Element and System Level Impact of Strength Loss on Cyclic Performance of Sensitive Clays

This paper presents the results of a numerical investigation into the combined influence of static shear bias and post-peak strength loss on the cyclic behavior of plastic silts and clays at the element and system level. Numerical analyses were performed using the finite difference program FLAC 8.1 with the PM4Silt constitutive model. The element-level impact was investigated using stress-ratio controlled, undrained, cyclic direct simple shear loading simulations with different magnitudes of initial static shear stress and uniform cyclic stress cycles. System-level impacts were investigated with nonlinear dynamic analyses of a levee using a ground motion recording from the 1999 Kocaeli earthquake. Six PM4Silt calibrations were considered to represent a range of clay soil properties. Study findings show that strength loss did not significantly influence the cyclic behavior at the element level; however, strength loss had substantial impact on the overall performance of the levee system, particularly regarding crest deformations and accelerations. The implications of the results on practice and future research needs are discussed.