experiences of damage compare with those in Europe.

Jan 1, 1991

By J. A. L. Napier

An analytical solution to the best choice of cutoff grade for a mine is deduced for an assumed model of selective mining. It is found that this choice is determined by the constancy of a special function, the Hamiltonian, over the life of the mine. It is suggested that the appropriate constant value for this function should be determined by the expected long-term average of the paylimit. In that case, the optimum profile can be calculated at each point in time according to the prevailing working cost and product price. In particular, a decision can be made between operation at the true paylimit or at the subsidized paylimit implied by either the lease and tax formulas or the assistance formula for gold mines. It is also shown how the basic formulation can be extended for 'use in the determination of the optimum joint paylimit for two products over the life of the mine.

Jan 1, 1983

By R F. Sandenbergh, Y Wei

The flotation separation of the Rosh Pinah ore into lead and zinc concentrates are based on the selective flotation of the lead containing minerals followed by the activation and recovery of the zinc sulfides. In the present work the influence of the composition of the water on the selective flotation of the lead containing minerals is reviewed and the results given of the laboratory investigation of the influence of activating species such as silver, lead and copper, on the selective recovery of lead minerals from the Rosh Pinah ore. It was found that it was difficult to prevent the activation of the sphalerite by the metal species in solution in the absence of cyanide, and that colloidal precipitates most probably also serves as a significant carrier of these activators in the flotation circuit. Removal of heavy metal species from the solution by means of an adsorbent is possible, but most probably not practical.

Jan 1, 2007

By K. I. Afewu, L. C. Woollacott

The design of in-pulp adsorption vessels in the gold industry has, for the most part, been seen as a problem involving the suspension of fine particles o ore in a slurry. The need for the vessel to be designed as a mass-transfer contactor has received insufficient attention. The current series of papers addresses this need The previous paper considered the question of the scale dependence of the film transfer coefficient. This paper examines the mixing considerations that are relevant. A review of the literature and an examination of a limited set of data provide some insight into the mixing conditions needed for the dispersion of the particles of adsorbent. The mixing requirements for the suspension of the ore particles are also considered, and conclusions are drawn in regard to the design of mechanically agitated vessels for gold in-pulp adsorption circuits.

Jan 1, 1995

This paper describes an interactive personal computer program, ENVIRON, which simulates cooling and ventilating systems on gold mines. An example of the practical application of the program is given and proposed future developments are discussed. The program consists of two main modules, HEATFLOW and VENT- FLOW. HEATFLOW calculates the heat loads and the effect of air coolers, while VENTFLOW estimates the air flow distribution. As the calculation of the heat loads requires a knowledge of the air flow and vice versa, the two modules are run iteratively until the solution converges. The program is written in Pascal and runs on any IBM-compatible personal computer.

Jan 1, 1987

By J. M. Barnard, M. P. Brandt, L. E. Korwin-Kossakowski, W. H. Smith

Petrographic analyses of coal rank and maceral-group composition are widely used in the characterization of coal. This paper describes the use of an image analyser (IBAS Kontron) for fuly automated measurements of the rank and maceral groups of seam coals. The rank is then derived from reflectance histograms, or 'fingerprints', of coal reflectance distributions (being expressed as the mean random reflectance of vitrinite). The volume proportions of the maceral groups are calculated from the histograms. The results obtained with the IBAS were generally in agreement with those obtained by conventional methods of reflectance measurement and point-count analysis. However, the results were inconsistent for coals with a bimodal character or a wide V-class distribution. The rank of the analysed coals ranged from 0,50 to 1,10 per cent mean random reflectance. The lowest reflectance that can be analysed with the IBAS is 0,4 per cent. The speed, objectiveness, and repeatability of this technique make it exceptionally suitable for use in the quality control of large numbers of samples.

Jan 1, 1990

By C. L. Workman-Davies

Noise is a form of pollution arising mainly from the activities of man. One such activity is mining, in which man, as in many of his other activities, uses machinery of various kinds to achieve safe, healthy, and economic production. Trackless mining makes use of an advanced state of technology over that required In traditional mining methods. One of the advantages of the former, as distinct from any disadvantages it may have, is a reduction in noise levels, the number of people exposed to noise, and the duration of their exposure to noise. This paper briefly examines why noise is a problem and what various countries are doing about it in terms of standards, codes of practice, and regulations. It also investigates the extent to which noise is a problem in mining and how trackless mining alleviates this problem. The question is then posed as to whether South Africa is not setting too high a standard at this stage of its national development by comparison with what is being done by other, more-advanced countries.

Jan 1, 1989

By Y. G. Che, M. Brown, R. L. Gandhi, M. D. Watson

Slurry pipelines have proven to be an economical method of mineral concentrate transport over long distances. Some of these pipelines are internally lined with high-density polyethylene (HDPE) to avoid internal corrosion. HDPE is an inert and extremely smooth material, and it was believed hat scale deposits would not form on it. However, there have been instances of scaling on HDPE lined pipes. Scale problems have also occurred on bare steel pipes. In this paper experience with scale problems in some of these pipelines will be summarized. Alternatives available for control of scale problems will be discussed, and a success story for the control of scale problems in the 300 km long Century zinc and lead slurry pipeline will be presented.

Jan 1, 2007

By I. D. Wood

Deposition of gold-bearing deposits in the Witwatersrand Basin was controlled by hydraulic processes. These resulted in the formation of independent sedimentological facies areas having different statistics and semivariograms. Consequently, when there are indications that data are a mixture of statistical populations, it is important to decompose them into statistical subpopulations and analyse these independently. However, in the case of actual mining, physical position and extent of sub- populations are important and, as a consequence, any decomposition of data must take space into account if it is to be of use. An algorithm for the spatial decomposition of data into its sub-populations is described and is applied to real data taken from the Witwatersrand. Two distinct areas with completely different geostatistical parameters were revealed.

Jan 1, 1987

By J. Trcková

This paper describes the method of modelling rock mechanical problems on experimental models. Based on an actual experiment used as an example, assessment of the surface deformation due to undermining, the extensive possibilities of using a 3-D physical model and application results in practice are demonstrated. A special method of modelling the underground mine progress by using paraffin melting is presented. Keywords: undermining, subsidence of surface, 3-D experimental model

Jan 1, 2009

By L. Wade

The advent of relatively cheap computing power has precipitated a rapid growth of computer usage in the mining industry. In order to obtain most benefit from this development a need is recognised for the future mining graduate to be trained in computer literacy. This paper outlines the type of training required and describes progress to date with such a programme at the University of the Witwatersrand. Certain challenges concerning the teaching effort are discussed.

Jan 1, 1987

By A. Mitchell

On 25 August 2011, Andrew Mitchell, Lucas Moalusi, and Matthew van der Want of Bell Dewar hosted a presentation on Mining and Communities in Mooinooi, in the North-West Province. The conference was attended by traditional leaders in the North-West Province, officials from the Department of Local Government and Traditional Affairs, and executives from the mining industry. The presentation concerned traditional governance in mining, communities? rights in terms of applicable legislation, and the corporatization of community affairs.

Jan 1, 2012

By K. R. Johnson

Changes in the pattern of computer systems for mine planning and geologic evaluation are occurring as a consequence of the introduction of 3-D high performance graphics terminals. The VULCAN system is described and an outline of its functionality is discussed. Increasingly, the integration of both database systems and graphics and databases will occur, allowing a greater degree of information access to mine operators. The system covers areas of database, drillhole graphics, mine design and layout, surface and solid modelling as well as reserve inventory generation. The design of the software is such that it is fairly commodity-independent and entirely menu-driven, to enable non computer-trained personnel easily to access the system.

Jan 1, 1987

By C. J. Van Niekerk

When gold plant residues are cycloned for producing a coarse product for backfilling the gold and uranium values are upgraded in the backfill product. Gravity concentration, wet high intensity magnetic separation and froth flotation were investigated as first-stage recovery processes to recover these economic values from backfill prior to placement underground. This paper addresses the recovery of values from flotation concentrates and also details the economic feasibility of a treatment route including flotation, followed by roasting of flotation concentrate to liberate gold entrapped in pyrite and reverse gold leaching of the calcine so produced.

Jan 1, 1988

Currently the most widely used formula in pillar design is the power formula, which implicitly assumes a volume effect. This assumption is critically examined, and it is proposed .that a limiting strength value, the critical rock mass strength, be used for pillar design instead. A methodology is provided to determine this value. It is suggested that the effects of geometry on pillar strength are well described by a linear function and the power formula, for w/h ratios less than or equal to about 5. This approach together with the use of the critical rock mass strength, removes the volume effect. Various factors that affect pillar strength are examined. The concept of explicitly determining the stability of each component in the pillar system is briefly discussed. It is proposed that pillar design be expanded to a pillar system design procedure that incorporates the interaction of the pillar, roof and floor strata, and the loading system.

Jan 1, 1998

By D. Ackerman, S. Cole, G. Langefeld, I. Parker

The removal of gravel from the seabed using a hydraulic mining tool is a complex multi-phase problem that cannot be analysed using traditional continuum based simulation techniques. One potential approach is to simulate the behaviours of the solid phase via the discrete element method and the liquid phase via finite volume based computational fluid dynamics. The interaction between the phases is accounted for by Eulerian coupling. The feasibility of using the combined computational fluid dynamics-discrete element method to simulate gravel entrainment from an idealized seabed is evaluated. The simulation results are validated using experimental data. It is concluded that while the current approach appears feasible, further work needs to be done to improve the accuracy of the simulation and to evaluate the approach?s ability to model more complex behaviours.

Jan 1, 2007

By C. Dechert, J. Norwood

Compañia Minera Antamina, Peru has recently completed a fifth year of operation of their 301-km concentrate pipeline. The pipeline was commissioned by PSI in May of 2001. The Antamina pipeline is generally accepted as one of the most complex slurry pipeline operations worldwide. The pipeline transports an average of 1.6 million tonnes of copper and zinc concentrates from the Yanacancha mine site at an elevation of 4 155 metres above sea level (masl) to the port of Huarmey at an elevation of 62 masl. Currently ten different types of concentrates are being transported as separate batches. The pipeline traverses oneof the most rugged areas in the world. It utilizes three different pipe diameters, and four remote valve stations to optimize the hydraulic design. PSI has recently completed an overall operational audi tof the Antamina pipeline. This paper evaluates the operational effectiveness of specific design features and operating philosophies, implemented during the engineering phase, over the last five years of operation.

Jan 1, 2007

By G. A. Bezuidenhout

Lonmin Platinum installed a concentrated mode dual-alkali scrubber at the smelter in Marikana in 2002. The dual-alkali scrubber was the technology of choice at that time as a sulphur fixation plant, due to the perceived benefits of handling both the high SO2 concentrations of converter off-gas and the swings in SO2 concentration that are linked to Peirce-Smith operation. Owing to current and impending legislative requirements for air quality and waste, Lonmin is currently considering additions to the dual-alkali plant, but is also evaluating alternative technologies for sulphur fixation. This paper reviews the decision of Lonmin to install a concentrated mode dual-alkali scrubber and presents plant performance achieved. It also describes the important control variables and sensitivities of the plant, and the final product that is produced by the operation of the plant. The legislative requirement that drives the Lonmin technology evaluation is also discussed.

Jan 1, 2012

By A. Singh, R. R. Maclachlan

SYNOPSIS A back-analysis procedure based upon 35 mm photography was developed on a laboratory scale for the pur¬pose of determining the percentage of oversize particles known to be present in heaps of fragmented rock. Eight simple blends of crushed stone containing varying percentages of oversize on a 1:40 modelled scale were examined. Simulated test conditions for the following were subjected to the photographic study: (1) a bench heap, (2) the surface exposure of a partially excavated heap, (3) a gravity-sorted surface as occurs on an apron dump, and (4) four quadrant views of an incrementally built conical heap of rock fragments. The best back-analysis determinations were obtained from (4), the cone, over all eight blends of fragments. The mean error was within -0,16 per cent of the true value, with a range of ± 1,872. This was for oversize contents of 5 to 20 per cent where a minimum 25 per cent of the photograph area was processed by digitizer. The worst results were from the apron dump at - 1,462 per cent for a mean error of ± 4,174 per cent. The intermediate results were from the undisturbed bench at -0,186 per cent with a mean error of ±2,862 per cent.

Jan 1, 1989

By K. F. Lane

Mine planning is a complex function and also a vital one. The quality of the planning has a profound effect on the efficiency and the economics of every mining operation. It is therefore important that the function should not be reliant upon only a few techniques but should have command of an orchestra of them. Then the most appropriate can be selected for each application or, if it is advantageous, a group can be employed in concert. This paper introduces peripheral algebra as a set of techniques which should be included in the mine planning orchestra. Its objective is primarily to stimulate more development not only of these techniques but also others of a similar kind which will increase the effectiveness of mine planning.

Jan 1, 1987