Study On The Influence Applied To Surrounding Environment Induced By The Construction Of Tunnel

When built underground tunnels in soft soil area, hidden excavation method has much advantages in changes in the tunnel section and construction cost aspects. This kind of approach will inevitably has an impact on surrounding environment. In this paper, random medium theory and three-dimensional finite element program Ansys were used to analysis the infection that the tunnel act on the environmental geotechnology, and give the following conclusions :(1) According to the soil disturbance mechanism analysis of tunneling construction: after a tunnel excavation is completed, its convergence section is not uniform, it relevant to the tunnel cross-section shape, the tunnel section convergence can be decomposed into circular cross-section uniform and circular cross-section elliptic convergence.(2) According to the theory of random medium basic formula, we give a formula to calculate the tunnel section convergence, and analyzed the value of the parameters in the calculation formula . Finally, we compared the calculating values with measured values in two engineering examples. the results showed: random medium theory calculation formulas can predict the vertical surface subsidence due to underground tunnel construction exactly.(3) The plane finite element program was applied on the tunnel excavation process simulation. With the anlysis of different excavation ways , different excavation order, we know: the construction of urban underground tunnel generally use crossover construction of the fence method.(4) We anlysis the impact on the pipeline due to unnel construction in 3D FEM. With other factors remain unchanged, when the modulus of the underground pipeline increase, the deformation of the underground pipeline became smaller; With increasing depth of underground pipelines, the maximum horizontal and vertical settlement of the underground pipelines increased, but its settlement groove width gradually narrowing. the largest displacement of the pipeline is a mutation value when pipeline and soil modulus ratio for 1000.(5) Through the analysis of the underground pipeline parallel to the tunnel ,we know: the ratio of the space between tunnel and underground pipeline to the depth of underground pipelines is greater than 2.5, the horizontal displacement of the underground pipeline due to tunnel construction can be neglected; the ratio of the space between tunnel and underground pipeline to the depth of underground pipelines is greater than 10, the vertical settlement of the underground pipeline due to tunnel construction can be neglected; parallel pipeline depth ratio equal to 5, the maximumtensile stress and stress of the underground pipeline is a value of mutation; When the depth ratio is less than 5, the tensile stress and compressive stress underground pipeline increases rapidly, it will be easy for damaging the underground pipeline; When the depth ratio is greater than 5, the tensive stress and compressive stress of underground pipeline is relatively small, it will not do harm to underground pipeline.(6) Under the elastic foundation theory, we give the vertical settlement formula of pipeline due to the construction of tunnels.