Keisuke Shimamoto

BASIC STUDY ON THE FLOOR HEAVE AND ITS COUNTERMEASURES OF THE MOUNTAIN TUNNELS

Some mountain tunnels suffer from floor heave after completion, and some of them require countermeasures. This phenomenon occurs if there are no big deformation during construction, therefore, under existing circumstances, based on preliminary survey and condition of excavation, to predict the floor heave deformation after completion is difficult. In this study, to help the improvement of the prediction accuracy, first, construction data of Shinkansen tunnels suffered from floor heave were analyzed, so that the concernment between deterioration of ground by water and floor heave was confirmed. Second, make the model ground using the rock of actual tunnel, and recreate the floor heave by adding the water to model ground. Finally, tunnel excavation and floor heave after construction are consistently modeled in the numerical analysis. As the result, the effect of early closure and invert shape for floor heave were confirmed. 山岳トンネルにおいて，完成後しばらくして盤ぶくれが発生し，対策が必要となることがある．この現象は施工時に大きな変状のなかったトンネルでも発生しており，事前調査や掘削時の状況から，完成後の盤ぶくれを予測することは難しいのが現状である．本研究ではその予測精度向上の一助とすべく，まず盤ぶくれの発生した新幹線トンネルの施工データを整理，分析した．その結果，地山の吸水劣化が盤ぶくれに関係することを確認した．続いて，実トンネルの岩石試料で模擬地山を作成し，加水により強度低下させ盤ぶくれ現象を再現した．さらに，トンネル掘削から完成後の盤ぶくれ発生までを対象とした数値解析を実施し，早期閉合やインバート形状が施工時および完成後のトンネル底盤部に与える影響を検討した．