| Project/Area Number |
10555166
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Geotechnical engineering
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
SEKIGUCHI Hideo Kyoto University, DPRI, Professor, 防災研究所, 教授 (20027296)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAKE Michio Toyo Construction, Naruo Res. Inst. Vice-director, 鳴尾研究所, 副所長
MASE Hajame Kyoto University, Ibid, Associate Professor, 防災研究所, 助教授 (30127138)
YAMASHITA Takao Kyoto University, Ibid, Associate Professor, 防災研究所, 助教授 (30111983)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥6,500,000 (Direct Cost: ¥6,500,000)
Fiscal Year 1999: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1998: ¥4,100,000 (Direct Cost: ¥4,100,000)
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| Keywords | Liquefaction / wave loading / Centrifuge modelling / coastae erosion / 遠心模型実験 |
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| Research Abstract |
This report first describes results from a range of centrifuge wave tank tests performed on sand deposits with a level surface. The measured traces of excess pore pressures at different soil depths clearly indicated that under severe wave conditions, liquefaction first took place at shallow soil depth and then propagated downwards, eventually bringing the entire soil bed into liquefaction. The motion of the fluid/soil interface during wave loading was captured by means of a high-speed CCD camera. The images taken showed that the fluid/soil interface began vibrating significantly upon the occurrence of liquefaction at shallow soil depth, and that the amplitude of soil vibration increased markedly with time in accordance with the downward advancement of the liquefaction front and leveled off at a constant value when the entire soil bed was in a state of complete liquefaction.
These interesting observations led to the development of a simple yet workable theoretical model. It is an extension of Lamb's (1932) two-fluid-layer theory in the sense that the liquefied soil is regarded as an inviscid fluid with a particular mass density and is underlain by a deposit of sub-liquefied, elastoplastic soil. The performance of the theoretical model compares favourably with what has been observed in the centrifuge wave experiments.
Furthemore, efforts were directed to investigating the soil instability at and around the toe of much coarser granular slopes, through a series of centrifuge wave tank tests. The results from the experiments showed that upon the occurrence of liquefaction at shallow soil depth in the free field, the toe of the rubble mound started settling at an only discernible rate. This was in fact followed by extensive spread of the liquefied zone in the course of wave loading, thereby causing the entire body of the rubble mound to settle deep into the liquefied foundation sand.
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