| 講演要旨(和文) | | 河川堤防へ統合物理探査を適用する場合，河川堤防と支持層が本来的に有する小スケールの不均質性に留意する必要がある．物理探査は平均的でかつ非ユニークな解を提供するので，地質学的・地質工学的モデルに基づいた合理的な解釈を加えることが重要である．土質ボーリングや原位置試験は局所的な物性情報しか提供せず，それらから全体を類推することはほとんど不可能であり，統合物理探査結果をそれに牽強付会することは適切ではない．それらについて事例を紹介し，統合物理探査の意義と方法を強調する． |
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| | 講演要旨(英文) | | Levee systems are inherently heterogeneous because they are characterized as manmade earthen structures. Underlying natural sediments are also heterogeneous in the scale of a hundred meters or shorter. Geotechnical or river engineers in Japan have divided their governing levees into segments of usually 200 m long and treated the internal structures of each segment as homogeneous. On the other hand, they have struggled to reconstruct structural conditions of levees from limited information obtained usually by visual inspection and spot geotechnical boring. It is fundamentally impossible to reconstruct a 2D or 3D structure from sparse, spot data. In contrast, geophysical techniques can provide spatially continuous profiles of physical properties of not only natural sediment layers but also artificial materials. Regretfully, the near surface geophysicists in Japan have had limited knowledge on levee systems. Accordingly, geotechnical engineers have often criticized to us that geophysical profiles were too complicated to understand and inconsistent with geotechnical information they had collected. It is crucial for the geophysicists to understand the heterogeneous structure in levee systems and to explain it properly to the geotechnical engineers. It is the key to widespread integrated geophysical investigation techniques for the safety assessment of levee systems. |
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