2006 年 46 巻 2 号 p. 189-207
Two-dimensional (2D) and three-dimensional (3D) model tests of tunnel excavation with nearby existing foundation are carried out to investigate the influence of the existing foundation due to the interaction between ground and the existing structures. Three types of foundations: flat foundation, group-pile foundation and piled raft are considered. 2D and 3D finite element analyses using subloading tij model are also conducted. The deformation mechanism and distribution of earth pressure during tunnel excavation in the ground with nearby foundation are found to be different from those of green field condition. Surface settlement trough due to tunnel excavation in the ground with existing foundation does not follow the usual pattern of a Gaussian distributive curve, which can be observed in the case of green field. Especially, in the case of pile foundation, Dp, the distance between pile tip and tunnel is an important factor for the ground deformation and surface settlement. For a short distance Dp, although the length of pile is long, the ground deformation is concentrated at a place near the front pile and the rotation of foundation becomes larger. The maximum surface settlement in the case of existing foundation is also larger than those in the case of green field. Due to the existing foundation, unsymmetrical distributions of earth pressure occurred at the bottom of the ground due to tunnel excavation, both in model tests and numerical analyses. The earth pressure at the crown of tunnel in the case of existing foundation is almost the same as those in the case of green field. The arching at the shoulder of tunnel in the case of existing foundation, however, is much larger than those in the case of green field due to the dead load exerted on the foundation. The numerical results agree well with the results of the model tests.
