CS18A - Concurrent Session 18A: Static Liquefaction: An Exploration of Advancements and Mitigation Strategies in Dam Safety for Cross-Industry Collaboration

Following the May 2020 Edenville Dam failure, the Independent Forensic Team (IFT) appointed by the Federal Energy Regulatory Commission (FERC) concluded that static liquefaction was the primary failure mechanism. Initial reactions from dam practitioners, operators, and owners understandably varied from skepticism of the mechanism’s applicability to water dams to anxiety regarding the potential for sudden failure of existing structures with little warning. These experiences are not unlike those within the mining industry following a series of recent tailings dam failures abroad, the consequences of which were significant in terms of environmental and property damage, as well as loss of life. However, the tailings dam failures resulted in a step change within the industry and widespread improvement in terms of the state of practice. In sharing lessons learned by the mining industry, this paper aims to promote collaboration with earthen water dam practitioners, as well as other industries that operate impoundments with potentially liquefiable material, such as coal combustion residuals and dredged materials. This paper presents the authors’ perspective on the advancement of the tailings dam practice and culture over the past decade to mitigate the potential for and consequences of static liquefaction. In doing so, select static liquefaction failure case histories will be presented to help illustrate the mechanism and commonalities between tailings dams and earthen water dams will be identified. Recent tailings dam guidance documents will be highlighted, with a focus on improved governance. With respect to advancements in the evaluation of static liquefaction, major themes in the current state of practice for geotechnical field and laboratory investigation will be introduced along with the shifting perspective from deterministic to performance-based analysis approaches that focus of the potential triggers. Finally, implementation of risk mitigation measures being utilized by the mining industry will be reviewed, such as buttressing, downstream containment, decommissioning, and early warning systems.