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By F. P. Hassani

Today, mine backfilling has become an integral part of mining operations, both from a local and overall ground control point of view, and as regards mining techniques and environmental considerations. During the past decade, substantial research has been carried out to contribute to the better understanding of the mechanisms involved in mine backfill behaviour. This work involved analytical, experimental and numerical studies at different scales. Accordingly, this work has been aimed at developing backfill design guidelines for actual working conditions. Backfill design for deep mining conditions is complex and requires understanding of various elements. The most important of these elements are: backfill inherent strength parameters, backfill placement method, stope geometry and interaction between backfill and host rock. The mobilization of backfill strength parameters controls the backfill behaviour and thus, its failure mode. It is believed that the governing boundary conditions and backfill-rock interaction influence the backfill strength mobilization significantly. Accordingly, the interaction between backfill and host rock is an influential factor in overall backfill behaviour under applied loads. The focus of this research is to investigate the backfill-rock interaction, considering a nonlinear behaviour for both backfill and rock mass. Assuming typical stope geometry, the FLAC code was used to model the complex boundary condition associated with narrow vein mining conditions and to simulate the backfill behaviour. A comprehensive numerical study was conducted and the results obtained were compared against field observations. The analysis of findings provides qualitative results, which can be used for backfill design. Keywords: Numerical modelling, backfill, deep mining, non-linear behaviour, rock mechanics, backfill behaviour, narrow vein mining.

Jan 1, 2008

By P. J. Bartlett

Premier Diamond Mine exploits a kimberlite orebody using cave mining methods. A drilling level is established at the base of a block of ore to effect undercutting that leads to caving of the overlying ore. A second level is developed some 15 metres below the undercutting level to allow extraction of the ore once it has caved. As much as 45 per cent of the rock is removed on the extraction level creating a series of pillars. Undercutting creates abutment stresses, as high as 3 times the virgin stress, which affect the rock mass to a distance of 20 metres from the undercut face on the undercut level and on the extraction level 15 metres below. If the extraction level is completely developed prior to undercutting, where stress levels exceed 20 percent of the rock mass strength, extensive rock mass and support damage occurs as the undercut passes overhead. Rock mass damage takes the form of movement along existing joints and minor shear failure through intact rock. Support damage takes the form of cracking in rigid concrete linings. Where induced stresses exceed 50 per cent of the rock mass strength it is often impractical to keep excavations on the extraction level open. Rock mass damage takes the form of extensive failure of the rock in shear which evidences itself as propagation of the fracture zone around tunnels and footwall heave. Support damage results in destruction of shotcrete linings and concrete footwalls. As the interbolt support fails, badly fractured rock ravels around the steel tendons. Observation and monitoring at Premier Mine and on other cave mines has shown that induced stress levels and consequent damage are a function of :?the extraction ratio on the undercut and extraction level prior to undercutting ?the shape of the undercut face ?the rate of undercut advance ?the distance of leads and lags between adjacent tunnels on the undercut level. To ensure the stability of excavations, all of the above parameters must be carefully planned and the planned mining sequence rigidly enforced. The minimum of development is completed on the extraction level prior to the undercut passing overhead. Required development is then rapidly completed once the area has been de-stressed. Support is installed in three phases: ?Rockbolts are installed as soon as excavations are developed ?Wire mesh, steel tendon straps and a layer of shotcrete sufficient to protect the mesh and straps from damage by blasting and LHD loading is installed as soon as practical thereafter. Inevitably the shotcrete lining has to be replaced once the undercut has passed overhead.. ?Rigid shotcrete linings and concreted footwalls are completed only after the undercut has passed overhead and the area has been de-stressed.

Jan 1, 2000

[COUNCIL FOR 1991/92 President R.D. Beck President Elect JP. Hoffman Vice Presidents Senior Junior Dr H. Scott-Russell J.A. Cruise Immediate Past President Honorary Treasurer H.G. Mosenthal J.A. Cruise Members of Council Dr N.A. Barcza G.A. Brown B.R. Broekman Prof. RJ. Dippenaar B.R. Fleetwood* J.S. Freer P.R. Janisch P.J. Knottenbelt Dr J. Lurie R.P. Mohring *Co-opted K.C. Owen P.D.K. Robinson D.A.J. Ross-Watt P. Smith K.A. van Gessel DJ. van Niekerk P. van Schaardenburgh* CJ.C.J. van Vuuren* P.M.T. White]

Jan 1, 1992

By G. Lyman

The cross-belt sampler is a device that is very widely used even though it has not been ratified by the Standards associations. This paper is concerned with the bias testing of two cross-belt sampler designs against stopped belt samples and a cross-stream cutter at the belt end. The bias analysis is carried out using size distribution as the analyte and conventional t-testing and the Hotelling T squared test, which are compared for their effectiveness. The paper considers the issue of detectable bias and the statistical planning of bias tests.

Jan 1, 2010

By Y. Z. Ma

This paper presents a matrix formulation of factorial kriging, and its relationships with simple and ordinary kriging. Similar to other kriging methods, factorial kriging can be applied to both stationary and intrinsic stochastic processes, and is often used as a local operator. Therefore, the concepts of intrinsic random function and local stationarity are first briefly reviewed. Kriging is presented in a block matrix form in which the kriging solution is useful not only for understanding the relationships between simple and ordinary kriging methods, but also the relationships between interpolative kriging and factorial kriging. When used as a signal/noise-filtering method, factorial kriging is especially useful for multiscale modelling. Examples for general signal analysis and geophysical data signal filtering are given to illustrate the method..

Jan 1, 2014

By X. Goso

Laboratory-scale tests were conducted at Mintek for the production of titanium powder from particulate Kroll sponge by the hydrogenation-dehydrogenation (HDH) process. The aim of this work was to produce titanium powder for powder metallurgical consolidations. The work involved the production of titanium powder at optimized conditions, which included hydrogenation in a horizontal tube furnace at 600°C for 2 hours, milling using planetary and roller mills, and dehydrogenation in a vacuumed retort fitted in a muffle furnace running at 700°C for 36 hours. The titanium powder produced in this project matched the elemental specifications of commercially available titanium powder, except for high carbon content. Nevertheless, the powder has been tested further in mechanical alloying and has been found suitable for the production of powder metallurgical compacts. Keywords Powder metallurgy, titanium components, HDH process, ball milling.

Jan 1, 2011

By J. P. Gous, J. J. Sutherland

"Transalloys is a silicomanganese (SiMn) producer located in South Africa, and uses only local manganese ores to produce SiMn alloy. The plant operates five open submerged arc furnaces (SAFs) with an annual capacity of 180 000 t of saleable SiMn.Maintaining tap-holes is critical for effective furnace operation, allowing proper drainage of the furnace with minimal operator interference. Using a claygun and drill arrangement installed at each furnace, tapping occurs every four hours. Tap-holes are maintained through mickey replacement and brick repairs. Three furnaces have SiC tap-holes and two have graphite tap-holes.This paper gives a review of SAF operation, furnace and tap-hole design, daily tapping operation, and maintenance practices for repairing tap-holes.IntroductionDefining tap-hole life cycle, Steenkamp et al., (2016) highlighted four main steps: installation during furnace relines, day-to-day operations, tap-hole maintenance, and tap-hole repair. The authors argued that the design of the tap-hole area should allow for all four stages in the tap-hole life-cycle. Design principles for each stage were presented using silicomanganese (SiMn) production as a case study. Here we present a further analysis of the case study by providing practical examples of how the tap-hole life-cycle is managed at Transalloys during the design, operation, and maintenance of submerged arc furnaces (SAFs) applied in the production of SiMn.BackgroundTransalloys is the largest producer of SiMn in Africa. Its smelter complex is based outside the town of eMalahleni, in the Mpumalanga Province of South Africa. Transalloys was commissioned in the mid- 1960s as a high- and low-carbon ferrochromium plant based on the Perrin process. In 1967 the plant was converted to SiMn production because of constraints in the ferrochrome market (Basson, Curr, and Gericke, 2007; Bezemer, 1995). Today, the installed production capacity is 180 000 t of SiMn annually. Plant operations consists of five SAFs (see ratings in Table I), operating 24 hours a day, 365 days a year (including maintenance), involving 280 permanent employees, with up to 120 contract employees on site at any given time."

Jun 1, 2019

By C. Musingwini

The subject of optimal planning of level and raise spacing for inclined narrow reef deposits has received intermittent attention over the years because the subject matter is inherently complex. Previous work has approached the problem as simply that of simultaneously minimizing the total excavation and haulage cost associated with the development workings. However, when level and raise spacing are altered, other factors such as productivity are negatively affected, thus requiring a delicate trade-off of contradicting planning or optimization criteria. The paper concludes that the problem is actually of the multi-criteria decision analysis (MCDA) type, contrary to traditional thinking that the planning problem is achieved solely by minimizing waste development.

Jan 1, 2010

By D. J. de Beer

South Africa had a late start with rapid prototyping (RP), with the first system being available in 1991. Up to 1994 only three systems were available in SA. Through active research participation from the CSIR and a number of universities, supported by technology transfer programmes and industry awareness workshops, adoption of RP technologies started to grow. Internationally, RP grew to the extent that several country-based member organizations were formed, and an initiation meeting of the Global Alliance of RP Associations (GARPA) took place during the SME Rapid Conference in Dearborn, USA in 1998. South Africa (SA) was invited under the auspices of the Time Compression Technologies Centre (TCTC) launched by the CSIR, and received an invitation to become a member of GARPA through the launch of a national, inclusive organization. The latter gave rise to a RAPDASA planning/launch meeting held at the University of Stellenbosch, which culminated in the first RAPDASA international conference held in November 2000 at the CSIR, and the election of a first RAPDASA management committee, also at the 1st AGM held during the conference. RAPDASA has been a pillar of strength since then, with an annual international conference being presented. As South Africa?s RP awareness grew through the RAPDASA and independent activities, so did the availability of RP platforms in SA.SA also became a benchmark for other countries/late adopters to follow, as slowly a position of following became a position of leading through innovative applications. The paper highlights SA?s development approach and history, together with the discussion of case studies in various fields. Contribution to the light metals industry will also be discussed. Keywords Rapid prototyping, additive manufacturing, product design, rapid tooling, rapid manufacturing, medical product development.

Jan 1, 2011

By P. Falcão Neves

A detailed analysis of the geomechanical behaviour in rock cutting with a diamond saw is provided to obtain a better understanding of the mechanisms involved in the process. The energy of elastic deformation (before failure) and plastic deformation (post failure) was determined in uniaxial compression tests as well as the energy consumed per unit volume in the cutting process. The test samples are White and Ruivina marbles from Borba - Vila Viçosa in Portugal. Correlations between total deformation specific energy and cutting specific energy, normal and tangential forces and diamond indentation are analysed, and some conclusions are presented.

Jan 1, 2012

By David J. Blackwell

The challenge; to design production facilities and in particular separation equipment which have the ability to deal effectively with the ever changing composition of well fluids, over the life time of the field in which it is operating, ensuring maximum uptime of the asset coupled with consistently effective separation. Design engineers are, however, continually confronted with a dilemma when selecting materials of construction for Oil/Gas separation equipment, since they are generally obliged to select an acceptable material of construction, based on ?predicted? operating conditions, at the lowest acceptable cost. Consequently many designs are somewhat basic and do not take into account the constantly varying dynamics of the well fluids being released into the separator. As oil fields mature, oil companies endeavour to maximize revenue by maintaining oil and gas throughputs. This often results in an associated increase in water and sand volumes and, in order to maintain efficient separation, an increase in operational temperature and pressure; subjecting the equipment to operational conditions for which it was never designed. In reality, therefore, the limitations and constraints placed upon new construction design often result in Maintenance Engineers having to solve the ensuing problems in difficult ?in-field? environments. Should refurbishment or upgrade be required then the status of the platform and that of the vessel during shutdown will dictate how this is achieved. Hotwork on the vessel is generally not preferred due to the requirement for post weld heat treatment and re-classification of the pressure vessel, not to mention the added risk in terms of safety. Unfortunately, until recently, there have been few alternatives to conventional ?hotwork? repair and protection systems, especially since the performance of cold curing polymer based repair and coating systems, for use in oil and gas process equipment, has, until recently, been limited by their resistance to temperature and pressure in immersed conditions. In line with the continued development of high temperature / high pressure oil and gas fields however, recent breakthroughs in polymer technology can now offer both repair and protection solutions which are able to function effectively at temperatures up to 180°C in immersed conditions combined with resistance to the destructive forces of explosive decompression from pressures in excess of 90 bar. This paper will look at recent work that has been undertaken to determine the suitability of modern polymer based repair and protection systems as an alternative to hotwork; thus enabling newly designed and upgraded internals to be cold bonded into position and further protected with temperature resistant coatings, in order to minimize the downtime of the asset and further to protect the vessel internals from the Erosive Corrosive environment.

Jan 1, 2006

By A. Amiel

Tarkwa Gold Mine is owned by Gold Fields Ghana, IAMGOLD and the Government of the Republic of Ghana in a 71%, 19% and 10% ratio. The mine is operated by Gold Fields Ghana. This large, low-grade, open pit, gold mining operation is located in Tarkwa, in the Western Region of Ghana, approximately 320 kilometres by road, west of Accra, the capital of Ghana, West Africa. In the Financial year ended June 2007, the operation mined a total of 108 million tons of which 22 million tons was ore. The mined ore is processed through three gyratory crushers supplying two heap leach pads (north and south) and a carbon-in-leach (CIL) plant. Before the 6 Sigma project commenced, the current fragmentation was resulting in sub-optimal feed size to these crushers. It was decided to use 6 Sigma methodology to improve the fragmentation. A defect was defined as a fragmentation analysis indicating less than 95% passing 750 mm. The objective was to improve fragmentation in order to achieve a constant throughput to the north heap leach crusher of 1500 t/h, a 5% increase in pit loading efficiency and a 50% decrease in rock breaker hours, equipment damage costs and in-pit sheeting costs respectively. However, this was not to be achieved at the expense of grade control as Tarkwa is exploiting a low grade, high volume deposit and therefore ore dilution must be kept to a minimum. This paper is intended to take the reader through the various 6 Sigma phases of the project (define?measure?analyse ?improve?control), which have resulted in a 10% reduction in loading times, of which half has been attributed to improved fragmentation, as well as a substantial increase in blasted stocks. The focus has been on both drilling and blasting parameters as both processes had to be taken into account. These parameters are technical but personnel factors were also identified and dealt with as they arose. In order to measure the impact of any change in the process parameters on the fragmentation size distribution, cameras have been acquired. One has been installed looking into the bowl of the north crusher and the other one was dedicated to field observation, of individual blasts. Both are used for ongoing fragmentation analysis. At Tarkwa, mining efficiency is strongly dependent on good fragmentation as well as the presence of unblasted ?toes? on the pit floors. Crusher throughput depends on an acceptable ore fragment size. Compliance with plan for actual hole depths was temporarily monitored by manual hole dipping, but this is now being replaced with a fully automated drill data management system developed by Sandvik and Modular Mining. The Six Sigma methodologies, using control charts based on data collected in the field, allowed the mine to improve methods for the control of blasted material. It also enforced the implementation of a quality control programme encompassing the entire drill and blast process.

Jan 1, 2008

By P. Falcão Neves

A detailed analysis of the geomechanical behaviour in rock cutting with a diamond saw is provided to obtain a better understanding of the mechanisms involved in the process. The energy of elastic deformation (before failure) and plastic deformation (post failure) was determined in uniaxial compression tests as well as the energy consumed per unit volume in the cutting process. The test samples are White and Ruivina marbles from Borba - Vila Viçosa in Portugal. Correlations between total deformation specific energy and cutting specific energy, normal and tangential forces and diamond indentation are analysed, and some conclusions are presented.

Jan 1, 2012

By J. H. Maritz, Uludag. S.

"*Paper written on project work carried out in partial fulfilment of B.Eng(Mining Engineering) degreeAfriTin Mining Limited plans to reopen the Uis tin mine in Namibia and establish a pilot processing plant for phase 1 of the Uis tin project, which is scheduled to commence in the last quarter of 2018 . A mining plan is required for phase 1 to supply the new pilot processing plant with 500 kt of run-of-mine ore per annum, for a period of 5 years. New geological mapping and three-dimensional modelling of the mining area were utilized to identify the most optimal mining locations that require low initial waste stripping. An open-pit mining method was selected to target the surface outcrops of the pegmatite orebodies. The mine design criteria were determined and used as input to generate the mine design by utilizing professional engineering software. The mine design was optimized and an overall stripping ratio of 0.81 was achieved. A 5-year production schedule was developed for the mine design according to quarterly periods of three months. A fixed production target of 125 kt of ore was assigned to the quarterly periods, and a ramp-up production target of 65 kt of ore was assigned for the first period. The mobile mining equipment requirements were calculated, and recommendations were made for implementing the 5-year mining plan. IntroductionAfriTin Mining Limited is the owner of the Uis tin project in Namibia and plans to reopen the Uis tin mine, which is located near the town of Uis, approximately 164 km north of Swakopmund. The Uis tin mine was owned and operated by Imkor Tin, a subsidiary of Iscor South Africa. Mining commenced in 1958, and the operation was closed in 1991. Steffen Robertson & Kirsten (SRK) defined the life of mine (LOM) plan for the historical Uis mine in 1989. The SRK report estimated the historical resources and reserves, which consisted of sixteen cassiterite-bearing pegmatite orebodies. SRK developed the most economical pit designs to provide the highest average tin grade at the lowest practical waste stripping ratio. Exploration data from the SRK report of 1989 was used extensively throughout this study, since no new exploration drilling has been conducted. The pegmatites are present as large, subvertical and outcropping veins up to 100 m in thickness. Once phase 1 is operational, mining will be conducted using conventional open pit mining methods. Initial production will be from exposed pegmatite veins in the old mine workings. AfriTin plans to establish a pilot processing plant by the end of 2018 to beneficiate run-of-mine ore at a rate of 500 kt per annum."

Jul 1, 2019

By A. W. Dougall, T. M. Mmola

"SynopsisThe global resources and commodities market has become highly competitive. While southern Africa’s abundance of minerals resources is still unrivalled, it has lost considerable dominance in terms of production output. The sustainability of southern Africa’s mining industry is increasingly becoming dependent on its ability to manage the performance of its operations well. A valuable tool for monitoring and managing performance is the use of key performance areas (KPAs) – which are those areas of performance that are reflected explicitly or implicitly in the vision and strategies of an organization and reflect the critical success factors of the organization. This paper is a review of key performance areas in the southern African mining delivery environment. The KPAs discussed in this paper have been identified by comparing KPAs of the several mining houses engaged in surface mining operations in southern Africa and then extracting those KPAs that are common to most of them. Although the authors support the view that each organization should develop KPAs to specifically fit its needs, the study reveals that five KPAs – safety and health, costs, product quality, fleet management, and delivery should form a default list that covers the key areas that any organization should consider when choosing KPAs. KPIs are those subsets of KPAs that we measure in order to manage KPAs.IntroductionThe global resources and commodities market has become highly competitive. While southern Africa’s abundance of minerals resources is still unrivalled, it has lost considerable dominance in terms of production output. The sustainability of southern Africa’s mining industry is increasingly becoming dependent on its ability to manage the performance of its operations well. A valuable tool for monitoring and managing performance is the use of key performance areas (KPAs), which are ‘those areas of performance that are reflected explicitly or implicitly in the vision and strategies of the organization’ (Barker, 1997). The terms KPA and KPI (key performance indicator) are often used interchangeably – whether correctly or erroneously is debatable. KPIs are ‘quantifiable measurements, agreed to beforehand, that reflect the critical success factors of an organization’ (O’Neill, 2007). Each KPA probably has multiple KPIs associated with it."

Jan 1, 2015

By F. M. G. Egerton

Mechanisation of mining operations is not a new concept in the world of mining. Machinery has been developed, manufactured and used for many decades in massive orebodies and coal mines, both locally and abroad. Because of their size and the huge tonnages available, massive ore bodies lend themselves very easily to mechanisation. However, little progress in mechanisation has been made in narrow tabular orebodies in South Africa. The equipment available for narrow tabular orebodies requires excavations of a size that introduce large volumes of waste dilution. Nevertheless, it is essential for South African miners to experiment with mechanisation and to find a solution to the problem. This address looks at current conventional mining methods and compares them to bord-and-pillar type mining methods. Off-reef mechanisation is also touched on. It then looks at different hybridised mining methods that are being used, i.e. a mixture of conventional mining and mechanisation. It finally looks at future prospects for mechanisation in narrow tabular orebodies.

Jan 1, 2004

By J. He

The separation performance of a raw coal sample from South Africa based on the dense gas-solid fluidized bed beneficiation technique was investigated. Analysis showed that the raw coal sample distributes mainly in the -50+6 mm size range with the -1.6 g/cm3 density fraction accounting for 78.20% of the cumulative mass distribution. A flow sheet of the sequential coal beneficiation technique was introduced. The experimental and simulation results of the hydromechanical and density distribution stability indicate that the dense gas-solid fluidized bed could provide a stable separation environment with uniform density fluctuations under suitable operating conditions. With the application of this technique on the raw coal sample, the separation results show that three products, consisting of 73.25% clean coal with an ash content of 9.59%, 11.31% middlings, and 15.44% gangue were effectively separated at two different densities of 1.82 g/cm3 and 1.57 g/cm3. This study provides an effective flow sheet for achieving the high-efficiency separation performance on raw coal from arid areas. Keywords dense gas-solid fluidized bed, dry coal beneficiation, density distribution, separation efficiency.

Jul 1, 2013

By K. L. Morton

Groundwater and associated pore pressure represent elements that can have a negative impact on surface mining and slope stability. Groundwater flow and deformation within a slope influence each other. An increase in pore pressure will result in a decrease of effective stress; and conversely, if the pore pressure decreases, the effective stress increases. Slope analysis and slope design calculations require good information on pore pressure distribution around an open pit excavation. Until recently very little pore pressure data were available and assumptions had to be used. Location and design of measuring points depend on geological and structural setting, geotechnical domains and practicality. Good planning and the use of sensitive point piezometers to measure in situ pore pressures means that real-time data can be collected and used for the construction of flow nets, the determination of pore pressure distribution around an open pit mine, the validation of the dewatering/depressurization requirements, the calculation of the efficiency of the dewatering system and finally the use of pore pressure data in slope stability analysis. The recommended layout for a monitoring system, types and design of piezometers, data collection and use of the pore pressure data are presented.

Jan 1, 2008

By Dolly Chakraborty, S. Ranganathan, S. N. Sinha

Pre-reduction of chromite outside the submerged-arc furnace (SAF) can significantly lower the specific power consumption in the SAF process. Conventional processes for the pre-reduction of the ore operate at relatively high temperatures, at 1400-1500°C. It is possible to enhance the rate of reduction at low temperatures by optimizing the flow rate of inert gas over the reaction site. The influence of the flow rate of inert gas on the rate of reduction of chromite ore was investigated. The rate of reduction initially decreased wit the flow rate of the gas. It increased subsequently at higher flow rates to be followed by a decrease again. There was an optimum flow rate at which maximum reduction could be obtained. It was possible to achieve high levels of reduction at 1200°C by optimising the flow rate of the gas. The degree of reduction obtained was comparable to that obtained at 1400-1500°C, by conventional process routes.

Jan 1, 2007

By J. Wills

The use of drilling rigs to increasingly mechanize stope drilling has been acknowledged as important for the S.A. mining industry in it ís efforts to tackle the challenges of low productivity, AIDS and an ageing driller workforce. The spin-offs of increased safety, cost-effectiveness and better mining performance provide advantages to all?from the driller to the shareholder. However, implementation or product rollout has varied from outright success to dismal failure. A study of various cases by Novatek and Anglogold TDS showed clear reasons for these differences. Whereas the successes were characterized by clear objectives, accountability, user buy-in, a commitment to make the technology work and no-nonsense reporting, these were typically absent in failed implementations. The attitude at unsuccessful mines was to ?trial? the equipment?even subconsciously, a ?trial? is a test where failure becomes an acceptable outcome. During the study it became clear that mining management are not adequately trained to manage the often-tricky rollout process. They are often also not empowered or clearly mandated to deal with the organizational, human and technical issues that must dovetail to create a success. The output of the study was to develop a basic rollout process that could be used to formally manage the implementation of new drilling technology. Creating an alignment between the mine, workforce and supplier promotes a win-win situation that will not otherwise spontaneously arise.

Jan 1, 2002