## 5 Conclusions  
This paper considers a subway station pit project in Nanjing, which is adjacent to an existing tunnel, and firstly analyzes the tunnel's deformation monitoring data, and derives the change rules of horizontal and vertical tunnel displacement and differential settlement of structural joints during the construction of the pit. Then, the ABAQUS software is employed to establish a two-dimensional pit-tunnel numerical model, through the comparison of measured data and numerical simulation results. This is done in order to verify whether the model parameters are set reasonably, and to summarize the tunnel's deformation in the process of pit excavation, the structural stress, the horizontal displacement of the support piles, and the change rule of the surface settlement. Finally, the effects of pit excavation depth, pit-tunnel horizontal spacing, support system stiffness (support pile wall size, insertion ratio and horizontal support stiffness) and different stratigraphic conditions on the structural stress and deformation of the tunnel were investigated, and the following conclusions were drawn:  
1. Concerning the impact of excavation depth on the tunnel structure, the greatest influence is observed on the vertical displacement, followed by horizontal displacement, with the smallest impact seen on structural stress. There is an obvious linear relationship between the stress and deformation of the tunnel structure and the excavation depth. Greater excavation depth corresponds to increased stress and deformation of the tunnel. In the case of a tunnel situated in a silty clay stratum, the excavation depth of the laterally adjacent foundation pit should be limited to within 20 m to ensure that tunnel deformation resulting from excavation adheres to the deformation control standard outlined in the existing specifications. 2. Stress and deformation of the tunnel structure decrease exponentially with increasing horizontal spacing. The variation in horizontal spacing of the tunnel exerts the most important influence on vertical displacement, followed by horizontal displacement, with structural stress being least affected. If the distance is less than 1.5 H, the tunnel is significantly impacted by the excavation of the laterally adjacent foundation pit. 3. The degree of influence of the support system's stiffness on the tunnel's horizontal displacement follow the order of insertion ratio > horizontal bearing stiffness > support pile wall size. The degree of influence of the factors influencing the tunnel's vertical displacement follow the order of horizontal bearing stiffness > support pile wall size > insertion ratio. The degree of influence of the factors influencing the tunnel structure stress follow the order of horizontal bearing stiffness > insertion ratio > support pile wall size. In summary, the change in the horizontal bearing stiffness has the greatest influence on the tunnel, followed by the change in the insertion ratio, and the change in the supporting pile wall size has the least influence. Therefore, in future similar projects, priority should be placed on enhancing the stiffness of horizontal supports, potentially through augmenting their number. 4. Among the effects of ground types on the deformation and stress of the tunnel structure during foundation excavation, muddy-silty clay and silty soils have the greatest degree of influence on the tunnel in question. The results can be used as a reference for strata with similar soil parameters. Conceptualization, T.F. ; methodology, J.Z. and P.P. ; software, [PERSON] ([PERSON]); validation, [PERSON] ([PERSON]); formal analysis, [PERSON] ([PERSON]); investigation, [PERSON] ([PERSON]); resources, T.F. ; data curation, [PERSON] ([PERSON]); writing--original draft preparation, [PERSON] ([PERSON]); writing--review and editing, [PERSON] ([PERSON]); visualization, H.C.; supervision, H.C.; project administration, [PERSON] ([PERSON]); funding acquisition, T.F. All authors have read and agreed to the published version of the manuscript.