Solidified soil prefabricated pile (PPSS) is a new type of pile formed by extruding solidified soil with hydraulic equipment. The PPSS includes two parts: precast pile and core pile, which can be used to strengthen soft foundation. To study the deformation characteristics of PPSS under vertical load, the nonlinear mechanical behaviour of the double-contact interface of PPSS is analyzed by using the bond slip model and hyperbolic model. A settlement calculation method is proposed considering the displacement coordination of the doublecontact interfaces, e.g., interface between precast pile and surrounding soil, and interface between core pile and precast pile. The bearing characteristics of the double-contact interfaces are studied by using the numerical results. Based on the numerical results, the effects of elastic modulus ratio, diameter ratio, length and initial cohesion on the deformation characteristics of PPSS are analyzed.

Offshore wind turbines are often constructed on the foundation of soft clay, which often experience strength and stiffness weakening and internal plastic strain under cyclic loading. These changes in the mechanical properties of soft clay foundation can negatively impact the normal operation of the upper turbine. Due to the complexity of the mechanical properties of soft clay, most of the existing cyclic pile-soil load transfer models for soft clay foundations are based on hyperbolic models, which are more complicated and less efficient. To address this problem, this paper introduces a mechanical model that can describe the cyclic weakening characteristics of soft clay in pile-soil interaction, and realizes the weakening characteristics of the soil with the cyclic loading by using ABAQUS subroutine secondary development. By introducing the cyclic weakening model of soft clay into the numerical simulation of pile-soil model, the weakening law of side resistance of pile with the number of cycles is obtained. The pile side load transfer model under the traditional static condition is improved, and a trilinear model of pile side load transfer that can consider the cyclic weakening effect of soft clay is proposed; in addition, the calculation method of pile foundation vertical bearing capacity is established according to the load transfer method which can consider the cyclic weakening effect of soft clay, and compared with the model test results in the existing literature, the correctness and effectiveness of the calculation method of pile foundation vertical bearing capacity considering the cyclic weakening effect of soft clay proposed in this paper are verified. Finally, the method is applied to the actual project of an offshore wind power pile foundation, and the vertical bearing capacity of offshore wind power pile foundation is calculated.