| 講演要旨(和文) | | 硬質岩盤中の水みちとなる割れ目を対象とした探査技術の高精度化を目的に、数m規模の岩石ブロックによる音響トモグラフィ法の室内試験を行った。直方体に加工した2体の花崗岩片を積み重ね、数mスケールの岩石模型を作成し、上面より1mの深度に水平割れ目(開口幅0.5mm)が位置するようにした。割れ目を貫通するよう鉛直孔2本を2mまで掘削し、割れ目内に水および高粘性流体を飽和させた。試作した送信・受信装置により発信周波数10k〜50kHzを使用し、測点10cm間隔でトモグラフィ計測を行った。2次元逆解析により得られたP波速度断面では不明瞭であったが、減衰率断面では割れ目の連続性を検出できる結果が得られた。また、割れ目を飽和した流体は水より高粘性流体の方が明瞭な結果となった。以上より、孔間距離数mにおける硬質岩盤中の水みちとなる割れ目の連続性を従来の探査法より高精度に調査できる可能性が示された。 |
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| | 講演要旨(英文) | | The purpose of this study is to develop the data acquisition system to explore accurately the fracture, water pass way, in hard rocks. We make hard rock model, L2.5m, D0.6m, H2.5m, including horizontal fracture. The aperture is 0.5 mm by stacking two blocks of granite. Two boreholes are drilled trough the fracture, which is located 1 m from the top of the model. The distilled water or the high viscosity fluid is saturated in the fracture. The acoustic tomography method was conducted using the rock model. The interval of measurement points is 10cm, and the frequency of the transmitter ranges from 10kHz to 50kHz. P-wave velocity section and attenuation section were analyzed by 2D inversion. As the result, the fracture position was explored clearly in the attenuation section, however it was very difficult to locate the fracture in the velocity section. And fracture saturated by high viscosity fluid is detected more clearly than the case of distilled water. It is indicated that the acoustic tomography is more available to explore the fracture in hard rocks than conventional geophysical exploration methods. |
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