| 講演要旨(和文) | | 河川堤防に対する統合物理探査の適用結果を検証することを目的として，堤防開削予定箇所において開削前に統合物理探査を実施し，開削後に堤体内部構造を調査するとともに開削面において比抵抗およびS波速度測定を系統的に実施してきている．このうち比抵抗測定には小間隔ウェンナー電極アレイを用いた．またS波速度は高周波表面波探査データから求めた．得られた物性値を，開削面から直接採取した試料に対する土質特性と比較検討した．その結果比抵抗値が粒度特性と良い相関を有すること，一方S波速度との相関は低く，逆にそれから締固め度を推定可能であることがわかった． |
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| | 講演要旨(英文) | | In-situ detailed geophysical measurements and laboratory geotechnical analysis have been systematically conducted at excavated sites as for the ground truthing or the verification of the result of integrated geophysical surveying conducted on levee systems before excavation. Resistivity mapping on dense grid points and high-frequency surface wave surveying along short lines set on the excavated surfaces were the major geophysical techniques in the field. A 10 cm spacing Wenner type electrode array was used to estimate the apparent resistivities at the points assuming half-space homogeneous structure. S-wave velocities at the corresponding points were calculated by averaging values for surficial 40 cm portion along the line. The laboratory geotechnical analyses consisted of specific grain size characteristics (D20 and Fc), and water contents. Dataset more than 500 pairs of the field and laboratory data were correlated with each other to clarify the relationship between them. A clear relationship was identified between resistivity and the specific grain size characteristics whereas the water contents varied and the specimens were unsaturated. In contrast, S-wave velocities showed a low relationship with the laboratory data, presumed to be influenced of loosening by excavation. |
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