| Project/Area Number |
18360226
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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 | 一般 |
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| Research Field |
Geotechnical engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TOHATA Ikuo The University of Tokyo, Graduate School of Engineering, Professor (20155500)
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| Co-Investigator(Kenkyū-buntansha) |
UCHIMURA Taro The University of Tokyo, Graduate School of Engineering, Associate Professor (60292885)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥17,090,000 (Direct Cost: ¥15,500,000、Indirect Cost: ¥1,590,000)
Fiscal Year 2007: ¥6,890,000 (Direct Cost: ¥5,300,000、Indirect Cost: ¥1,590,000)
Fiscal Year 2006: ¥10,200,000 (Direct Cost: ¥10,200,000)
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| Keywords | sand / shear / liquefaction / zero-gravity test / seismic performance-based design / deformation characteristics / viscosity / damage mitigation / せん断変形 / 性能設計 / 無重力 / せん断実験 / クリープ |
|---|
| Research Abstract |
In the recent times, much effort has been made to introduce into practice the principle of performance-based design, and geotechnical earthquake engineering is not an exception. The present study concerns evaluation of liquefaction mitigation technologies by which residual deformation of ground is reduced. This is particularly the case of mitigation technologies for a river dike, harbor quay wall, and buried pipelines. The investigators have been doing efforts to develop a deformation model for liquefied sand m which effective stress is extremely low Encountered problems are, for example, that laboratory shear tests with extremely low effective stress resulted in self-weight collapse of sand specimens and the stress nonuniformity due to self weight of sand particles. On the other band, shaking model tests could not precisely reveal stress-strain states of sand, although the state of full liquefaction was easily developed. To overcome these problems, the present study conducted shear te
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sts under zero-gravity environment. A triaxial shear device was specially designed and fabricated so that it would suit a zero-gravity testing facility which made use of a deep vertical shaft Special machine control was needed for satisfactory tests because the duration time of zero gravity was merely a few second during flee fall of the shear device.
There were three difficulties in running experiments. First; controlling the operation in line with the commencement of free wall required care. Second, development of a small loader for triaxial compression test needed efforts. The size had to be small to be cased in a limited size of a free-fall capsule. The most difficult problem was the removal of effective stress developed by positive dilatancy of water-saturated sand during fine fall. This last problem was overcome finally by employing dry specimens for which drained shear was conducted. Tests showed that strain increased at a constant rate under constant stress, implying viscous nature of sand. The friction angle under the extremely low stress was nearly 70 degrees. Consequently the viscosity coefficient was about 400 kPaSec. This data was employed in assessment of the mitigative performance of measures for river dike such as underground sheet piles and berms. Less
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