| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
In the 2004 Niigata-ken Chuetsu Earthquake and 2003 Tokachi-oki Earthquake, many underground structures, especially manhole, were uplifted caused by soil liquefaction of the backfill materials. The amount of maximum uplift were over one meter half and total uplift manholes were frequent. On the contrary, the amount of uplift of manhole was less than 20 cm in 1995 Great Hanshin Earthquake. The difference between the two types of damage derives from depositional conditions of peripheral ground. From the observation of damage, the amount of uplift of the manhole buried in liquefiable ground was less than in un-liquefiable ground. The authors conducted model tests for back filling simulation and shaking table tests in order to clarify a mechanism of uplift of underground structure due to liquefaction of backfill sand. From the experimental study, we suppose the additional mechanism on the uplift of manhole. At first, when liquefaction occurred in the back fill soil, upward force depended on the degree of liquefaction will act to the bottom of manhole as trigger of uplift. While manhole slightly move upward, cavitations and suctions was generated around the bottom of manhole. In the sandy ground, liquefaction will occurred not only in backfilled soil but also in the surrounding ground. Considering liquefaction damage, we often concentrate to the sandy ground. However, we also have to pay attention to the under ground structures in the soft ground.
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