Kanto Development Bureau, East Japan Expressway Kanto Branch Office/Gaikan Expressway Oizumi JCT southbound main line shield, resumed excavation in November
Confirmation status of shield machine damage (from press release materials)
The Kanto Regional Development Bureau and the East Japan Expressway Company announced on November 21 that excavation of the Oizumi JCT Main Line Tunnel (south bound) on the Tokyo Outer Ring Road (Gaikan Expressway), which had been suspended, would resume on November 1. The tunnel was damaged in April when the shield machine came into contact with underground steel. I was investigating the cause and repairing the damaged machine. For the time being, drilling will be carried out within the Gaikan Expressway business area while taking measures to prevent recurrence and monitoring.
The machine touched part of the continuous underground wall that was installed for the purpose of stopping water. As a result of the investigation, it turned out that the hard urethane that the shield machine was supposed to penetrate was misaligned. A shaft was cut from the ground to the front of the machine to investigate and repair damage to the shield machine.
After excavating to the bottom end of the machine, a detailed investigation revealed that 109 out of 1062 bits were damaged. In addition, 7 stirring blades, 15 peripheral ring protection bits, and 35 backfill injection pipe protection bits were reportedly damaged.
With the removal of earth and sand from the chamber and the repair of damaged areas completed, it is expected that the excavated area will be backfilled and excavation resumed from November. As a measure to prevent recurrence, the same hard urethane underground wall was confirmed, and in other construction, the check system including design verification by designers and builders will be strengthened with the aim of improving quality.
