## 3 Results and Discussion
### Analysis of Reliability Test of Pile-Column Connection  
Figure 12 shows the field reliability test of pile-column connection. After the loads at all levels are loaded and the displacement data is stable, the displacement value of each measuring point could be read and the displacement curves with a load of each transverse displacement measuring point on the selected test pile No. 5 are shown in Figure 13.  
Figure 11: Vertical compressive static load test results of single pile No. 5: (**a**) horizontal load–displacement (\(H\)-\(Y_{0}\)) and (**b**) displacement–time logarithm curve (\(Y_{0}\)-\(\mathrm{lgf}\)).  
Figure 12: Field reliability test of pile–column connection: (**a**) arrangement of strain measuring points and (**b**) arrangement of displacement measuring points at flange connection.  
It can be seen from Figure 13a that when a load of single pile No. 5 is loaded to 300 kN, the displacement of each measuring point is relatively stable, and the maximum horizontal displacement is 31.38 mm. There are no problems found through the appearance inspection of the flange connection. From the results in Figure 13b, it can be seen that the displacement of single pile No. 5 at different distances from the ground changes smoothly, indicating that the flange connection is relatively intact. Moreover, through Figure 13b, according to the results, the displacement curve of single pile No. 5 at the flange connection position under various loads of the test pile does not have an obvious angle break, and there is no sudden change in the slope, indicating that the flange connection quality is good.  
The variation curve of strain with load at each measuring point of single pile No. 5 is shown in Figure 14. Through the strain test results in Figure 14, it can be seen that the strain results are subject to many interference factors, and some strain measurement point data are abnormal, so the strain data can only be used as an aid to the displacement results.  
Figure 13: Displacement test results of single pile No. 5: (**a**) displacement-load curve of each transverse displacement measuring point and (**b**) displacement curves under various loads.  
Therefore, the quality of the connection cannot be directly judged by the strain distribution curve in Figure 14.  
According to the above analysis of the reliability test of pile-column connection, when a load of single pile No. 5 reaches 300 kN, the displacement of each measuring point is relatively stable, and the maximum horizontal displacement is 31.38 mm. Meanwhile, there are no problems found through the appearance inspection of the connection, and the displacement of single pile No. 5 at different heights changes smoothly, indicating that the connection is relatively intact. On the other hand, because the strain results are subject to many interference factors and some strain measurement point data are abnormal, the strain data can only be used as an auxiliary to the displacement results.  
Figure 14: Strain test results of single pile No. 5: (**a**) strain–load curve of strain measuring point on the left side and (**b**) strain–load curve of strain measuring point on the right side.