河川•都市施設と都市高速道路トンネルの一体整備: 阪神高速道路2号淀川左岸線 正蓮寺川トンネルー

摘要

About 80% of Phase 1 of Hanshin Expressway Route 2 Yodogawa-Sagan Line is cut-and-cover tunnels and the tunnel on 2.4km-section of this line was built at place where the ShorenJi-gawa of the 1st Class River that was relocated underground once exited. Problems of this relocating works was treatment methods for the thick sediment of the river. The in-situ solidification improvement method with cement-type solidification material executed previously emitted a strong odor during the following excavation works. After reviewing this method a different method was employed that dehydrate and solidify sediment with an ultra-high pressure filter press that are pressure-fed to the on-site plant after dredging. In addition, part of the sediment was polluted with PCB, etc. We proceeded with works such as sealing the treated soil while monitoring the environment taking the conservation of the surrounding environment into consideration. We also tried various measures in design and construction for building cut-and-cover tunnels. This report contains an overview of expressway tunnel construction using river space in an urban area.%大阪都市再生環状道路の一翼を担う，阪神高速2号淀川左岸線1期区間(約4.3km)は開削トンネル構造が8割を占め，そのうち2.4kmは1級河川正蓮寺川を陸地化したあとにトンネルを構築した.この陸地化工事では厚く堆積していた底質の処理方法が課題となった.先行して行ったセメント系固化材による原位置固化改良工法では，のちの掘削工事で強い臭気を放ったことから，工法の見直しを行い，底質を浚渫して現地プラントに圧送し超高圧フィルタープレスで脱水固化を行う方法を採用して対応した.また，底質の一部はPCBなどで汚染されていたため，環境監視を行いながら処理土の封込めを行うなど，周辺の環境保全に配慮して施工を進めるとともに，開削トンネルの構築にあたって設計•施工上の工夫を行った.本稿は，都市部の河川空間を活用して建設した高速道路トンネル工事の概要を述べる.