Experimental test on communication cable tunnel constructed by shield tunneling method for maintenance

Cable tunnels for communication are mostly constructed by the primary lining of steel segment and the secondary lining of concrete. Some leakage can be found from the primary lining of the tunnels constructed before 25 years. The secondary lining is loaded by water force due to the leakage where there is a cavity between the primary lining and the secondary lining. The secondary lining is made of concrete, because it is assumed that the secondary lining is loaded only by gravity during designing some cable tunnels in Japan. It is essential to evaluate the health of secondary lining due to the leakage of primary lining. In this paper, the two prototype cable tunnel models were used and the cavities between the primary lining and the secondary lining were man-made. The models were tested by loading the water pressure in the cavities and the strains of central section of secondary lining were recorded. The models were analyzed by using three dimensional finite element method and the results were compared with the experimental values. The behavior of secondary lining and the adaptability of numerical models to the specimen were discussed.