| 講演要旨(和文) | | 河川堤防の堤体の基礎地盤と土質を、表面波探査と電気探査から得られたS波速度と比抵抗のクロスプロットから、統計的に求めることを試みた。用いた物理探査の測線長は37の河川堤防で計600�勸幣紊任△襦Ｂ�線上にある400本のボーリング柱状図を収集し、N値および土質が明らかな深度のS波速度と比抵抗を抜き出してデータベース化した。抜き出したデータは約4000である。データベース化する際に、土質は粘土、砂、礫に大きく分類し、データは堤体と基礎地盤に分けて集計した。構築されたデータベースを用いて、多項式近似により、S波速度と比抵抗から統計的に土質を推定することを試みた。この近似では土質分類を、粘土は1、砂は2、礫は3と数値に置き換え、S波速度と比抵抗の関数となる多項式は1から3の連続値を与える。多項式の係数は最小二乗法で求める。ボーリング地点の実際の土質と比較することにより、推定精度を統計的に評価した。 |
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| | 講演要旨(英文) | | Soil type of levee body and foundation is statistically estimated using cross-plots of S-wave velocity (Vs) and resistivity in levees. Vs and resistivity are collected from surface wave methods and resistivity methods. Total survey line length is about 600km on 37 rivers. Relationship between Vs, resistivity, N-value and soil type is collected and stored in a database. The N-value and soil types are collected from about 400 boring logs. Vs and resistivity at the depth of the blow counts were extracted from geophysical sections. The total number of extracted data is about 4000. Soil type is classified as clay, sand and gravel. The data is grouped in levee body and foundation. A polynomial approximation was used to estimate soil type from Vs and resistivity. In the approximation, soil type is represented by discontinuous numbers one (clay), two (sand) and three (gravel). Polynomial equations are functions of Vs and resistivity and yield a continuous number between one and three. Coefficients of equations are optimized by a least squares method. A soil type section can be estimated from Vs and resistivity sections using the polynomial approximations. Accuracy of estimation can be statistically evaluated by comparing estimated and actual soil types. |
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