# Large Deformation Settlement Series Solution and Numerical Simulation for Underpass Project Track
## 5 Results and Discussion
### Comparison Analysis between Measured and Numerical Solutions of Roadbed Settlement  
In order to study the track settlement law of the numerical model, the actual measured data of roadbed 4 and roadbed 7 are selected to compare and analyze with the numerical simulation results, while the numerical analysis simulation results are called numerical solutions. Roadbed 4 is located at the midpoint of the entire topping area and is most obviously disturbed by the box culvert topping; the settlement of roadbed 1 is affected by both the excavation of the adjacent pit and the box culvert topping, while the settlement of roadbed 7 is only caused by the box culvert topping, which better reflects the change of roadbed settlement caused by topping. Therefore, the measured data of roadbed 4 and roadbed 7 were selected for comparison. The measured data of roadbed 4 and roadbed 7 are plotted with the numerical solution of the final settlement obtained at the end of the numerical jacking simulation, as shown in Figures 10 and 11, respectively. Figure 10: Roadbed 4 settlement curve. Figure 9: Track lateral settlement curve. (**a**) Overall. (**b**) partial enlarged. From Figures 10 and 11, it can be seen that the measured data curves of each cross section and the numerical solution curves match and are roughly in line with the Peck curve. The measured settlement is larger than the numerical solution, with the main reasons as follows: Because the numerical simulation is in an ideal state, it cannot fully consider all the factors that can affect the soil during the construction; the location of the box culvert and the upper space of the soil are fully excavated, and the loss rate of the soil is larger than that of the upper cover of the box culvert, resulting in a larger measured settlement value. The main reason that the measured values are not completely symmetrical is that during the actual jacking process, the jacking direction often has a slight deviation and correction, and the box culvert is approximately \"snake\" forward, which leads to the measured values on both sides not being completely symmetrical. Comparison of Measured Value, Numerical Solution, Fourier Series Solution, and Cosine Function Solution  
The box culvert jacking track is erected in the upper part of the track, and has a good connection with the track. Because the settlement value of the track cannot be measured directly, the site through the monitoring of the displacement value of the beam achieves the monitoring of the track settlement, erected in the upper part of the track beam distribution on both sides of the track. Therefore, the average value of both sides of the beam is taken as the settlement value of the track. The work point data of the project is adopted as follows: track linear density is 60 kg/m, cross-sectional area is 77.45 cm\({}^{2}\), cross-sectional moment of inertia is 3217 cm\({}^{4}\), modulus of elasticity is 210 GPa, the friction coefficient is 0.3, foundation coefficient is 50 MPa/m, gravitational acceleration is taken as 9.8 m/s\({}^{2}\), beam height is 0.176 m, track width is 1.435 m, calculated length of Half \(L=5i\). The settlement curves of different roadbeds can be obtained by numerical simulation, which is used as the nonlinear boundary condition for the previous level solution, i.e., \(S_{0}\) is the maximum settlement value of different roadbeds obtained by numerical simulation. The series solution of track settlement can be obtained by using the theoretical model of track settlement to realize the prediction of track settlement through roadbed settlement, where the series solution of track settlement is obtained by iterative calculation using MATLAB programming.