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.
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.