Calibration Chamber Testing on Tailings for Interpretation of Partially Drained CPT

Abstract

The Cone Penetration Test (CPT) is the primary site investigation tool in silt-rich tailings. The permeability and compressibility range of tailings often puts the standard CPT penetration rate in the partial drainage range where the tip resistance, pore water pressure, and sleeve friction become functions of not only the state, but also drainage conditions. This makes interpretation of the state parameter, which represents liquefaction susceptibility and residual strength of tailings particularly challenging. It is not clear whether existing CPT interpretation frameworks are capable of accounting for effects of partial drainage. Developing field correlations for interpreting partially drained CPT data in tailings is hampered by spatial variability and sampling disturbance. CPT tests were performed in a calibration chamber and in the field on a gold tailings material. Dissipation tests were performed, and the pore water pressures on the cone at the u2 position were monitored. The degree of partial drainage was estimated based on the coefficient of consolidation inferred from these dissipation tests. Similarities and differences of the calibration chamber and field CPTs were discussed.

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