UC Davis

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.