| 講演要旨(和文) | | 昨夏に出水被害の発生した千曲川右岸57km付近の堤防において,ランドストリーマー表面波探査と牽引型比抵抗探査を組み合わせた統合物理探査を実施した.測線長は約3kmで,堤体内部および支持層のイメージングとアノマリの検出,出水被害の解釈,作業性の確認を目的とした.探査の結果,堤体と下位の支持層とを明瞭に識別できた.また堤体および支持層の一部に高比抵抗・中S波速度のアノマリが認められた.アノマリの出現位置は,出水被害発生箇所ともよく対応していた.このことは,統合物理探査によって堤防の浸透安全性を効率的に評価できることを示している. |
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| | 講演要旨(英文) | | Vulnerability assessment of levee has been fundamentally based on visual inspection and compiled information about the levee and underlying layers. Generally, the complied data does not include detailed information on the levee body materials or the underlying layers. PWRI started a research and development project on the integrated geophysical methods to assess the vulnerability of levees and their foundations. The objective of this research is to find the effective survey methods and spread them to the actual levee assessment. A field survey was conducted along a 3 km stretch of the levee of the Chikuma River, Nagano Prefecture. The purpose of the investigation was to detect anomalies inside the levee body and the underlying layers, and to correlate them with actual incidents observed there at the high water event last summer. The geophysical techniques applied to the survey consisted of capacitively coupled resistivity (OhmMapper) and surface wave method using Land Streamer. In addition supplementary DC resistivity measurement was conducted partly along the levee. The integrated survey successfully delineated the anomalies inside the levee body and the underlying layers, and the mode of occurrence of the anomalies was concordant with the high water incidents. |
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