Abstract: In order to explore the response of the foundation pit and the surrounding environment during the excavation of the foundation pit, taking the actual foundation pit project in the northwest as the background, the corresponding model was established by Plaxis 3D software, and the deformation of the foundation pit and its surrounding environment and the change of the force on the anchor rod of the retaining structure during the excavation of the foundation pit are analyzed. The results show that the soil deformation caused by the excavation of the foundation pit is a three-dimensional problem. The deformation of the soil body in the profile is affected by the yin and yang angles of the foundation pit. The extent of this effect is related to the distance between the profile and the internal and external corners of the foundation pit.In the retaining structure of foundation pit, the anchoring effect of anchor bolt is about 30% better than that of soil nail, and the supporting effect of pile anchor is about 20% better than that of composite soil nail wall. The lower row of bolts bears more active earth pressure than the upper row of bolts, and the axial force in the free section is greater than the upper row of bolts. The road near the composite soil nailing wall support section is affected by the excavation of foundation pit, and its inclination direction changes from the initial inclination towards the outside of the pit to the inside of the pit. The deformation of existing buildings near the pile anchor support section is within the allowable range of relevant specifications, and the surrounding existing buildings are in a safe state.

Key words: composite soil nail wall, pile anchor support, foundation pit excavation, surroundings, FEM analysis