de Oliveira, LA, de Oliveira, ÂH, de Souza, CS, Beteli Silva Zanon, B & Beirigo, EA 2026, 'Liquefaction in tailings dams: critical assessment of susceptibility in underflow tailings', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-10, https://doi.org/10.36487/ACG_repo/2655_30
(https://papers.acg.uwa.edu.au/p/2655_30_Oliveira/)
Abstract: Liquefaction in tailings storage structures represents one of the most critical instability mechanisms in geotechnical works. In such systems, the presence of fine-grained, unconsolidated, and saturated materials promotes a sudden loss of shear strength under undrained loading, particularly in contexts where contractive behaviour predominates. The assessment of liquefaction susceptibility requires an integrated approach, grounded in detailed geotechnical investigations, representative laboratory testing, and interpretive models based on critical state soil mechanics.
In this context, the present study investigates the liquefaction susceptibility of a cyclone-deposited tailings dam with underflow material, constructed using the centreline method. The analysis is based on the reinterpretation of geotechnical data obtained from field and laboratory campaigns. Seismic piezocone tests (SCPTu) were employed and interpreted according to the methodologies proposed by Robertson (2009), Jefferies & Been (2016), and Plewes et al. (2017), enabling the identification of zones with predominantly dilative behaviour, as well as the detection of localised layers exhibiting contractive tendencies.
This interpretation was complemented by undrained triaxial tests and the evaluation of state parameters, allowing for the vertical discretisation of the tailings based on their mechanical response. Saturated zones exhibiting contractive behaviour were incorporated into stability analyses through limit equilibrium methods, considering critical piezometric conditions. Despite compliance with regulatory criteria, the presence of liquefiable materials highlights the importance of real-time monitoring, continuous geotechnical characterisation, and the adoption of robust preventive strategies in the risk management of tailings dam stability.

Keywords: liquefaction, tailings dams, SCPTu tests, contractive behaviour, critical state