The application of inspection and monitoring in the reduction of risk for mine tailings dams

The recent high-profile failures of mine tailings dams across the globe have once again raised geotechnical interest in these structures. Much of the recent discussion in the technical press has concerned the prediction of ultimate stress state and thus of the failure potential of the tailings materials. The concentration solely on geomechanical properties is important in the understanding of the fundamental characteristics of extractive waste but limits the appraisal of risk potential in these complex and multifaceted structures. It is evident from the author's study of failures of these extractive waste facilities over a period of some 50 years that knowledge of geomechanical properties alone would not have prevented disasters in many instances. The paper reviews the fundamental risks posed by these structures with respect not only to their design but to their construction, operation and eventual closure. The analysis confirms that other crucial elements of their design and construction, if neglected, potentially pose higher risks than a lack of knowledge of geomechanics alone. The paper presents a broad list of risk reduction criteria which should be applied to mine tailings dams, and cites examples of where and how such neglect has resulted in the recent high-profile failures. The paper concludes with a review of general risk reduction criteria and compares these with existing standards and guidelines.