| In recent years, a lot of tunnel projects were built in the world greatly promote the technology of shield tunnel, and the fixed methods are forming in most country about the design of shield tunnel segment structure. But there are no definite rules about the computing models or computing methods of load on deferent soil, so many numerical methods are spring up about tunnel and underground project.In this paper, taking a shield tunnel in Shenyang Metro as an example, three internal force computing methods of shield tunnel are reviewed and analyzed. A new load-structure model of calculating the segment internal force is proposed based on earth pressure calculation method in soil mechanics. Analyzing the factor of segment internal force, such as the different joint type, tunnel depth, the diameter of segment, the elasticity modulus and Poisson's ratio of soil. The distributions of internal forces on segments are simulated by using finite element method while the ground stress release rates induced from shield tunneling are considered. The practical ground stress release rate of a tunnel is determined by comparing settlements computed by finite element method with in-situ observed data. The numerical simulation shows that the maximum settlement of ground surface is proportional to ground stress release rate. Based on plane assumption of beam in bending state in material mechanics, the analytical expressions of bending moment allocations on double-layer linings of shield tunnel are deduced. Two examples for double-layer linings of shield tunnel are numerically simulated with FEM in order to compute moment allocation ratio. Analytical solutions for allocation ratio of bending moments agree well with numerically simulations. Analyzing the relationship between the first lining and second lining; Analyzing the influence of internal force on shield tunnel segment by soil relaxation pressure on the example subsea tunnel of QIONGZHOU strait with high water pressure and great depth. |
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