Research On Mechanical Behavior Of Segmental Lining Structure For Underwater Shield Tunnel With Large Cross-Section

In recent years, a large number of cross-sea or cross-river traffic channels have been started construction in China, and most of them emerging in form of underwater shield tunnels with large cross-section. However, with regard to large cross-section shield tunnel, the structure design experience is not yet complete or consummate. There is not specific design code as reference to the design of segment structures, so the domestic designer have to consult the foreign code or design methods. Meanwhile, China has a vast territory, and the geological conditions are quite different from different regions. Especially for the complex underwater environment, the existing construction experience and design theories for shield tunnel could not be applied appropriately. In view of this, the mechanical characteristics of segmental lining structure for underwater shield tunnel with large cross-section is studied in this paper, and the results will have important practical significance.Supported by National High-Tech Research and Development Program of China (863Program):’Research on mechanical characteristics and integral design method of large underwater tunnel structures’, and many other major national research projects, the theoretical analysis, model tests, prototype tests, full-scale tests, numerical simulation and many other methods are carried out in this study. The mechanical properties of segmental structure for large underwater shield tunnel are studied comprehensively and systematically. And the research achievements are directly applied to the design and construction of several underwater shield tunnels in China, including the first high-speed railway underwater tunnel-Guangzhou Shiziyang Tunnel and Nanjing Changjiang Tunnel. The main works and research achievements include:(1) By means of full-scale tests and3D numerical analysis, which considered the joint surface interaction, properties of concrete cracking, crushing and bolt fracture, the bending behavior, failure characteristics and mechanical properties were clarified and acquired. Meanwhile, the mechanical model of segmental joint for large underwater shield tunnel was established. The model consdering the phenomenon such as cracking, crushing of concrete and yield, fracture of bolt, the models made up the defect that the previous mechanical models of segment joint could not analyze the large deformation or damage cases. The bending stiffness of segment joints of Shiziyang Tunnel was clarified under different mechanical state.(2) Using’shield tunnel-ground complex simulation facility’and’water pressure device’, Large-scale similar model tests, which considered the interaction of tunnel structure, ground and water, were carried out against the characteristics, such as high water pressure, crossing through stratas with different mechanical properties. The behavior of segmental lining structure was ascertained under different load condition, different assembling methods and different stratas.(3) Using the "Multi-function Shield Tunnel Structure Test System" device, the prototype tests were carried out agaist large-cross section underwater shield tunnel. The distribution and changes of internal forces and deformation under normal use stage, cracking damaged stage was clarified. Meanwhile, the effect of assembling method on inner force was discussed by theoretical analysis. And the distribution of circumferential internal forces and suface stress under different load conditions and different assembly methods was clarified respectively.(4) The relationships between maximum rate of diameter change, maximum longitudinal seam opening, expansion of cracks and structure stiffness was acquired by destructive prototype tests. The failure characteristics of segmental lining structure under different assembling methods were acquired respectively. Meanwhile, the deformation features during the damage process was explored, and the effect of maximum longitudinal seam opening and cracking on structure deforming was discussed in the perspective of structural stiffness.(5) Compared with the most widely-used analytical models, advises and recommendations were given according to the feature of underwater shield tunnel with large cross-section. The relationship between deformation properties and structure stiffness under different load conditions, different assembling methods and different stucrure types was acquired by prototype tests. Furthermore, suggestions on the effective bending rigidity ratios and moment increasing rates, which were key parameters of uniform rigidity ring model, were given when using the model to conduct large cross-section shield tunnel analysis. Meanwhile, solid-contact model considered crack propagation was established to discuss the distribution and stretching of cracks, the structural deformation and the stress after cracking.