Dynamic Stability Analysis of a Wharf under Cyclic Loading Considering the Weakening Effect of a Soft Foundation

Creep deformation and softening of soft soil foundations under long-term wave loading can cause gravity wharves to experience problems such as excessive settlement, displacement, and sliding, compromising the safety of the wharf structure. In this study, we conduct mechanical index and vibration tests on consolidated and undrained soft soil specimens to analyze the changes in the soil dynamic characteristics with strain under different confining pressures. Subsequently, the dynamic deformation and strength characteristics of the soft soil obtained from triaxial tests are used to develop a finite element model of the wave–gravity structure–soft soil foundation system. Using this model, analyses are conducted by varying the friction angle to simulate the change in the soft soil strength as the number of wave cycles increases. The results are evaluated to investigate the failure mechanism of the foundation and the bearing characteristics of the riprap bed atop the soft soil. The results indicate that the shear modulus of the soil is related to the effective confining pressure and the shear strain; this relationship is fitted using the Van Genuchten equation. As the internal friction angle of the soft soil foundation decreases, its stability decreases nonlinearly, its strength decreases, and its sliding failure surface lengthens. However, simply increasing the riprap layer thickness has a limited effect on the overall wharf stability. These findings will improve the design of gravity wharves founded on soft soils in port areas with intense wave action.