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Abstract

To understand the influence of foundation pit excavation on zero-distance underground shield tunnels, this paper built a section excavation model of interval tunnel foundation pits by employing PLAXIS 3D geotechnical finite element software based on the first zero-distance upper-span subway tunnel project in China, which is an overlapping section of a parking lot in Xiamen Metro and the main line. Meanwhile, soil excavation schemes were developed by adopting layered, zoning, strip, symmetrical and other methods to investigate the response of underground shield tunnels under three different excavation schemes. The results show that due to the consistent total excavation unloading amount, different layered and zoning excavation processes of foundation pits have little effect on the strata and underlying tunnels, with generally consistent response patterns. Under the three excavation schemes, the differences in extreme surface sedimentation behind the foundation pit wall, underground tunnels' vertical displacement and extreme bending moments are about 1%, 10%, and 3% respectively. Additionally, timely construction of the bottom plates of the foundation pits can provide the function of back pressure, which to some extent suppresses stratum displacement, tunnel deformation, and extreme internal force. On-site practice shows that the actual construction scheme is reliable, and the shield tunnel structure is safe and stable.

Publication Date

1-18-2024

DOI

10.14048/j.issn.1671-2579.2023.06.040

First Page

253

Last Page

260

Submission Date

March 2025

Reference

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