Structural Stability Study For Underwater Shield-driven Tunnel Lining Under High Hydraulic Pressure

With the development of economic and overall strength of the country, utilizing and empowering underground space becomes very significant. The shield tunneling method is more and more widely used in tunnel excavation. And it has played an important role in the construction of subways and river-crossing tunnels. In that case, the theory about design and excavation engineering of the shield tunnel segment becomes more and more important. The design method, loading model, and their numerical simulation are the key points of research for a long time. At the same time, some problems, such as large diameter, big width and high hydraulic pressure, are very popular for the scholars at present.Relative domestic and overseas theory and numerical simulation research achievements about shield tunnel are first summarized systemically. Then, this article deals with the segment of Weisan Road over-river tunnel at Nanjing City. Using modified ring model and the beam-spring model, the numerical simulation of shield tunnel lining is carried on and the load distribution and deformation law of the two models under five different working conditions. Adopting entity-joint fluid & solid coupled model of continuous medium, the study of load distribution of large segment structure under high hydraulic pressure is carried on in a deep-going way. The main research contents and conclusions are as follows:(1) Research of numerical simulation methodology for underwater shield tunnel. The mode of loads acting on the shield lining and load reduction factor are studied.(2) Force analysis of over-river shield tunnel lining structure. Based on the theories above, finite element analysis software-Ansys is used to build equivalent stiffness ring model and beam-spring model in order to calculate for five different cross-section of Weisan Road shield tunnel and compare the calculations. Besides, the effect of different thickness to the force distribution of segment structure is considered.(3) Reliability analysis for shield tunnel crossing under river using load-structure method. Load-structure method model is built to study the reliability of the segment, and the influence by relevant parameters of surrounding rock and construction on segment internal force is analysed.(4) Study of fluid & solid coupled model under high hydraulic pressure of crossing-river tunnel. Using finite element analysis software-ABAQUS to build the entity-joint fluid & solid coupled model of continuous medium under high hydraulic pressure and analyze the calculations.