| 講演要旨(和文) | | 積雪地域の山岳道路では，融雪期に盛土斜面が不安定化し斜面災害が発生する危険性が高まる．これまでは特定の横断面における計算結果を一定区間に適用して安全性を評価していたため，縦断方向の不均質性の検討が充分ではなかった．斜面上に測線を設定し物理探査を実施すれば，より詳細に盛土内部構造を把握できると期待される．そこで斜面湧水対策を実施予定の山岳道路盛土区間において稠密比抵抗探査等を実施した．探査は2013年積雪期前と斜面対策工施工後の2014年融雪期に2回実施した．その結果，対策工施工区間では相対的に比抵抗が増大し水抜き工の効果が認められた．また表面波探査の結果から湧水区間では低速度層が厚いことがわかった．これらの現地探査の結果は，盛土斜面に稠密に測線を配置して統合物理探査を適用することによって，盛土斜面の安定性に影響する不均質内部物性構造を高分解能かつ低コストで把握可能であることを示している． |
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| | 講演要旨(英文) | | Dense and high-resolution geophysical surveys were conducted at an embankment slope of a mountain road situated in the heavy-snow region, Sapporo, Hokkaido. The surveys consisted of 3D resistivity measurements, surface wave survey, portable dynamic cone penetrometer testing, and pore water pressure monitoring. Stabilization work was to be implemented to the target slope mainly purposed for the groundwater discharge. We conducted the field measurements twice before the snow season in 2013, and just after the snowmelt season in 2014 when the slope surface had been scraped and protected with caged riprap. No obvious change was observed in the resistivity profile along the reference line set outside the stabilization work zone. In contrast, the resistivities distinctively increased in the groundwater discharged zone. Surface wave survey clearly delineated the deepening of embankment thickness at the surface seepage zone in the slope. In conclusion, small scale inhomogeneous structure in the embankment, which might cause irregular distribution in the slope stability, was clearly identified by means of dense and high-resolution geophysical survey. In addition, the periodic measurement was useful to evaluate the effect of slope stabilization work. |
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