Mechanical Analysis On Secondary Lining Of High Speed Railway Tunnel

In recent years, the construction of railway network with emphasis on passenger transport line has been processed and booming on a national scale over China, leading China ranking first in the world in terms of numbers of tunnels, total length of tunnels. However, the parameters of tunnel design and construction are decided on a considerable degree of empiricism or extrapolation from established principles, which implies a lack of a strong conceptual foundation for tunnel design. In this paper, the emphasis is mainly put on the study of mechanical properties of secondary lining. Study methods including theoretical analysis, on-site monitoring and numerical calculation are adopted herein. The main conclusions can be drawn as follows:(1) Analysis is conducted concerning failure phenomenon of secondary lining. With the finite element program, ABAQUS, simulation is conducted using a three-dimensional ground-structure model. By utilizing eXtended finite element method, crack properties of secondary lining, like distribution law, propagating process and appearance, are analyzed. The ground condition has a great influence on distribution and type of crack of secondary lining.(2) Analysis is conducted concerning failure mechanism of secondary lining. By using concrete damage plasticity constitutive model, bearing capacity of secondary lining is studied. The typical progressive failure process of secondary lining is shown clearly. Tunnel knee is the weakest part, which should be strengthened. Concerning secondary linings with and without reinforcement, the failure law under various ground conditions is clarified. Meanwhile, the function of reinforcement embedded in secondary lining is also discussed. Moreover, the numerical study is validated by comparing with analytical solution for ultimate contact pressure.(3) On-site monitoring and statistical study of secondary lining are both carried out. By combing monitoring and statistical results, the actual load-carrying condition of secondary lining can be concluded. The most unfavorable stress state for secondary lining occurs when the tunnel lining trolley is removed. The stress acts on secondary lining is actually deformation pressure which is totally different from loose pressure prescribed in China Tunnel Standard.