Small-Strain Dynamic Behaviours of Reconstituted Soft Clay Under Different Initial Water Contents

High-water-content dredged slurry from port dredging requires geotechnical improvement via drainage and consolidation. The small-strain dynamic properties (shear stiffness, damping characteristics) of reconstituted and consolidated clays are critical to the dynamic response and serviceability of overlying infrastructure. This study uses resonant column tests to investigate how initial water content affects the small-strain dynamic behaviour of reconstituted Ningbo soft clay, focusing on the evolution of the dynamic shear modulus (G) and damping ratio (λ) under different initial water contents and confining pressures. The test results indicate that the initial water content exerts a pronounced effect on the maximum small-strain shear modulus (Gmax) and on the strain-dependent degradation pattern of G. Gmax increases with decreasing water content, and confining pressure exerts a more pronounced enhancing effect on Gmax under low water content conditions. For specimens with different initial water contents, the maximum shear modulus normalised by confining pressure (Gmax/(σ0′/Pa)n) exhibits a consistent, material-specific functional relationship with void ratio (e) within the investigated ranges. By contrast, initial water content exerts limited effects on the normalised G/Gmax−γ and λ−γ curves in the tested small-strain range. On this basis, an empirical model for small-strain shear modulus incorporating initial water content effects is proposed to guide dynamic soil parameter selection for geotechnical design under the tested conditions.