| 講演要旨(和文) | | 孔井内で実施する検層と同様の方法論でトンネル坑内でも各種物理探査が適用可能である．これまでもHSPや地表−坑間トモグラフィ探査などが考案適用されてきた．近年供用から数10年経過したトンネルで変状が発生して重大事故につながる事例が増加しつつあり，健全性点検とその基礎技術開発が重要な課題となっている．そこで廃道になった道路トンネルを利用し，坑内で高周波表面波探査と牽引式表面波探査で構成される統合物理探査を実施し，トンネル健全性点検への適用性を検証した．その結果，路盤下の物性構造を反映した2次元断面構造をイメージングすることができた．探査結果は支保パターンおよび掘削後の補強工事実績と調和的であり，また既往坑内地震探査結果とも整合的であった．探査結果は，統合物理探査がトンネル路盤の健全性点検にも有用であることを実証した． |
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| | 講演要旨(英文) | | Engineering geophysics has played an important role in planning and constructing of mountain tunnels. Moreover, recent increase in collapses occurred in active tunnels has led us to utilize geophysics for the safety check of existing tunnel structures. Besides the estimation of thickness of concrete lining and detection of voids behind the lining, measurements for the concrete pavements and tunnel formations is one of the major targets of the safety check of tunnels. We conducted field measurements in an abandoned tunnel to evaluate geophysical methods for the characterization of the basement structures of tunnel. Tested methods were capacitively coupled resistivity measurement using OhmMapper and high-frequency surface wave measurement. As a result, near surface structures up to 20 m beneath the tunnel floor were clearly imaged. The reconstructed structure was concordant with excavation and maintenance history of the tunnel. Furthermore, the reconstructed geophysical sections matched with a previously reported P-wave velocity section. In conclusion, combined resistivity and surface wave survey is capable for the evaluation of physical properties of basement structure and surrounding rocks of tunnels. |
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