完成後の盤ぶくれを防ぐ新たなインバートの抑制効果

Abstract

近年, 山岳トンネルにおいて完成後に盤ぶくれが発生し, 対策を実施した事例が報告されているが, 鉄道などの走行安全性を確保するためには, 盤ぶくれを未然に防ぐことは非常に重要である. しかし, 掘削時の地山状況から盤ぶくれがわずかでも懸念される地山に対して, 曲率が大きいインバートや鉄筋コンクリート構造のインバートを採用することは, 現実的ではない. 本研究では, これらの課題の解決をすべく新たに整備新幹線の山岳トンネルで採用されているインバート構造1)を対象に模型実験と数値解析を行い, 盤ぶくれの挙動を把握するとともに, 標準的なインバート構造と比較し盤ぶくれの抑制効果について検証を行った. その結果, 新たなインバート構造は施工性, 経済性は従来の構造と同程度でありながら, 盤ぶくれ抑制効果が向上することを確認した.

Recently, many cases have been reported in which mountain tunnels have been occurred floor heaving after completion and countermeasures were forced. In particular, since the floor heaving is a problem directly related to the running safety of the train, invert is the most important structure and it is difficult to permit large displacements resulting from floor heaving. However, it is not easy to adopt invert with a large curvature or reinforced concrete structure for all grounds where floor heaving is concerned from the ground condition during excavation from the viewpoint of workability and economy. For this reason, it has been desired to provide an invert structure which is relatively easy to construct, capable of flexibly coping with on-site and economical, and having a high effect of inhibiting the floor heaving. In this research, we performed a model experiment and numerical analysis on the new shape invert structure devised to solve these problems, grasp the behavior of it, compare it with the standard invert structure, verified the inhibitory effect.