Tailings Critical State Line Estimation Using Standard Instrumented Triaxial Equipment

Damian D.; Cardenas J.; Soto C.; Rivas L. · World Congress on Civil, Structural, and Environmental Engineering (2026) · DOI: 10.11159/icgre26.184

Resumen

The critical state theory is a well-established framework for understanding the phenomenon of flow liquefaction, which has been responsible for several failures in operating tailings impoundments, including Merriespruit–South Africa (1994), TVA Kingston–USA (2008), Fundão–Brazil (2015), Cadia–Australia (2018), and more recently Brumadinho–Brazil (2019) [1]. The critical state line (CSL) enables the characterization of geomaterials, such as soils and tailings, as either contractive or dilative, thereby allowing evaluation of their susceptibility to liquefaction. In this context, the objective of this study is to determine the CSL for fine-and coarse-grained tailings under loose conditions through a series of drained and undrained triaxial compression tests [2]. A standard triaxial apparatus was employed and instrumented with an internal load cell to eliminate friction effects in load measurements. In addition, the triaxial pedestal was modified to reduce boundary effects and to facilitate specimen decoupling for post-test freezing. The freezing procedure enabled accurate determination of final void ratios, resulting in a more reliable estimation of the CSL. A real-time data acquisition system was also used to improve the accuracy of displacement, load, and pore pressure measurements. Three tailings samples were tested: one fine-grained and two coarse-grained, all reconstituted at minimum densities using moisture contents of 5% and 8%, respectively, and subjected to a range of confining pressures. The selected initial conditions, together with the enhanced instrumentation and freezing technique, allowed for a robust characterization of the CSL for all materials. Furthermore, the strain-softening behavior observed in the coarse-grained tailings enabled delineation of the flow liquefaction surface (FLS).

Instituciones: Universidad Nacional de Ingeniería