The Influnence Of Tunneling On Adjacent Group Piles Foundation

Urban traffic congestion has become an extremely thorny problem with the rapid development of rail transit. However, high-rise buildings with the pile foundations are all over the limited urban space. The tunnel excavation inevitably leads to the additional inner forces and additional deformation of foundation. Accordingly, the bearing capacity of the pile will be reduced, even be lost. Thus, the large settlement or turnover may appear for adjacent structures, which result in a great loss of people’s life and property. Thus, the study of influence of tunnel excavation on adjacent pile is urgent and valuable. In response to the problems and deficiencies of extant research, the three-dimensional numerical analysis was adopted in this paper. Basing on the elastic-perfectly plastic constitutive model and D-P criterion, a three-dimensional whole model of the shield tunnel and the group piles foundations was established. Then, the additional influence of shield tunneling on adjacent group piles foundations was investigated. The different cap types of group piles foundation, relative stiffness ratio and restrained condition were taken into account respectively.Many useful conclusions can be drawn. The law of additional influence of shield tunnel excavation on adjacent pile foundation with different cap types was nearly identical; the additional influence to the near piles is greater than the far piles. The law of additional inner forces and additional displacement is different obviously. For the piled-box foundation, the additional axial force of the near piles is larger while the vertical superimposed displacement is smaller. Meanwhile, the larger additional longitudinal bending moment can be seen to the near piles. As far as relative stiffness ratio is concerned, the additional displacement and the additional inner force of the pile are apparently different when the relative stiffness ratio is less than0.09. In addition, with the constraint condition of cap enhancing, the transverse and longitudinal additional displacement of the group piles foundation diminishes while additional inner force increases.The research results is expected to accurately predict the effects to the adjacent group piles foundation is hopefully to provide essential theoretical supports for the design and construction of rail transit.