## 6 Conclusions  
Based on a deep foundation excavation for the reconstruction of urban subway station project, the influence of foundation excavation on the viaduct pile foundation considering the train dynamic load was analyzed numerically. The results were compared with monitoring data. The main conclusions are as follows.  
1. The maximum settlement of soil around the excavation occurred at approximately 0.53 times of the excavation depth, which was named the \"groove type\". The dynamic load had a significant influence on soil settlement. The main influence area was near the station, and the settlement increased by approximately 49% compared to the case without the train load.  
2. The horizontal displacement of the pile along the long side of excavation gradually increased as the excavation depth increased. The dynamic load had the greatest influence on the top displacement of piles A and B, and the displacement increased by 34% and 41%, respectively. For the influence on the piles C and D, and the displacement increased by 34% and 30%, respectively.  
3. For the horizontal displacement of the piles along the short side of the foundation excavation, the maximum displacement of the piles gradually moved from the top of the pile to the deep pile with an increase with the excavation depth. The final maximum displacement occurred in the middle of the pile body when excavating to the bottom. The dynamic load had an intensified influence on the horizontal displacement of the pile, and the most influential part was at the top of the pile. Compared with the condition without train load, the displacement of piles A, B, C and D increased by 46, 47, 43, and 51%, respectively.  
4. The vertical displacement of the pile was analyzed. The pile in this study was a long pile with a negative friction resistance such that the pile showed a settlement trend. However, the vertical displacement of each pile was small, and had a small influence on the superstructure.  
5. By analyzing the internal forces and bending moment of piles A and C with an increase in the depth of the excavation, the bending moment of the piles increased, and the position of the pile corresponding to the maximum bending moment moved down. The maximum negative bending moment of the two piles occurred in the upper part of the pile. The maximum positive bending moment occurred in the lower part of the pile. Particularly, the negative bending moment significantly increased when applying the train load.  
6. Compared to the on-site monitoring data, the calculation results are in good agreement with the monitoring data, verifying the accuracy and applicability of the numerical analysis. The finite element simulation can reflect the general behavior of excavation deformation, and provide reliable data for foundation excavation in the construction of subway station.  
Conceptualization, X.B. and X.C.; methodology, Z.C.; validation, J.S., C.L. and H.C.; formal analysis, C.L.; investigation, Z.C.; data curation, Z.C.; writing--original draft preparation, C.L.; writing--review and editing, Z.C., J.S.; supervision, X.B.; project administration, X.C.; funding acquisition, X.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Key R&D Program of China, grant number 2019 YFC1511104 and the National Natural Science Foundation of China, grant number 52022060 & 52090084.  
Not applicable.  
The authors' gratitude goes to the reviewers for their helpful comments and constructive suggestions in improving this paper.  
The authors declare no conflict of interest.