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Cone penetration tests (CPTs) performed under controlled conditions in a centrifuge can improve understanding and interpretation of CPT data obtained in the field. However, the cone diameter and cone penetration velocity employed in the centrifuge differ significantly from their respective full scale values and the effect of these scale differences need to be understood to allow extrapolation to the field. This paper examines the influence of cone velocity on tip resistance and penetration pore pressures, and also investigates trends during pore pressure dissipation when cone penetration is halted. Piezocone penetration tests were performed at different rates in normally consolidated and overconsolidated specimens of clay and silty clay in a beam centrifuge. The penetration rate was varied by over four orders of magnitude to provide information on partially drained and undrained penetration resistance and on the associated pore pressure response. The overconsolidation ratio and silt content are shown to have significant effect on the rate dependency of cone tip resistance and pore pressures.

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The results from a laboratory testing programme designed to evaluate the behaviour of gold tailings are presented, and interpreted in the critical state framework. Drained and undrained triaxial tests sheared under monotonic loading allowed the critical state line (CSL) to be established. The observed highly non-linear shape of the CSL was used to investigate the intrinsic dynamics of the monotonic undrained response of tailings, and to define the undrained instability state. This behaviour is useful in explaining the mechanics of tailings, which exhibits relatively well-defined transitions of state captured by the state parameter.

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