| 講演要旨(和文) | | 駅・ホーム改良工事,橋梁基礎改良工事など狭隘かつ施工時間に制約のある基礎杭の施工には,施工機械が小さく,施工時間が短く,周辺環境への影響の少ない場所打ち杭工法が適しているが,施工中の列車運行の安心・安全を確保するためには掘削に伴う地盤の緩みが周辺構造物に与える影響に配慮する必要がある.筆者らは場所打ち杭の施工現場で施工前後の砂地盤の緩み領域を把握するために高周波数の弾性波トモグラフィを実施した.実験結果から,弾性波の減衰率は砂地盤の緩みに伴い増加すること,速度は変化しないことが分かった.砂地盤の緩み領域を把握するには速度トモグラフィではなく減衰率トモグラフィが有効であると考えられる. |
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| | 講演要旨(英文) | | Building a foundation in a narrow space where there are railways, platforms and buildings, it is necessary to use a small size machine and minimize a construction time and effects on surroundings. In this point, cast-in-place pile method is appropriate however it is also necessary to secure a safety operation. For example, we have to know whether drilling by earth auger generates loose area of the ground and affects existing structures. Authors experimentally conducted a high frequency seismic tomography for the purpose of imaging of loose sand area at the cast-in-place pile construction site. The results show that attenuation increased and velocity did not change after drilling by earth auger. It is concluded that the attenuation is more useful than the velocity to detect the loose sand area. |
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