JR Central finds damage in Shinagawa maglev tunnel machine; digging halted 6+ months
In short
JR Central said on October 8 that it had found damaged gears and bearings inside the shield tunnelling machine boring the Linear Chuo Shinkansen tunnel under Tokyo's Shinagawa ward, where digging stopped on July 29 after the machine made an abnormal noise. The company expects investigation and inspection to take at least six months, with a restart taking longer still. It said there was no impact on the surface and that the line's opening date will not be affected.
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JR Central said on October 8 that it had found damage in the large shield tunnelling machine boring the Linear Chuo Shinkansen tunnel under Shinagawa ward in Tokyo. Excavation has been halted, and the company expects detailed investigation and inspection to take at least six months, with a restart requiring a longer period still. JR Central said the surrounding environment, including the ground surface, had not been affected. [ 1 , 2 , 3 , 4 ]
According to JR Central, an abnormal noise came from inside the machine on July 29 while it was digging about 80 metres underground near Nishi-Shinagawa 1-chome, and work was stopped the same day for inspection. TBS reported that workers heard a "ga-ga-ga" noise from the machine. Damage was found in the gears and bearings that turn the roughly 14-metre-diameter cutter at the front of the machine. [ 1 , 2 , 4 ]
TBS reported that part of a gear linking the motor to the cutter was chipped and that bearings on other gears showed multiple areas of damage, found at 11 of the 19 points inspected. Because the inside of the machine is hard to examine and many points remain to be checked, completing the inspection will take at least six months, it reported. Asahi described a chipped metal gear and damage to a device that keeps rotation smooth, while Nikkei described the finding as a deformation in part of the machine. [ 2 , 3 , 4 ]
The site is the North Shinagawa section of the First Metropolitan Area Tunnel, which runs from near JR Shinagawa Station through Shinagawa and Ota wards towards the Tama River, Asahi reported. The section was scheduled to be finished by February 2030, and Asahi and Nikkei said that could be delayed. Nikkei reported that JR Central said it cannot yet foresee how long it will take to resume digging and has not given a revised completion date. Before resuming, the company plans investigation, inspection, repairs and briefings for local residents. [ 3 , 4 ]
JR Central said the halt will not affect the opening date of the line between Shinagawa and Nagoya. Nikkei reported that construction of the Shizuoka section of the Southern Alps Tunnel was approved in July but is expected to take more than ten years, and that JR Central expects the North Shinagawa section to be finished before it even with a delay. [ 2 , 4 ]
Shinagawa Ward Mayor Morisawa (森沢) asked JR Central on October 8 to establish the cause, prevent a recurrence and explain the situation carefully to residents, TBS reported. [ 2 ]
Why it matters
The halt could push back the North Shinagawa section, which was scheduled to be finished by February 2030, and JR Central has not given a new date. The company says the opening of the Shinagawa–Nagoya maglev will not slip because the Shizuoka section is expected to take longer. Shinagawa's ward mayor has asked JR Central to find the cause and explain it to residents.
Key facts
- JR Central announced on October 8 that damage was found in the shield tunnelling machine used for Linear Chuo Shinkansen tunnel work in Shinagawa ward, Tokyo. [ 1 , 2 , 3 , 4 ]
- Digging stopped on July 29 after an abnormal noise came from inside the machine. [ 1 , 4 ]
- Damage was found in gears and bearings that drive the cutter, which is about 14 metres in diameter. [ 1 , 2 , 3 ]
- TBS reported that bearing damage was found at 11 of the 19 points inspected so far. [ 2 ]
- Investigation and inspection are expected to take at least six months, and resuming work will take longer. [ 1 , 2 , 3 , 4 , 5 ]
- The site is the North Shinagawa section of the First Metropolitan Area Tunnel, scheduled for completion by February 2030. [ 3 , 4 ]
- JR Central said there was no impact on the surface or surrounding environment. [ 1 , 2 , 3 ]
- JR Central said the halt will not affect the line's opening date. [ 2 , 4 ]
Confirmed by several sources
- JR Central announced on October 8 that damage was found in the shield tunnelling machine for the Linear Chuo Shinkansen tunnel in Shinagawa ward. [ 1 , 2 , 3 , 4 ]
- Digging was stopped in July after an abnormal noise from the machine. [ 1 , 2 , 3 , 4 ]
- Damage was found in gears and bearings inside the machine. [ 1 , 2 , 3 ]
- Investigation and inspection will take at least six months, and resuming work will take longer. [ 1 , 2 , 3 , 4 , 5 ]
- JR Central said there was no impact on the surrounding environment or the ground surface. [ 1 , 2 , 3 ]
- JR Central said the opening date of the line will not be affected. [ 2 , 4 ]
- The North Shinagawa section's February 2030 completion schedule could be delayed. [ 3 , 4 ]
Still unclear
- When digging will resume and when the North Shinagawa section will be completed. Nikkei reported that JR Central cannot yet foresee the time to resumption and has not given a revised completion date.
- What caused the damage. The cause is still under investigation, which is expected to take at least six months.
- The full extent of the damage. TBS reported that many points inside the machine are still to be inspected; the figure of 11 damaged bearing points out of 19 comes from TBS alone.
- How the damage is described. Most outlets describe a chipped gear and damaged bearings, while Nikkei describes a deformation in part of the machine.
What local media are saying
Timeline, local time
- Tokyo Shimbun reports JR Central's announcement that damage was found in the Shinagawa shield machine and that inspection will take at least six months. [ 1 ]
- TBS NEWS DIG reports details of the gear and bearing damage and the Shinagawa mayor's request to JR Central. [ 2 ]
- Asahi Shimbun reports that the North Shinagawa section's February 2030 schedule may be extended. [ 3 ]
- Nikkei reports that JR Central cannot foresee when digging will resume but expects no change to the opening date. [ 4 ]
- Tokyo Shimbun reports that the halt at the North Shinagawa section is set to be prolonged. [ 5 ]