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Mechanical response mechanism and parameter optimization of double-arch tunnels without middle drift during
Junwu Chen1,2, Feng Huang3,4, Song Wang5,6
1School of Civil Engineering, Beijing Jiaotong University, Beiijing, 100044, China.
Scientific Reports
|September 2, 2025
Summary
Excavating secondary tunnels in double-arch tunnels without middle drift significantly increases front tunnel deformation and lining stress. Optimizing excavation methods and face staggering, like a 12m distance, mitigates these adverse effects.
Area of Science:
- Geotechnical Engineering
- Tunneling Engineering
- Civil Engineering
Background:
- Double-arch tunnels without middle drift offer construction efficiency and cost benefits.
- Excavation of adjacent tunnels can cause significant structural disturbance and instability in existing tunnel linings.
- Understanding the mechanical response during sequential excavation is crucial for safe tunnel construction.
Purpose of the Study:
- To investigate the structural mechanical response and failure evolution during the construction of double-arch tunnels without middle drift.
- To reveal the influence of secondary tunnel excavation on the stress mechanism of the front tunnel.
- To compare the effects of different excavation methods, footage, and face offsets on structural stress.
Main Methods:
- Case study of the Xinmajie Tunnel project in China.
- Physical model experiments.
- Finite element simulation analysis.
- Comparative analysis of excavation parameters.
Main Results:
- Surrounding rock deformation follows a three-stage pattern: rapid increase, rapid decrease, and slow increase.
- Secondary tunnel excavation increased front tunnel arch crown settlement by 25.56%.
- The right arch waist lining experienced the highest axial force and bending moment, indicating significant stress concentration.
- Lining cracks predominantly occurred in weaker zones like the arch shoulder, arch crown, and inverted arch.
Conclusions:
- Excavation method (left then right) and small excavation footage reduce disturbance and stress concentration.
- A 12m staggered distance between tunnel faces is optimal for controlling settlement and plastic zone expansion.
- These findings provide valuable parameter references for similar tunnel designs and construction.
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