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| | Abstract | | 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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