報告書番号

U99080

タイトル（和文）

物理探査データによる地盤物性値の評価法の開発(その２) --堆積性軟岩･硬岩を考慮した透水係数の解析法の適用--

タイトル（英文）

Development of a method for evaluating geophysical properties of rock mass using geophysical exploration data (2)- Estimation of hydraulic conductivity profiles for soft sedimentary rocks and hard rocks from well logging data-

概要 （図表や脚注は「報告書全文」に掲載しております）

地盤の比抵抗値から透水係数を導くには間隙の水理的な屈曲性を考慮するとともに、帯電した細粒分による表面伝導現象を除去する必要がある。泥質砂岩および割れ目を含む結晶質岩を対象とした電気比抵抗モデルを基に複数の物理検層データ(電気･自然γ線･中性子検層)から透水係数を推定する手法を提案した。この手法を新第三系の堆積性軟岩地点に適用したところ、推定された透水係数はコア試料のそれと調和的な値が得られた。次に，花崗岩よりなる硬岩地点に同様の手法を適用した結果，両者に明瞭な相関性は認められなかったが、フローメータ検層により検出された"水みち"の深度と整合的な結果が得られた。今後より正確に水理地質構造を評価するには、様々な岩石試料に対する室内試験結果を得るとともに、そのデータを用い物理探査データと透水性との相関性を解明することが必要である。

概要 （英文）

In order to derive hydraulic conductivity from electrical resistivity of layers, it is necessary to consider tortuosity of pore space and eliminate surface conductivity effects due to charged fine particles. We have reviewed empirical equations relating electrical resistivity with hydraulic conductivity based on two idealized electrical conduction models; one for porous media and the other for fractured rock mass. We proposed techniques to calculate hydraulic conductivity from several geophysical logging data; electrical, natural gamma, and neutron logging. This technique has been applied to a well where soft sedimentary rocks are distributed. The calculated hydraulic conductivity of fine sandstone, mudstone, and tuff were consistent with those of several core samples at the well. However, thin layers (<10cm) of high permeability zone could not be detected by this technique. Secondly, the technique for fractured rock mass tested at a site where the rock mass consisted mainly of granite. Estimated hydraulic conductivity from well logging data were not consistent with the measured hydraulic conductivities at the well. However, several spikes of higher hydraulic conductivity obtained by this technique coincided with high permeability zones detected by flow-meter logging. In the future, in order to evaluate hydro-geological structures more exactly, we should reveal the relationship between geophysical data and hydraulic conductivity by laboratory tests using core samples obtained from various layers.

報告者

キーワード