# Model Test Study on a Shield Tunnel Adjacent to Pile in the Sub-Clay of a Coastal Area
## 4 Test Results
### Pile Response  
When the coverage-span ratio \(H/D\) was 1, 2, 3, the bending moment of pile with the different pile-tunnel relative position is shown in Figures 22-24. The reduction ratio in the bending moment of the pile caused by the lateral and vertical transformation of the pile position is shown in Table 10. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{\(H/D\)} & \multicolumn{2}{c}{**Horizontal**} & \multicolumn{2}{c}{**Vertical**} \\ \cline{2-5}  & **1D\(\rightarrow\)2D** & **1D\(\rightarrow\)3D** & \(-\)**0.5D\(\rightarrow\)0D** & \(-\)**0.5D\(\rightarrow\)0.5D** \\ \hline
1 & 65.68 & 90.54 & 57.09 & 80.61 \\
2 & 59.23 & 84.11 & 60.28 & 53.29 \\
3 & 60.01 & 83.94 & 39.49 & 67.54 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: The reduction percent of bending moment at different position of pile (%). Figure 21: The soil pressure at different position of piles when \(H/D=3\). Figure 23: Bending moment of pile at different vertical positions when \(H/D=2\): (**a**) \(V=0.5D\); (**b**) \(V=0D\); (**c**) \(V=-\,0.5D\). Figure 22: Bending moment of pile at different vertical positions when \(H/D=1\): (**a**) \(V=0.5D\); (**b**) \(V=0D\); (**c**) \(V=-\,0.5D\). The following conclusions and rules were obtained from the above tests:  
1. The greater the coverage span ratio was, the bending moment of the pile at the same level was larger; when the pile bottom was located at or above the tunnel chamber line, the maximum bending moment was generally located at the middle or lower part of the pile. When the pile bottom was located below the tunnel chamber line, the pile appeared at the negative bending moment, and the maximum negative bending moment was located at the arch waist. 2. The bending moment value change was obvious due to the influence of the lateral position change for the pile-tunnel system. The maximum influence area was \(1D\)\(\rightarrow\)\(2D\), and the influence degree outside \(2D\) was significantly weakened. The change in vertical position has a great influence on the direction of the bending moment. The maximum influence range was that the pile bottom located in the range from the arch waist (v = 0d) to the arch bottom (v = \(-\)0.5d), and the bending moment from the arch waist (v = 0d) to the arch crown (v = 0.5d) was similar and affected much by the buried depth. The larger the cover-span ratio \(H/D\) was, the weaker the influence of tunnel excavation on piles would be. When the coverage-span ratio \(H/D\) was 1, 2 and 3, the vertical settlement of piles at different relative positions of pile-tunnels was shown in Figure 25. The reduction ratio of pile settlement due to the lateral and vertical transformation of the pile position is shown in Table 11. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Horizontal**} & \multicolumn{2}{c}{**Vertical**} \\ \cline{2-5}
**H/D** & **1D\(\rightarrow\)2D** & **1D\(\rightarrow\)3D** & **0.5D\(\rightarrow\)0D** & **-0.5D\(\rightarrow\)0.5D** \\ \hline
1 & 41.44 & 63.63 & 8.33 & 19.54 \\
2 & 56.11 & 65.69 & 9.27 & 19.28 \\
3 & 61.41 & 72.56 & 7.42 & 13.69 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: The reduction percentage of settlement at different position of pile (%). Figure 24: Bending moment of pile at different vertical positions when \(H/D=3\): (**a**) \(V=0.5D\); (**b**) \(V=0D\); (**c**) \(V=-\) 0.5D. From the above test data, it could be seen that the larger the coverage-span ratio was, the smaller the pile settlement was. The lateral position change in the pile-tunnel had a great impact on the settlement. The \(1D\)\(\rightarrow\)\(2D\) settlement decreased greatly, with an average reduction of 52.99%, and the \(2D\)\(\rightarrow\)\(3D\) settlement reduced, on average, by 14.31%. When the pile bottom was vertically located at the horizontal line of the arch crown (\(V=0.5D\)), the settlement was the largest. When the pile bottom was below the arch waist, the vertical settlement was controlled to a certain extent.