Research About South-To-North Water Diversion Shield Tunnel Under-Crossing Beijing Subway Airport Line

East canal is an important part of South-to-North Water Diversion Auxiliary Project, the length of East canal is 44.7km, the tunnel use single circular section with inner diameter of 4.6m, outer diameter of 6m, and the tunnel is constructed with TBM methods. The Airport Express line of the Beijing Subway is 28.1km long, from DongZhiMen station in the 2nd ring to Beijing International airport T2 and T3 terminal on northeast of Beijing. Inevitably, the shield tunnels of the South-to-North Water Diversion Project need to under-cross the Beijing Airport Express Line section between Sanyuanqiao station and T2 terminal, the metro line structure is U-groove, and the depth of East canal tunnel is 16.5m, the net distanse between metro structure and canal tunnel is 14.36 m. The under-crossing work will bring adverse effects to metro line. The metro structures may deform to some extent, which without correct design and construction may influence the normal speed of subway trains and even greatly low down the metro service level. Thus, the choosing of crossing proposals, the controlling of construction sequences standards, the prediction of deformation under construction and other factors will greatly influence the under-crossing results and are of significance to the project construction.The thesis focuses on the schemes of design and construction in water conveyance tunnels of east canal of the South-to-North Water Diversion under-crossing Beijing metro airport line, through the safety analysis of the metro structures. The analysis method, analysis results and experience of this thesis may provide a valuable reference for other similar projects.The main contents of this thesis are as follows:(1)Build three different numerical models with ANSYS software based on three construction methods of this project, compare with three different construction methods(without grouting, with grouting, and with pile supporting), and calculate the structure deformation and land subsidence, eventually find the best solution which is the grouting method that shows minimum deformation for this project through comparison.(2)Based on the recommended solution of this project and the current standards,the deformation control standards are proposed through numerical analysis. And the deformation survey is carried out during the construction, and the real time measured data and subsidence results are similar to calculation conclusions.( 3) Some successful experiences are summarized for providing practical experience for similar projects. The numerical analysis using finite element method can be used to calculate the different proposals and construction methods, and make qualitative and quantitative conclusions, and do comparison of the proposals, ensure the safety of the under-crossing project.