Full-face tunnel excavation has been increasingly employed for SEM (sequential excavated method) tunneling by the virtue of enhanced capacity of roadheaders as well as the ground control effect of early ring closure. As the stability of the tunnel face is essential to full-face tunnel excavation, the tunnel stabilizing method utilizing curved tunnel faces, which would naturally form as part of the tunnel excavation sequences, can be considered effective. This paper addresses an investigation into the characteristics of the shape of curved tunnel face employing numerical models, and the stabilizing effect of tunnel face reinforcing methods, such as shotcrete on tunnel face, using physical models. Further, the constructability and stability of curved tunnel face were verified through trial excavations at an actual tunneling site. As a result it is confirmed that curved tunnel faces are advantageous and the stability of the tunnel face can be improved by a simple reinforcing method such as shotcrete on tunnel face. The trial excavations undertaken have proved the favorable constructability and stability of curved tunnel face. In addition, a conceptual approach to selection of the shape of curve tunnel face and its stabilization behavior is suggested together with a concept of tunnel face stabilizing method proposed.

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 This paper describes experimental and numerical studies on the influence of the earth pressure of side wall and seismically isolation effect of under ground box-culvert by installing “shear stress reducer” on the top slab. Under ground structures are designed to improve deformation and toughness performance of the structure against seismic force. On the other hand recently technology to reduce seismic force acting on the under ground structure is proposed. This paper proposes an idea for the improvement of seismic performance of box-culvert. The idea is to reduce shear stress acting on the top slab by installing “shear stress reducer” between soil and the top slab. Low friction sheet and soft material were adopted as the shear stress reducer. Shaking table test using scaled models in soil box and the nonlinear numerical simulations of the test results by FEM were carried out. As a result, the shear deformation of the box-culvert with the shear stress reducer decreased due to the reduction of the shear stress acting on the top slab. From the results of the experimental and numerical studies the mechanism of reduction of the shear deformation was made clear.

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 This paper investigates the influence of opening at side wall on the members of existent cut-and-cover tunnels by means of 3D FEM. The calculation results obtained by 3D FEM was compared with those by 2D frame analysis under the condition that there is no opening at side wall. The influence of opening was investigated based on 3D FEM. The calculation results revealed the change of sectional forces near the opening and the influence of opening width on the values of sectional force. The applicability of conventional methods with 2D frame analysis and 2-direction slab method was also investigated by comparing with the results of 3D FEM.

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 In this paper, we have clarified the relationship between aging of subway cut-and-cover tunnels and rate of cracking that is caused by carbonation or chloride attack. First, field data analyses were carried out to characterize the material deterioration in the tunnels. Next, laboratory experiments were conducted to introduce a method of estimating the amount of corrosion products and the resulting expansion coefficient at the onset of cracking around a round steel. Finally, based on these findings, the statistical prediction method for material deteriorations was proposed and its usage in conjunction with numerical analyses was demonstrated. The proposed method is expected to be utilized for maintenance planning of tunnels, many of which were constructed about 40 years ago.

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 Deep underground tunnels should be designed with some surcharge in consideration of the building load of overlying structures such as skyscrapers. However, current design methods do not consider the concept of load share between the ground and the tunnel. Therefore, tunnel linings need to be designed such that they have high rigidity and bearing force. To overcome this problem, in this study, we conducted centrifuge model tests to clarify the load share mechanism in consideration of tunnel flexibility, ground elasticity, and boundary conditions between the tunnel and the ground. In a rigid tunnel, the surcharge was supported by the tunnel, whereas that in a flexible tunnel was supported by the ground. As a result, the cross-sectional forces of the flexible tunnel were smaller than those of the rigid tunnel. This finding indicates the importance of introducing the load share concept in the model used for calculating the surcharge. A 2D theoretical model that considers the elasticity of the tunnel and the ground was studied for calculating the surcharge. The experimental and FEM analysis results confirmed its applicability to elastic ground such as soft rock but not to soft ground lacking tension strength.

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