Scielo RSS <![CDATA[Journal of the Southern African Institute of Mining and Metallurgy]]> http://www.scielo.org.za/rss.php?pid=0038-223X20100008&lang=en vol. 110 num. 8 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>A review of optimal planning of level and raise spacing in inclined narrow reefs</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800001&lng=en&nrm=iso&tlng=en 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. <![CDATA[<b>Techno-economic optimization of level and raise spacing in Bushveld Complex platinum reef conventional breast mining</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800002&lng=en&nrm=iso&tlng=en The Bushveld Complex is economically significant and strategically important to South Africa, thus it is imperative that optimal extraction of platinum group metal (PGM) resources on the Bushveld Complex is achieved. Optimal extraction broadly requires that the maximum amount of ore is extracted by excavating and hauling the minimum amount of waste in the shortest possible time, at the least cost, and in the safest and most environmentally acceptable manner. In open-pit mine planning this entails among other things, minimizing the waste stripping ratio, whereas in underground mine planning it includes minimizing the metres of waste development. In conventional mining, the main development that is in waste or partly in waste and defines the mining grid pattern, includes levels and raises. It was prudent to consider optimizing level and raise spacing in conventional mining because the method is a prevalent mining method on the Bushveld Complex accounting for nearly 70% of platinum production. The techno-economic optimization of level and raise spacing is characteristically a multi-criteria decision analysis (MCDA) optimization process and should therefore be analysed using MCDA techniques. The analytic hierarchy process (AHP) was the most appropriate MCDA technique for this research study. By using an orebody code named OB1 based on real geological data that was typical of Bushveld Complex platinum reef deposits, the derived optimal range of vertical level spacing was 30 m-50 m, and the optimal range of raise spacing was 180 m-220 m. The research methodology used in this study and the results obtained were received positively by the South African platinum mining industry because for the first time in several decades, a holistic methodology and practically acceptable solution had been developed for the controversial debate of optimizing level and raise spacing for conventional mining. <![CDATA[<b>A new mathematical programming model for production schedule optimization in underground mining operations</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800003&lng=en&nrm=iso&tlng=en Mixed integer programming (MIP) has been used for optimizing production schedules of mines since the 1960s and is recognized as having significant potential for optimizing production scheduling problems for both surface and underground mining. The major problem in long-term production scheduling for underground orebodies generally relate to the large number of variables needed to formulate a MIP model, which makes it too complex to solve. As the number of variables in the model increase, solution times are known to increase at an exponential rate. In many instances the more extensive use of MIP models has been limited due to excessive solution times. This paper reviews production schedule optimization studies for underground mining operations. It also presents a classical MIP model for optimized production scheduling of a sublevel stoping operation and proposes a new model formulation to significantly reduce solution times without altering results while maintaining all constraints. A case study is summarized investigating solution times as five stopes are added incrementally to an initial ten stope operation, working up to a fifty stope operation. It shows substantial improvement in the solution time required when using the new formulation technique. This increased efficiency in the solution time of the MIP model allows it to solve much larger underground mine scheduling problems within a reasonable time frame with the potential to substantially increase the net present value (NPV) of these projects. Finally, results from the two models are also compared to that of a manually generated schedule which show the clear advantages of mathematical programming in obtaining optimal solutions. <![CDATA[<b>Investigation into how the magnesia, silica, and alumina contents of iron ore sinter influence its mineralogy and properties</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800004&lng=en&nrm=iso&tlng=en The influence of varying amounts of magnesia, silica, and alumina in iron ore sinter on its mineralogy, reducibility index (RI), reduction disintegration index (RDI), physical breakdown (AI and TI), and production properties (coke breeze rate) were examined. It was found that the mineralogy of iron sinter can more easily be predicted from its chemical composition than from the RI, RDI, AI or TI. Anticipating the consequence that varying amounts of MgO and SiO2 would have on sinter properties is complex, and not necessarily predictable. High concentrations of Al2O3 in the sinter result in high concentrations of the SFCA phase, but with drastically deteriorated properties. This study also confirmed that the form in which fluxes are added to the raw material sinter mixture affects the mineralogy and properties of the produced sinter. <![CDATA[<b>The development of a comprehensive, practical, and integrated management method for the South African mining industry</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800005&lng=en&nrm=iso&tlng=en This paper briefly reviews the adequacy of existing management theories and practices and the managerial proficiency or competency in the South African mining industry. The investigation revealed that existing management practices are totally inadequate to enable all employees on all the levels of the mining industry to achieve the results required from them, in all aspects, at all times. As a result, the South African mining industry is gradually losing its long standing reputation as a relative cheap, competitive, and reliable supplier of minerals to the local and global markets. According to some prominent management authors and theorists, an all-inclusive unified management theory does not exist at present. In this paper the authors summarize the main aspects of a newly developed comprehensive, practical, and integrated management method. It is believed that the application of this method would significantly improve the future performance and competitiveness of the South African mining industry. <![CDATA[<b>Mine dumps under the amended Mineral and Petroleum Resources Development Act 28 of 2002</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800006&lng=en&nrm=iso&tlng=en This paper briefly reviews the adequacy of existing management theories and practices and the managerial proficiency or competency in the South African mining industry. The investigation revealed that existing management practices are totally inadequate to enable all employees on all the levels of the mining industry to achieve the results required from them, in all aspects, at all times. As a result, the South African mining industry is gradually losing its long standing reputation as a relative cheap, competitive, and reliable supplier of minerals to the local and global markets. According to some prominent management authors and theorists, an all-inclusive unified management theory does not exist at present. In this paper the authors summarize the main aspects of a newly developed comprehensive, practical, and integrated management method. It is believed that the application of this method would significantly improve the future performance and competitiveness of the South African mining industry. <![CDATA[<b>Efficiency analysis of armed-chained cutting machines in block production in travertine quarries</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800007&lng=en&nrm=iso&tlng=en This study analyses the results of a pilot trial of a newly developed armed-chained stone-cutting machine. The machine was developed in Turkey and trialled at the Kaklk/Kocaba travertine quarries in the Denizli District. An armed-chained cutting machine is an alternative to the diamond wire cutting method more frequently used in the production of natural stone quarry blocks, and increases production efficiency and quality. Since there is no need to collapse the blocks using the armedchained cutting production process, there is no risk of the block developing cracks. This results in a considerable increase in the efficiency of natural stone block production. The armed-chained cutting machine is easier both to assemble and run when compared to other block cutting methods. This process resulted in the production of a larger number of blocks at a lower cost within the same time frame, particularly in travertine quarries and in all other natural stone quarries. The block efficiency in travertine quarries was calculated as 65-80% using the armed-chained cutting machine, compared with 7-14% using the normal diamond wire cutting method. <![CDATA[<b>Prediction of blast induced ground vibrations in Karoun III power plant and dam: A neural network</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000800008&lng=en&nrm=iso&tlng=en In this research, in order to predict the peak particle velocity (PPV) (as vibration indicator) caused by blasting projects in the excavations of the Karoun III power plant and dam, three techniques including statistical, empirical, and neural network were used and their results were interpreted and compared. First, multivariate regression analysis (MVRA) was used as statistical approach. Next, PPV was predicted using some widely used empirical models. Lastly, an artificial neural network was used. In the ANN model, maximum charge per delay, total charge per round, distance from blast site, direction of firing, blasthole length, number of blastholes, total delay in milliseconds, number of delay intervals, and average specific charge were taken into consideration as input parameters and consequently the PPV as output parameter. The results of the techniques were interpreted from two points of view. Firstly, the correlation between the observed data and predicted ones, secondly the total error between observed data and predicted ones. The MVRA had a satisfactory correlation but its error of estimation was comparatively very high. The empirical model had reliable correlation and a small error of estimation; in total the results of empirical method were more reliable than those of MVRA. Generally, the ANN approach showed very high correlation and a very small error. The results of this research indicated that the ANN model is the best predicting model for PPV in comparison with other approaches.