[JP] JR Central Completes Exploratory Tunneling in Onoji Section Amid Safety Concerns

[Miss Maglev]

東京・町田のリニア調査掘進終わる　昨年10月に気泡出た小野路工区　JR東海「その後は異常なかった」
JR Central Completes Exploratory Tunneling in Onoji Section Amid Safety Concerns

On April 18, Central Japan Railway Company (JR Central) announced the completion of exploratory tunneling in the Onoji section of the Linear Chuo Shinkansen project, located in Machida, Tokyo. Excavation had commenced in July 2023, but operations were suspended in October following an incident in which water and air bubbles emerged in the garden of a residence located directly above the tunnel site. Tunneling resumed in January 2024 after a temporary halt for safety assessments. According to JR Central, no further surface anomalies were detected during continued monitoring.

The Onoji section is part of the project’s first Metropolitan Area Tunnel, spanning approximately 37 kilometers between Shinagawa (Minato Ward, Tokyo) and Kanagawa Prefecture (provisionally Sagamihara City). Approximately 33 kilometers of this stretch, including the Onoji section, is situated in "ultra-deep underground" zones, more than 40 meters below the surface. Under Japanese law, landowner consent is not required for such deep underground construction, as it is presumed to have minimal surface impact. Nonetheless, the 2023 bubble and water eruption incident has heightened public concern among local residents.

Originally, 5 kilometers of the Onoji section’s planned 12-kilometer length were scheduled to be completed by March 2024. However, as of the end of the exploratory phase, only 321 meters had been excavated, indicating significant delays. JR Central plans to release data on ground stability to local residents in upcoming informational sessions and aims to begin full-scale tunneling in autumn 2025.

This development recalls a similar case in Chofu, Tokyo, where in October 2020, a deep-underground tunnel project for the Tokyo Outer Ring Road led to surface subsidence and underground cavities, prompting suspension of work. Public distrust regarding the environmental and structural impact of such projects continues to pose a major challenge for Japan’s high-speed rail expansion.

Info based on https://www.tokyo-np.co.jp/article/399531 Accessed 2025-04-18