電気防食を適用した地中送電洞道の劣化対策事例

摘要

都心への電力供給の要である地中送電洞道（M洞道）は，1973年に竣工した現場打ちボックス力ルバートである.経年劣化ト漏水による内部跌筋の腐食に伴い，コンクリートの劣化(浮き，剝離.剝落）が著しく，補修が必要ト判断された,劣化機構を特定して顕在化した部位を復旧したのち，今後の内部鉄筋の腐食を確実に防止して洞道の耐久性を確保する目的から，初めて外部電源方式の電気防食工法を実施した.本稿では，この補修設計時の検討内容ト施工概要を報告する.%A power transmission tunnel(M tunnel) that is central to electricity supply to the city core is in-situ RC box tunnel built in 1973. Concrete of M tunnel was judged that its deterioration (expanded crack, spalling) was considerable due to time-related deterioration and corrosion of rebar by leakage and that repair was required. After specifying deterioration mechanisms and repairing degraded spots, with the aim of guaranteeing cable tunnel durability we first installed cathodic protection system using an external power supply in the M tunnel to reliably prevent future corrosion of internal rebar. This is a report of items considered in maintenance design and of the construction outline.