The Effectiveness Study Of Foundation Excavation To Adjacent Underground Tunnels

With the development of city, it is a new problem that the influence of foundation excavation on adjacent existing tunnel. Consequently, how to predict and control the displacement and how to protect the existing tunnels become the important engineering issue. Applying the traditional design theory (strength-controlling design) and routine construction technology ,there is inevitable difficulty about protecting the adjacent existing tunnel. This paper analyzed the deformation factors and the displacements and inner forces of tunnels from different numerical simulation models. Finally, the study achieve deformation discipline of tunnels effected by foundation excavation. The main contents are as follows:1,Introducing the constitutive relations of soils and the elasticity and elastoplastic model of soils. Then discussing the mechanical properties of the soil and factors of the elastic deformation of foundation bottom.2,Analyzing the longitudinal deformation factors and theory of beam on elastic foundation of tunnel. Theorized for the after studying3,Discussing detailedly about the knowledge of finite element method and the application of FEM software ANSYS.4,Finally, Using software ANSYS , the paper analyzed the influence of the foundation excavation on adjacent existing tunnels through different numerical simulation models(tunnel beside and below foundation ). Several simulated factors are taken into account in the study. Including : the different excavation step ,depth of tunnel below ground surface, the depth of diaphragm walls below the soil , the thickness of diaphragm walls and soleplate, the reinforcement to the soil inside the pit and the reinforcement to the soil near the pit, and the contrast between planar model and the three-dimensional model. The displacements of horizontal and vertical and inner forces along the longitudinal axis of tunnel and transect of tunnel. Paper achieved the displacements and inner forces discipline of tunnels effected by foundation excavation.Main conclusions were get as follows:(1),If the distance between the foundation and tunnel is large enough , the influence of foundation excavation on adjacent existing tunnel should not be considered.(2),It is should not always improve the values of some factors to eliminate the influence of foundation excavation on adjacent existing tunnel. The economy values should be considered.(3),It is very important to consider the space effect in this study.