Geotechnical Characterization of Cyclone Underflow Tailings under High Confining Pressures
Authors: Shona Vaughan Williams1, Thomas E. Sully1, Daniel Friedman1
Conference: Tailings and Mine Waste 2025
Date: November 2-5, 2025
1 Knight Piésold Ltd., Vancouver, British Columbia, Canada
ABSTRACT
Despite the widespread use of cyclones for dam construction, limited published data exists on the geotechnical behaviour of cyclone underflow tailings, particularly under high confining pressures. This paper presents the results of a comprehensive laboratory testing program aimed at characterizing the geotechnical properties of cyclone underflow tailings to inform stability analyses of cyclone-constructed embankments subjected to high stress conditions. The program included triaxial compression, direct simple shear (DSS), bender element, and flexible wall permeability tests on specimens reconstituted both loose via moist tamping and compacted to 95% Modified Proctor density. A composite lower-bound strength envelope was developed based on DSS and triaxial tests for input into limit equilibrium stability analyses. Permeability tests revealed stress-dependent reductions in hydraulic conductivity, particularly for samples with fines content exceeding 15%. The test data suggest that the fines content for the cyclone underflow should be limited to approximately 10% to maintain drainage performance near the base of the proposed embankment.
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