Study On The Influence Of Shield Tunneling On Surrounding Environment

The shield tunneling is one of the main methods to construct tunnel in soft ground region. But shield tunneling inevitably brings about the ground and earth's surface movement and additional stress in soil and structure nearby. That is environment problem. The thesis studies additional stress of soil surrounding shield tunnel due to excavation, and the response of tunneling to adjacent pipelines, pile foundation and surface structure. The thesis also discusses the prevention and cure methods on environment problem caused by tunnel shielding. The main works of thesis are as follows:(1) Analysis of additional stress of soil surrounding shield tunnel due to excavation. The Mindlin integral formula is applied to calculate the additional stress of surrounding soil induced by pressure of excavation face. Based on the theory of expansion-shearing of cylindrical cavity, and considering the effect of shearing force, the calculation of additional stress of the soil induced by shield cutting is obtained. According to the space regularities of distribution of ground loss, and by image method theory, the calculation formula of additional stress is deduced. In order to analyze the disturbance influence induced by grouting pressure, the theory of cavity expansion is used to calculate the additional stress and the radius of plastic zone of surrounding soil. Finally, combined with the practice of subway engineering in Shanghai, the distribution law of the additional stress caused by pressure of excavation face, shield cutting, ground loss and grouting pressure is analyzed. The results of the calculation formulas are validated by three-dimensional numerical analysis.(2) Prediction for response of tunneling to adjacent pipelines. The tunnel excavation generates soil settlement around the pipeline, and causes the pipeline to deform and suffer bending moment. The Loganathan's formula is used for predicting the soil displacement at the pipeline level, and the equivalent model of the forces acting on the pipeline is given. A Winkler solution is presented for estimating the bending moment for the pipeline affected by tunneling. A case is analyzed, and the solution is compared with an elastic continuum solution and Attwell's solution. The results show that the method is validated. The shielding tunnel construction is modeling by finite element code MIDAS/GTS, and the parameter's sensitivity such as the distance between shield machine and pipelines, the relatively depth of pipelines and tunnel is analyzed. The safety of the pipeline is discussed, and the prevention method is summarized.(3) Prediction for effect of tunneling on piled foundations. The effect of shield tunneling on adjacent pile can be divided to two stages: the adding pressure stage and the uninstalling stage. The shield tunneling disturbs the soil, and generates soilsettlement around the pile, and causes the pile to deform and suffer bending moment. According to the space regularities of distribution of ground loss and by image method theory, the calculation formulas of additional stress in the soil are obtained. A Winkler solution is presented for estimating the lateral action for the adjacent pile. The Loganathan's formula is used for predicting the soil displacement around the pile, and a Winkler solution is presented for estimating the axial action for the adjacent pile. A three-dimensional numerical analysis is conducted to investigate the effect of shield tunneling on the adjacent pile by MIDAS/GTS. The parameter's sensitivity is analyzed.(4) Behavior of surface frame structure and masonry structure due to tunnel induced subsidence. Considering the weight and stiffness of the structure, numerical modeling of damage to structure due to tunneling is established. The effect of structure on deformation of ground surface is analyzed. The deformation and force behavior of frame structure influenced by tunneling is studied. The behavior of masonry structure influenced by tunneling is studied. The performance of the structure is studied, when the structure is located on different placement of the settlement curve of the ground surface. The damage forms of the structure induced by tunnel exaction are summarized, and safe evaluation standards are given, and lastly, protective measures are brought forward.