The dynamic behavior of marine soft soil under cyclic wave loading

Abstract

Many engineering activities are conducted on marine soft soil foundations, with various types of soft soil influencing these projects differently. Studying the engineering characteristics and deformation mechanism of marine soft soil is crucial for the design and construction of marine structures. To reveal the dynamic mechanical characteristics of marine soft soil under wave loading, a set of soil samples under different confining pressure conditions were tested via a dynamic triaxial apparatus. Furthermore, a constitutive model was developed to predict the dynamic strength of marine soft soil subjected to wave loading. The experimental results demonstrate that the dynamic stress‒strain behaviour of marine soft soil progresses through three stages: compaction, deformation, and failure. The dynamic strain‒time history curve of the soil exhibited a cyclic trend characterized by a superposition of monotonic changes, which was attributed to the simultaneous occurrence of plastic deformation and cyclic deformation. The strain rebound gradually disappears with increasing number of loading cycles; the strain accumulation mainly occurs as compressive strain during the postvibration period. Within each stage, the dynamic shear modulus decreases with increasing shear strain, showing consistent curve characteristics across different dynamic stress amplitudes. During long-term cyclic loading, the damping ratio initially decreases and then stabilizes, with a negligible influence from the confining pressure. The Martin‒Davidenkov constitutive model effectively characterizes the correlation between the dynamic shear modulus and shear strain, with fitting curves closely matching the measured data.