ken09207

Kohei HIROSE

On Seismic Failure Mechanism of Intermediate Soil Embankment Considering Groundwaterlevel

Satoru OHTSUKA Koichi ISOBE

The fill at large-scale embankment collapsed in Nagaoka city Takamachi housing complex during the 2004 Niigata-ken Chuetsu earthquake. As a result of site investigation, intermediate soil that the distinction points out none of them sand with clay as for Takamachi housing complex∏s banking material. Receive this scenery, inspected it about failure embankment mechanism examine the shaking table test which paid its attention to seepage water level in ground use intermediate soil for banking material.In the study, a distinct difference was recognized for the failure embankment mechanism by the difference of seepage water level in ground was confirmed. Therefore this study inspected a difference of failure embankment mechanism by changing in seepage water level in ground and fine contents. The experiment examined seepage water level in ground and fine contents as a parameter. It was all cases to compare only failure embankment mechanism and used 1¨1 for rock mass in intermediate soil(1¨1) which mixed Tohoku silica sand and Fhjinomori clay in 1 to 1 ratio or intermediate soil(3¨1) which mixed it with 3 to 1, and changed fine contents in banking material. As a result, dynamic magnification acceleration factor by the difference of seepage water level did not have the big difference in 3¨1 and increased gradually in the action of dynamic magnification acceleration factor on embankment together toward the ground surface. While, in low seepage water level of 1¨1,there was the case that f increased rapidly in embankment hillside like last year when there was a difference in degree of saturation in ground surface and bottom. Such a behavior was caused by degree of saturation, and a difference did not go in dynamic magnification acceleration factor because a big difference of degree of saturation by the difference of seepage water level was small in 3¨1.Dynamic magnification acceleration factor showed behavior such as high seepage water level when distributed over widespread even if it was case that low seepage water level of 1¨1 without seismic force coming to an ground surface. And, in 3¨1, liquefaction which was partial (place, degree) was confirmed in , neighborhood of stage or below stage. Compare failure form so that embankment slides from bottom in 3¨1 and crack occurs in rock mass side, and embankment failure. As for 1¨1, bottom became the weak point, and embankment upside failured by shake force, and top of slope side understood that it occurred, and crack did big failure

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