Scielo RSS <![CDATA[Journal of the Southern African Institute of Mining and Metallurgy]]> http://www.scielo.org.za/rss.php?pid=0038-223X20120002&lang=en vol. 112 num. 2 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Journal Comment - mine safety with heritage security</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200001&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200002&lng=en&nrm=iso&tlng=en <![CDATA[<b>Spotlight - MineSafe Conference</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200003&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200004&lng=en&nrm=iso&tlng=en <![CDATA[<b>A new mathematical programming model for long-term production scheduling considering geological uncertainty</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200005&lng=en&nrm=iso&tlng=en Determination of the optimum production schedules over the life of a mine is a critical mechanism in open pit mine planning procedures. Long-term production scheduling is used to maximize the net present value of the project under technical, financial, and environmental constraints. Mathematical programming models are well suited for optimizing long-term production schedules of open pit mines. There are two approaches to solving long-term production problems: deterministic- and uncertainty- based approaches. Deterministic-based models are unable to deal with grade and geological uncertainties, which are two important sources of risk in mining industries. This may lead to discrepancies between actual production obtained by these algorithms and planning expectations. In this paper, a new binary integer programming model was developed for long-term production scheduling that incorporates geological uncertainty within the orebody. Then, traditional and uncertainty-based models are applied to an iron ore deposit. Results showed that the uncertainty-based approach yields more practical schedules than traditional approaches in terms of production targets. <![CDATA[<b>A risk evaluation model for support design in Bushveld Complex underground mines</b>: <b>part I-Description of the model</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200006&lng=en&nrm=iso&tlng=en A risk evaluation model has been developed, that enables the quantification of expected injuries and economic losses resulting from rockfalls associated with a support system in a given geotechnical environment. This enables the comparison of different support systems based on the expected frequency of injuries and the total cost of the support system, including the expected economic losses. The model takes into consideration the variability in joint orientations and joint strength within the geotechnical environment and the variability and quality of support systems. The quantification of the benefits of other rockfall risk-mitigating strategies, such as the effectiveness of barring or monitoring, are also incorporated in the model. The risk model is described in this paper and the validation of the model and case studies are described in Part II. <![CDATA[<b>A risk evaluation model for support design in Bushveld Complex underground mines</b>: <b>part II-Model validation and case studies</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200007&lng=en&nrm=iso&tlng=en A risk evaluation model has been developed that enables the quantification of expected injuries and economic losses resulting from rockfalls associated with a support system in a given geotechnical environment, which is described in Part I (Joughin et al., 2011b). Part II presents the validation of the risk evaluation model. Underground mapping of joints and rockfalls was carried out to provide data for field calibration of the model. This survey was limited to small rockfalls,due to the relatively short period of mapping. Therefore the model was also correlated with rockfall and rockfall injury data collected by mine personnel. The analyses showed that the model provides a reasonable estimate of the expected frequency and size of rockfalls and the frequency of rockfall injuries, but further work is required to enhance the model. Three case studies are presented, which show the benefits of improved support systems from both economic and safety perspectives. This work has demonstrated that the risk evaluation model and the software developed are immediately useful, but further work is required to develop and improve the tools. <![CDATA[<b>Managing the geotechnical and mining issues surrounding the extraction of small pillars at shallow depths at Xstrata Coal South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200008&lng=en&nrm=iso&tlng=en Pillar extraction at shallow depths with small pillars that were not originally intended for secondary extraction can provide a huge benefit to the coal mining industry in those areas where a significant percentage of the remaining coal reserves are locked up in small pillars at shallow depths and where opencast mining methods are simply not as cost-effective and practical to implement. A system considering all of the pertinent geotechnical and mining aspects for the safe and efficient pillar extraction of small pillars at shallow depths at Xstrata Coal South Africa (XCSA) has been further developed and implemented as part of an ongoing improvement process addressing all of the relevant legal and associated risk aspects. This work follows on from the previous pillar extraction work carried out at the ATC, Boschmans, and Spitzkop Collieries. The process involved a number of in-house workshops and sessions arranged with all key personnel from Tavistock Colliery, and also included Professor Nielen van der Merwe of the University of the Witwatersrand, a world renowned authority on pillar extraction, towards reviewing and developing the Modified NEVID pillar extraction system employed previously at Boschmans Colliery. The system is currently being employed at Tavistock Colliery with success and no major accidents, with around 655 000 t of coal having been successfully extracted from the pillar extraction panels. <![CDATA[<b>Optimum Coal Mine</b>: <b>striving towards a 'zero effluent' mine</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200009&lng=en&nrm=iso&tlng=en Optimum Coal Mine comprises numerous defunct, active, and future mining sections. The mine is primarily a large opencast coal mine; however, underground mining activities will be increasing steadily over the next five years. Opencast and underground mining activities have a significant impact on surface and groundwater resources. To ensure that the mine will be able to continue with its mining operations in the catchment, the extent of this impact requires that substantial intervention and mitigation measures need to be implemented to ensure the environmental integrity and economic use of the catchment's water resources. In developing a sustainable long-term mine water management strategy, numerous scenarios had to be analysed. The various scenarios are a combination of water and land management activities. The main components of the mine's integrated water management strategy include: <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">Management of water recharge by continual and appropriate rehabilitation of disturbed land <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">Beneficial re-use of impacted mine water for coal plant process water and mining operations <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">Reclamation and desalination of remaining excess impacted mine water to potable standard. From the mine's long-term water balance, it is evident that the continued implementation of numerous water management actions is required to mitigate the water resources impact in a sustainable manner. In addition, the installation of a water reclamation plant at Optimum Coal Mine (15Mℓ/day) is a key step for the mine to achieve a zero impact target. <![CDATA[<b>Fast, safe, and fully mechanized installation of high-tensile chain-link mesh for underground support</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200010&lng=en&nrm=iso&tlng=en The ever-increasing depth of mineral extraction presents a challenging environment for hard-rock underground mines. High in situ stresses and associated seismicity with potential rockburst hazards are the major decisive factors contributing to the choice of a ground support regime. Conventional ground support systems, designed primarily for static loads, are not always capable of providing safe working conditions for underground personnel in seismically active mines. Systems specifically developed to resist dynamic loading and allowing for larger deformations are therefore preferred alternatives. High-tensile chain-link mesh has a proven record of successful use in open cut operations in various rockfall barrier installations due to its high energy absorption capacity. It has also been used in underground operations in various parts of the world. Its application in South African underground mining, however, is limited due to the high labour intensity. This paper describes a method of mechanized installation of a chain-link mesh as evaluation at Gold Fields' South Deep Gold Mine situated some 45 km south-west of Johannesburg. A purpose-built mechanized roll mesh handler, developed in Australia, was used in this trial. The handler is compatible with all standard multi-boom underground drill rigs and is operated utilizing the hydraulic circuit normally used for the feed arrangement. A number of key performance indicators have been specified as success criteria by Gold Fields: <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">A 30% faster installation compared to the conventional methodology <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">The mesh should sustain any blast damage when applied to the blasting face <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">No unravelling of the mesh when cut <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">No failure of mesh under normal conditions <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">Reliability of the MESHA┬« installation handler (availability >90%) <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">Compatibility of the MESHA┬« installation handler with AC 282 boomers. Although the energy-absorbing mesh combined with yielding rockbolts is a ground support system of choice for rockburst-prone conditions, the operational upsides recognized during the trial imply that this product can also be competitively used in less demanding ground conditions where weld mesh or shotcrete are customarily used as a primary surface support. <![CDATA[<b>Sustainability through responsible environmental mining</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200011&lng=en&nrm=iso&tlng=en The Constitution of the Republic of South Africa advocates the importance of sustainable economic development and justifiable environmental consciousness by business. The government needs to ensure that every citizen of the Republic has access to an environment that is protected, pollution free, and sustainable by enacting certain regulations. However, there are more than 5 700 derelict and unrehabilitated mines of all types in South Africa. Former asbestos operations were among the first to be targeted for clean-up under the programme instituted by the Department of Mineral Resources (DMR), owing to the proven direct impact of asbestos pollution on health. This paper seeks to investigate the challenges faced by the coal sector as far as mine rehabilitation and closure is concerned. For the purpose of this paper rehabilitation is defined as per the Chamber of Mines Rehabilitation Guidelines publication, which defines rehabilitation as putting the land impacted by mining activities back to a sustainable and usable condition. Some of the current rehabilitation challenges are technical skills (know-how), leadership focus, poor planning, cost saving initiatives, and the government's lack of capacity to enforcement rehabilitation requirements. It is imperative that mining companies identify rehabilitation as a critical strategic pillar that directly influences license to operate. The case study evidence indicates that relevant policies, appointment of accountable people, sufficient leadership support, and the correct choice of rehabilitation equipment can assist to improve the rehabilitation and land management challenge. <![CDATA[<b>The application of GRP and thin spray liner support products in a typical block cave mining method to enhance safety and productivity</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200012&lng=en&nrm=iso&tlng=en A typical sub-level block cave mining extraction method employs an undercut level to establish a cavity in hard rock, and as such requires special support methods and products to be installed during the development phase. The undercut level development in the block cave orebody is then sacrificial, and support elements will eventually report to the crusher and perhaps conveyor belt systems for transportation to surface. The choice of support products installed in the undercut level development should take cognizance of the detrimental effect these could have on the mining system such as cutting of conveyor belts, obstructing crushers, safety aspects, and productivity. This work explores the probability and practicality of making use of new-generation support products to make the operation safer as well as enhance productivity in the development phase and during the undercut operation. This paper will investigate the use of glass reinforced plastic (GRP) rockbolts and GRP mesh instead of conventional steel bolts and mesh along with resin capsule-filled holes with the GRP bolts. Complementing this with thin spray liner (TSL) application as another means of creating a safer operating environment, as well as a productive support medium, will also be addressed. These proposed items are envisaged to reduce production downtime and improve the safety of our people. These items are all easy and light to handle, cuttable and crusher friendly, as they will break up during the crushing process. <![CDATA[<b>The Avatar syndrome</b>: <b>mining and communities</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200013&lng=en&nrm=iso&tlng=en A typical sub-level block cave mining extraction method employs an undercut level to establish a cavity in hard rock, and as such requires special support methods and products to be installed during the development phase. The undercut level development in the block cave orebody is then sacrificial, and support elements will eventually report to the crusher and perhaps conveyor belt systems for transportation to surface. The choice of support products installed in the undercut level development should take cognizance of the detrimental effect these could have on the mining system such as cutting of conveyor belts, obstructing crushers, safety aspects, and productivity. This work explores the probability and practicality of making use of new-generation support products to make the operation safer as well as enhance productivity in the development phase and during the undercut operation. This paper will investigate the use of glass reinforced plastic (GRP) rockbolts and GRP mesh instead of conventional steel bolts and mesh along with resin capsule-filled holes with the GRP bolts. Complementing this with thin spray liner (TSL) application as another means of creating a safer operating environment, as well as a productive support medium, will also be addressed. These proposed items are envisaged to reduce production downtime and improve the safety of our people. These items are all easy and light to handle, cuttable and crusher friendly, as they will break up during the crushing process. <![CDATA[<b>Economics of mine water treatment</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200014&lng=en&nrm=iso&tlng=en Mine water poses a significant problem in lignite coal mining. The drainage of mine water is the fundamental prerequisite of mining operations. Under the legislation of the Czech Republic, mine water that discharges into surface watercourse is subject to the permission of the state administration body in the water management sector. The permission also stipulates the limits for mine water pollution. Therefore, mine water has to be purified prior to discharge. Although all mining companies operate mine water treatment plants, there is hardly any utilization of the final effluent. The high expenditure involved in the more sophisticated methods of mine water treatment has fuelled the search for the commercial utilization of the effluent. <![CDATA[<b>Practice and prospects of fully mechanized mining technology for thin coal seams in China</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000200015&lng=en&nrm=iso&tlng=en In China, thin coal seams are rich in resources but are technically challenging. The mineable reserves in these seams account for 20.4% of the total coal resources, while the current production accounts for only 10.4% of the total annual production. Characteristics such as narrow mining space, low level of mechanization, poor working environment, and high cost of mining, restrict the development of mining safety and efficiency. Recently, fully mechanized mining technology has developed rapidly for thin coal seams, the level of yield and efficiency has reached or exceeded the international standard, and some state-owned key coal mines are considering automation of their mining process. In thin coal seams with hard stone bands that contain concentrations of pyrite, a specialized software, LS-DYNA, is used to calculate the rational blasting parameters that are used in the deep-hole pre-splitting blasting. Using this method the hard stone bands are fractured effectively, and hence increasing the coal productivity. In addition, mining advance rate were increased by enhancing the level of fully mechanized equipment and safety improved by increasing gas drainage from the gas outburst prone seam located some 7 m below the coal horizon. At present, thin coal seam mining technology faces many challenges, including the low level of equipment automation, the low advance rate in mixed coal-rock ground, and the large number of the mine personnel underground. By lowering the labour intensity and improving efficiency through automation and other measures, more efficient working faces can be implemented in thin coal seams.