Search Documents

The paper deals with the importance of design, and of codes of practice, in ensuring safe working conditions in mines. The design principles involved in the design process are dealt with, and the importance of a logical design process is emphasized. The links between the requirements for developing a code of practice, embodied in the existing guidelines for the preparation of such a code, and the design principles and process are considered in some detail. Finally, suggestions are included which may provide improvements to the code and hence, ultimately, lead to further improvement in safe working conditions.

Jan 1, 2003

By D. M. MacHunter, T. Lawson, D. K. Henderson

The development and commercialization of new generation high tension electrostatic separators has provided a basis for simplifying mineral separation plant circuitry. The inclusion of new design features including insulated plate electrodes that have resulted insignificantly improved separation efficiencies in electrostatic separators are described. The increase in separation efficiency has resulted in a reduction in the number of treatment stages required to produce final high grade mineral products. Comparative performance data on different feed types are presented. A comparison between mineral separation plant flowsheets using both conventional and new generation high tension electrostatic separation technology is presented. A 55% reduction in the number of installed electrostatic separators and a 36% reduction in plant area was achieved through the use of this new electrostatic separation technology.

Jan 1, 2003

By H. C. de Wet

The predevelopment and preparation of a total infrastructure in a deep level mining environment, prior to the shaft system being commissioned has major advantages. This paper intends to indicate these advantages and outline an understanding of the disadvantages. These benefits can be classified in three basic groups: the financial and timing advantages, a knowledge of the ore body and the development of required technology to meet the design parameters. The required technology in many aspects was still to be developed prior to successful application. Stemming from the technological evolution are some secondary advantages which will be described in each of the groups. Safety and health considerations and some practicalities made some of the new technology redundant prior to the actual application. In each case the actual achievements and the anticipated benefits will be indicated to allow the reader to distinguish clearly between planned and actual achieved advantages.

Jan 1, 1997

By C. A. Preece

Finsch Diamond Mine, part of De Beers Consolidated Mines (DBCM), is situated between Kimberley and Postmasburg in the Northern Cape, South Africa. The kimberlite pipe was discovered in 1960 and De Beers assumed full mining rights three years later. Production commenced in 1966 from an opencast mine, and the operation moved underground in 1990 by developing and implementing a new mining method of blast hole open stoping. A mechanized block cave was brought into production in 2005. While block caving was not new to DBCM, with productive caves having operated in Kimberley and Cullinan, from the outset, the Finsch caving operation was designed as the most advanced with a semi-automated ground handling system. The extraction level was laid out as a single sided herringbone system due to the very poor ground conditions on the south side of the pipe. These factors combined to create a unique environment, which necessitated a completely new approach to draw control. The required system was developed by a team consisting of DBCM personnel from head office and Finsch, GEMCOM and Sandvik-Tamrock, the equipment manufacturers. It was essential that the system could be run quickly, provide daily updates and issue calls directly to the LHDs. It was also important that the base data were obtained from the resource model, which was to be depleted on a monthly basis, thus forming a close link between mine planning and draw control. A further requirement of the system was that it would form a central database for the extraction operation where all data pertaining to delays and changes in conditions, be they production or ground condition related, could be recorded and analysed. The design brought together empirical rules and tables developed at Cullinan plus concepts from programming developed for the front cave at Koffiefontein so that the new system was based on sound practical experience. These facets were incorporated into PCBC (GEMCOM) and CMS and PCS (Sandvik-Tamrock programmes). The system has now been operational for just under a year and while modifications have had to be made, it has proved itself as a practical and reliable tool with which to manage the draw control at Finsch. The system is unforgiving and has forced the production team to focus on the specified drawpoints. Problems have been encountered but most of these have been related to re-educating a workforce, familiar with a flexible mining method, to the strict discipline required for a modern block cave.

Jan 1, 2007

By H. C. van Zyl

Mine water in the Upper Olifants River Catchment in Mpumalanga(upstream of Loskop Dam) is at times discharged into local streams, resulting in local acidification and regional salination of surface water resources. Pollution of surface water can be prevented by collecting and treating mine water to a quality where it could be re-used without restriction (Cleanwater 2020 Initiative). Mine water in the Olifants River Catchment currently amounts to only 4,6% of the total water usage, but contributes 78,4% of the sulphate load. Limestone and lime treatment is the most cost-effective technology for neutralization and partial sulphate removal of acidic/sulphate-rich water to sulphate levels of less than 1500 mg/l due to precipitation of magnesium and removal of the associated sulphate fraction (through gypsum crystallization). Neutralized mine water of this quality may be suitable for irrigation. A number of alternative desalination treatment technologies were investigated (subsequent to gypsum crystallization pre-treatment) where treated mine water must meet more stringent quality requirements (e.g. less than 200 mg/lSO4). The capital cost of these processes varied between R4 million/(Ml/d) and R10million/(Ml/d) and the running cost between R2/m3and R5/m3. Water usage in the Upper Olifants River Catchment currently amounts to 947 Ml/d (including the power stations), and will increase to an estimated 1385 Ml/d by 2020. The additional water demand by2020 (438 Ml/d) will have to be supplied by importation from neighbouring catchments, and more efficient utilization of the local water resources, including excess mine water. Various levels of treatment are required to make mine water suitable for the following potential applications (acceptable treated water sulphate concentration shown in brackets): irrigation (2000 mg/l), coal processing plant (1000 mg/l), general industrial use (500 mg/l), discharge to public streams (500 mg/l), potable use (200 mg/l) and cooling water in power stations (20 to 40 mg/l). The following two options, or a combination thereof, can be considered for management of excess mine water in the Upper Olifants River Catchment: ?Collection and treatment of excess mine water to a quality suitable for selected urban and industrial applications (Option A) ?Collection and treatment of mine water to a quality suitable for irrigation (Option B). The estimated capital and running cost for Option A amounts to R528.5 million and R55.7 million/year, respectively, compared with R68,2 million and R11,9 million/year for Option B. It is recommended that Option B be investigated for implementation in the short to medium-term. Option B was selected due to cost benefits and the initial favourable results obtained by a joint Water Research Commission and Coal Industry initiative where mine water is used for irrigation. Option A may become feasible in the long-term to ensure maximum environ-mental protection and reduced treatment cost as a result of anticipated technological improvements over the next 5 to 10 years.

Jan 1, 2001

By A. Singh

The control of flotation plants is by no means trivial. Flotation is one of the most interactive minerals? processing operations. The interactive nature of flotation circuits results in oscillations of levels and hence of grades and recoveries. Also, poor level setpoint tracking and disturbances have negative influences on grades and recoveries. The result is an unstable plant with limited scope for optimization. An advanced controller, FloatStarTM, has been developed to provide tight control and to reduce the amount of disturbances in flotation levels. It has been shown on a number of plants that the system results in faster and better setpoint tracking, better regulatory control and faster settling times after start-ups and disturbances. The successful stabilization provided by FloatStar has made it easier to investigate the area of optimization on flotation circuits. Mintek has identified the need for a more meaningful set of setpoints or aeration rates to use as a basis for control than levels and have advocated flow control by looking after residence times. When the feed conditions change, the ideal solution would be an algorithm or strategy that finds the new optimum conditions rather than just having an unguided hunt from the previous point. A multivariable flow-optimizing algorithm, a new module in FloatStar, has been developed to calculate optimum level setpoints and/or aeration rates that will aim to optimize the residence times, mass pulls and circulating loads within a flotation circuit. Keywords: flotation, regulatory, FloatStar, start-up, disturbance, residence times, circulating loads

Jan 1, 2003

By D. J. Bosman

Rapid fouling of condenser tubes in underground refrigeration plants is a frequent occurrence. It leads to low heat transfer efficiencies, with consequent serious reduction in capacity and increase in the horse-power requirement of the units. High pressures develop in the condensers, and frequent cleaning of the tube bundles is required. The cleaning operation takes up to 8 hours and in some cases results in significant loss of production. One of the possible causes of fouling is deposition of scale, but this can be readily overcome by controlling the concentration of the water. When water evaporates, the dissolved solids remain behind; thus evaporation increases the amount of dissolved solids per unit volume. If half the original volume evaporates, the concentration of the dissolved solids is doubled and the water is said to have a 'concentration' of two. Concentration may be controlled by regulating the amount of water allowed to bleed from the system. The actual concentration value required is a function of the chemical analysis of the circulating cooling water. In one instance, where the problem of scale formation had been eliminated, fouling still persisted, and the possibility of excessive quantities of dust in the re-circulating water was investigated. A dispersing reagent was added to the condenser cooling water as a means of preventing sludge deposition in the condenser tubes. As shown by curve A in Fig. 1 the reagent addition did not decrease the rate of fouling.

By P. Share

As part of JAGUARS (JApanese-German Underground Acoustic emission Research in South Africa), high-resolution tiltmeters were installed during 2007 at Mponeng gold mine, South Africa, in an attempt to study and understand the risks posed by in-mine seismic events and to subsequently use the knowledge gained to mitigate these risks. In December 2007, an M2.2 event occurred at Mponeng and was detected by the tiltmeters installed. The tilt expected for the M2.2 event is modelled through the use of numerical and analytical tools and utilizing, as input parameters, characteristics of the event such as the rupture area, the amount of slip, elastic properties of the rock, the state of stress before the event occurred, and frictional parameters of the rupture. The calculated tilt values are correlated and compared with the recorded data, and are found to be of the same order. Certain input parameters, such as the initial rupture point, are further constrained by varying them, during modelling, until the calculated and observed tilt values are approximately equal. From modelling, it can be concluded that the rupture point had to be closer to the location of the tiltmeters. In addition, possible locations acting as source areas for the observed aftertilt are determined. Further modelling still needs to be done to quantify the effects of the tunnel close to the tiltmeters and plastic deformation of the rock mass. Keywords high-resolution tilt data, Mponeng gold mine, M 2.2 seismic event, analytical modeling, numerical modeling, rupture plane.

Oct 1, 2013

By C. Sawmliana

Deep-hole blasting operations in opencast mines are always associated with some annoyance to the surrounding areas in terms of ground vibration, noise, flyrock, etc. These become more severe when underground mines run parallel to them. Blasting in opencast mines may pose danger to the underground mines in terms of roof/side failures, damage of water dams, isolation/ventilation stoppings and other underground installations. The paper discusses a case study in India on the impact of deep-hole blasting in Ramagundam Opencast Project ? III on the stability of various water dams of GDK-6B Incline coal mine operating in close proximity. The stability of underground water dams of GDK-6B Incline mine was endangered due to deep-hole blasting at OCP-III. There were 15 water dams in seam 3 and 16 dams in seam 4 of the underground mine. The physical strength tests using a Schmidt Hammer instrument were carried out in all the 15 water dams of No. 3 seam and 16 water dams of No. 4 seam. The test revealed that there is a decrease in compressive strength values of three dams of seam 3, namely 6A, 6B and 7. Theose three dams were also directly connected to the water source. Water seepage was also observed from the surfaces of the three dams. However, they were found to be stable in accordance with their design parameters and damage point of view while considering a threshold value of ground vibration as 25 mm/s. It was found that the value of tensile stress generated by a vibration of 25 mm/s was much lower (i.e. 0.171N/mm2) than the tensile strength of the two weakest concrete dams (1.85 N/mm2). Ten experimental blasts were conducted at different working benches of the opencast mine and the ground vibration data were recorded in roof and pillars near various underground water dams. The maximum value of vibration data recorded was 5.9 mm/s in roof near dam no. 1 in seam 3 with the dominant peak frequency of 22 Hz. No adverse effect on either of the dams was observed after that blast. During the period of study, no deterioration/adverse impact was found in any dam of the mine. Based on the results of the study and the analyses of the data, optimized blast design parameters and explosives weight per delay were suggested for the opencast mine to maintain the safety of the underground water dams. Keywords: Opencast blasting, damage, water dams, underground mine, ground vibration

Jan 1, 2009

By R. Zivojinovic, S. Vujic

The structural age of the capital mining machinery, representing a part of the system of the Electric Power Industry of Serbia, has been dictated by the initiation and development of open pit coal mines. For example, the oldest bucket wheel excavators were installed some thirty-four years ago, and the average life of the relevant machinery exceeds twenty-two years. Operation of both capital equipment and machinery has direct effects on economic and business activities of open pit mines, and consequently forced us to make a decision and study thoroughly the problem of establishing the optimum exploitation life of capital mining equipment at the open pit coal mines of the Electric Power Industry of Serbia. The aim of this paper is to define and discuss the relative problems as well as to find out the possible solutions and establish the methodology for estimating the optimum exploitation life of machinery. The study was successfully carried out by a team of scientists engaged from and coordinated by the Department of Computer Science of the Faculty of Mining and Geology, University of Belgrade. This paper presents the key observations covering the subject problem. Keywords: Mining, Opencast exploitation, Coal, Optimization, Exploitation life, Capital machinery, Electric power industry, Dynamic programming.

Jan 1, 2003

By K. Cybulski

In 2002 a coal dust explosions occurred in the Polish collieries “Jas-Mos” and “Rydultowy” in the Upper Silesia coal basin. In the “Jas-Mos” colliery the coal dust explosion was initiated in the face of gallery by explosives and causing ten death. The stone dust barrier extinguished the flame, stopped the explosion development and saved forty nine miners working in that area. In the “Rydultowy” colliery methane inflammation caused three deaths and seven serious burns and ignited the coal dust explosion. The coal dust explosion was stopped by stone dust barrier and did not cause any victims itself. This paper presents the investigation carried out by the Central Mining Institute Experimental Mine “Barbara” and shows that the stone dust barriers remain still a basic mean for suppression of coal dust explosion in mines. The investigation were aimed at determining the cause of explosion and circumstances that led to their propagation. The evaluation of the state of dust explosion hazard in the areas of accidents have been performed, and the range of flame estimated.

Jan 1, 2003

By B. Mienie, J. F. Morrison, C. H. Wyndham, M. J. Martinson, N. B. Strydom

Contribution to discussion M. J. Martinson (Associate Member)*: Application of the simple selection test mentioned in the penultimate paragraph of the paper (reference to a more detailed description of the test would not have been inappropriate) should assist South African mining engineers to make more efficient and possibly more humane use of available labour. The authors mention that the test 'is in use in the gold mining industry', and it would be interesting to know the extent of this usage in terms either of number of mines or as a percentage of the total number of labourers employed on 'heavy' tasks. The paper would have been of greater interest had the authors attempted to relate their findings to the statistics of labour usage in gold mines, members of the Chamber, and to the 'heavy' tasks in particular. On this the authors confine themselves in their Introduction to the somewhat ambiguous statement that 'A relatively high proportion of the 360,000 Bantu mine labourers are employed underground on manual tasks'. To appreciate the practical significance of the authors' work one needs a detailed breakdown of the underground labour force by occupations, together with estimates of quantities such as: (a) total stope and development tonnages moved manually per shift: by shovelling by shovel/tram by tramming together with distances and any other relevant data; (b) theoretical energy expenditures required to accomplish (a); (c) actual energy expenditures required to a accomplish (a); (d) energy theoretically available to accomplish (a) based on 50 per cent of the total maximum oxygen intakes of the labour force allocated to these tasks. Analyses of this sort on an industry basis might demarcate the more promising areas for detailed investigation. Stress is often laid on the need for increased mechanisation to increase stope productivity, but it may be questioned if enough is known about the characteristics, performance and potential of our underground labour force to warrant blind acceptance of stope mechanization as the industry's panacea. Provided that health and safety are not compromised, the ultimate yardstick for assessing any form of stoping is profitability; obviously the industry must investigate very thoroughly any form of mechanization which might reasonably be expected to increase profitability, but it should also be remembered that a radical overhaul of existing systems-which have after all evolved by trial and error over the past 75

Jan 11, 1968

By Y. Hwang, C Kang

To understand the effect of thermal loading from HLW on the groundwater flow nearby, the coupling of TH in an equivalent porous medium is studied. Results indicate that under given conditions the alteration of groundwater flow by decay heat is localized phenomena. More comprehensive studies are underway for THM coupling. Zum Verstandnis fur die Wirkung der thermischen Belastung von HLW in der Nahe von Grundwasserstrom, ist die Verbindung von TH in den entsprechenden porigen Medium erarbeitet. Die Ergebnisse zeigen, dass unter vorgegebenen Bedingungen die Anderung von Grundwasserstrom durch Zerfallwarme lokalisiert wird. Zusatzliche umfassende Arbeiten sind fur die THM Kupplung auf dem Wege. Pour comprendre l'effet du chargement thermique de HLW sur l'écoulement d'eaux souterraines tout près, l'accouplement du TH dans un milieu poreux équivalent est étudié. Les résultats indiquent que dans des conditions données le changement d'écoulement d'eaux souterraines par la chaleur d'affaiblissement est des phénomènes localisés. Des études plus complètes sont en cours pour l'accouplement de THM.

Jan 1, 2003

The application of modifying factors to the Merensky Reef and UG2 Chromitite Layer has a number of challenging aspects as the deposits are tabular and consist of a number of separate geological entities that are grade bearing. The important aspects of the conversion include mineral holdings, dilution with grade bearing material, mining and geological losses, marginal cut offs and recoveries especially where open pit or weathered material is being considered. It is considered inappropriate to add material for dilution at zero grade as the associated material generally comes with an associated low grade. The Merensky Reef Is typically a pegmatoidal feldspathic pyroxenite with bounding chromitite layers. The Merensky Reef is senso stricto too narrow to be considered as a mineable entity and therefore any reserve must include material at low or marginal grades. This is further complicated as the typical mine cut or approach varies across a mine of project. This variation must be included in the mineral reserve conversion. The UG2 Chromitite Layer is typically lithologically bounded i.e. chromitite hosted. However, this adds interesting aspects particularly where leaders are intersected in the hangingwall. These can contribute to unstable hangingwall. It may be considered appropriate to include these in the mineral reserve. One of the overarching principles is that the reserve can be demonstrates to be feasible i.e. can be mined at a profit. Here aspects of a feasibility including infrastructure (power, water etc) needs to be properly considered. The paper will attempt to describe these and other relevant issues and highlight examples from experience together with proposed solutions.

Jan 1, 2007

By E. M. Bloomfield, C. A. Jermy

Geotechnical tests were carried out within an area of the coastal sand dune cordon of northern KwaZulu-Natal which is currently being exploited through mining of heavy mineral sands. In situ and laboratory tests were carried out to assess the density, strength and stability of the dune sand material before and after mining. The most stable combination of sand (>63µm) and fines(<63µm) material was determined as well as the effects of compaction on the strength and permeability of the sand dune samples. In situ DCP and density tests showed that the sand dunes fall in density immediately after mining has taken place. However, settlement of the dunes occurs with time and the density increases within the top 2 metres, and particularly once the dunes become re-vegetated. Laboratory tests carried out showed that the dune sand with between 20% and 30% added fines had the highest shear strength and dry density, but the permeability was shown to decrease steadily with increasing fines up to 40% fines added. The addition of fines would result in steadily increasing water flow problems. Compaction of the dune sands was shown to significantly increase the density and the shear strength, but with a corresponding dramatic decrease in the permeability of the material. Slope stability analysis carried out on models of the dunes with increasing fines showed that the addition of fines increases the stability of the dune sands up to a peak of about 30% fines added, and compaction further increases the stability of the dune sands. Despite the benefits of compaction on the stability of the tailings dunes, the loss of permeability is thought to outweigh the benefits as well as the high costs involved. The stability of the tailings dunes greatly increases after re-vegetation. Compaction and densification of the tailings dunes may be necessary within the top 2 m interval if large-scale construction takes place on the sand dunes. Petrographic analysis was performed to understand the granular interactions of the sand and fines fractions, and the effect of the in situ weathering of the dune sands on the stability of the sand dunes. As the fines contents increase the gaps between the sand grains are filled, until a point where the percentage of fines begins to push the sand grains apart.

Jan 1, 2003

Mr G. Maude was educated at Huish&apos;s Grammar School (Taunton) and Leeds University. He graduated in 1961 with a B.Sc. degree in Mining. Mr E.B. Crocker was educated at Florida Park High School, Witwatersrand Technical College, and the University of the Witwatersrand.

Jan 1, 1985

The paper discusses the improvements achieved after an external sparger flotation column was installed as a final cleaner at the Northam Platinum Ltd. UG 2 concentrator in South Africa. It further discusses the improvements achieved after the conversion of a conventional flotation column, utilized as cleaner in the Merensky concentrator, to an external sparger flotation column. Finally, the application of the above knowledge in the design and commissioning of an external sparger flotation column as final cleaner in the furnace slag concentrator, is also discussed. 1. FINAL CLEANER AT THE UG 2 CONCENTRATOR The MF2 designed UG 2 concentrator is processing 75 000 tonnes run of mine ore at a head grade of 4.0 g/t 3PGM+Au and a feed Cr2O3 concentration of 28 %. Since commissioning of the plant in 2001, Cr2O3 in final concentrate amounted to approximately 5 % of the total mass. Although final concentrate produced from the UG 2 concentrator is blended with final concentrate obtained from the Merensky concentrator before smelting, blended Cr2O3 values in excess of 1.6% lead to difficulties in the subsequent smelting process. Several options for reducing the amount of Cr2O3 in final concentrate have been evaluated namely:- ? Differing types of depressants at various dosing rates. This test work did not reduce the amount of Cr2O3 reporting to final concentrate by any significant extent. ? Reduction in mass pull to minimize the entrainment of Cr2O3 in the concentrate stream.. This process change had a detrimental effect on PGM recovery. Conclusions were drawn that conventional mechanically agitated flotation cells could not achieve the required selectivity without sacrificing PGM recovery. As a consequence an alternative mechanism needed to be incorporated for the final cleaning of PGM concentrate.

Jan 1, 2007

The Annual General Meeting of the South African Institute of Mining and Metallurgy was held in Kelvin House on Wednesday, 24th August, 1977. Dr M. D. G. Salamon (President) was in the chair and declared the meeting open at 16h00. Obituaries The President: It is my sad duty to announce the death of the following members of the Institute : C. G. Evans, J. P. Rees, Life Fellows ; S. R. Bryant, H. MacConachie, M. Mrost, and A. W. van Zyl, Fellows; L. T. Campbell-Pitt, F. W. Collins, A. J. Duncan, I. G. Evans, F. W. Kleinschmidt, P. L. Vaughan, R. W. Wallace, and H. Wason, Members. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, I would ask you to rise and observe a few moments&apos; silence. Minutes The President: May we confirm the minutes of the General Meeting held on 23rd March, 1977, as published in the June issue of the Journal? Agreed.

Jan 1, 1978

By E. Laine

Rock density determinations are necessary for ore resource evaluations from estimated block grades in g/t. Rock density depends on the mineral composition and, thus, it is specific for each rock type. The rock density distributions for different rock types are often symmetric. Hence, the arithmetic mean is a good approximation for the average density for lithological units. However, there may exist spatial variation in density values due to alteration, fracturing and original heterogeneities such as layering. This study compares the kriged density model with the one with constant density values for different lithological units in the evaluation of metal amounts in rock blocks. The case study consisted of rock densities measured from the drill cores at Ahmavaara PGE deposit in northern Finland. The used Ni contents were simulated in accordance with the spatial distribution of rock densities. The Ni amounts in 2x2x2 m3blocks are higher for the kriged densities than for the average densities. The difference is increasing with the increasing metal amounts due to the nonlinear correlation between Ni content and rock density. The final effect on the resource estimation depends on the cutt off grade and prices of the metal, for example, for a very valuable metal the small differences are significant

Jan 1, 2003

By R. Strydom, J. H. Selby

Published information is available on the radiological impacts of disposing of zircon sand in a landfill. Zircon flour by virtue of its finer particle size presents a different set of issues during disposal. This paper describes two options for disposal of such fine grained materials – namely incorporation into concrete aggregates and agglomeration by addition of cement. The study considers the radiological exposure of the public from such disposal methods and concludes that these options are viable alternatives for the safe disposal of waste zircon flour. The disposal of zircon into concrete aggregates at a rate of 10 per cent produces a sufficiently low effect to allow such aggregates to be used in building foundations or other such mass concrete applications. The use of cement agglomeration methods will also provide a safe method of landfill disposal provided at least 20 cm of soil cover is included.

Jan 1, 2003