Cyclic shear strength of marine clays

Undisturbed clay samples were taken from alluvial deposits at seven different urban coastal locations in Japan using a thin wall sampler. The samples were then triaxially tested in both undisturbed and remoulded states. The cyclic data for the normally consolidated samples was used empirically to define the cyclic strength of the clays as an intrinsic function of the plasticity index I-p. This was then modified taking into account the vertical yield stress ratio sigma (vy)'/sigma (v0), degree of aging. The cyclic strength of anisotropically consolidated clays at low initial drained shear stress ratios increased with decreasing plasticity. This reversed as the drained shear stress ratio increased. It was possible to define a simple function for the cyclic strength normalised by the isotropic cyclic strength R-ISO against the initial drained shear stress ratio. This function was shown to be dependent on plasticity index I-p.