## 3 Test Results and Analysis
The ultimate pile-top settlement of the pile-side grouting group is much smaller than the other two grouting groups, indicating that pile-side grouting greatly improves the shear performance of the soil around the pile and reduces the pile-soil relative displacement. In the pile tip and pile side grouting groups, the ultimate bearing capacity exhibits a decreasing then increasing trend as the grouting pressure increases from 0.5 MPa to 0.6 MPa and 0.7 MPa. Regarding the ultimate settlement, the pile tip grouting group shows a positive correlation with grouting pressure, while the pile side grouting group has a negative correlation. Therefore, the influence of grouting pressure does not exhibit a particularly clear pattern in terms of the load-settlement relationship. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Pile Number** & **S16** & **S26** & **S36** & **S25** & **S27** \\ \hline Ultimate bearing capacity/kN & 4.4 & 5.2 & 7.3 & 6.4 & 6.7 \\ Pile top settlement/mm & 5.17 & 2.24 & 1.86 & 3.47 & 2.50 \\ \hline \end{tabular}
\end{table} 
Table 4: Ultimate bearing capacity and pile top settlement for the side grouting group. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Pile Number** & **T16** & **T26** & **T36** & **T25** & **T27** \\ \hline Ultimate bearing capacity/kN & 1.6 & 3.4 & 5.7 & 4.8 & 6.0 \\ Pile top settlement/mm & 11.38 & 3.97 & 8.90 & 2.93 & 9.65 \\ \hline \end{tabular}
\end{table} 
Table 3: Ultimate bearing capacity and pile top settlement for the tip grouting group. \begin{table}
\begin{tabular}{c c c c c} \hline
**Pile Number** & **N00** & **TS16** & **TS26** & **TS36** \\ \hline Ultimate bearing capacity/kN & 0.8 & 4.4 & 6.4 & 7.9 \\ Pile top settlement/mm & 3.86 & 14.62 & 5.75 & 6.94 \\ \hline \end{tabular}
\end{table} 
Table 5: Ultimate bearing capacity and pile top settlement for the non-grouting and combined grouting group. Figure 10: Ultimate bearing capacity and pile top settlement under different grouting forms. Figure 9: Pile top load–settlement relationship with different grouting volumes. (**a**) Pile tip grouting group; (**b**) pile side grouting group; (**c**) combined grouting group. ### Pile Top Load-Settlement Relationship  
A model pile can be divided into several sections according to the position of strain gauges. Pile axial force \(N_{i}\) at section \(i\) is:  
\[N_{i}=E_{\text{p}}\epsilon_{i}A_{\text{p}} \tag{2}\]  
where \(E_{\text{p}}\) is elastic modulus of each pile, which was measured separately, \(\epsilon_{i}\) is section strain, and \(A_{\text{p}}\) is section area. The average lateral friction resistance of a certain section \(\tau_{si}\) can be expressed as:  
\[\tau_{si}=\frac{N_{i-1}-N_{i}}{A_{i}} \tag{3}\]  
where \(A_{i}\) is the lateral area of the pile section. Figures 12 and 13 illustrate the distributions of ultimate pile lateral friction resistance for different grouting groups. The pile lateral friction resistance at each depth of N00 is below 3.0 kPa, while the lateral friction resistances of some sections near grouting outlets of grouted piles are significantly enhanced. The grout will spread along the pile-soil surface, resulting in the soil near a grouting outlet being strengthened first. The enhancement of a section of the same grouting group is proportional to the grouting volume. A sufficient volume of grout can fully fill the weakening pile-soil surface, resulting in denser soil cement within the range of grout reinforcement, which can improve shear performance. Except for some pile sections out of reinforcement areas, an increase in grouting volume will lead to an increase in pile lateral friction.