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By Hao Li, Allan Moss, Richard K. Brummer

At the Palabora Mine, the transition to caving 400 m below the bottom of the 800 m deep pit resulted in a slope failure of the North wall that began in 2003, and is still mobile. This failure can be explained by the daylighting into the cave zone of a prominent joint set. The failure was modelled by the 3-dimensional code 3DEC, which is capable of modelling the nonlinear behaviour of discontinuum materials with large displacement.

Jan 1, 2006

By L. A. Cornish, L. H. Chown, M. Matema, R. Süss, L. Glaner, A. Douglas

Mintek has been developing Pt-based alloys for high temperature applications in aggressive environments, for example, land-based turbine engines, to replace the currently used nickel-based superalloys (NBSAs). The Pt-based alloys have a similar structure to the NBSAs, and since Pt is more chemically inert and has a higher melting point, the Pt-based alloys can potentially be used at higher temperatures. The greater chemical inertness of the Pt-based alloys compared to the NBSAs means that coatings can be simpler, or perhaps not even used at all, depending on the environment. TEM work was done at NIMS, Japan, to investigate the changes in the microstructure o f Pt-Al and Pt-Al-Ir alloys at elevated temperatures using in-situheating up to1100°C. Initial casting trials showed that work needs to be done to optimise casting parameters before commercialisation can take place. Room temperature tensile tests were performed and results were variable mainly due to microstructural differences. The alloy hardnesses were in the order of 300-350HV with ultimate tensile strengths of ~800 MPa and elongations of less than 10%. These results are comparable to other alloys used at high temperatures, which is very encouraging. Keywords: platinum, super alloys, hardness, tensile

Jan 1, 2006

By C. M. Rule, A. K. Anyimadu, L. Knopjes

Ongoing development work on ultra-fine grinding for various applications at the Group?s concentrators has been conducted by Anglo Platinum over the last few years. Current potential applications for mainstream grinding and concentrate grinding are the subject of a group-wide research and development programme. The first 10 000-litre 2.6 MW IsaMill was jointly developed by Anglo Platinum, Xstrata Technology and Netszch for installation at the Western Limb Tailings Re-treatment project in Rustenburg, South Africa. The unit was commissioned in late 2003/early 2004, and has operated in an intermediate concentrate regrind application successfully since. This paper describes the operational performance to date, as compared with the original duty specifications and objectives. The first mainstream M10 000 IsaMill with a 3 MW drive will be operational in November2006 at the Potgietersrus Platinum (PPL) ?Platreef? Sandsloot Concentrator in South Africa?s Limpopo Province. Key Words: Western Limb Tailings Re-treatment Plant, IsaMilling, Platreef, Platinum, Palladium, PGMs, tailings.

Jan 1, 2006

By R. P. H. Willis

Uranium is back on the radar. Uranium has always been a controversial metal, from its role in the arms race to its claim to be the only viable alternative to fossil fuel. This paper will cover its properties and use, its occurrence and production in South Africa, the current market drivers and its future role as a primary energy fuel. It will highlight the difference between uranium used to make a bomb and uranium used in a power station. The recent significant uranium price rise will be put into context of the market drivers including geopolitical issues. Planned expansions in nuclear power station capacity will be reviewed, as will new mine production. Future demand will also be speculated on.

Jan 1, 2006

By R Ratlou

Increased contamination due to sand in spiral feed has had a negative effect on the efficiency of spiral concentrators at Navigation Plant. The no. 1 seam at Kromdraai opencast, which was previously mined by underground bord and pillar methods, is now susceptible to spontaneous combustion because of air ingress into the old workings which are exposed in the opencast high wall. This posed a risk in the loss of reserves to burnt coal. As solutions, buffer blasting of the preceding cut to collapse bords and soft overburden dressing of un-collapsed bords were implemented to prevent air entering the workings. The latter remedy resulted in increased contamination due to addition of sand in Run of Mine. After evaluating alternatives, a low capital option was selected. The 110t/hr Teetered Bed Separator (TBS) has been installed, primarily to desand and upgrade the feed to the spiral concentrators. The unit indicated an upgrade with a yield increase of 0.4% during test work and is currently showing an overall plant yield increase of 0.97%.

Jan 1, 2006

By David Colloby, Darelle T. Janse van Rensburg

Premature coating failures of new and refurbished structural steelwork of clarifiers have been a common occurrence at power generation plant in recent years. Several of these failures have ended in disputes regarding which party was actually to blame for the early degradation of the coating system, i.e. quality of the power station?s water, poor application, substandard materials, outdated corrosion protection specifications, etc. Having investigated several of these premature failures, it is clear that the corrosion protection of clarifier steelwork is a highly complicated process and that the painting work needs to be closely monitored in order to ensure long-term protection by whichever product that is applied. The need for quality control inspections during the painting of the plant is often underrated during the project planning stage, also the importance of detailed corrosion protection specifications that consider not only the practical application of the materials, but also the quality control responsibilities of the Contractor, End User and Third Party Inspectorates that may be involved. This paper considers the application constraints of coatings to clarifier structural steelwork and importance of stringent quality control procedures in order to ensure the long-term performance of the corrosion protection systems.

Jan 1, 2006

By N September, R Abate

Bateman Modular (previously Van Eck and Lurie) has been building and supplying the mining industry with modular DMS plants for the last 30 years. These DMS modules range in capacity from 1 tph to 200 tph. The most popular unit produced by Bateman Modular over the years has been the 50 tph module. Development In the last 7 years a need has arisen from the industry to provide Modular DMS plants that can treat higher tonnages (150 to 200 tph). The first DMS provided to the mining industry based on the modular concept was a 150 tph DMS Module to MIBA in the DRC. Since then Bateman Modular has provided some 14 Mega DMS modules over the last 7 years with the latest two orders from Debswana (Damtshaa double up project) and Namdeb. Ever since the first Mega Module was supplied Bateman Modular has been improving the Modules. Implementation The modules can be supplied in different configurations so as to improve the overall availability of the plant. Two off 150 tph DMS modules were supplied for a Transhex operation. This allowed the client to still operate one DMS module while maintenance is being performed on the other DMS module. The client also has the option of choosing a single module. Successes The following list of projects provides the base for the success of the Mega Modules.

Jan 1, 2006

By A. Haines, O. Varaud, I. Baidoo

Abosso Goldfields Limited (AGL) is in the process of developing an expansion of their Damang Open Pit gold mine in Ghana. AGL acquired the Damang mine in January 2002, with SRK participating in the geotechnical investigation and design for the project since 2001. A deep resource drilling program, completed during 2004, intersected an extension of the orebody below the then planned final pit floor. A feasibility study has been completed to determine the economic extraction of this deep ore with an expanded pit shell. The Damang mine is in a stockwork sulphide deposit at the culmination of the Damang anticline. The deposit occurs as hydrothermal mineralisation associated with dominantly east dipping thrusts and sub-horizontal quartz veins. Primary gold mineralisation also occurs in the conglomerates of the Tarkwaian Formation. The geological units consist of steep easterly dipping dolerite, sandstone, siltstone and phyllite beds, with the weathering profile comprising saprolites overlying a relatively thin joint oxidized horizon. It is planned to deepen the current open pit to a final depth of up to 270 m, primarily by the development of a push-back of the eastern and western walls. The edge of the Eastern Tailings Storage Facility (ETSF) is currently located within 80 to 100 m of the crest of the existing pit. The geotechnical design focused on the optimization of the bench face angle and finally recommended a ?Steep Slope Strategy?, involving 24m high near vertical benches. Limiting bench stack heights of 96m at a maximum of 66° were derived from the influence of major structures and the variation in rock mass conditions. The overall slope angles in each pit sector were developed around the requirement for haulage ramps. One of the main design challenges was to optimise the standoff distance between the final pit crest and the ETSF. This process had to consider maximum access to the resource without undue influence on or from the nearby tailings dam. A planned increase to the height of the dam wall was an additional factor in the design. Dewatering of the pit walls was also a major consideration in this tropical environment.

Jan 1, 2006

By P. Saayman

The mining industry has much potential for automation. A great deal of work has been done on this subject and is still ongoing. With automation comes the possibility for optimization, because more information is available and actions can be repeated with more accuracy. This paper looks at possible solutions to the problem of optimizing the autonomous vehicle dispatch system in an underground mine. Possible optimization strategies are evaluated using a simulated environment. The majority of the results indicate that improvements on current methods are possible. Keywords: mining automation, simulation, vehicles, dispatching strategy, optimization.

Jan 1, 2006

Sandsloot open pit is situated on the northern limb of the Bushveld Complex, 250 km north east of Johannesburg, South Africa. Sandsloot is currently the largest open pit platinum mine in the world and is one of six potential open pits in the area. The geotechnical strength properties of the Platreef have posed significant mining and processing challenges to the PPRust operation since inception in 1992. In order to optimize the whole business as opposed to isolated cost centres a mine to mill initiative was embarked upon in 1997. Initial work focused on ore characterization and an entire suite of data was collected for each rock type. This included mineralogy, geochemistry, geotechnical, blast ability indices, as well as metallurgical strength data. The second phase involved the clear definition of customer requirements, namely the optimum performance criteria for the plant and mining departments. This involved extensive field trials and data capture to measure the interaction and influence of the mine to mill value chain. Once the design targets were defined, a 3D geotechnical model was constructed to ensure that the targets were consistently achieved. The model is very similar to an ore reserve model; however, it is populated with geotechnical, metallurgical and blast index data. Through software queries the appropriate blast powder factor for each mining block can be obtained, thereby ensuring the correct fragmentation is blasted for the plant and mining operation. The initiative has delivered significant results showing improvements across the mine to mill value chain. These include increased loading rates, reduced electricity and crushing consumables, as well as higher plant throughput. Additionally, the initiative has benefited both brownfield and greenfield projects on the PPRust operation

Jan 1, 2006

By S. Maluadzi, D. Rocchi, S. Luyckx, S. S. Potgieter-Vermaak, C. Machio, J. H. Potgieter

The aim of this work was to compare the corrosion behaviour of thermal spray WC ? based coatings before and after annealing. X-ray diffraction (XRD) was used to determine the phases present in the coatings at various stages. The corrosion resistance of the coatings was measured using electrochemical and immersion corrosion tests. The results obtained from electrochemical corrosion (quantified by corrosion current density) and immersion corrosion tests showed that annealing appears to decrease the corrosion resistance of the coatings. From the XRD results it was determined that the phases that corroded preferentially were cobalt (Co), eta (Co6W6C) and W2C. Keywords: Corrosion, thermal spray, coatings, hardmetals.

Jan 1, 2006

By John V. Simmons, Peter J. Simpson

Excavated slopes in open pit coal mines are designed to be as steep as possible consistent with stability and safety requirements. Slope failures occur for many reasons, including oversteepening. This paper is concerned with slope design and excavation experience in the Bowen Basin coalfields of central Queensland (Figure 1), [ ]

Jan 1, 2006

By Simon St J Tose

The objective of this paper and presentation is to review the different criteria and methodology used by AEL and other organisations to create a pre-split design which delivers a stable highwall for the life of that part of the mining operation. It will look at the need to adapt and change the way, size and direction of the production blasts as the mining phase approaches the highwall position for which a pre-split has been created. Key Words: Pre-split: Design; Highwall; Perimeter

Jan 1, 2006

By C J. de Beer

The Kwaggashoek East pit is one of the four production areas of Thabazimbi Iron Ore Mine. The Kwaggashoek East Open pit mines through the abandoned sublevel caving operations of the Kwaggashoek East underground workings. A risk assessment indicated that the primary risk is the occurrence of surface subsidence. Based on local knowledge, a hypothesis, that most of the cavities were filled with broken rock as a result of roof collapse and bulking of failed material was formulated. To test the hypothesis a number of geophysical methods as well as probe drilling was utilized. The results of the resistivity, gravity and ground penetrating radar surveys were inconclusive in determining the position of voids. Either there were no voids present or the resolution of the surveys was not high enough to pick it up. It is accepted that only small voids remained, and that the supported roof hypothesis is valid. As a precautionary measure all the production blast holes within the caving area were over-drilled by forty percent. This would collapse the roof of any small voids or tunnels immediately below the block. This operation proved to be successful as two of the three underground levels have been mined out with no subsidence occurring in the pit floor.

Jan 1, 2006

By G. Humphries, E. Wolmarans

The PPRust North project is an expansion of existing operations on the ?Platreef? orebody in the Limpopo Province of South Africa. Anglo Platinum has been mining and processing the Platreef since 1993 at the adjacent Sandsloot and Zwartfontein South open pits at a current rate of approximately 4.5 million tons per annum. This paper describes the origin of the proposed process flow sheet. A comprehensive test work programme has been conducted evaluating the best process flow sheet for the very hard and variable ore in the proposed mining area. The selection of the comminution circuit is discussed where conventional crushing and SABC options were analysed based on both extensive test work and analyses of current operational data at the existing concentrator. The application of the high pressure grinding roll technology has significant advantages?it replaces the 3rd and 4th stage crushing stages in a conventional circuit. This programme has been conducted over several years and has involved work done at site at pilot scale, internally at the company?s research facilities and externally at various sites. The on-site pilot work was completed over a 7-month period at the existing concentrator facility using a ThyssenKrupp-Polysius, ?Polycom?, 950 mm by 350 mm, high pressure grinding rolls (HPGR) machine. In excess of 185 000 tons of ore was processed through the unit during the trial period. This paper describes the test work programme and particularly the proposed application of high pressure grinding technology and its potential for further application in the platinum industry.

Jan 1, 2006

By V Kveldsvik, N Ragvin, T Eiken, G Grøneng, G V. Ganerød

Catastrophic rock slope failures have caused destructive tsunamis in Norwegian fjords. At the Åknes rock slope the tsunami generating potential is large due to the potential large volume involved in a possible catastrophic failure. Widening of the upper crack has been recorded since 1986, and in recent years, a quite extensive investigation and monitorin campaign has been conducted. Data from some of these investigations are presented and analysed with respect to a preliminary evaluation of the stability of the slope.

Jan 1, 2006

By L. A. Cornish, S. N. Prins, R. Süss

The work is being done using the Thermo-CalcTM software, and the database is being built up by obtaining good thermodynamic descriptions of all of the possible phases in the system. The database supplied did not cover all of the phases, and these had to be gleaned from literature, or modelled using experimental data. Similarly, not all of the experimental data were known, and where there were gaps or inconsistencies, experiments had to be undertaken. A preliminary version of the database was constructed from assessed thermodynamic data-sets for the binary systems only. The binary descriptions were combined allowing extrapolation into the ternary systems, and experimental phase equilibrium data were compared with calculated results. Very good agreement was obtained for the Pt-Al-Ru and Pt-Cr-Ru systems, which was encouraging and confirmed that the higher-order systems could be calculated from the binary systems with confidence. Since some of the phase models in databases were different, these phases had to be remodelled. However, more work is ongoing for information concerning the ternary phases present in the Al-Cr-Ru, Pt-Al-Ru (two ternary compounds in each) and Pt-Al-Cr (possibly more than three ternary compounds) systems. At later stage of the work, problems with the thermodynamic descriptions of the Cr-Ru and Pt-Cr binary systems were found. A programme of experimental work to overcome these has been devised, and is being undertaken. Keywords: Pt-based alloys, phase diagram calculations.

Jan 1, 2006

By R. M. Lamya

The leaching behaviour of nickel?copper matte in an acidic?copper sulphate solution during the repulping stage at Impala Platinum Refineries has been studied. The base metal recovery process consists of a matte repulping stage prior to a series of pressure leach stages. Therefore, the repulping stage is basically an atmospheric leach stage in which the matte containing mostly Niand Cu is leached in copper-spent electrolyte from the tank house, resulting in dissolution of nickel and precipitation of almost all the copper. To understand the nature of the leaching process during this stage of the operation, the effects of temperature stirring rate and matte particle size on the rate and extent of base metal dissolution and copper rejection from the solution have been investigated. The leaching mechanism of the matte in the investigated system is alsoproposed.

Jan 1, 2006

By P M. Bradbury

The nature of aggressive process chemical requirements typically in the Platinum Refinery Industries, lend themselves to the use of Polymer Composite Glass Reinforced plastics for pipework and other associated equipment in these types of Plants. This paper discusses the basic characteristics of a Polymer Composite glass reinforced piping system and gives sample examples of applications in current present day use.

Jan 1, 2006

By H. W. Read

The South African platinum industry finds itself in the midst of a rapidly evolving society that is no longer characterized by the apparent stability of the previous decades. The features of this society include increasing global competition, rapid technological innovation, a declining skills pool, major political transformation, a more challenging working environment as the mines reach deeper into the earth?s crust and a greater concern for human welfare. It is therefore axiomatic that new ways will have to be found to engage the all-pervasive change in the mining environment. Although in general terms project management is a universal endeavour for managing change, it takes place in a specific socio-techno-economic environment and geographical setting that gives it a particular context. The argument of this paper explores, analyses and synthesizes the impact of these changes on the emerging project management methodology. In essence, the management of change will inevitably contribute to the emergence of new dilemmas, issues and challenges. The change management process and procedures will also be affected by this change and in response, drive internal change of its own structures and organization. And, therefore, a new paradigm of project management will become apparent. A new project management model will then be proposed to the industry.

Jan 1, 2006