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By J. H. Bulloch

This paper describes detailed fractographic analyses of several specimens that had undergone corrosion-fatigue tests at high stress ratios in simulated pressurized water-reactor environments. The distribution and morphology of non-metallic manganese sulphide inclusions are shown to strongly affect the growth of environmentally assisted cracks (EAC), and certain features suggest that a hydrogen-assisted mechanism is responsible for the observed EAC growth. The incidence of transient EAC growth in isolated regions suggests that the critical conditions that trigger this type of growth are the 'right' local chemistry at the crack tips and imposed mechanical conditions.

Jan 1, 1987

By D. H. Batchelor

Efficient modern-day mining operations are turning increasingly to technology to combat rising operating costs in an adverse economic climate for the industry. Computerised truck dispatching is one such technological advance that has enhanced the efficiency of the mining operation at Palabora. The economic incentives, basic operation and general system benefits of Palabora's computerised truck dispatching system are considered.

Jan 1, 1987

By D. Royston

Mill liners provide the wear-resistant surface within grinding mills, they also impart motion to the mill charge, ie the grinding process, by providing the key between the charge and mill shell, and, at the discharge end, they remove the ground contents of the mill. As semi-autogenous grinding (SAG) mills have grown in size the process aspects of liner design and their impact on mill performance have become particularly important. While feedback from practical experience is critical to good mill liner design, increasingly sophisticated computer-based tools are being developed to assist in mill liner design.

Jan 1, 2007

By S. M. Rupprecht

"Artisanal mining is basic mining characterized by manually intensive work methods utilizing primitive or simple equipment and conducted by individuals or small groups exploiting deposits. Artisanal mining in Rwanda and Burundi is further complicated in that the techniques applied are often inadequate, resulting in low productivity and poor recoveries, and workers are paid low wages with owners reluctant to reinvest in the mining operations. A consequence of this vicious circle is often poor working conditions, with miners operating under unsafe and/or unhealthy working conditions. An additional problem is that mining is conducted in a manner that is detrimental to the environment.Artisanal mining is commonly more dangerous than large-scale modern mining operations. Artisanal operations are generally subsistence activities with the miners focusing more on immediate concerns than the long-term consequences of their activities. When miners have no other source of income, they will usually find ways to evade controls and carry on working. Machinery tends to be expensive and often far beyond the reach of most artisanal miners, and therefore there is a general tendency for workers to focus on labour intensive and riskier mining methods.This paper proposes the introduction of small-scale mechanization with labour-intensive manual mining utilizing a bench mining approach in artisanal mines operating in Central Africa. From the 1950s to the 1980s bench mining was successfully conducted in Burundi utilizing manual labour. In order to achieve a balance between job creation and project economics, the combination of manual and mechanized mining is proposed. Manual mining offers the benefit of local job creation while ensuring good mining techniques, such as minimizing mining loses and dilution. Through the introduction of mechanized loading and hauling activities, areas of high stripping ratios can be viably mined, thus increasing the amount of resources that can be exploited. The use of a loader and tractor-trailer arrangement is proposed, thereby improving throughput, productivity, and worker safety and, reducing the impact on the environment."

Jan 1, 2017

By Z. Song

Real-time monitoring makes it possible to detect any disturbance occurring in production, while decision instruments can efficiently assist decision-makers to optimize production, reduce iterative workload, obtain better solutions, and preview possible results. Technologies for the above already exist and have been proven in the process industry, i.e. refining and smelting. Optimization is also essential for profitable and stable mining production. Real-time monitoring has already taken hold in mining operations, especially in surface mining, while optimization techniques have also been widely used in underground mining, particularly for planning and scheduling. This review is limited to the hard-rock mining production of metallic ores such as gold and copper. It reviews optimization techniques developed for mine planning and scheduling, and communication technologies suitable for underground applications. It also presents control features for individual operation units, and discusses the technical viability of a mining production real-time optimization (MPRTO) system for underground mines, with possible benefits and challenges. Operational disturbances always occur in mine production. An MPRTO system can be useful to maintain operational effectiveness and efficiency by allowing quick changes to short-term plans. This paper briefly describes the MPRTO system, including the input, output, and basic algorithms. The technical prerequisites for the system specified here are already available. Further studies that are required to improve the system are discussed. Keywords real-time optimization, underground mining, production, operation.

Dec 1, 2013

By D. Fourie

A brief history of channel sampling in South African gold mines is followed by a chronicle of different sampling events and sampling methods that used the traditional ?hammer and chisel? approach as well as diamond core extraction of the sample. The problems associated with each method of sample collection are documented and the use of a laser scanner to measure the exact volumes of sample material extracted from a correctly delimited sample site are considered. Areas where increment delimitation errors (IDEs), increment extraction errors (IEEs), increment weighting errors (IWEs), and increment preparation errors (IPEs) occur were investigated. A ?simulated chip sample model? is introduced and provides the basis for comparing the percentages of error introduced as a result of improper sampling. The heterogeneity experiment showed that reefs that are more homogenous tend have lower extraction errors than the more complex carbon-rich reefs, which may contribute to understanding the poor mine call factor on mines exploiting the latter types of reef. Keywords channel sampling, chip sampling, error, bias, modelling.

Jan 1, 2014

By M. Kumral

One of the most significant elements in solving the co-kriging equations is the matrix solver. In this paper, the singular value decomposition (SVD) as an equation solver is proposed to solve the co-kriging matrices. Given that other equation solvers have various drawbacks, the SVD presents an alternative for solving the co-kriging matrices. The SVD is briefly discussed, and its performance is compared with the banded Gaussian elimination that is most frequently used in co-kriging matrices by means of case studies. In spite of the increase in the memory requirement, the SVD yields better results.

Jan 1, 2012

By H. Gumede

The challenges of noise emission in the mining industry are well known. These challenges are exacerbated by the increasing trend towards mechanized mining, and there is general consensus that an effective industry-wide Buy Quiet initiative (BQI) will significantly assist in reducing noise-induced hearing loss by minimizing noise at its source. In its endeavours to improve the health of workers, the MOSH Noise Team has facilitated development of a proposed strategy and structure for a BQI. Extensive consultation with stakeholders resulted in support for the initiative. The MOSH Noise Team was advised to solicit the contributions of consulting mechanical and electrical engineers (CM&EEs), whose support is viewed as critical for realization of the initiative, since elimination of noise at source is an engineering challenge, and most procurement standards and specifications are set and managed by engineers. A workshop with CM&EEs and their representatives, as well as group environmental engineers (GEEs), confirmed the urgent need for the initiative and provided valuable insights. The workshop used obstacle based planning techniques to identify the factors on which the success of this BQI will depend. Most potential obstacles to the implementation revolved around proper scoping, leadership commitment, and companies? adherence to the initiative. Lack of involvement by the relevant stakeholders and economic issues were also identified as potential obstacles. Delegates at the workshop felt that the successful implementation of the industry-wide BQI, will depend on the mining industry addressing the specific obstacles. The most critical and urgent issue was identified as the formation of a properly constituted industry-wide BQI task team that includes representatives from critical stakeholder groups and which is mandated and empowered to drive the initiative.

Jan 1, 2014

By R. G. B. Pickering

The Faculty of Engineering at the University of the Witwatersrand and the Mining Technology Division of the CSIR have co-operated to define the problems associated with deep level mining and in this paper they will identify what they consider to be the critical areas requiring technological solutions. This perspective will then be applied to work currently being carried out by both the organizations and gaps for additional developments will be identified. Finally the Co-operative Research Centre methodology operating in Australia is described. The purpose of this CRC is to provide a vehicle for R&D co-operation to develop and implement technologies which will increase the competitiveness of the mining industry. A further objective is to develop an appropriately skilled human resource base.

Jan 1, 1996

By R. L. Robinson

An analytical framework is formulated to assist mining companies in assessing the relative merits of mineral exploration and acquisition strategies. The anticipated costs, risks, and returns of each strategy are conceptualised using decision trees. Economic criteria - expected net present value, expected return per unit of investment, and the probability of success - for each strategy are derived(from the appropriate decision tree network. Application of the analytical framework is illustrated using the example of a medium-size company in the Canadian base metal sector.

Jan 1, 1987

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, 2009

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009

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 C. Montoya

This paper shows, through a case study, the impact of multivariate grade modelling upon mine design and mine planning. A deposit explored by drill holes is considered, in which the grades of five elements (copper, silver, molybdenum, arsenic, and antimony) are of interest. Forty alternative models of the deposit are constructed by fitting the joint correlation structure of the grade variables and using conditional cosimulation. In addition, a reference model, obtained by averaging the alternative models, is also considered. The study shows that the resulting mine design (final pit characteristics and production schedules) is sensitive to the grade model under consideration, and that the design based on the reference model may not be optimal when compared to the alternative models based on cosimulation. However, when assuming a given long-term plan and extraction sequence, the grades and net present value (NPV) calculated on the reference model are unbiased with respect to those calculated on the alternative models with the same extraction sequence. The latter allow assessing the possible dispersion of the actual grades and NPV around their expected values, and are useful for the planner in order to determine the probability of meeting given production targets and of exceeding or falling short of given threshold grades. Additionally, unlike cosimulation, the separate simulation of each grade variable leads to unrealistic resource models and to biased results in mine design and mine planning. This approach should therefore be avoided, unless the grade variables are spatially uncorrelated.

Jan 1, 2012

By L. Gunnewiek

An advanced real-time monitoring system called the tapblock diagnostic system (TDS) has been developed. The purpose of the TDS is to help furnace operators manage the safe operation and economical maintenance of furnace tapblocks. This system is an evolution of the current practice of using historical records and operator interpretation to assess the ?health? of a tapblock. The main parameters affecting tapblock health are heat removal capacity and refractory wear, and these are currently difficult to assess in situ except in a global way. By using monitored and operating data together with predictive numerical modelling and multivariate statistical methods, real-time tapblock performance is assessed relative to expected performance. A state indicator in the form of a green, yellow, and red light is used by furnace operators to monitor the tapblock performance and health status during operation. Access to historical operating data and the provision of diagnostic functions allow for probable health degradation events to be deeply investigated. A recent opportunity to evaluate the actual performance of a first generation TDS installed in the KIVCET furnace at Teck Cominco?s Trail Operations showed that a reasonable estimate of tapblock health was made. However, the evaluation also found that some areas of refractory wear were missed, and a new mechanism affecting refractory wear was discovered that was not previously known. This has reinforced the belief that there is a need to develop improved methods of monitoring so that data used to define the health of the tapblock is more comprehensive and accurate.

Jan 1, 2008

By T. Feroze, B. Genc

"The ventilation of underground coal mines plays an important role in minimizing the risk of methane and coal dust explosions. The ability of ventilation, with the use of line brattices (LBs), to remove methane and coal dust in empty headings is dependent on the amount of air leaving the LB and entering the heading. The quantity of this air depends on the associated system variables, namely heading dimensions, settings of the LB, and velocity of air in the last through road (LTR). However, the exact effect of these system variables on the flow rate at the exit of the LB in an empty heading is not known. The installation of LBs in South African coal mines is generally carried out based on experience. This can result in overor under-ventilation and may increase the cost of providing ventilation or cause accidents, respectively. In this paper, using computational fluid dynamics (CFD), the air flow rate at the exit of the LB in an empty heading was estimated using full-scale three-dimensional models. The CFD model used was validated using experimental results Firstly, the settings of these three system variables were varied, the flow rates at the exit of the LB were measured, and finally the results were used to calculate the effect of each system variable. The outcome is a mathematical formula that can be used to estimate air flow rate at the exit of the LB in empty headings for any practical scenario.This paper will help the coal mining sector in South Africa by providing estimation models based on scientific reasoning for the installation of LBs, and will also serve academia as part of the curriculum towards educating future mining engineers."

Jan 1, 2016

By C. Ringas

Pipelines are used extensively in industry to convey various products. Internal corrosion of pipelines can lead to perforation and leakage of the product. A growing problem, not often accurately recognized, is internal corrosion of pipelines caused by bacteria. Microbiologically-induced corrosion (MIC) refers to corrosion caused by a variety of micro-organisms. This form of corrosion is not widely recognized in many industries, although it is widespread and causes many corrosion problems in pipelines, both internal and external. Sulphate-reducing bacteria (SRB) are responsible for the bulk of the corrosion problems caused by MIC. Corrosion caused by SRB is found extensively in water pipelines conveying raw, potable and waste water, as well as in pipelines conveying slurries. This problem also occurs in pipelines conveying crude oil. This paper describes internal corrosion problems of slurry pipelines caused by bacteria and outlines mitigation methods to improve slurry pipeline integrity, thereby extending the life of such pipelines.

Jan 1, 2007

By K. Koruyan

Although remote sensing technology has been available for many years, it has rarely been used for monitoring mining activity. Recent studies indicate that remote sensing is also a valuable tool for managing and planning certain aspects of the mining operation. In this paper, we examine areal expansion of marble quarries and the affected vegetation over a period of 10 years in the Mugla region in Turkey, using geographic information system (GIS) and remote sensing (RS) techniques. Images captured by ASTER Level 3A01 (3D Ortho Data Set), Landsat 5, and Landsat 7 satellites between 2001 and 2009 were used for the analysis. Changes in the natural vegetation as a function of the production level in the marble quarry were calculated using the normalized difference vegetation index. According to the study results, land cover and natural vegetation decreased by less than 3 per cent and 1 per cent respectively between 2001 and 2009, following an upsurge in mining activity in the region.

Jan 1, 2012

By P. Ramphisa

In South Africa reprocessing used oil into industrial fuel is commercially attractive. The reprocessed product is sold as a substitute for heavy fuel oil that is derived from crude oil (Rose Foundation, 2008). The objective of this investigation is to evaluate the use of petroleum products such as oil, petrol and diesel in Driefontein Gold Mine. The recovery of oil through recycling has costs implications to the mine while the release of petroleum hydrocarbons due to the poor management of the use of petroleum products has potential to cause pollution and negatively affect soil and water. Environmental legislation such as the Minerals and Petroleum Resources Development Act (Act 28, 2002) requires that such negative impacts to the environment be rehabilitated. The rehabilitation cost of pollution caused by petroleum products to the environment increases operational costs in business. Field assessment is conducted to identify the main sources of petroleum product contamination such as leaks in piping, overfills and petroleum spills. The areas that require mitigation would be mapped in the study. Recommendations for mitigation measures will focus on using the best practicable environmental option (BPEO) as well as the best available technology not exceeding excessive cost (BATNEEC). The recovery of oil from the mining industry is generally low and very poor. In this study, the effect of proper management of petroleum products to the mine?s operational costs is investigated and compared to there mediation costs of the impacts caused due to poor management of these products. The study investigates the financial benefit that could be obtained from proper environmental practices and efficient usage of petroleum products in the mining.

Jan 1, 2009

By A. F. Mulaba-Bafubiandi

Pseudomonas spp was isolated from mine water and tailings samples collected from mining effluents and mine dumps in the Gauteng and Northern provinces of South Africa respectively. Adsorption properties of Pseudomonas spp were then tested for the removal of Cu and Co initially from their synthetic sulphate solutions, subsequently from effluents derived from metallurgical operations. The effects of experimental conditions such as pH, temperature, time, volume and metal concentration on the efficiency of the biosorption process were studied. Absorption of 45% Cu (pH 6, 37°C, 24 hours) and 40% Co (pH 6, 37°C, 24 hours) was observed from solutions with low concentrations (0.07 M). A maximum of 73% and 65% of Cu and Corespectively were recovered from the mine water samples derived from effluents.

Jan 1, 2009