This paper presents a geotechnical assessment of a tailings storage facility (TSF) developed in a tropical mountainous region with complex subsurface conditions. The containment structures consist of downstream-raised embankments built over saprolitic and colluvial foundations, later expanded using non-conventional elements such as gabions and modular blocks. The facility has experienced localized deformations, foundation settlements, and drainage challenges, prompting a comprehensive diagnostic study.
The investigation included review and interpretation of historical site investigation data, geophysical surveys, laboratory testing, and monitoring instrumentation. Static and pseudo-static stability analyses were conducted under five loading scenarios, including drained, undrained, and post-liquefaction conditions. Particular attention was paid to the uncertainty of geotechnical parameters for both tailings and foundation soils. A series of sensitivity analyses were performed, the results were created using spider plots to identify dominant parameters affecting stability.
Findings revealed that the variability in tailings strength, particularly under undrained and post-liquefaction conditions, has a significant impact on global factors of safety. Similarly, foundation soils exhibited a wide range of strength and stiffness characteristics, with implications for long-term deformations and embankment performance. Instrumentation data indicated that consolidation of the foundation is still ongoing in some zones, which correlates with observed displacements.
The study highlights the importance of site-specific characterization and the incorporation of uncertainty in geotechnical design and risk assessment for TSFs, particularly those built using mixed construction techniques. It also highlights the relevance of sensitivity-based approaches to prioritize investigation efforts and inform contingency planning.
