| 講演要旨(和文) | | 開削工事が予定されていた河川堤防において，比抵抗の経時変化を3次元トモグラフィ配置でモニタリングした．堤防天端に溝を掘り，総量約4000Lの水を断続的に注水した．これを堤防天端からのり尻にかけて電極間隔50cm，24電極8列の測線を設定し，3.5m×11.5mの範囲の応答電位を2日間のうちに総計44ステージで測定した．取得したデータセットに対して3D time-lapse ERT解析を施した結果，溝直下からのり尻方向にかけて，最大約30%比抵抗が低下した浸透域とその進展を明瞭にイメージングすることができた． |
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| | 講演要旨(英文) | | Infiltration process of water into the surficial vadose zone of a levee system was monitored at short intervals by means of a newly developed high-speed resistivity measurement tool. The tool can transmit 24 individual current signals simultaneously and measure 24 potential responses. Because of its short interval time, only 30 seconds are spent to obtain and store a total of 576 (24 x 24) dataset. Using the system, we could conduct not only near real time monitoring but also dense 3D time-lapse resistivity measurements in the field. We set a total of 4 current lines and 4 potential lines parallel on the slope of a levee, and infused water into the vadose zone from a small trench dug on the levee crest. Electrode stakes were placed at 50 cm spacing along each line, and spacing between the lines was set to 50 cm. A total of 6,912 (12 pairs x 576) data were acquired at 5 min to 30 min. Difference inversion as well as ordinary 3D tomographic analysis, applied to the dataset composed of a total of 44 stages during the infiltration across two days, successfully imaged the extent of infiltrated water in the vadose zone. |
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