## 4 Data Processing and Analysis  
### Standard Penetration Data Analysis of Large-Diameter Tubular Piles  
In the test, the pixel displacements of the reference points were supposed to be zero in theory. However, their pixel displacements were not zero in the cooperative transform shifting parallax method. As such, these values were deemed as the measurement accuracy of pipe pile penetration test. Due to the large amount of data, the authors selected 12 tests of pipe pile 1-2 penetration test for data processing. The measurement accuracy is shown in Table 3. In Table 3, 1-Point 0, 1-Point 1, and 1-Point 2 represent the control point 0, 1, and 2 in pipe pile #1 penetration test. 2-Point 0, 2-Point 1, and 2-Point 2 represent the control point 0, 1, and 2 in pipe pile #2 penetration test. MSE is mean square error, its maximum is 0.84 mm, and its minimum is 0.14 mm. Figure 8: Experiment and schematic diagram, showing the (**a**) schematic diagram of model design, (**b**) laboratory test site, and (**c**) model box with stained sand. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Blow Counts**} & \multicolumn{3}{c}{**Pile 1 Blow Test**} & \multicolumn{3}{c}{**Pile 2 Blow Test**} \\ \cline{2-7}  & **1-Point 0** & **1-Point 1** & **1-Point 2** & **2-Point 0** & **2-Point 1** & **2-Point 2** \\ \hline
1 & 0 & 0.73 & 0.73 & 0.99 & 0 & 0 \\
2 & 0 & 0 & 0.73 & 0.99 & 0 & 0 \\
3 & 0 & 0 & 0.73 & 0.49 &  
The penetration data of tubular piles at different time points were acquired through image processing (Table 4). Figure 9a,b show that a Logistic functional relationship exists between the penetration and blow counts. The penetration rate of Pile #1 was relatively large, and it penetrated the strata completely after 12 blow counts. This indicates that the soil structure at 0-10 m below the surface was relatively loose, agreeing with the observations regarding actual strata. Figure 9c,d show that a single exponential decay function relationship exists between penetration and blow counts. The penetration rate increased first and then decreased, and Pile #2 penetrated the strata completely after 153 blow counts. Pile #2 penetrated about 7.69 m after 60 blow counts. At this moment, it had passed through the loose silt and silly clay strata. Subsequently, it entered the stratum dominated by aleurite, leading the penetration rate to decrease due to the hard texture. Since Pile #3 had the highest number of blow counts, several images existed for analysis. Hence, the penetration data of Pile #3 were divided into four stages to facilitate independent processing. In Figure 10a-d, we can see the spatial evolution patterns of the underground part and the above-ground part of the pipe pile in four monitoring stages. It can be seen from Figure 10e,f that the penetration rates of Pile #3 show a trend of single exponential decay functions. However, the penetration rate of Pile #3 was significantly  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Hit Times** & **Displacement/m** & **Hit Times** & **Displacement/m** & **Hit Times** & **Displacement/m** \\ \hline
1 & 0.099 & 42 & 6.190 & 83 & 8.801 \\
2 & 0.157 & 43 & 6.323 & 84 & 8.883 \\
3 & 0.267 & 44 & 6.433 & 85 & 8.921 \\
4 & 0.314  
lower than those of Pile #1 and Pile #2. Pile #3 was penetrated completely after 1200 blow counts. Currently, the bottom of Pile #3 was in the aleurite. Moreover, the strata pressure increased with increases in depth, making soils harder and harder. Consequently, the penetration rate of Pile #3 was relatively low. Similarly, the data of Pile #4 were divided into three stages for independent processing and fitting. In Figure 11a-c, we can see the spatial evolution patterns of the underground part and the above-ground part of the pipe pile in three monitoring stages. It can be seen from Figure 11d,e that the penetration rates of Pile #4 show a trend of the piecewise linear function. Its slope decreases first and then increases suddenly.