Study On Soil Deformation And Building Settlement Caused By Construction Of Twin Shield Tunnels

The shield method is one of the most important construction methods in the construction of underground space. Although the disturbance to the overlaying soil layer is relatively small, it is inevitable to disturb the surrounding soil, causing the deformation of the soil and resulting in a series of environmental problems. The method of theoretical analysis and practical analysis is adopted in this thesis, in order to study the calculation method of the deformation of soil and the building settlement which are both caused by the construction of shield tunneling. Main innovation work in this thesis is listed as follows:(1)The deformation of soil caused by shield tunnels construction mainly includes:1)The two-dimensional analytical formula based on a uniform ground movement pattern of shield tunnels is corrected and used to predict the total deformation caused by adjacent parallel twin shield tunnels construction. This method is applicable only when it is adjacent parallel twin shield tunnels that are being constructed, so the definition formula of close range is studied.2)Considering the influence of many factors (soil loss, frontal additional thrust,friction force and grouting force), a mechanical model is established to study the calculation method of soil deformation caused by the construction of horizontal parallel twin shield tunnels. Horizontal offset b value of the later tunnel settlement trough can reflect the effects of the excavation in the first tunnel on the construction of the later tunnel, so the statistical results of 21 groups of 5 measured project are analyzed and the value of b is studied.(2)The settlement of buildings caused by shield tunnel construction mainly includes:1)There are obvious differences between the settlement trough which is formed when there is no building on the shield and that formed when the shield construction goes through the existing building on it. Considering foundation stiffness, foundation depth and asymmetry of soil settlement curve caused by tunnel construction,the solution of Ouyang Wenbiao is modified, with the adoption of uniform ground movement model for shield tunnels. The two-dimensional solution is extended to the three-dimensional solution, and the post construction settlement of the building is calculated simultaneously.2) Assuming that the building is an elastic foundation beam,a practical method is proposed to predict the settlement curve of the building under the influence of the building stiffness. Ground settlement caused by construction of shield tunnels without considering buildings is calculated according to the analytical formula of uniform ground movement model. Then the ground settlement is converted to the settlement force acting on the elastic foundation beam according to the elastic foundation beam theory. The settlement force is applied to the elastic foundation beam through using MIDAS-GEN finite element software, and the settlement of buildings is calculated under the condition of considering the stiffness of the building. The method is verified by three engineering examples, and the relative positions of tunnels and buildings, the k value of the subgrade coefficient and the influence of the stiffness of buildings (El)on the settlement of buildings are analyzed simultaneously according to some examples.