Abstract: In the deep excavation engineering, excavation and dewatering will cause settlement of surrounding soils. Especially, when the foundation pit is adjacent to existing interval tunnel, the interval tunnel deformation owing to excavation should be paid more attention to. In this paper, the excavation of deep foundation of Henglong square, which is adjacent to Shenyang headrace tunnel, is numerically simulated by the means of finitedifference program FLAC3D. The results show that, ground surface settlement after excavation overall assessment is not very large under waterrich sandy layer geological condition. Comparing with noconsidering fluidsolid coupling analysis and considering fluidsolid coupling analysis, the dewatering influence on soil around the foundation pit and tunnel can't be neglected. The main deformation of tunnel is horizontal deformation. During the construction, right tunnel near the foundation pit should be emphasizly monitored.

Key words: foundation pit, excavation, dewatering, water rich sandy layer, interval tunnel, numerical simulation