Surface settlement characteristics of adjacent building groups during excavation

To clarify the surface settlement characteristics induced by pile foundation building groups and to obtain the surface settlement profiles in the areas outside the foundation pit under their influence, this study employs the PLAXIS 3D finite element software, with the excavation of a interval station pit on the Line 4 of the Tianjin Metro as the engineering background. A systematic analysis is conducted on the spatial distribution of surface settlements in the vicinity of the building groups during the excavation process. By comparing the surface settlement behaviors in zones with and without building groups (including shallow foundations and pile foundations), the influence of building location and foundation type (shallow foundation or pile foundation) on the evolution of surface settlements is investigated. Based on these findings, the surface settlement curves and influence zones beyond the foundation pit affected by pile foundation building groups are proposed. The results indicate that the surface settlement during foundation pit excavation exhibits a typical "V"-shaped distribution; the presence of adjacent building groups can partially mitigate the surface settlement. Pile foundations, through the enhancement of surrounding soil stiffness and strength, effectively constrain surface settlements, demonstrating a synergistic protective effect. According to the surface settlement curves, the area outside the foundation pit is classified into three settlement zones: Zone Ⅰ, Zone Ⅱ, and Zone Ⅲ. This study provides a systematic method for settlement prediction and risk assessment in foundation pit excavations adjacent to high-rise building groups in complex environments. The findings offer a theoretical guidance for the optimization of support design during construction, and thus have significant reference value for ensuring the safety of surrounding structures and improving the overall safety of foundation pit engineering.