T－EAGLE®杭の超高層建物における施工事例
当社は，近年増加している超高層建物や長スパン建物などで生じうる大きな常時荷重，引抜き荷重に対応するため，場所打ち杭の先端と中間部に最大径5.5mの拡大部を設けて高支持力化を図る大口径多段拡大場所打ちコンクリート杭工法「T－EAGLE杭工法」を開発し，適用を進めている。今回，都内の超高層案件において，高軸力が作用する柱位置での沈下抑止を目的に，T－EAGLE杭（軸部径3.0m，拡大部径5.3m，杭長30m）が採用される運びとなった。杭の施工にあたっては，杭の鉛直支持性能や施工精度を確保するために工夫を加えた施工手順を計画した。その結果，鉛直支持性能に寄与する支持層管理や安定的な拡大部の掘削を確実に実施することができた。また，掘削後の超音波孔壁測定では所定の形状を満足する掘削形状が得られていることを確認した。
キーワード：場所打ち杭，多段拡大杭，逆打ち工法，施工手順，施工精度
＊１ 技術センター 都市基盤技術研究部 構造研究室
＊２ 設計本部 構造設計第一部
＊３ 建築本部 技術部
＊４ システム計測（株）
Practical Case of Constructing "T-EAGLE" Pile in Super High-rise Building
Large-diameter multi-belled cast-in-place concrete piling method T-EAGLE has been developed, and its application is being aggressively promoted. A pile made by this method has a bell with a maximum diameter of 5.5m at its midpoint and bottom so as to provide greater bearing capacity and resist large constant loads and pull-out loads that can occur in super high-rise buildings or long-span buildings that are recently increasing in number. A T-EAGLE pile (shaft diameter of 3.0 m, bell diameter of 5.3 m, and a length of 30 m) is adopted in a super high-rise building construction project in Tokyo to prevent settlement of the column area on which high axial force acts. Prior to piling, the construction procedure designed to ensure the vertical bearing capacity of piles and pile installation tolerance was developed. This led to the successful management of the bearing layer, which helps achieve the appropriate vertical bearing capacity, and to the stable excavation for enlarged parts. Supersonic hole wall measurement after excavation confirmed that the excavation shape that satisfies the predetermined shape was obtained.
Keywords: cast-in-place pile, multi-belled pile, top-down construction method, construction procedure, construction accuracy
*1 Structure Research Section, Urban Engineering Research Department, Taisei Advanced Center of Technology
*2 Structural Engineering Department I, Design Division
*3 Technology Control Department, Building Construction Division
*4 System Measure Co., Ltd.