Abstract: The installation of bridge piles near existing subway tunnels is an inevitable result in the utilizing urban underground space. Quantifying the disturbance zone of the surrounding soil layers caused by the bridge pile installation is an important measure to ensure the safety of existing subway tunnels. Providing a safer and cost-effective construction process according to the corresponding soil disturbance has also the technical significance of related research. Therefore, by using the finite element software, the construction of a large-diameter and extra-long bored bridge pile near a subway tunnel in Fuzhou was numerically studied. From the theoretical and numerical analysis results, the three-stage evolution characteristics of the soil stratum disturbance propagation with the excavation depth were investigated and an “upper part” method was proposed. The rapid construction method for this extra-long and large diameter bored piles combined with the micro-disturbance penetration of permanent steel casing and the lower slurry retaining wall. The field measurement results of a large-diameter and extra-long bored bridge pile near the subway tunnel construction in Fuzhou show that the final deformation of the tunnel disturbance guided by this method is within the allowable safe value. The method is demonstrated to be economical and safe.

Key words: Pile and Tunnel Engineering, Shielded Tunneling, Soil Disturbance, Combined Technology