報告書番号

N04038

タイトル（和文）

断層破砕帯を対象とした原位置簡易透水試験装置の開発と適用性検討

タイトル（英文）

Development and application of the portable test instrument for the In-situ permeability test to be applied for a fault zone

概要 （図表や脚注は「報告書全文」に掲載しております）

地表やトンネル坑壁から断層破砕帯の透水性を簡易に把握するため，変水位法による簡易透水試験装置を開発した。透水性の程度により孔径を変化させ，ジョイントロッド（内径33mm）およびスタンドパイプ（内径6.35mm）内での水位変化を計測する。予備試験として，ローム層を対象とし，地表からの鉛直孔～急傾斜孔で，本試験装置の試験手順や方法を確認した。計測範囲，試験前の孔底洗浄の影響などを検討した結果，今回の試験装置で試験可能と判断した。また，片麻岩中の断層破砕帯および周辺堅岩部を対象とし，横坑内の鉛直孔～急傾斜孔と水平孔で，本試験装置の適用性を検討した。計測範囲，断層破砕帯の性状と透水性，孔傾斜の影響などを検討した結果，断層破砕帯は堅岩に比して低透水性であり，堅岩内では透水性のバラツキが大きく，想定していた透水性状と同様であったことなどから，透水試験装置の適用性を確認した。

概要 （英文）

The portable permeability test instrument based on the falling head method was developed for the purpose of simple permeability measurements of a fault zone (fractured zone) at the ground surface and excavation surface. This instrument to measure changing water levels is characterized by a large caliber joint rod (33mmφ) and a small caliber stand pipe (1/4 inchφ), which is selectively used corresponding to the degrees of permeability. In the case of preliminary tests of the loam around the ground surface, simple permeability tests were conducted in the vertical and high-pitched drillings. After the preliminary tests the procedure and method were confirmed reliable. After having tested the available range of the measured permeability coefficients, the effect of cleaning before the test in the drillings and the influence of the geologic characteristics were examined. As a result, it was confirmed that these procedures were applicable to in-situ test. In the case of permeability tests of the fault zone (fractured zone) in gneiss, simple permeability tests were conducted in the vertical to high-pitched drillings and horizontal (< 3 degrees). The available range of the measured permeability coefficients, the influence of the geologic characteristics and the effect of drilling angle were examined. The permeability coefficients of the fault zone (fractured zone) are low. The dispersion of permeability coefficients in fresh and hard gneiss is large. These facts agreed with the predicted permeability characteristics of fault zone. From the findings mentioned above, it was confirmed that these procedures were applicable to in-situ test.

報告者

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