報告書番号

N08080

タイトル（和文）

EK(Electro Kinetic)現象を利用した岩盤透水性評価法の開発（その1）－低透水性岩盤におけるEK現象の特性－

タイトル（英文）

Development of rock's hydraulic conductivity evaluation using EK (Electro Kinetic) phenomenon (Part 1) -EK phenomenon characteristics for low hydraulic conductivity rocks-

概要 （図表や脚注は「報告書全文」に掲載しております）

物理探査手法を用いて、地下深部における岩盤の透水性を簡易に低コストで推定する技術の開発が期待されている。そこで、地盤に弾性波が伝播する際に発生する微弱な電位差（EK（Electro Kinetic）電位）が透水性と相関を持つ点に着目し、低透水性岩盤におけるEK電位と透水性との相関について検討するための室内試験、原位置試験を行った。室内試験の結果、既存の理論と整合したEK電位の特性が捉えられ、低透水性岩盤であってもEK電位から透水性を推定できる見通しを得た。また、原位置試験（新第三紀堆積岩地域における検層）の結果、EK電位が発生する位相遅れの値が透水性と相関を持つことが明らかになり、低透水性岩盤の場合には位相遅れの値から地盤の透水性を推定できる可能性が示された。

概要 （英文）

It is very important to evaluate engineering properties of rock by using geophysical exploration methods. Especially, hydraulic conductivity is one of the most important engineering properties to investigate geological structure for high level radioactive waste disposal or carbon dioxide (CO2) geological storage. However, measurement of hydraulic conductivity requires huge consumption times. So if hydraulic conductivity is estimated by geophysical methods cost-effectively, the measurement time will be reduced.
When elastic wave is propagated into rocks, small streaming potential is generated. This is called EK (Electro Kinetic) potential, which may have a correlation with hydraulic conductivity. Hydraulic conductivity can be estimated easily by measuring the potential of rock during propagation of elastic wave.
We have reviewed the theoretical methods to estimate hydraulic conductivity from EK potential measurements, and found some promising methods. To verify these estimation methods, we have constructed the equipments to measure the EK potential of rock samples, and conducted laboratory measurements. We have also conducted EK logging in Neogene sedimentary rock area. As a result, hydraulic conductivity was related to phase delay of EK potential. This suggests that hydraulic conductivity can be estimated by measuring the phase delay of EK potential.

報告者

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