## 3 Analysis of Discussion  
### Analysis of Static Loading Test Results  
In order to determine the horizontal ultimate bearing capacity of the offshore wind turbine monopile foundation model under the action of horizontal loads, a static loading test is firstly carried out. Because the failure and damage of offshore wind turbine foundations are usually characterized by excessive deformation, the excessive deformation of the foundation at the mud surface will cause the wind turbine to take protective measures and stop running. Therefore, the pile foundation reaction force corresponding to a certain displacement at the test loading point is taken as the ultimate bearing capacity of the existing pile-soil system. This study comprehensively considers the actual site conditions and model test conditions and is based on the field test conclusions of [PERSON] (1964) [25]. When 0.2D displacement occurs at the loading point, the pile foundation reaction force collected by the actuator pressure sensor is the horizontal ultimate bearing capacity of the pile-soil system. According to the test situation in this study, the static ultimate bearing capacity of the pile-soil system in this model test is 263 N.  
The strain of the pile body during the test can be obtained by the strain gauges arranged on both sides of the pile body, and then the bending moment of the pile body during the loading process can be obtained by the bending moment calculation method proposed by [PERSON] (2006) [26]. In the process of model test, because the soil pressure of pile-soil interaction below the mud surface is not easy to measure, according to the knowledge of material mechanics, there is a certain mathematical relationship between the bending moment of the pile and the radius of curvature of the pile. Therefore, the displacement of the pile body, the bending moment of the pile body and the resistance of the surrounding soil can be calculated by mutual derivation. [PERSON] (2015) [27] et al. verified the feasibility of deriving displacement and soil resistance from the measured pile body bending moment. In this study, the same method is used to obtain the expression of the bending moment from the discrete data of the pile body bending moment six times, and then the second difference of the expression can be used to obtain the result of the soil resistance around the pile in this test. Figure 9 shows the results of the distribution of soil pressure around the pile along the depth obtained by the second difference of the bending moment of the pile body. According to the results shown in the figure, the displacement area of the entire pile body under the action of horizontal load can be divided into a passive area where the pile and soil squeeze each other (the upper part of the A side and the lower part of the B side around the pile) and the active area where the pile and soil tend to be separated (the pile around A side lower and B side upper). It can be seen from the figure that the distribution forms of soil resistance \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Test Conditions** & **Group Number** & \(\xi\) & **Cycle Times** & **Control Method Category** \\ \hline Static loading & S1 & 1 mm/s (Loading rate) & / & Displacement control \\ \hline \multirow{3}{*}{Extreme wind and wave short-term conditions} & D1 & 0.3 & 27 & Force control \\ \cline{2-5}  & D2 & 0.4 & 27 & Force control \\ \cline{2-5}  & D3 & 0.5 & 27 & Force control \\ \hline \multirow{3}{*}{Normal wind and wave long-term conditions} & L1 & 0.1 & 5000 & Force control \\ \cline{2-5}  & L2 & 0.2 & 5000 & Force control \\ \cline{2-5}  & L3 & 0.3 & 5000 & Force control \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Test conditions. under different load levels are basically the same. From the mud surface to the bottom of the pile, the overall curve of soil resistance first increases and then decreases, gradually decreases to zero, and then increases to trend of maximum value.