Abstract: The tense land use environment and the complex main structure demand in the city lead to the more and more common special-shaped foundation pit. The analysis methods recommended by the current domestic foundation pit specifications can not satisfy the influence of shape on the deformation of foundation pit. Based on a large special-shaped foundation pit in Beijing,the Midas-GTS simulation model of special-shaped foundation pit is established,and the deformation characteristics of surface settlement and envelope structure of special-shaped foundation pit are studied in combination with the deformation data measured on site. The results show that the surface settlement and the deformation of the supporting structure have obvious spatial effects under the influence of the shape characteristics of the foundation pit: the surface uneven settlement is significant,the settlement near the long side of the foundation pit is greater than the short side,and the settlement increases significantly with the increase of the distance from the pit angle. The deformation of the middle area of the long side of the wall is larger,followed by the middle of the short side,and the deformation of the corner of the structure is the least. So when designing and supporting foundation pit,the space effect of foundation pit deformation should be fully considered to save project cost and improve the overall stability of foundation pit.

Key words: special-shaped foundation pit, numerical analysis, spatial effect, settlement, retaining structure deformation