Introduction  Wind power projects in Jiangsu Province are mainly located in the offshore radiant sandbank sea area. It is of great significance to study the bearing capacity of the large diameter single pile in this stratum.

  Method  Based on the test pile test of the steel pipe pile in the radiant sandbank area， the FLAC^3D numerical model of the single pile foundation was established， and the numerical simulation study of bearing performance of steel pipe pile foundations with different diameters was carried out.

  Result  The results show that： The vertical load-displacement （Q-s） curve of the steel pipe obtained by FLAC^3D numerical simulation is basically consistent with the change trend of the measured curve； as the burial depth increases， the axial force of the pile body below the mud surface continuously decreases. Most of the axial bearing capacity is provided by the pile side friction， and the axial bearing capacity borne by the pile tip resistance is relatively small； the pile diameter and the ultimate vertical bearing capacity of steel pipe piles conform to a non-sexual relationship. The ultimate vertical bearing capacity of a single pile increases with the increase of the pile diameter. When the pile diameter increases by 2 times， the corresponding vertical ultimate load increases by 3 times.

  Conclusion  The corresponding results can provide reference for practical engineering.