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During the excavation of foundation pits, the excavation process also serves to unload the surrounding soil. This process can cause an uplift of the underlying intermediate tunnels, significantly impacting existing tunnels and planned new subway lines. This study employed finite difference modeling based on a subway transfer station project in Hangzhou. The investigation considered the cumulative effects of excavation stages and proposed a unified evaluation criterion for deformation control efficiency. Various control measures’ impacts on vertical and horizontal displacements in the primary and passive zone tunnels were analyzed. The research findings indicate that the excavation unloading ratio and unloading sequence have no significant effect on the overall final displacement of tunnels in complex foundation pit projects. However, they have a notable impact on the vertical displacement of the passive zone tunnels during the excavation process. When using the jump excavation method, appropriate spacing should be selected based on the number of foundation pits. The control pressure location has a cumulative effect on restraining the uplift range of passive zone tunnels, and it is recommended that the pressure ratio rp be ≤ 25% during construction.

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Deformation Behavior of Adjacent Underpass Tunnels Due to Foundation Pit Excavation in Soft Soils

  • 会议论文

  • 发表日期：

    2025年

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  • Qiang Xie,
  • Zhengnan Tu,
  • Jun Wu,
  • Baolong Cheng,
  • Haiyou Peng,
  • Yuanjie Ma,
  • Yuxing Ban,
  • Xiang Fu,
  • Bo Zhang,
  • Xigang He,
  • Mohd Nur Asmawisham bin Alel

摘要

During the excavation of foundation pits, the excavation process also serves to unload the surrounding soil. This process can cause an uplift of the underlying intermediate tunnels, significantly impacting existing tunnels and planned new subway lines. This study employed finite difference modeling based on a subway transfer station project in Hangzhou. The investigation considered the cumulative effects of excavation stages and proposed a unified evaluation criterion for deformation control efficiency. Various control measures’ impacts on vertical and horizontal displacements in the primary and passive zone tunnels were analyzed. The research findings indicate that the excavation unloading ratio and unloading sequence have no significant effect on the overall final displacement of tunnels in complex foundation pit projects. However, they have a notable impact on the vertical displacement of the passive zone tunnels during the excavation process. When using the jump excavation method, appropriate spacing should be selected based on the number of foundation pits. The control pressure location has a cumulative effect on restraining the uplift range of passive zone tunnels, and it is recommended that the pressure ratio rp be ≤ 25% during construction.