## 3 Test Results
### Excess Pore Water Pressure  
Figure 7a presents excess pore pressure over time during hammer-driven pile construction in three stages. In stage one, the first pile driving at 0.5 h raised the pore pressure by 100 kPa at 12 m, dissipating post-drive until the next stage. Stage two began at 1 h, driving increased excess pore pressure to about 150 kPa at 22 m. The pressure dropped after driving, and was slower in the shallow layer. There was a 50 kPa rise at 12 and 32 m. The third pile's construction saw a sharp 150 kPa increase at 32 m below 30 m depth. Half-hour post-construction, the excess pore pressure halved, further flattening in 8 h. At 24 h, 12 m pressure dissipated, and 22 and 32 m retained 25 kPa. At 48 h, the pressure at a depth of 22 m decreased. Increasing excess pore water pressure correlates with pile depth. Maximum increase: 100 kPa at 12 m, 150 kPa at 22 m, 200 kPa at 32 m. Mainly generated at pile tip. After the second pile section, 12 m depth pressure rises due to diffusivity of more than 3 m range. Pore pressure peaks post-hammering, then diminishes. The dissipation rate starts fast, slows, and stabilizes till gone. Dissipation time linked to depth: deeper soil, longer time for pressure to dissipate. Figure 7b-g depict pore pressure changes around the PGP pile during construction. After drilling the first section of rod, the excess pore water pressure at \(z=12\) m with the distance increases by about 75 kPa, 60 kPa, and 30 kPa, respectively. During the drilling of the second section of rod, it can be seen that all the pore pressure gauges have a small increase. At this time, the drill pipe is about to reach a depth of 0.5 \(L\), and B-KY1-2 generates an excess pore pressure of about 100 kPa, while the other pore pressure gauges have little change. There was a short pause in the construction at 13.5 h, and the excess pore water pressure began to dissipate, and then continued to increase due to the drill pipe. On the whole, the drill pipe in the first stage mainly causes the change of pore water pressure in shallow and middle soil, and the process is slow, continuous, and stable, with strong diffusion. When drilling the third section of rod, B-KY1-2 and B-KY1-3 increased the most, both reaching about 140 kPa, but when rotating the drill pipe for expanding head grouting, the excess pore water pressure of B-KY1-2 increased to about 180 kPa. B-KY2-3 increases by about 100 kPa, and B-KY2-2 also increases by about 90 kPa during the construction of the expansion head. B-KY3-3 increases the excess pore water pressure of about 45 kPa. At the depth of 12 m, the pore water pressure has only an increment of about 10 kPa. In the stage of drilling and grouting, the pore water pressure generally shows a dissipation trend. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**No.** & \begin{tabular}{c} **Min Displacement** \\ **(mm)** \\ \end{tabular} & **Depth (m)** & \begin{tabular}{c} **Max Displacement** \\ **(mm)** \\ \end{tabular} & **Depth (m)** & \
\begin{tabular}{c} **Displacement after** \\ **1 Day Rest (mm)** \\ \end{tabular} &
\begin{tabular}{c} **Rebound Rate** \\ **(\%)** \\ \end{tabular} \\ \hline A-CX1 & \(-\)1.02 & 46.5 & 28.47 & 4.0 & 10.61 & 62.73 \\ A-CX2 & 0.28 & 48 & 18.85 & 4.0 & 14.85 & 21.22 \\ B-CX1 & \(-\)7.48 & 13.0 & 9.39 & 8.5 & 0.26 & 97.23 \\ B-CX2 & \(-\)6.83 & 0.5 & 5.81 & 20.0 & \(-\)2.87 & 149.40 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Maximum horizontal displacement of soil around the pile. During the process of pile planting, the pore water pressure at \(z=12\) m has no obvious change, because the cement soil is accumulated under the borehole, and the fluidity can make the pile flow upward when it is displaced, which is not enough to squeeze the surrounding. At \(z=22\) m, the increment of pore pressure due to pile planting increases with distance is 140 kPa, 50 kPa, and 15 kPa, respectively; \(z=32\) m, the pore water pressure increases with the distance of 130 kPa, 60 kPa, and 25 kPa, respectively.