Comprehensive monitoring strategy for tailings dams

Abstract

The demand for tailings storage, and in turn the associated risk, is increasing exponentially with time. It has been estimated that the potential risk posed by tailings dams increases by 20-fold approximately every 30 years, as tailings storages become larger, are built faster and must remain stable for longer. The social, environmental, and economic consequences of tailings dam failures are globally significant, and more readily scrutinised and observed by the general public than ever. As a persistent liability, how does the tailings dam avoid being dismissed as an expenditure until such time as a serious deterioration or failure occurs?In hindsight, there have been no tailings dam failures that are unexplainable. Through the appropriate investigation into their root causes, each and every failure has been able to have its mechanism described using the data available. Switching this to a proactive perspective, it is suggested that through access to and the use of the appropriate design and construction, and operational and monitoring approaches, tailings dam practitioners can be more readily equipped to understand and foresee the deterioration of their unique tailings dam structure. In turn, this allows for a safer, collaborative approach between the different stakeholders and provides a vessel for healthy and informed discussion and decision-making. Today, challenges arise in identifying and utilising monitoring systems to understand the complex performance and rapid behaviours of these dams, in turn reflecting on the system’s ability to be able to predict deterioration before failure occurs.This thesis developed a comprehensive monitoring strategy for tailings dams. Focusing predominantly on onsite monitoring techniques, the research explored the role that appropriate monitoring can play in understanding and assessing the performance of the dam against its expected behaviour. The research explored the state of practice for monitoring techniques, developed catalogues of instrumentation types and the systems that these integrate with in practice, described analysis techniques in relation to risk management processes in combination with the observational approach and numerical model calibrations, and demonstrated the effectiveness of these techniques through a number of case studies.The research found that by appropriately acknowledging the advantages and limitations of different monitoring methods, tailings dam practitioners have the opportunity to foresee certain types of failure ahead of time and implement appropriate responses prior to a catastrophic consequence. Monitoring strategies and technologies need to be simple and user-friendly enough to accommodate the cost-effective collection of information, which introduces a shared responsibility between operators, suppliers, and designers. The data collected from different instrumentation should fundamentally link to potential failure modes and should be used to iteratively update original design assumptions and the design intent of a safe, stable and non-polluting tailings dam. The research acknowledged the variability of tailings dam environments, while reiterating a focus on core mechanisms and the understanding gained from geotechnical theory, lessons learned from previous failures, and a structured baseline approach allows tailings dam practitioners to spend more of their time focused on the unique challenges onsite. Collaboration between the global community of tailings dam practitioners is needed, whereby data are proven to enable greater understanding through real demonstration of the trends, patterns, and data behaviour.