| 講演要旨(和文) | | 大規模土石流に直撃されたコンクリート製砂防堰堤が，一部損壊・流出し，さらに打設面で分離し堤体表面に変位が発生するという事故が発生した．堤体内に生じた亀裂の位置と連続性は，当該砂防堰堤の損壊メカニズムの解明の重要な手掛かりとなるとともに，今後の復旧対策，新設堰堤の安全設計にも有用な基本情報である．物理探査は非破壊でかつ面的に内部亀裂分布をイメージングすることが可能な手法として適用が期待されている．本発表では加速度センサアレイを用いた高周波弾性波探査の適用結果として，散乱波マイグレーション処理により亀裂をイメージングした結果を紹介する． |
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| | 講演要旨(英文) | | On July 9, 2014, Nashi-zawa Sabo Dam was damaged by a huge debris flow. It swept away the upper part of the left bank dam body, and caused distinct dislocation of the body particularly at the lower part of the left bank. It is essential to delineate the distribution of internal fractures for the deep understanding of collapsed process. However, visual inspection only provides surface information. Whereas geophysical surveying has been rarely applied to the investigation of sabo dams, it might play an important role for the identification of the internal fractures. Therefore we tested high-resolution seismic survey using piezoelectric type accelerometers. Prestack kirchhoff time migration was adopted to enhance reflected and diffracted events recorded in the obtained data. As a result, clear events indicating internal fractures were clearly reconstructed. Additional data processing is needful to improve the spatial resolution of fractures inside the dam body. |
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