Search Documents

A systematic study of groundwater conditions at eight underground mine sites exhibiting a wide range of groundwater qualities throughout Australia has been completed at the WA School of Mines. This has resulted in a new corrosivity classification for groundwater driven corrosion processes for cement grouted cable strand used in the Australian underground mining industry. The new corrosivity classification is simple to use and corrosion rates may be predicted from readily obtained in situ measurements of groundwater dissolved oxygen.

Jan 1, 2008

By M. Sanchez, C. Morales, J. Palacios

The slag produced in the Peirce Smith converters at the Ilo smelter of Southern Peru Copper Corporation has shown a wide range of magnetite content, which introduces an additional problem in the smelting units due to materials? recirculation. However, the operation data analysis and the application of thermodynamic concepts have made it possible to produce slag with magnetite content between 18 and 20%. The results have suggested that matte grade enhances magnetite formation while silica controls its precipitation, and they are also influenced by the increasing temperature of the slag. Thus, in order to obtain the required magnetite content in the slag, matte grade is gradually enriched in equilibrium with slag containing from 25 to 32% silica.

Jan 1, 2004

By M. Grodner

Ground Penetrating Radar (GPR) is an electromagnetic geophysical reflection technique that maps reflections associated with a change in electric properties of the target medium. It can thus be used to map the geometry of geological features and fractures as these can have different electromagnetic properties to intact rock. GPR was used successfully to determine the position and nature of the fractures in the tunnel sidewall, in the area of the simulated rockburst experiment. By comparing the radar scans acquired before with those acquired after the blast, it was possible to determine which fractures were reactivated by the blast and where new fractures were developed. It was found that the mining-induced fractures that formed during the development of the tunnel were re-activated by the simulated rockburst, as indicated by their increased reflectance on the radar scans. In addition, several new tunnel sidewall parallel fractures developed in the area of the blastholes. GPR thus clearly shows how and where the fracture pattern changed as a result of the blast and contributed to the understanding of the mechanisms of damage associated with the blast, and perhaps rockbursts in general.

Jan 1, 2001

By J. M. Ortiz

This paper shows the usefulness of geostatistical conditional simulation combined with the quantification of sampling errors obtained from the analyses of fundamental errors ? validated from duplicate data ? to assess the relevance of the quality and quantity of the information, for short-term mine planning purposes. Traditional blast-hole drilling equipment has been designed for efficient drilling, but not for obtaining high-quality samples. Furthermore, blast-hole sampling interferes with production, and thus usually produces poor-quality results. These results are the basis of short-term plans, where the grades of selective mining units are estimated and used for distinguishing between ore and waste. Under these conditions, misclassification (ore blocks sent to the waste dump and waste blocks processed at the plant) is inevitable, leading to significant hidden losses that can amount to millions of dollars per annum. Reverse circulation drilling with the latest automated sampling technology improves significantly the quality of the information used for short-term planning, and thus reduces misclassification, improving the financial returns of the operation. In this paper, we present the general methodology for assessing the effect of poor blast-hole sampling, as compared to advanced reverse circulation drilling grids at several spacings, in order to arrive at the most appropriate grid for short-term planning. This plan can be prepared well in advance using several additional variables that are usually not available when the plan is based on blast-hole samples. Furthermore, blending options can be analysed in order to optimize plant recovery, minimize the use of sulphuric acid, etc. Three case studies are presented, namely a typical porphyry copper deposit, an exotic oxide copper deposit, and a complex gold deposit, where mineralization is controlled by structures and lithology. This paper shows that in all cases, advanced reverse circulation drilling grids provide good-quality information that, coupled with the use of geostatistics for short-term mine planning, significantly improve the financial returns of the operation.

Jan 1, 2014

By S. M. Spottiswoode

Crush pillars are widely used in mine workings on the Merensky Reef in the Bushveld Complex to prevent panel collapses. Crush pillars are expected to fail as or soon after they emerge from the face and failure should occur non-violently. Unfortunately, violent failure occurs frequently and is said to be the main cause of seismicity associated with mining of the Merensky Reef. Recent work by Napier, Malan, and du Plessis has shown that limitequilibrium quasi-static models are able to simulate pillar failure using three states of strength of rock in pillars, namely intact, residual after failure, and decayed strength after later time-dependent (viscous) weakening. We have previously introduced an additional state of strength to account for the dynamic failure that results in seismic events, and found that this approach could be used to generate synthetic seismic catalogues similar to observed seismicity for deep-level gold mines, where seismicity takes place mostly on advancing faces. The less brittle seam material of the Merensky Reef, compared to the brittle quartzites and lavas of the Witwatersrand reefs, results in little or no face bursting and is modelled with an assumed plastic strain of some 0.005 over an effective stope width of 2 m before failure. When this plastic yield is surpassed, we allow the reef to fail ?seismically?. We show that synthetic seismic catalogues modelled in this way have some of the features of observed seismicity. Analysis is greatly facilitated using our custom-built software that reads the mine?s survey data into a database and presents results in an interactive graphical form.

Jan 1, 2014

By A. P. Squelch

The high incidence of accidents and fatalities in the South African mining industry, in particular those associated with falls of ground, is often attributed to ineffective and/or inappropriate training methods and material. Recently introduced mine health and safety legislation in South Africa also requires that all mine workers receive appropriate and effective training to enable them to operate safely in their given mining environment. There can, therefore, be no doubt that methods to provide effective training, in particular safety related training, are urgently required in the South African mining industry. In the search for alternative and improved training approaches, attention has fallen on virtual reality (VR) technology as a possible solution. VR has found acceptance in a number of industries as an effective method of training for a variety of work place activities, including those of a safety related nature. VR has successfully been applied in a number of industries to improve the effectiveness of safety and hazard awareness training. The CSIR: Division of Mining Technology (CSIR Miningtek), in conjunction with the Safety in Mines Research Advisory Committee (SIMRAC), therefore evaluated the potential of VR to be used as a training medium in the South African gold and platinum mining industry. Aspects of the evaluation included an assessment of the technical capability of VR to represent a typical underground mining environment with sufficient realism and the relevance of the VR training concept for a largely illiterate workforce. For these purposes, a prototype PC-based VR hazard awareness training simulator has been developed by CSIR Miningtek, and a series of evaluation sessions conducted at a typical deep level gold mine. The conclusion from this evaluation work is that virtual reality technology has the potential to provide effective training systems that are relevant to the South African mining industry. Keywords: Virtual reality, mine training, safety training.

Jan 1, 2001

By A. J. Lynch

Mineral processing models have been discussed for many years but it was not until digital computers became available about 1960 that serious attempts at circuit simulation could be carried out. Even then the work was primarily academic until PCs could be used by engineers in plants and design offices in the mid-1980s. Since then simulation has moved quickly and it is now at the point that most processes can be simulated reasonably accurately for purposes of design and optimization. There are still some significant deficiencies, notably in dry grinding and separation, and in the chemical interactions in flotation. Future work will involve: ?improvements of existing models ?dynamic simulation for automatic control and, in particular ,for training which is a weak link ?using advanced simulation models to predict liberation and separation from data acquired from SEM-based liberation analysers. Eventually mineral processes models will be part of total simulation systems which will incorporate mining and downstream processes including all environmental impacts.

Jan 1, 1999

Gravity-driven rock falls account for a large proportion of all fatalities and injuries in underground mines. Potentially unstable blocks of rock are found in the hanging wall of excavations, which may be delineated by natural joints or stress fractures. These blocks, referred to as keyblocks, will fail if their weight exceeds the support capacity or if they are located between support units. This paper describes a computer program which simulates blocks in the hanging wall of an excavation based on measured properties of fractures and joints. Keyblocks are identified and placed at random locations in a predefined excavation. The keyblocks are tested against the support to determine whether they fail the support, drop out between the support or are stable. By repeating the procedure several thousand times, statistics of the probability of failure of the keyblocks are obtained. This approach allows the relative hazard associated with different types of support or excavation orientations to be obtained. It is concluded that a probabilistic approach is suitable for the evaluation of supports effectiveness in situations where large numbers of discontinuities or stress fractures are exposed in excavations.

Jan 1, 1998

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, 2004

The aim of this research was to study the absorption characteristics of thermally dried fine coal from South African collieries. After milling to ?150 µm and pressure filtration, the samples were subjected to either air drying or thermal drying at 150°C. The samples were then put into a climate box at 28°C and at three different relative humidity levels, namely 30, 60 and 94 per cent. It was found that the equilibrium moisture content of thermally dried coal at a specific relative humidity was lower than that of air dried coal. The relationship between the equilibrium moisture content and relative humidity is described by 1 ? RH = exp (-KTMen). There was no relationship between the volatile matter content and equilibrium moisture content, but there was an increase in the equilibrium moisture content of the coal with an increase in mineral content. The moisture uptake rate increased with an increase in temperature and a decrease in particle size. A model is discussed that fitted the experimental data and gave a good prediction for changes in the conditions. There was no evidence of greater moisture absorption by thermally dried coal. Keywords: Fine coal, thermal drying, drainage, South Africa, drying

Jan 1, 2002

By I. Mc Dougall

Finite element models were generated of two submerged arc furnaces of different geometries. A 48MW circular furnace and a 68MW 6-in-line rectangular furnace were studied. The electrodes, raw material, slag and molten metal were included in the model. ANSYS/Multiphysics was used to predict the current density distribution in the electrodes, raw material, slag and molten metal as a result of the three phase AC current. The effect of the electrode immersion on the current path was studied. The ?proximity effect? caused a pronounced asymmetry in the electrode currents in the circular furnace, whilst the electrode currents in the rectangular furnace exhibited radial symmetry. The current distribution in the melt in both furnaces indicated that the bulk of the current flows between phases. The current density is greatest between electrodes. Results were compared to qualitatively similar published work, operating experience and results of furnace dig-outs.

Jan 1, 2007

By P. C. Schutte

The objective of ergonomics is to enhance the effectiveness and efficiency with which human tasks are carried out. Furthermore, the objective is to improve desirable human values. This can be achieved by enhancing safety, reducing fatigue and stress, increasing comfort, increasing job satisfaction, having greater user acceptance and thereby improving the quality of life. Mechanization has influenced the prevalence of injury, mainly due to the application of human physical effort as the power source. With mechanization, the operator?s function is now essentially one of control rather than being an energy source, however, the risk of injury has not diminished. Mechanization in itself has introduced inefficiencies, health risks and physiological stress. The major objectives of ergonomics are discussed through examples of acceptable and less successful implementation of ergonomics within mechanized mining. The influence of the machine system on the human is addressed and practical solutions to improve and optimize the interaction of the human and the machine are outlined. Furthermore, practical examples of control and display integration, anthropometric and biomechanic influences on design, orientation, posture and stereotypes are used to accentuate the advantages of the application of sound ergonomics principles to the specialized area of mechanized mining.

Jan 1, 2002

By L. Rademan

The kinetic leaching behaviour of a low-grade surface gold ore and a high-grade reef ore were evaluated to determine the achievable gold recovery from these ores and particularly mixtures of these ores. The reef ore material has a head grade of 13.40 g/t with a relative standard deviation of 3%, and the unprocessed surface ore material a head grade of 0.43 g/t with a relative standard deviation of 15.6%. It is concluded that the kinetic leaching behaviour of these free milling gold ores during cyanidation, is not influenced by mixing of reef and surface ore material. No statistically significant relationship exists between the achievable recovery by direct cyanidation and the head grade of the material fed. No ideal ratio of surface ore to reef ore could be established. It is recommended that these materials should be processed simultaneously to minimize the costs, security risks, and losses incurred in transportation.

Jan 1, 2012

By L. K. Bandyopadhyay

The expert system component of Knowledge Base System supports the analysis and interpretation phases of ventilation design with an algorithmic program used for the solution of alternate design. The paper describes the ?ES-VENT? knowledge based system developed at Central Mining Research Institute, Dhanbad, India for an on-line diagnosing of the ventilation problems using the ?IITMRULE? expert system development tool. In the ?IITMRULE? expert system tool, it has been decided to use a backward chaining reasoning process to reach the goal state i.e. the final conclusion. ES-VENT system is made of three modules: On-line Data, Diagnostics and KBS. Each module is being a collection of several programs. The paper mainly deals with the parameters affecting the ventilation of underground mines such as air-velocity, air pressure, temperature, dust, and humidity and gas contents. The graphical presentation of these parameters on the computer and the interactive part of the developed program is expected to help a ventilation officer to determine the changes in a ventilation circuit necessary to bring the mine ventilation to the desired value. Once such changes are physically effected, the display will indicate if the changes have brought the desired effect or not on ventilation. Keywords: Ventilation network, on-line data, expert system, intelligent system, knowledge base, inference engine.

Jan 1, 2002

By M. Kumral

The efficiency of an ore-processing unit depends on the consistency of the characteristics of raw material entering the plant. When the mined ore is highly variable in quality, the only way to ensure consistency is to homogenize the ore prior to feeding to the processing plant. The homogenization can generally be achieved by the bed blending operation. Given that the stockpiling and reclamation processes are very expensive, it is necessary to design the process in such a way as to minimize variabilities of specified properties of raw material. In this paper, for alternative stacking types, optimal stockpile geometry is found in three stages: First, stockpile input is simulated by sequential Gaussian simulation, and then the variance reduction ratios (VRR) as a criterion of stockpile efficiency are calculated for various stockpile geometry scenarios by a stockpile simulator written in FORTRAN. Second, multiple regression analysis is performed to model the VRR by the use of stockpile length, the number of layers and stacker speed as the independent variables. Finally, the model is an optimization problem. Decision variables are the stockpile length, the number of layers, stacker speed and stacking type. The genetic algorithms (GA) are used to minimize the VRR. The approach was demonstrated on data from an iron orebody. The problem was to reduce fluctuations of iron, silica, alumina and lime contents in the stockpile output. The results showed that the approach could be used for the bed blending design efficiently. Keywords: bed blending design, multiple regression analysis, genetic algorithms, iron ore, content fluctuation

Jan 1, 2006

By M. Nyoka

Historically bauxite-based refractories have been used in applications where andalusite-based refractories could work. Bauxite-based refractories were chosen over andalusite-based refractories mainly because of the availability of low-cost Chinese bauxite and also because many furnaces were designed by international companies that cannot easily access high-quality products. Currently, the availability of low-cost bauxite is under threat as a result of high export duties and tariffs as well as restrictions on the amount of material that China allows to be exported. South Africa is a major producer of andalusite, and this guarantees stability with respect to both availability and price. Refractories based on andalusite have an added economic advantage over bauxite-based refractories in that unlike bauxite, which requires high-temperature calcination before use, andalusite is used in its raw state. This paper constitutes a literature study of the merits, both technical and economic, of using refractories based on andalusite compared to bauxite-based refractories. Keywords bauxite, andalusite, refractory, furnaces, calcination.

Aug 1, 2013

Electrochemical measurements are presented on electro-deoxidation of silica in molten calcium chloride at 900°C, with porous silica pellets as starting material. Measurements during pre-electrolysis (to remove water from the melt) showed electrochemical noise, which is consistent with the evolution of hydrogen. Throughout, the dominant anodic reaction appears to be CO2formation, based on the observed potential at the anode, and measured anode wear. Because of the presence of dissolved CaO in the melt, some of the CO2 candissolve in the melt; the resulting calcium carbonate formation was confirmed by electrolyte analysis after reduction runs. Reduction of dissolved CO2 at the cathode is likely to contribute to the background current during the reduction process. For the electrode and cell configuration used here, most of the over potential arises from polarization of the anode, and ohmic potential drop in the electrolyte.

Jan 1, 2006

By G. E. Blight

Wind erosion can be a major cause of the loss and dispersion of tailings material from a tailings dam into its surrounding environment. Such dust dispersion can be a serious nuisance, as well as a health hazard to inhabitants in nearby settlements, and can also damage the health of animals, degrade crops, making them less marketable, and cause soil and water pollution. The problem of wind erosion can affect tailings dams in all types of climate, but becomes worse as climatic aridity increases. Because clouds of dust are often observed billowing across the top surfaces of tailings dams in dry windy weather, there is a common misconception that the dust arises from wind erosion of the top surface. As a result, much effort and money is vainly spent on treating the tops of tailings dams to prevent dust generation, whereas the slopes of the dams are the true major dust source. This paper briefly reviews what is known of erosion of tailings dams and then proceeds to describe the mechanics of wind erosion in general, and how it affects tailings dams in particular. Finally, recommendations are made for mitigating wind erosion of tailings dams and the resulting blowing dust.

Jan 1, 2007

By R. P. H. Willis

For technology transfer to be successful a process, from research to full scale application, has to be followed. This paper describes such a process and how it is applied in practice. Some of the ?do?s? and ?don?ts? are highlighted. Recommendations are made on how to communicate existing knowledge and to ensure that a framework exists to effectively plan future projects with final technology transfer objectives firmly in place. The Impact Ripper System is used as a case study to illustrate lessons learned. Key words: Technology transfer, implementation

Jan 1, 2002

By R. Altindag

In rock cutting mechanics, the effects of the rock and coal brittleness on the efficiency of cutting bits are examined by many researchers. There is no universally accepted brittleness concept as a measure of cutting efficiency. The effect of the brittleness on rock cutting has not been completely explained. The aim of this study is to correlate the relationships between Specific Energy (SE) and brittleness concepts. The applicability of various brittleness measurement methods for rock cutting efficiency has been investigated. In this study, the raw data derived from previous experimental studies were used, and the relationships between SE and brittleness concepts were investigated. The two previously used brittleness concepts, which are named as B1 (the ratio of compressive strength to tensile strength) and B2 (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength), and a new introduced brittleness concept named B3 (the area under line in relation to compressive strength and tensile strength) were evaluated in this study. The relations among these brittleness concepts for rock cutting efficiency were established using regression analysis. There is no correlation found between the SE values and the brittleness of B1and B2values. But, the SE is strongly correlated with the brittleness of B3. It was seen that the suggested brittleness of B3concept could be used as an indicator in rock cutting efficiency analysis.

Jan 1, 2003