## 1 Introduction
[14] studied the stability of excavation in soft soil using a two-dimensional finite element analysis method. Factors affecting the stability of the foundation pit after excavation were determined. [PERSON] et al. [15] explored the dynamic response of a steel pipe pile foundation during the construction process of an adjacent deep foundation pit using measured data and numerical calculation results. The results were in good agreement based on a comparison of the numerical simulation results with the measured results. [PERSON] et al. [16] used three-dimensional finite element software to study the shielding effect of pile groups and the mechanical response of pile groups under soil deformation. The simulation result was compared with existing solutions. [PERSON] et al. [17] simulated pile-soil interaction using a Timoshenko beam, and derived an explicit solution of the pile-soil interaction by using the finite difference method. The shear properties of piles and the non-uniformity of multilayer soil were further considered. Through numerical analysis and field monitoring data, the maximum errors of the predicted and simulated pile deflection under different excavation depths were 4.5% and 1.8%, respectively. [PERSON] et al. [18] used finite element software to simulate the excavation process of a deep foundation pit to study the excavation effect of a deep foundation pit on an adjacent pile foundation. The results showed that the excavation of the foundation pit caused a large horizontal displacement in the adjacent pile foundation, with a maximum value up to 28 mm. [PERSON] et al. [19] adopted a method by coupling the consolidation parameter in three dimensions. The settlement and load transfer mechanisms of a single pile caused by different construction sequences of double-pile tunnels in rigid saturated clay were investigated. The results showed that the construction sequence of double-pile tunnels with different depths had a significant influence on the settlement and deformation of the pile, but had a small influence on the load transfer mechanism in the pile. [PERSON] and [PERSON] [20] and [PERSON] et al. [21] used finite element simulation to simulate the excavation process of the foundation pit, and concluded that the excavation of the foundation pit would cause an additional bending moment of the pile foundation. However, this method did not consider the shear fluidity of the soil around the pile. Therefore, the establishment of the finite element model seriously affected the correctness of the calculation results. This study relied on a deep foundation excavation engineering in the Greater Bay Area in Shenzhen, south China. The minimum distance between the foundation excavation and adjacent viaduct foundation pile was only 2.1 m. Two-way double-track train loads run on both sides of the upper part of the viaduct every 4-6 min. The train load is considered to have an impact on the excavation deformation and pile foundation of the viaduct. The interaction between the three coupling factors of the train dynamic load, foundation excavation, and viaduct pile foundation cannot be ignored. Therefore, in this study, a large 3D finite element model was built. The train dynamic load operation of a two-way double-track train was simulated by a set of codes using the Fortran language. Combined with numerical simulation and construction monitoring, the influence of the dynamic load on the excavation of deep foundation excavation was explored. We propose reasonable suggestions for the construction of this project and provide a reference for urban subway station reconstruction.