Chengdu Metro Running Tunnels In The Shield Construction Caused The Numerical Simulation Of Surface Subsidence

Shield tunneling is one of the most important method of tunnel construction, however, it will bring influence on ambience inevitably, especially stratum settlement is very distinct. So it is essential to study the stratum displacement caused by shield tunneling. The thesis has discussed the shield tunneling process and influence of stratum displacement disturber caused by shield tunnel construction. The process of shield tunneling is simulated and all kinds of factors are considered carrying ground settlement by using Finite difference software of the FLAC. Some rules about Stratum longitudinal settlement, Crosswise settelment and Horizontal displacement are gained, then to propose measures to control settlement.In this paper, with the functions of Zero model and changing the functions of cell material properties and the stress release of the FLAC Finite difference software, the process of shield tunneling, pouring thick liquid into shield tail and lining supporting are simulated. But it difficult to simulate shield tunneling process directly, especially considering shield tail crevice, disturbance to the surface of tunnel and disposeing of pouring liquid. So another shield tunneling simulating method is presented, which transfer some variable (such as shield tail crevice size, the degree of pouring thick liquid and the scope of disturbance on soil around the tunnel surface etc,) closed to construction but hard to scale to isotropic, equal thick layer. The later method not only objectively reflect the influnce of some not easy quantified factors on the surface displacement but also avoids attend to one thing and lose another. So that it can reflect the actual situation of project and simplify the computation model.The influence of tunnel burying depth, Grouting the end of the shield, boring pressure and two-lane tunnel different shield excavation programme, crosswise and the level to the settelment influence are detailedly analyzed in this paper. Some changing rules which changes with some factors are gained, then to propose measures to control settlement. It is expected that it can take some advice on the project construction.