Effects of cyclic loading on lateral bearing capacity of single pile in silty seabed

Under larger wave loading, the bearing capacity of marine single pile foundation will be reduced, even instability occurs. A series of undrained shear triaxial tests on the remolded marine silt in Hangzhou Bay are carried out by means of the GDS triaxial apparatus, including monotonic, cyclic and post-cyclic monotonic loading. The effects of cyclic loading on the post -cyclic monotonic deformation and undrained strength of silt are studied, and the relationships among dynamic pore pressure ratio, cyclic stress ratio, cycle number, post-cyclic undrained strength ratio and secant modulus ratio are established, respectively. On this basis, according to the distribution of shear stress ratio induced by wave loading along the seabed depth, the lateral soil stiffness and strength reduction ratio of single pile are calculated, and the influences of wave loading on the lateral deformation and bearing capacity of single pile foundation are calculated. In the presented example, the strength and stiffness reduction of silt seabed caused by wave loading decrease sharply with the depth, and the affected depth is about 40 m. Liquefaction occurs in the shallow part of the seabed about 5 m. After cyclic loading, the rigid response of pile body is enhanced, the displacement of pile body and the depth of the reverse bending point increase, the bending moment and the lateral pressure decreased, and the total lateral bearing capacity was reduced about 40%.