12か所•計34枚の残置鋼矢板を泥水式シールドで直接切削: 四日市市　東町•吉崎南雨水幹線

摘要

四日市市の東町•吉崎南雨水幹線管渠布設工事では，シールドの通過部に12か所•34枚の鋼矢板が支障することが判明した.この残置鋼矢板を泥水式シールド工法で撤去するために，シールドのカツタビットによる直接切削工法を用いることとした.シールドには，鋼矢板切削ビット，円錐型ヵッタ，微速掘進機能，カツタの高速回転機能を装備し，残置鋼矢板の周辺地盤は薬液注入により鋼矢板を固定した.実施工においては，切羽圧力，排土量および泥水品質などを厳格に管理するとともに，振動計測など近隣に配慮したシールド掘進，鋼矢板切削を実施した.その結果，近隣に影響を及ぼすことなく，所定の工期を遵守して中間立坑に到達し，カッタビットなどに今後の掘進に支障がないことが確認された.本稿はこれらの残置鋼矢板の直接切削に関する施工報告である.%In the construction of the Higashi-cho/Yoshizaki Minami rainwater trunk line, it was discovered that 34 steel sheet piles were left behind in 12 locations that were obstacles in the passage of the shield. We planed to directly cut these steel sheet piles with cutter bits of the Slurry Shield TBM.We equipped the shield with steel sheet pile cutting bits, conical cutters, a very slow speed excavation function and a high-speed rotation function of cutters and grounds surrounding the steel sheet piles were injected with chemical grout to fasten the piles to ground. During the construction, along with strict control of face pressure, the amount of tunnel muck and the quality of slurry, shield excavation and steel sheet pipe cutting were conducted taking the neighborhood into consideration such as measuring vibration, etc. As a result, the shield arrived at the intermediate shaft within the prescribed construction schedule without any effects on the neighborhood and it was confirmed no trouble of such as cutter bits that would affect future excavation. This report gives construction information on the cutting the left steel sheet piles.