Placement of compacted filtered tailings within the target range of the standard Proctor curve: experimental results and operational implications

Authors: da Silva, DM; Neto, ANS; Nazare, MV; Pirete da Silva, W; Silva, R; Saar, R; Azevedo, A Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2655_20

Cite As:
da Silva, DM, Neto, ANS, Nazare, MV, Pirete da Silva, W, Silva, R, Saar, R & Azevedo, A 2026, 'Placement of compacted filtered tailings within the target range of the standard Proctor curve: experimental results and operational implications', 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. 1-14, https://doi.org/10.36487/ACG_repo/2655_20



Abstract:
The growing demand for safer and more sustainable tailings disposal solutions has driven the adoption of alternative technologies to conventional dams, with filtered tailings gaining increasing prominence. This study presents the results of a quality control campaign and geotechnical testing conducted on a structure located in Brazil’s Iron Quadrangle, where layers of filtered tailings – consisting of mixtures of sandy and ultrafine fractions – were compacted under controlled moisture and dry density conditions. To verify the effectiveness of the compaction process, triaxial tests (consolidated isotropic drained [CID] and consolidated isotropic undrained [CIU]), piezocone penetration tests (CPTu), and direct simple shear (DSS) tests were carried out to assess the stability and liquefaction susceptibility of the compacted layers. The results indicated predominantly dilative behaviour, with friction angles exceeding design values (ϕ’ ≈ 39°) and a high undrained shear strength ratio (Su/σ′v) averaging 0.47, consistent with dense sands and low susceptibility to static flow failure. CPTu data supported this interpretation, indicating dense and partially drained behaviour with Bq ≈ 0, Ic < 2.2, and negative state parameter values (ψ < 0) throughout the profile. The findings demonstrate that strict field control protocols, combined with well-defined geotechnical acceptance criteria, can result in compacted tailings structures with performance significantly above minimum design thresholds, thereby enhancing overall stability and operational safety.

Keywords: filtered tailings, compaction, static liquefaction, CPTu

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