In this report, the effective and economical design methods for reinforcing the shield tunnel of underground transmission cables in the case of the changes of external loads are described. First, the necessary of reinforcing were evaluated based the maximum of external load changes. Then, the soundness of a tunnel was evaluated by both site measurement of present external loads and structural calculation. The effective and economical design methods were studied by focusing on the concept of changing reinforcement specifications according to reinforcement duration, and considering the measurement method of external loads. The reinforcement range and interval in the longitudinal direction of a tunnel were designed based on the results of site measurement. Moreover, the simple load test on an existing tunnel was conducted for investigating the mechanism of a tunnel and improving the accuracy of the design methods and structural calculation methods.

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 A cast-in-place lining method had been applied for a Shinkansen double track tunnel in mountain area with diluvial soil. A cast-in-place lining was cons tructed as a stable stru cture without remarkable deformations but we found some cracks on the lining which had a specific inclination to tunnel direction and occurred regularly. Cracks and water leakages were admitted on this site, but the control of cracks and leakages is important to apply a cast-in place me thod to more constructio n sites. So, this study compared distribution of cracks to various data and analyzed influence of construction factor. Furthermore we assumed a mechanism of crack s and confirmed it by numerical analysis.

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 The grouting materials based on cement and sodium silicate were grouted in Seikan undersea tunnel. The grouting materials were developed to overcome the special condition to be located in the 240m bottom from the sea level. In this paper, fundamental properties of the grouting materials are explained. In addition, long-term properties of the grouting materials are discussed by the results of long-term measurement and chemical analysis of the specimen taken by investigation in the tunnel.
 By these experimental results, it is concluded that the hardened grouting materials in Seikan undersea tunnel have secured stable quality for a long term.

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 In this report, the methods of management and maintenance of the shield tunnel for underground transmission cables were studied. These studies are based on the Performance-Based Design concept, and focused on the load bearing capacity of a tunnel. First, the maintenance cycle were reviewed for improving efficiency and effectiveness by considering the present inspection period and the soundness of a tunnel. For reviewing the maintenance cycle, the changes of load bearing capacity due to the changes of external loads and soundness caused by aged deterioration of segmental joints, and the criteria and the standardization of inspection results were investigated. Moreover, the corrosion speed and the fastening force of a segmental joint were inspected. The changes of external loads were assumed and used them for evaluating the load bearing capacity of a tunnel. The standard of an inspection was also reviewed based on the standards of deterioration materials, and the load bearing capacity obtained by structural calculation. Based on results of all investigation, the rational management and maintenance methods of a shield tunnel and the applying methods for existing tunnels are proposed.

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 There is no quantitative method which can explain the deformation behavior and suffering mechanism of mountain tunnels upon earthquake, consequently an earthquake-proof design method has not been established yet.
 We carried out field measurements of the seismic behavior at an in-situ tunnel. As a result, it is cleared that shear deformation is dominant in shallow mountain tunnels under earthquake conditions. In addition, model tests and numerical analysis considered shear deformation behavior were executed to clarify the mechanisms of earthquake damage. Based on the above-mentioned results, we suggested the earthquake-proof design method of shallow mountain tunnels.

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