運用中のダム直下で地下発電所を建設: 中部電力 徳山水力発電所

摘要

Chubu Electric Power's Tokuyama Hydro-Electric Power Station was planned after Chubu Electric Power participated in the Tokuyama Dam construction project by the Japan Water Agency in order to operate as power business. The construction of the power station was executed adjacent to the facilities of Tokuyama Dam in operation. In order to objectively evaluate the effects on existing structures, a third-party construction council (the chairman: Takaji Kokusyo, a professor of the Chuo University) was set up and construction was conducted with ICT system. Traditionally, detailed data on geological condition, etc. for underground power station construction is gathered through investigation drifts but in-situ tests were conducted at the time of excavation for underground power station to re-evaluate support design because it was not possible to secure a survey period due to changes of the power business plans. In addition, it is an underground power station works without working adits so that shaft of decharge channel was effectively utilized digging downward in order to reduce cycle time for efficient construction.%徳山水力発電所は，(独)水資源機構による多目的ダムである徳山ダム建設事業に，中部電力(株)がのちに発電参加して計画されたものである.発電設備の建設は運用中の徳山ダム本体をはじめ貯水池などのダム構造物に対し近接施工となる.そのため既設構造物への影響を客観的に評価するため第三者からなる工事検討会(委員長：國生剛治•中央大学教授)を設置し，情報化施工とあわせ，工事を進めた.従来，地下発電所建設においては調査横坑にて地質などの詳細データを収集するが，発電事業計画の変更により調査期間も確保できなかったことから，地下発電所掘削段階で原位置試験を行い，支保設計などを再評価した.また，取付け横坑がない地下発電所であり，盤下げ掘削時にはサイクルタイム短縮のため放水路調圧水槽用の立坑を有効に活用し効率的に施工した.