In recent years, the underground space has overcrowded with the overcrowding of urban areas. Therefore, the adjacent construction of underground structures is increasing. In such a construction, an influence of the construction of a new structure on the existing structure has to be considered. In order to minimize the influence on such existing structures, application of the underpinning method is expected. The underpinning method is a construction method that attempts to reduce the influence on the existing structures by excavating the ground around existing structures with constructing, rebuilding, and reinforcing new foundations. This study focuses on the underpinning method using pipe jacking. In order to ensure the effectiveness of the underpinning method, 3D finite element analysis was carried out. In particular, four major considerable factors were discussed: the influence of pipe presence, comparison of using conventional underpinning and pipe jacking, the influence of the distance between the pipes and new structure, the influence of pipe length. Based on the numerical results, it is possible to reduce the vertical displacement on the existing structure by using the underpinning method using pipe jacking. Additionally, the underpinning method using pipe jacking is effective to reduce the displacement over a wide range compared with the conventional underpinning method. Furthermore, the influence on the existing structure and the surrounding ground can be minimized by adopting the proper distance of pipe length and the space between the pipes and the new structure.

1. Introduction

In recent years, overcrowding has occurred due to the factors such as population increase in urban areas. Various structures are complicated in the underground space and the underground space is overcrowded along with the overcrowding of urban areas. Therefore, adjacent constructions of underground structures are increasing in the underground space of urban areas. Adjacent construction of the underground structure is the construction such as adding an underground tunnel to the surroundings of the drainage pipeline. In adjoining constructions of such underground structures, it is a problem that the influence on existing structures becomes particularly large when constructing new structures. Application of the underpinning method is expected as a construction method to reduce the influence on existing structures. Recently construction methods such as cutting edge jacking method, and shielding method are mainly applied when constructing an underground structure. (Matsumoto et al., 2015) These construction methods are required to occupy a wide range of construction area, long construction period and high cost, so it is difficult to apply those construction methods in urban areas. Therefore, pipe jacking method which is non-cutting technique is required as an effective construction method in urban areas (Japan Tunneling Association, 1997). For the above reasons, construction of the underpinning method using the pipe jacking method is expected for adjoining construction of underground structure.

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