Referring to the Shiziyang Tunnel – the first underwater shield tunnel for high-speed railway (HSR) in China, model tests and field tests are carried out to study the mechanical properties of the single-layer and double-layer lining structures under hydrostatic water pressure and the interaction between the lining and the stratum. The impact of assembling modes, various ground conditions and water level change on the mechanical behavior of the single-layer lining structure, the influence of the secondary lining construction time, the interface working modes of the double-layer lining structure, and their failure characteristics are investigated and explored in this study. The rationality and reliability of using double-layer lining structure is also discussed.
The assessment of the impact of urban area shield tunneling on adjacent pile foundations is essential to ensure the stability and integrity of the piled buildings. Sandy cobble strata has force transmission feature of strong dispersion; therefore the equilibrium state of original strata would be easily destroyed by shield tunneling. In this study, model tests referring to the Chengdu Metro Line 1 and using the Φ520 mm EPB model shield machine are carried out to investigate the impact of shield tunneling on the existing pile foundation deformation and internal forces. Meanwhile, particle distinct element method is applied to analyze the soil particle movement feature surrounding the pile foundation from the micro view. Results showed that soil disturbance surrounding the pile foundation caused by shield tunneling makes the ground surface subsidence and pile foundation tilt, leading to the occurrence of stress concentration at the pile foundation base and nearby regions. Cutter head positive resistance and friction effect between shield machine and surrounding strata lead to the pile foundation three-dimensional movement and deformation during the shield tunneling.
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