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Geomechanics and Engineering
  Volume 35, Number 5, December10 2023 , pages 525-538

Mechanical evolution law and deformation characteristics of preliminary lining about newly-built subway tunnel closely undercrossing the existing station: A case study
Huijian Zhang, Gongning Liu, Weixiong Liu, Shuai Zhang and Zekun Chen

    The development of a city is closely linked to the construction and operation of its subway system. However, constructing a new subway tunnel under an existing station is an extremely complex task, and the deformation characteristics and mechanical behavior of the new subway tunnel during the excavation process can greatly impact the normal operation of the existing station. Although the previous studies about the case of underpass engineering have been carried out, there is limited research on the condition of a newly-built subway tunnel that closely undercrossing an existing station with zero distance between them. Therefore, this study analyzes the deformation law and mechanical behavior characteristics of the preliminary lining of the underpass tunnel during the excavation process based on the real engineering case of Chengdu Metro Line 8. This study also makes an in-depth comparison of the influence of different excavation methods on this issue. Finally, the accuracy of numerical simulation is verified by comparing it with on-site result. The results indicate that the maximum bending moment mainly occurs at the floor slab of the preliminary lining, while that of the ceiling is small. The stress state at the ceiling position is less affected by the construction process of the pilot tunnel. Compared to the all-in-one excavation method, although the process of partial excavation method is more complicated, the deformation of preliminary lining caused by it is basically less than the upper limit value of the standard, while that of the all-in-one excavation method is beyond standard requirements.
Key Words
    deformation law; mechanical behavior; preliminary lining; process correlation; undercrossing
Huijian Zhang, Gongning Liu, Weixiong Liu, Shuai Zhang and Zekun Chen:School of Civil Engineering, Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University,
No. 111, North Section, Second Ring Road, Jinniu District, Chengdu, Sichuan Province, 610031, China

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