Application of Under-pinning Pipe Jacking on Tunnel Auxiliary Construction

When a new structure is constructed in an overcrowded underground space, it is necessary to consider how to reduce the impact of the new structure on the surrounding existing structures and the surrounding ground, and one of the methods is the under-pinning method using pipe jacking. The under-pinning method is a general term for the method to reinforce the lower part of an existing structure with piles and pipes in advance to reduce the impact of new construction on the existing structure and surrounding ground. In this study, various numerical analyses were carried out assuming that the under-pinning method using pipe jacking was applied to the case where a new structure was to be installed underneath the existing structure. As a result of comparison with the under-pinning method, it was clarified that the under-pinning method with pipe jacking suppressed the influence on the existing structure and the surrounding ground by supporting the overburden pressure above the pipe over a wide area. In addition, it was found that the combination of the under-pinning method with the pipe-roof method, in which pipes are placed on top of the new structure, is more effective to suppress the deformation of the surrounding ground around the new structure than the under-pinning method alone.