Study On The Longitudinal Design Method Of Shield Tunnel In Soft Soil

It has been shown from a lot of shield tunnels in soft soil that the longitudinal settlement and uneven settlement of shield tunnel is gradually obvious. Its unfavorable influence on tunnel structure and waterproofing of joints is more and more serious. As the background, the theory of solving those problems has been carefully studied with longitudinal simulation model test, analysis and numerical simulation. The main contents and conclusions are as follows:In order to solve the problems caused by the uneven settlement of shield tunnel, the theory of the beam on double elastic foundation has been put forward by analyzing the design methods of shield tunnel in soft soil and the characteristics of shield tunnel in soft soil in Shanghai And the analytic solutions of beam on double elastic foundation on concentrated force, concentrated force couple, partially uniform load and partially linearly distributed load have been deduced. For testing and verifying the theory of beam on double elastic foundation., more studies have been done as follows.Shanghai Metro Line 2 was selected as the prototype of the simulation model test. The tunnel models were made in different patterns (the continuous pattern, partly continuous pattern, nonstaggering installation pattern and staggering installation pattern) and their longitudinal rigidity ratios were different. By test, the value of longitudinal rigidity ratio of shield tunnel in Shanghai was obtained. Under the same load condition, the tunnel model with different pattern (the continuous pattern, partly continuous pattern, nonstaggering installation pattern and staggering installation pattern) has differently deformation. On the same load, the vertical displacement and subgrade reaction of the beam on double elastic foundation are very similar with that of model test.The principle of beam on elastic foundation is one of methods of analyzing shield tunnel in soft soil. The analytic solutions of the internal force,deformation and subgrade reaction of beam on elastic foundation on partially uniform load, partially...