| 講演要旨(和文) | | 本研究では,三次元GPR探査を用いた河川堤防周辺での地下水探査結果について述べる。実験を行った場所は,埼玉県比企郡吉見町の荒川の河川堤防周辺である。GPR探査にあたっては,中心周波数250MHzのパルスレーダアンテナを用い,測線間隔50cm以下で4方向の稠密な三次元GPRデータ取得を実施した.データ取得に要した時間は約3時間と実用的なものであり,調査効率は十分に高いと結論できる.可探深度は3m以上であり,この領域での地下水位(約1.5 m)までの深度範囲を十分にカバーする事が可能であった.三次元マイグレーションにより,地下の三次元性を考慮した.その結果,地下水面や地層の分布を高精度にイメージングする事が可能となった.また,稠密な三次元探査結果を用いる事により,地下水面分布を視覚的にとらえる事が容易となり,会話的なデータ解釈も同時に可能となるため,地下の把握も容易となった. |
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| | 講演要旨(英文) | | In our country, surroundings of a river are highly developed, and there are many human activities and important buildings around a river. Therefore, maintenance of the levee which had the enough strength to protect them from a flood and an earthquake impaction is important. For the levee maintenance, we should evaluate inside the levee body and its surroundings and, investigations on ground water are quire essential among all investigation menus. As geophysical surveys have non-invasive and non-destructive natures, they are desirable for levee surveys. Ground Penetrating Radar, GPR, survey has characteristics such as highest resolution and highest survey speed among all geophysical survey methods. In this paper, we describe three-dimensional GPR survey results around a river levee. Data acquisitions are carried out at around Ara River, Yoshimi-town, Saitama. After flooding caused by a typhoon of last autumn, change of levee shape was observed behind the levee at some spots around Ara River. Therefore, it comes to be necessary to investigate ground water distributions around Ara River and inside its river levee. As a result, we obtained a highly precise subsurface image. In addition, we can understand subsurface visually and interactive interpretations are now possible on a precise three-dimensional image. |
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