# Study on the Influence of File Installation Disturbance on the Settlement of Composite Foundation
## 4 Results
### Comparison Between Measurement Results and Calculated Results  
To facilitate the analysis of the proportion of settlement caused by construction disturbances relative to the total settlement, calculation scenarios were established based on the site cross-section conditions, as shown in Table 7: \"C\" represents CMP, \"\(P\)\" represents PHC pile, and \"1\" to \"5\" represent the fill heights ranging from 0.5 m to 2.5 m. Total settlement \(S_{e}\) and disturbance-induced settlement \(S_{f}\) were conducted using the stress modified method (SMM) and finite element method (FEM) proposed in Section 3.  
* Total settlement after pile installation  
Considering the influence of construction disturbances, the total settlement ranges for CMP and PHC pile foundation within fill heights of 0.5-2.5 m are 56-356 mm and 29-207 mm, respectively, using the stress modified method. However, the FEM results are 111-568 mm and 56-265 mm.  
As is shown in Figure 11, the FEM results are 30% to 60% larger compared to those obtained using the stress modified method. The results from the stress modified method are closer to the measured settlement, with a difference of 10% to 15%, which falls within an acceptable range.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{\(S_{e}\) (mm)} & \multicolumn{2}{c}{\(S_{f}\) (mm)} & \multicolumn{2}{c}{\(k=S_{f}S_{e}\) (\%)} \\ \cline{2-7}
**Case** & **SMM** & **FEM** & **SMM** & **FEM** & **SMM** & **FEM** \\ \hline \(C_{1}\) & 56 & 111 & 6 & 7 & 10.2 & 6.3 \\ \(C_{2}\) & 144 & 260 & 8 & 13 & 5.8 & 5 \\ \(C_{3}\) & 223 & 386 & 10 & 19 & 4.3 & 4.9 \\ \(  
* Disturbance settlement  
As illustrated in Figure 12, when the fill height increases, the settlement induced by the pile driving disturbances gradually increases, but the rate of increase slows down. When the embankment fill height is 0.5 m, the settlement, \(S_{f}\) is approximately 6 to 7 mm for CMP composite foundations. With the gradual increase in fill height, the settlement \(S_{f}\) at 2.5 m fill height is approximately 12 to 36 mm. When using PHC pile treatment, with an embankment fill height of 0.5 m, the settlement is approximately 7 to 16 mm, and with an embankment fill height of 2.5 m, the settlement is approximately 16 to 60 mm.  
As illustrated in Figure 13, when the fill height increases, the proportion of disturbance settlement to total settlement gradually decreases. When the fill height is 0.5 m, the proportion of disturbance settlement to total settlement for CMP is \(k=6\%\sim 10\%\). For PHC pile, it is \(k=23\%\sim 28\%\). When the fill height is 2.5 m, the proportion for CMP is \(k=3\%\sim 4\%\), and for PHC pile it is \(k=17\%\sim 22\%\).  
Figure 11: Total settlement of embankment with filling height from 0.5 m to 2.5 m.  
Figure 12: Disturbance settlement of the embankment with filling height from 0.5 m to 2.5 m.  
The reasons for the above result are as follows:  
Firstly, with the increase in upper load, the influence depth of additional stress increases, leading to greater settlement in the lower subsoil layers and a smaller proportion of disturbance settlement.  
Secondly, the magnitude of the upper load affects the pile-soil stress ratio. Under low loads, the soil between piles bears more load. Taking into account both the increase in load and the decrease in the ratio of load borne by the soil between piles, the overall disturbance settlement exhibits a trend of decelerated growth.