Tunnel lining concrete is generally placed by a concrete pumping method. Since this method fills concrete while pumping, material segregation and poor compaction are easily to occur. This may lead to quality deterioration such as floating and spalling. In this study, core samples of lining concrete were collected from a road tunnel that had reached the end of its service life and examined focusing on cracks at the joint parts of the lining concrete spans and gradation of coarse aggregate as an index of material segregation. As a result, it was confirmed that quality of the concrete deteriorated. For improving that, volcanic glass powder using as a concrete additive in order to increase resistance to material segregation and improve quality of the lining concrete was proposed, and its effectiveness was verified through the model construction test and the actual construction test. As a result of the verification, it was confirmed that volcanic glass powder contributed to spreading coarse aggregate sufficiently to the joint parts of the lining concrete spans and improved quality of the lining concrete surfaces.

 In this study, a new granular distinct element method was developed to model excavation by releasing stress. The outline of the analysis method was described, and the validity of the analysis method was evaluated for ground behavior and collapse earth pressure by comparison with the stress boundary type model test. From this, it was found that this method is useful for evaluating the discontinuous behavior peculiar to sandy ground and the earth pressure at the time of tunnel collapse. In addition, the analysis was expanded to release the initial ground stress considering the tunnel section’s own weight and the static earth pressure coefficient, and the results were described. In the analysis and model experiments, the tunnel collapse earth pressure was compared with the Terzaghi’s loosening earth pressure, and the relationship with the deformation behavior was discussed.

 In recent years, cases of new or reinstalled inverts in mountain tunnels have been reported in many areas due to the occurrence of in-service ground heaving. It is assumed that the number of such cases will increase in the future, and the authors have been studying the rationalization of reinforcement measures. In this study, new invert shapes were assumed with work-saving construction in mind, and model experiment were conducted on a 1/100 of a full-scale tunnel, in which loads were applied vertically and horizontally assuming external forces, to verify the feasibility of the new invert shapes as a tunnel structure. The results showed that, although the shapes proposed in this study are not as good as the conventional inverted arch, it can be expected to have a certain degree of reinforcement effect. The validity of the experimental results was verified by reproducing the model experiments by numerical analysis, and the influence of the change in invert shape on the tunnel structure was discussed in terms of the tendency of stress generation.

 At coastal areas, there exist most of the shield tunnels for power transmission line, whose reinforcing bars are going to be suffered with corrosion by chloride ion attack. To plan rational maintenance countermeasure of such shield tunnels, the method to predict the start of chloride ion attack is needed. By the occurrence of water leakage and salt concentration in these tunnels, the chloride ion concentration on the concrete surface increases due to the heat generated by transmission lines. In this study, we discussed the chloride ion concentration on the surface of the concrete, and estimated increasing rate in the chloride ion concentration on the concrete surface. Then, a method for predicting the start of chloride ion attack were devised in the case of that the chloride ion concentration on the concrete surface increases.

 In a situation where social attention is focusing on a sinkhole caused by tunnel construction works, we constructed the TBM tunnel with high advance rate in a highly collapsible sandy ground. In this construction, we adopted the Dual Mode TBM which is a combined Slurry & EPB type TBM that can be switched to either of the mode as needed, to achieve both the TBM face pressure stability and high-speed construction. However, an appropriate index for switching between two modes has not been established. Therefore, in this construction, we controlled the TBM parameters based on the provisional indicators, analyzed the data obtained from the construction results, and carried out the construction by reflecting it to the subsequent construction. In this paper, we have implemented a series of countermeasures for the Dual Mode TBM to achieve both face stability and high-speed construction and proposed an excavation management index.