The Ginza Line subway tunnel was opened for service in 1927. A large amount of data on various deterioration indices was acquired. This report describes the results of the diagnoses by utilizing these data. The results of the visual inspection, strength test, and structural analysis indicated the tunnel proved highly satisfactory in terms of load bearing capacity. As regards the durability, the tunnel was almost free of progressive corrosion because of limited water supply if there was no water leakage. Our projection of the progress of deterioration confirmed that there was no possibility of reinforcement corrosion and resultant cracks even 140 years later. Maintenance and repair work, including leak repair and recovery patching, will be implemented for those sections around water-leaking locations where the water content was high and thus the possibility of corrosion was high. We think that it is extremely significant that the maintenance and repair policy could be clearly defined on the basis of quantitative evaluation by acquiring deterioration index data.
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