About the depression of the ground surface near the construction site of the Tokyo outer ring road (Kan-etsu-Tomei) [14th report]

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Regarding the ground surface depression that occurred near the construction site of the Tokyo Outer Ring Road (Kan-etsu-Tomei) main line tunnel (southbound), a new underground cavity was confirmed in the ground survey around the depression.

1. 1. place

Near 2-chome, Higashi Tsutsujigaoka, Chofu-shi, Tokyo

2. Cavity situation

The estimated size of the cavity is about 16m deep from the ground surface, about 4m wide x about 10m long, and about 4m thick.
(Attachment [PDF: 566KB] reference)

3. 3. Future response

With safety and security as our top priority, we explain this event to neighboring residents and take necessary measures.
In addition, experts have commented that due to the condition and size of the cavity, it does not immediately cause deformation on the ground surface and does not require urgent action, but it is desirable to fill the cavity early. ..
In response to this, we will take the following measures for the cavities confirmed this time.
-Promptly carry out filling work to the confirmed cavity.
・ We will continue to constantly observe the displacement of the ground surface. No abnormalities have been confirmed at this time.

We will continue to investigate and examine the mechanism of depression and cavity formation at an early stage, including the cavity confirmed this time.