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発表 高周波弾性波探査による土石流被災砂防ダム堤体内構造のイメージング

作成年度 2019 年度
論文名 高周波弾性波探査による土石流被災砂防ダム堤体内構造のイメージング
論文名(和訳)
論文副題
発表会 第140回物理探査学会学術講演会
誌名 第140回物理探査学会学術講演会
巻・号・回 140 
発表年月日 2019/06/03 ~ 2019/06/05
所属研究室/機関名 著者名(英名)
土木研究所稲崎 富士
土木研究所木佐貫 寛
土木研究所小河原 敬徳
土木研究所清水 武志
土木研究所藤村 直樹
抄録
High-resolution seismic reflection measurements were conducted repeatedly on the rear wall of a sabo dam, which had been damaged by a huge debris flow occurred on July 9th 2014. The debris flow attack caused distinct dislocation of the body particularly at the lower part of the left bank. To image the internal structure in the concrete dam body by seismic methods, we employed piezoelectric type accelerometers instead of geophones, because high-frequency range measurements were indispensable for obtaining high-resolution spatial data. High-speed and high-resolution recording systems were also used too. Repair work had started in the fall of 2015 enabled us to deploy survey lines at higher levels on the wall and to conduct stepwise measurements. Manual hit by a rock hammer was effective to generate high-frequency signals. 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 and frontal face of the dam body were clearly delineated. Distinct attenuation of first breaks were also useful for fracture characterization. The measurements demonstrated the importance of choosing suitable measurement tools and setting appropriate survey parameters.
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