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<p>The emergency escape passage provides the designated evacuation route during tunnel emergencies, critically enhancing pedestrian safety. Artificial Ground Freezing (AGF), renowned for reinforcing surrounding rock and soil while improving structural waterproofing, is widely used in constructing emergency escape passages across diverse geological conditions. While extensive research exists on freezing methods for transverse connections between parallel tunnels, studies on vertical connections for twin stacked shield tunnels remain scarce. This research integrates actual engineering applications, employing numerical simulation and field monitoring to evaluate an existing freezing scheme for a concealed-excavation vertical connection tunnel in shield tunnels. The primary objectives are simulation and design optimization. Results indicate maximum structural vertical settlement (19.51&#xa0;mm) occurs at the crown of the primary support. The largest net convergence deformation (8.99&#xa0;mm) appears within the upper connecting tunnel, while peak structural stress (22.5&#xa0;MPa) arises at the junction between the upper and middle segments. All simulated values remain within specified control limits, confirming the initial freezing plan’s safety. Validation against field monitoring data further corroborates the simulation’s accuracy. Comparison with control values revealed excessive conservatism in the initial design. Consequently, the freezing scheme was optimized: retaining the freezing curtain thickness and ensuring safety, the number of horizontal freezing pipes was reduced from 205 to 103. This significantly improved construction efficiency. The findings provide valuable guidance for designing similar connecting tunnel structures.</p>

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Simulation and Design Optimization of Ground Freezing for Vertical Connection in Stacked Shield Tunnels

  • 期刊论文

  • 发表日期：

    2025年7月8日

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  • Jinhui Liu,
  • Wantao Ding,
  • Yiran Wen,
  • Hang Ruan,
  • Yuting Liu,
  • Fengkai Zhang

摘要

The emergency escape passage provides the designated evacuation route during tunnel emergencies, critically enhancing pedestrian safety. Artificial Ground Freezing (AGF), renowned for reinforcing surrounding rock and soil while improving structural waterproofing, is widely used in constructing emergency escape passages across diverse geological conditions. While extensive research exists on freezing methods for transverse connections between parallel tunnels, studies on vertical connections for twin stacked shield tunnels remain scarce. This research integrates actual engineering applications, employing numerical simulation and field monitoring to evaluate an existing freezing scheme for a concealed-excavation vertical connection tunnel in shield tunnels. The primary objectives are simulation and design optimization. Results indicate maximum structural vertical settlement (19.51 mm) occurs at the crown of the primary support. The largest net convergence deformation (8.99 mm) appears within the upper connecting tunnel, while peak structural stress (22.5 MPa) arises at the junction between the upper and middle segments. All simulated values remain within specified control limits, confirming the initial freezing plan’s safety. Validation against field monitoring data further corroborates the simulation’s accuracy. Comparison with control values revealed excessive conservatism in the initial design. Consequently, the freezing scheme was optimized: retaining the freezing curtain thickness and ensuring safety, the number of horizontal freezing pipes was reduced from 205 to 103. This significantly improved construction efficiency. The findings provide valuable guidance for designing similar connecting tunnel structures.