## 3 Stratum-Foundation Pit-Station-Track Interaction Model
### Comparative Analysis of Monitoring Results and Numerical Simulation  
#### 3.3.1 Comparison of the Horizontal Displacement of the Retaining Pile  
The measured and simulated data of horizontal displacement monitoring measuring points ZQT-4, ZQT-9, ZQT-15 and ZQT-21 of foundation pit retaining piles at the completion of foundation pit excavation are selected for analysis. As shown in Figure 22, the actual measured deformation trend of each measuring point is consistent with the simulated calculated deformation trend. By comparing the numerical simulation with the actual measurement data, the numerical simulation can basically reflect the deformation trend of the retaining structure in the construction of deep and large foundation pits. As seen in Figure 22a, after the foundation pit excavation is completed, the position of the maximum horizontal displacement of the retaining pile at measuring points ZQT-4 and ZQT-9 is basically consistent. Similar to the longitudinal measuring points of the foundation pit, at both positions, the maximum value is 0.6 times the excavation depth along the vertical direction of the pile. The simulated value of the maximum deformation of measuring points ZQT-4 and ZQT-9 is slightly different from the measured value. The main reasons are as follows: (a) The interlayer of the ground surface at measuring points ZQT-4 and ZQT-9 has the effect of grouting reinforcement, which reduces the horizontal displacement of the retaining pile in the process of foundation pit excavation. (b) The actual construction of the inner support in the foundation pit is more complex; thus, it is difficult to simulate the entire construction process of the internal support by numerical simulation, and there are \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Serial Number** & **Name** & **Poisson Ratio** & **Density (g/cm\({}^{3}\))** & **Elastic Modulus (MPa)** \\ \hline
1 & C30 & 0.25 & 2.3 & \(3.0\times 10^{4}\) \\
2 & C40 & 0.20 & 2.3 & \(3.25\times 10^{4}\) \\
3 & Steel & 0.20 & 7.5 & \(2.1\times 10^{5}\) \\
4 & Grouting & 0.20 & 2.1 & \(2.0\times 10^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Finite element model to simulate material parameters. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Construction Phase** & **Serial Number** & **Construction Name** \\ \hline  & Stage 0 & Initial ground stress balance \\  & Stage 1 & Grouting properties of grouting layer soil \\ Phase 1 & Stage 2 & Drilling piles, temporary columns and pile foundations for foundation pit envelopes \\  & Stages 3–6 & Earth 3.5 m in the first stage of excavation \\  & Stage 7 & Poured crown beams and first internal supports \\ Phase 2 & Stages 8–15 & Earth 6 m in the second stage of excavation \\  & Stage 16 & Pouring the waist beam and the second inner support \\  & Stages 17–24 & Earth 5 m in the third stage of excavation \\ Phase 3 & Stage 25 & Pouring the waist beam and the third inner support \\  & Stages 26–33 & Earth 6 m in the fourth stage of excavation \\ Phase 4 & Stage 34 & Laying the anchor cable and applying preaxial force \\ Phase 5 & Stages 35–42 & Excavation of the fifth stage of the foundation pit earthwork 5 m to the bottom of the pit \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Excavation parameters of foundation pit soil.