Simulation Analysis Of Shield Tunnel Excavation-induced Additional Responses Of Adjacent Passive Pile Foundations

With the rapid development of urbanization in China, subway construction has become an important means to alleviate the traffic congestion problem. In the last decade, subway construction has been growing vigorously in many cities in China. However, tunnel excavation will inevitably damage adjacent buildings’ pile foundation. A large number of researches have been conducted to investigate this problem, but engineering accidents caused by tunnel excavation happen frequently. Generally, the field staffs’ negligence of safety consciousness should be blamed for some of these accidences. And the cause of tunnel excavation problems are not well understood by engineers, so they cannot solve the problems immediately. Combining with finite difference algorithm, programming by MATLAB numerical analysis software, the two-stage method is carried out in this dissertation to analyze the tunnel excavation-induced additional responses of adjacent passive pile foundations. This dissertation mainly consists of the following five parts.Firstly, this dissertation introduces the research background, systematically summarizes the research situations about tunnel excavation-induced additional responses of adjacent passive pile foundations, and proposes the research questions and the research methods.Secondly, it introduces the concept of shield tunneling and its construction process, describes the mechanism of soil deformation induced by shield tunneling, and summarizes the calculation methods of soil deformation.Thirdly, it comprehensively describes the solving process of additional responses of adjacent passive pile foundations, which includes the single pile mechanical characteristics before and after tunnel excavation, considering the pile-soil load transfer model of the excavation unloading effect, and the specific calculation process of pile additional response. It also uses MATLAB software to program and calculate, and the result is compared with previous centrifugal test and BEM(the boundary element method) to verity the rationality of the proposed method.Fourthly, it changes several model parameters to analyze the sensitivity of the additional response of passive pile to the parameters. The results prove that: the tunnel axis should not be designed near 1/2 length area of the passive pile where the maximum additional axial force occurred; the further the tunnel axis is away from passive pile horizontally, the smaller the pile additional bending moment is, and it eventually approaches to zero; theoretically there exists a maximum additional axial force line, and the closer the tunnel axis approaches to this maximum additional axial force line, the bigger the additional axial force will be; the increase of pile diameter will help to reduce the impact of tunnel excavation; the influence of the change of pile elastic modulus to pile additional axial force is very limited.At the end, this dissertation summarizes the risk management process, method, content and protective measures of tunnel construction and adjacent passive pile project. In order to reduce the additional responses of adjacent passive pile foundations from tunnel excavation, this dissertation proposes the following measures to help solve the problem: take preventive measures; cut off the influence source; take remedial measures, such as pile underpinning method, partition method and grouting method.