[M-TT30] Integrated Geophysical Survey

[MTT30-P06] Integrated Geophysical surveys in levee excavation sites on the Chitose river, Central Hokkaido

*Toru Mogi¹, Michiko Shigefuji¹, Nobuo Takai², KENJI OKAZAKI³, Toshiyuki Kurahashi³, Teruhiko Obinata⁷, Jun Horita⁴, Tomio INAZAKI⁵, Takaho Kita⁶ (1.Institute of Seismology and Volcanology, Faculty of Science, Hokkaido University, 2.Facultyy of Enigeneering, Hokkaido University, 3.civil Engineering Research Institute for Cold Resion, 4.Geo-Thchnical Research Co.Ltd., 5.Public Work Reserch Institute, 6.TK Ocean Land Investigation Ltd., 7.Hokkaido Regional Development Bureau)

Keywords:Integrated Geophysical Survey, Levee Survey

A levee excavation was conducted to construct a new sluice at two sites along Chitose River, Central Hokkaido. The high-density electrical resistivity survey and the surface wave survey were carried out on the levee at the crown and high-water channel before the excavation. The electrical resistivity and S wave tomography were also carried out across the levee at the excavation sites. After the excavation, the short electrode spacing resistivity mapping and the short spacing surface wave survey were carried out at the excavated slope surface to measure directly on the resistivity and S wave velocity (Vs).
The resistivity and Vs structures obtained by the surface surveys were verified by the resistivity and Vs distribution measured on the excavated slope surface. These surveys delineated imhomogeneity of soils in the levee and the basement. Comparing the resistivity and the grain size evaluated by soil tests, the resistivity structure identified a permeable zone in the levee and showed the extension to the basement.