## 4 Discussion
### Limitations and Prospects  
In the previous subsection, the Gaussian settlement curve was modified by considering the load characteristics of a super-large shield tunnel under-crossing the foundation pit. Although the proposed two modified parameters can well reflect the settlement of the soil in this project, there are several aspects worth improving. First, practically speaking, the correction factors \(\gamma\) not only reflect the strengthening effect from the piles, they include the unloading effect due to the excavation of the shield tunnel. Therefore, when calculating the value of \(\gamma\), it is more accurate to take the unloading effect into account. Second, there is no accurate formula for calculating these two parameters. In this research, the two factors were obtained by inverse analysis. If a more accurate correction factor needed to be obtained, a lot of data from similar practical projects would need to be collected. However, at present, super-large diameter shield tunnels are rare, especially those under-crossing a foundation pit. Therefore, Therefore, it is a long-term process to improve the correction parameters. In terms of the prospects of this research, the main application is to quickly determine the soil displacement field of pile-raft foundations under the influence of tunnel excavation. The determination of the displacement field can further identify potential negative skin friction areas on the piles, providing a possible quick calculation method for the calculation of the tunnel excavation's impact on the lateral skin friction of the piles. In the case of this study, it is possible to judge whether soil displacement can reflect the potential skin friction effect by comparing the soil displacement data with the variation of the axial force in the pile body. However, for further theoretical calculations, more detailed experiments are required for validation. This article does not discuss this aspect. As for the potential long-term effects of the excavation on the surrounding soil and structures, the impact of tunnel excavation on the surrounding soil and adjacent building structures can come from many aspects. For example, in practical engineering, the settlement of the soil at the bottom of the raft caused by soil loss from tunnel excavation may not fully manifest in the short term, which is closely related to the amount of grouting used in the actual construction process  
Figure 11: Corrected curve of ground subsidence at the bottom of the pit. and the grouting material adopted. If the grouting amount is insufficient, the upper soil of the tunnel may further settle in the future, resulting in settlement of the raft; on the other hand, if the grouting amount is appropriate, no further deformation may occur. As for the potential rapid calculation of the pile-side friction, according to the law of pile-side friction, the generation of negative frictional resistance is closely related to the relative displacement between the pile and soil. Therefore, it is necessary to quickly determine the distribution and variation of negative frictional resistance on the pile side under the influence of shield tunneling and quickly determine the displacement field of the pile-side soil. At the same time, by comparing the displacement of the pile-side soil at the corresponding position with the compression of the pile body, the distribution of the negative frictional resistance can be quickly determined. For the compression of the pile body, it can currently be assumed to be uniformly compressed under concentrated force. In addition, according to the solution provided by [PERSON], the calculation of additional stress at any position below the ground surface can be obtained through \(\sigma_{z}=\frac{p}{h^{2}}I_{p}\), where \(I_{p}\) is an integral coefficient considering the influence of the pile. Based on the settlement value, the force distribution of the pile-side soil at each position can be deduced using the layer summation method and different integral coefficients.