ABSTRACT
It is common to install pressurized water mains or heat supply pipes in tunnels. Highly pressurized pipes often leak through cracks or joints and may cause the tunnel to be pressurized. In this study a very special case of subsea tunnel collapse relating to internal pressure was investigated. It was found that the internal pressure of the tunnel was sufficiently high to cause the tensile failure of the segment lining joints, and probably caused the hydraulic fracturing at the surrounding soils. In this study the tunnel failure mechanism and hydraulic fracturing of surrounding ground was investigated. To identify the tunnel joint failure mechanism, back calculation using numerical structural analysis was carried out. The possibility of hydraulic fracturing was evaluated using theoretical method and small-scale model tests. It was found that the joints of the segment lining and the surrounding soils were relatively weak to resist internal pressure.
