Analysis and Evaluation of Geotechnical Design Method of Large Diameter Steel Tubular Pile for Wind Farm in Marine Soft Soil Area

Based on the field pile load test results of large-diameter steel tubular pile in offshore wind farm in deep soft soil area of China. Geotechnical parameter analysis and pile foundation design by CPT and SHANSEP methods had been carried out. The ultimate axial compressive and ultimate axial uplift capacity of single pile are 22 MN and 18.7 MN, respectively. Considering that the deep muddy soil is easy to be disturbed, and it is difficult to obtain undisturbed samples. In this paper, based on CPT interpretation and calibrated empirical parameters by SHANSEP method, key geotechnical parameters such as undrained shear strength of clay, effective internal friction angle and interface friction angle of sand are derived. By comparison of 6 commonly used design methods, it can be seen that UWA-13 and Fugro-10 method, which are directly based on CPT data, are both conservative in the calculation of compressive and uplift capacity. UWA-13 method is slightly better than Fugro-10 method, the calculated compressive and uplift capacity by UWA-13 method are 82.4% and 92.7% of the measured results, respectively. The uplift capacity calculated by ICP-05 method, which need a lot of geotechnical parameters, is difficult to use and could be not conservative.