| 講演要旨(和文) | | 主に河川堤防調査で用いられている牽引式電気探査は，線状のキャパシタ電極を用い，電極を設置することなく，測定機器を牽引することで連続的にデータを取得可能である．逆解析は測線長が長いことから連続一次元解析を実施することが多いが，PCの性能向上や並列計算の実装により，長大測線の2次元解析，3次元解析が実用的になってきた．そこで，本稿は線状のキャパシタ電極を用いた際の2次元，3次元解析手法に関して，数値計算によって検討した．感度分布を計算した結果，線電極の中央付近に正・負の境界が生じ，この地点に点電極を設定することで，点電極を用いた場合と同様の感度分布を示すことが分かった．3次元の数値解析の結果から，線電極の中央に点電極を置いた解析手法の有効性が確認でき，実データに対して2次元解析を実施することで，本解析手法が実用上問題ないことが分かった． |
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| | 講演要旨(英文) | | Capacitively coupled resistivity (CCR) measurement has been used for estimating resistivity structure, particularly on river levees. One of the advantages of this measurement is a capability of a continuous data acquisition. One-dimensional analysis has been applied in many cases to reduce time and cost for the data analysis of CCR. However, two- or three-dimensional analysis is now feasible due to an improvement in computation power. Thus, a practical method of two- or three-dimensional analysis for the CCR measurement is discussed in this study. First, the sensitivity distribution of the dipole-dipole array configuration using line electrodes is calculated by COMSOL Multiphysics. Then, the sensitivity is compared to that of point electrodes located at the center of each line electrodes. Since the two sensitivity distributions are similar, the resistivity measurement by the line electrodes is approximated as the resistivity measurement by the point electrodes. The approximation is validated by a three-dimensional numerical simulation and a two-dimensional field observation. As a result, we concluded that two- or three-dimensional subsurface resistivity model can be effectively obtained by using CCR measurement with this approximation method. |
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