Effect of initial water content on undrained cyclic behaviour of reconstituted marine soft clay

To elucidate the influence of initial water content on the undrained cyclic shear behaviour of marine soft clay, reconstituted specimens with initial water contents of 1.4wL, 1.8wL and 2.2wL were prepared using the slurry-consolidation method, and a series of undrained monotonic triaxial compression tests and cyclic triaxial tests were performed. The results show that, as the initial water content increases, the water content and void ratio of the consolidated specimens increase, whereas the monotonic and cyclic shear strengths decrease. During cyclic loading, excess pore-water pressure accumulates more rapidly, the effective mean principal stress decreases more markedly, and the double-amplitude axial strain enters the rapid-growth stage earlier. When the cyclic stress amplitude is normalised by the corresponding monotonic shear strength, i.e., qcyc/qf, the cyclic strength data for specimens prepared at different initial water contents converge to a unified curve. This indicates that the influence of initial water content on cyclic strength can be characterised through the corresponding monotonic shear strength under the tested effective confining pressure and loading conditions. In addition, analysis of the evolution of the cyclic secant modulus (E) using a stiffness degradation model shows that the initial water content mainly affects the shape of the E curve.