The evolution of cyclic resistance with multiple loading events is evaluated for nonplastic and low-plasticity silts with plasticity indices of 0 and 6, respectively. A series of direct simple shear tests with multiple cyclic loading and reconsolidation stages is performed on young slurry-sedimented specimens. Evolution of cyclic strength with a series of multiple loading events is examined with respect to densification from postcyclic reconsolidation, shear strain-induced fabric, and initial consolidation history. Initially normally consolidated specimens of both silts develop progressive increases in cyclic strength with prior strain history, with cyclic resistance ratios ultimately exceeding 0.6. Specimens consolidated with an initial overconsolidation ratio of 2 experience an 18-32% loss of cyclic strength following the first stage of cyclic shearing and reconsolidation. The two silts develop similar magnitudes of reconsolidation strain, but the low-plasticity silt requires more volumetric strain (and therefore more loading events) to develop large cyclic strengths. Implications for future advances in liquefaction triggering correlations and engineering practice are discussed.

The effects of soil plasticity and penetration rate on cone penetration resistance in low-plasticity fine-grained soils are evaluated. A series of centrifuge tests with in-flight variable rate cone penetration soundings was performed on models of four slurry deposited mixtures of nonplastic silica silt and kaolin clay (0%, 2.5%, 5%, and 20% kaolin by dry mass) with plasticity indices ranging from 0 to 6. Cone penetration resistances for an effective overburden stress of 100 kPa ranged from 26 to 40 MPa (260 to 400 atm) in the nonplastic silica silt to 0.4-1.8 MPa (4-18 atm) in the silt-clay mixture with a plasticity index of 6. The addition of a small amount of clay (as little as 2.5% by dry mass) to nonplastic silt resulted in an order of magnitude decrease in drained penetration resistance. Faster penetration rates produced partially drained and undrained conditions, with negative excess pore pressures developing in the nonplastic silica silt and positive excess pore pressures developing in the mixtures with 5% and 20% kaolin.