周辺環境に配慮した住宅密集地直下でのトンネル施工: 国道185号休山トンネル（Ⅱ期線)長迫工区

摘要

広島県呉市中心部と阿賀•広地域を結ぶ「呉越峠」と呼ばれる区間は，道路勾配が急でカーブも多いことから交通事 故が多発し，朝夕のラッシュ時には交通渋滞が発生していた.こうした問題を解決するため，「一般国道185号休山新 道」事業により，平成14年にⅠ期線(暫定2車線)が開通したが，その後も渋滞や事故が多発していることから，4車線 化事業を進めている.今回の呉市中心部側から施工を行った休山改良休山トンネル長迫工事は，トンネル直上に市道や 住宅などが近接していることから，トンネル掘削に伴う地表面沈下や振動•騒音の影響を抑制することが課題であった.本稿ではこれらの周辺環境への影響抑制に向けて行った対策および結果を報告する. Tunnelling Directly Under a Dense Residential Area with Consideration to the Surrounding Environment-tne National Route 185， the Yasumiyama Tunnel (Second Phase) Nagasako Lot一%A section of the National Route 185 called Kuregoe pass that connects the heart ot Kure with Aga district and Hiro district, Hiroshima Prefecture has steep slopes and many curves, which results in many traffic accidents, and traffic jams during the morning and evening rush hours. To solve these problems, the first phase road (two-lane expressway ) of " the National Route 185 Yasumiyama new road" project was opened in 2002, but due to traffic jams and accidents occurring frequently afterwards, the four-lane project has been moved forward. At the construction sire of Nagasako lot in the Yasumiyama Tunnel project that was conducted from the side of central Kure, there are the municipal roads and private residences above the tunnel, so controlling the ground surface settlement and vibration and noise impact associated with the tunnel excavation were the challenges. In this document, we report the results and measures taken to control impact to the surrounding environment.