Abstract: This paper presents the case history of construction of sewer outfall project of Qianpu wastewater treatment plant in Xiamen. In order to evaluate the mechanical effect of a deep excavation for the pipe jacking launching shaft nearshore under high groundwater table in high permeability sand layer, the numerical simulation and field measurement methods were used to study the internal force and deformation of soldier piles as well as the surrounding soils during the excavation. The results show that, the surface settlement area is mainly distributed outside the long side of the excavated area, and the cumulative maximum deformation value is less than 8.8 mm; The maximum horizontal displacement and bending moment of the retaining wall are 24.6 mm and 852.0 kN·m, respectively. The location of the maximum bending moment varies with the excavation elevation, and the axial force of the diagonal brace is larger, but they are in the allowable stress range. It is worth noting that the maximum horizontal axial force is 2267 kN per meter when the partition wall in front of the tunnel portal is broken, and the stress concentration is formed at the top and bottom of the tunnel after the tunnel portal is broken, and the axial force reaches 4744 kN per meter. Finally, combined with the field measured data, with the excavation retaining wall horizontal displacement gradually increases, and the location of the maximum horizontal displacement moves downward, through the effective control on site, the maximum lateral deflection value can be reduced from 24.6 mm to 18.6 mm.

Key words: sewage outfall, pipe jacking installation, pipe jacking launching shaft, finite element analysis, field measurement