The authors have developed the Mine Geotechnical Risk Index (MGRI), which has been advanced to attribute tolerable thresholds of risk in a given transitional mine closure context. This paper presents the philosophy behind the development of the MGRI using a conceptual case study and sets out how the authors propose it could be applied by practitioners in particular scenarios only when assessing tolerable thresholds of risk. The reader should note that this approach is not intended to replace conventional engineering risk assessments, it is merely an alternative method in evaluating the tolerability of elevated risk thresholds.
This paper reviews the progressive growth of awareness, adoption and practices with respect to geotechnical risk in mining in Australia over the last four decades, with a particular focus on underground mining. Initial experience in the 1980s was drawn from other high-risk industries such as nuclear and petrochemical sectors, and whilst the mining industry recognised the issue of a changing hazard and risk environment, it did not change practices significantly. Subsequent growth in understanding of the evolving discipline of risk management, coupled with major changes in mining legislation to a more enabling legislative framework, have led to a far more risk-aware industry where risk assessment and risk management practices have become a fundamental component of the overall mining management systems. In underground mining, geotechnical risk is at, or close to, the top of the risk priority list for proactive mine management today. The recognition of what are referred to as core risks associated with particular mining methods was a further development in the maturity of the industry management systems, with implications for all levels of management, right from feasibility through to design, planning and operations. One of the problems with the growth of risk-based management practices in Australia is that because we do so many risk assessments and develop so many hazard plans, we have, in some cases, become too blasé about them and do not give due recognition and priority to the ongoing management of important risks with the potential for serious consequences through lack of attention to detail and lack of integration of risk management into the mine management system. In an effort to overcome this issue and place higher priority on the most critical risks facing a mining operation, the International Council of Mining and Metals (ICMM) Critical Control Management (CCM) system, for focusing on the most critical risks, and then directing more attention to the actual control practices required to manage them, has been a valuable trend in recent years. In the Australian coal sector over the last 10 years, the industry-funded RISKGATE system has also been an extremely useful documentation of industry experience and a tool to assist operators either investigate incidents or plan risk assessments on new topics or areas. Geotechnical topics make up at least three of the 18 major topic areas covered by RISKGATE. This paper will briefly outline how RISKGATE operates and is applicable to the industry in the geotechnical space.
Rio Tinto Iron Ore operates 16 different mine operations in the Pilbara region of Western Australia. Across these operations, there could be more than 100 operational open pits at any given time. This poses a considerable challenge for the effective management of geotechnical risks with finite resources. There are also a number of external legislation and internal compliance requirements that need to be adhered to. A number of standardised systems and tools have been developed by the geotechnical teams to manage the geotechnical risks and this paper introduces the different components of Rio Tinto Iron Ores geotechnical management System (GMS). The GMS covers the complete process, from the geotechnical design of a slope, through implementation to verification of performance and feedback to the design engineer. The focus of the paper will be on the Geotechnical Risk and Hazard Assessment Management System (GRAHAMS) which is used to assess and document the safety and economic geotechnical risk assessments of different slope areas. A number of reports and visual summaries of the risk assessments are available in the system, offering leaders the opportunity to identify areas of elevated risk and allocate resources accordingly. Details of realised risks (geotechnical hazards) are also captured and GRAHAMS provides a process to communicate the hazard and relevant controls to operational personnel. The GRAHAMS system was recently enhanced, moving from a Microsoft Access front-end to a web-based platform. This will enable a number of system improvements to further increase its effectiveness.
Thin spray-on liners (TSLs) provide areal support to rock excavation surfaces, and have been implemented in the mining sector for over 20 years. However, scepticism over their usage still prevails, despite the results of laboratory research that has been carried out indicating their effectiveness for use in mines. The study described in this paper aims to highlight TSL performance as viewed by the mining industry. Some underground cases of practical performance have been singled out and compared with the expected performance based on information from suppliers and from laboratory testing perspectives, and the causes of the resulting quality of performances were categorised. Among the causes of the discrepancies between expectations and observations is the lack of inclusion of parameters such as temperature and humidity in the laboratory tests, which could have significant effects on the liner performance since, based on results from Brazilian indirect tensile tests on coated samples, their inclusion doubles the probability of failure and therefore, increases the predicted geotechnical risk of failure. Consequently, to take into account potential performance discrepancies, some existing recommendations and further potential recommendations are suggested in the paper. If later validated, these suggestions could be included in a good practice guideline for TSL application in underground mines.
AngloGold Ashanti (AGA) has developed a concept to integrate geotechnical input into long-term mine planning using a block model approach referred to as a geotechnical model for rapid integration (GMRi). The GMRi is a simple spatial collection of rock mass data integrated with empirical evaluations, numerical modelling results and monitoring data for a specific mine plan. In this paper, the value of using the GMRi to manage geotechnical risk and identify opportunities associated with ground support design, stress-induced damage, design stope spans and total extraction is demonstrated. The GMRi concept allows for the rapid evaluation of spatially distributed geotechnical data and identifies areas of risk and opportunity, demonstrated at two recent underground studies completed at AGAs Australian operations.