ABSTRACT
NATM is generally applied to construct mountain tunnels. The method had made construction of tunnels easy and safe in case of rather bad geological condition and tunnels with large cross sectional area. In Japan, cross sections of road tunnels have been enlarged because of increasing traffics and spaces for sidewalks. Such large-scale tunnels are generally designed individually because their standard design techniques have not established yet. And locations and geological conditions of newly planned tunnels have become more difficult. Under such conditions, it is important to predict deformation behaviour of surrounding ground of large-scale tunnels especially in urban area to consider influences on environments such as ground settlements. Pre-support methods are usually applied to secure stability of cutting faces of tunnels in earth ground. Besides, especially in cases of tunnels with large cross section, it is needed to increase number of divided heading sections to keep ground deformation in very small level. In such cases, it is important to predict deformation behaviour of surrounding ground in each construction stages. Amanosan No.1 tunnel mentioned in this paper is a road tunnel with three lanes mainly in earth ground of sands and gravels. To ensure stability of the tunnel and control ground settlements,
the center diaphragm method was applied and many kinds of measurements were carried out during the construction. In this paper, behaviour of the large-scale tunnel with center diaphragm in earth ground and deformation of the surrounding ground are described, based on the measured data and results of 2D-FEM and 3D-FEM analyses. Besides, the practical control measurement method for such tunnels will be proposed based on above results, followed by demonstrating its applicability.
