| 講演要旨(和文) | | 世界最大のダムである三峡ダムの上流部には古地滑りや、風化した岩盤斜面が多くあり、ダムの貯水に伴い、斜面の変形と古地滑りの活動が多く観測されているため、有効的な調査手法が求められている。我々は高密度表面波探査をダム上流にある千将坪地滑り調査に適用し、その有効性を検討した。千将坪地滑りは岩盤滑りで、深度10数mにある中〜強風化と微風化泥質シルト岩の境界面が滑り面となっている。表面波探査は地滑り体の頭部滑り方向に測線を配置し、受振器間隔2mでデータを収録した。データ解析はまず収録した波形データからレイリー波の位相速度を求め、さらに、位相速度インバージョンにより測線沿いのS波速度分布を求めた。得られたS波速度断面は4層構造を呈し、ボーリングデータと比較した結果、それぞれ、崩積土と中〜強風化層、中〜弱風化層、微風化層及び良好な岩盤に対応しており、手法の有効性を示していると考えられる。 |
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| | 講演要旨(英文) | | After the first impoundment of the Three Gorges Reservoir, the largest hydro-electrical project in the world, many ancient landslides and weathered slopes in her upstream began to activate, and effective investigation methods are demanded for collecting information when establish hazard control plans. The authors applied high-density surface wave survey in the investigation of Qianjiangping landslide and studied its effectiveness and applicability. The Qianjiangping landslide is a weathered rock landslide that located about 50km upstream of the Three Gorges Dam, occurred in July 2003 after the water level reached to 135m, caused serious damage to both estate and life. We conducted the surface wave survey in the head part of the landslide where geological compositions are confirmed. The result of surface wave survey shows that there are 3 main shear wave velocity (Vs) boundaries on the Vs section. Compared with drilling core, they correspond to the main geological boundaries in depth, especially, the boundary between Vs=600m/s and Vs =800m/s on the Vs section, agrees very well with the boundary between weathered siltstone and slight-weathered siltstone. This boundary is confirmed to be the slide surface. Furthermore, the Vs value also considered proper corresponding to the geologies. |
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