Helical pile foundations are a new foundation type for offshore wind power applications with high bearing capacity and good recovery that can be quickly and easily constructed. In this study, the finite element method was used to simulate the bearing characteristics of helical pile foundations after installation. For simulations, a blade, deeply buried in a single layer of sand, was selected. Through numerical simulations, the vertical bearing characteristics of a single helical screw pile and an ordinary pile without blades were compared, and the compression and uplift characteristics of the helical pile were revealed. In addition, the effects of pitch, blade diameter, inclination angle, number of blades, and blade spacing on the bearing characteristics of a single helical pile were analyzed. The results show that the single helical pile has the highest bearing capacity and bearing efficiency when the pitch is 0.02 times the blade buried depth, the blade diameter is 2.5 times the pile diameter, the multi-blade spacing is more than two times the blade diameter, and the number of blades is less than or equal to three. However, compared with the straight pile, the vertical bearing capacity of the single inclined helical pile did not improve significantly.

The mono-column composite bucket foundation has gained practical application in offshore wind power due to its advantages of simple fabrication, fast construction, and low cost. To ensure the safe and stable transportation of this structure to its designated sinking position, this study focuses on producing a scaled model of the mono-column composite bucket foundation. Through model testing, the floating characteristics of the structure during towing in regular waves are examined. The conclusion of the study is as follows: a significant towing force is required to provide the initial velocity of the structure. As the wave period and height increase, the structure necessitates a larger towing force, experiences greater pitch and heave responses, and exhibits more noticeable fluctuations in internal air pressure. The paper aims at providing practical engineering insights.

The composite bucket foundation (CBF) consists of a concrete curved transition section, a concrete beam-slab system, and a suction caisson and is increasingly used as the foundation for offshore wind turbines. The curved transition section transmits the upper load from the tower to the foundation, and its force and transmission characteristics are related to the safety of the entire wind turbine structure. The arced transition section has the characteristics of complex geometry, load conditions, and large curvature. It is difficult to determine its bearing characteristics and force transmission system. In this paper, the boundary conditions and loading device of the CBF model test are designed, and three 1:20 arced transition section model specimens are made. The mechanical characteristic experiments of CBF are used to analyze the failure process, failure characteristics, and seismic performance of the structure. Results show that the cracking effect of the arced transition section after prestressing is obviously better than that of a reinforced concrete arced transition section structure. The arced transition section specimens equipped with prestressed tendons can increase the structural cracking load ratio by about 35% for reinforced concrete members. The energy dissipation capacity of the specimens has been significantly improved, and the material properties can be fully utilized. The failure mode of the arced transition section structure under horizontal reciprocating load shows the characteristics of bending and shear failure.

To address the issue of seepage and soil plugging during the sinking of mono-column composite bucket foundations (MCCBFs), experiments were conducted on the installation of foundations under a variety of complex geological conditions. The effect of negative pressure sinking mode on the foundation’s seepage field was analyzed, the formation mechanism of soil plugging in sand was explained, and an efficient method for calculating the height of soil plugging was proposed in conjunction with these investigations. The findings demonstrate that the finite element method simulation of the soil’s seepage field is the most accurate, that the pumping volume of the foundation during sinking through is high, that the formation of the soil plug height is high, and that clear depressions can be seen on the foundation manifold’s exterior. The equation presented in this study makes it easier to forecast the height of a foundation plug and can offer direction for engineering design.