The Analysis Of The Influence On The Underground Pipeline By Shield Construction

Shield method is now widely used in urban subway construction because of its unique characteristics and advantages such as high efficiency, intelligence and security. But settlement of soil of different level will be caused in this way. When settlement becomes larger, it may change the shape of pipeline that buried in the soil, or it may break the pipeline when seriously, which will damage the city’s pipeline system, thus causing unnecessary economic loss and urban hazards.Aiming at a stretch along the subway line one in Hefei, the test studies the construction impact on surface subsidence by shield construction. With the finite element software MIDAS/GTS of three-dimensional method of excavation,the shield tunnel model is set up, thus change rule of pipelines and the surface settlement has been summarized,and different changes of earth surface in different excavation periods have been analyzed at the same time. Line of surface subsidence through curve is close to Gaussian normal distribution, the maximum settlement is directly above the tunnel axis, settlements on the two sides of the tunnel axis are approximately as symmetry state. From the axis to both ends, with the advancement of shield, the surface subsidence decreases, the increasing speed of surface subsidence is faster and faster. At the same time, the results of numerical simulation are fit to the calculated data of peck experience formula method. which proves the reliability of the numerical simulation method in this project.Changing the parameters such as the material of pipeline, the diameter of the pipeline and the relative distance of the tunnel, in the shield advance process, we conclude the change rule of the line and pipeline settlement. The smaller the diameter of the pipeline is, the deeper the buried depth is, the smaller the elastic modulus is, the greater its deformation is.Some pipeline control standards are presented at the end of this paper, meanwhile, pipeline’s allowing radius of curvature and open value of pipe joints have been calculated with different methods. Then we put forward several protection methods of pipeline during shield launching.