| Project/Area Number |
08650567
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | University of Tsukuba |
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Principal Investigator |
YAMADA Yasuo University of Tsukuba, Inst.of Engineering Mechanies Associate Professor, 構造工学系, 助教授 (90111476)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIOKA Takashi University of Tsukuba, Inst.of Engineering Mechanies Professor, 構造工学系, 教授 (30011141)
SAWAGUCHI Masatoshi University of Tsukuba, Inst.of Engineering Mechanies Professor, 構造工学系, 教授 (50132999)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1997: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1996: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | online test / drainage control / torsional shear appatus / cyclic loading / sand / liquefaction / fine content / permeability coefficient / 砂地盤 / 繰返し荷重 / 粗粒材料 |
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| Research Abstract |
The liquefaction behavior of sandy ground was investigated by means of the online test with drainage control based on Drecy's law, which incorporated both effects of the softening of ground due to cyclic loading and the volumetric change due to drainage. We developed a system consisting of a linear positioning table and a piston-cylinder for precise drainage control. The system was capable of direct control of volumetric strain, which reduced data scattering and improved precision in control.
The tests employed a control rule in which the volumetric strain per unit time was equal to the product of a drainage coefficient and excess pore water pressure. The larger values of the drainage coefficients corresponded to the higher permeability of ground and the shorter drainage distance. A series of online tests with different drainage coefficients showed the gradual changes in shear behavior from truly undrained condition with correction for the membrance compliance to drained conditions. In
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the case of speciments subjected to relatively low accelerations under higher drainage coefficients did not liquefied. Meanwhile specimens that developed excess pore water pressure equivalent to 65 to 70 % of the effective confining stress did liquefy immediately after because insufficient drainage.
The online tests were also carried out on sand specimens added with 5,10, and 15 % fines (kaolin). The resistance against liquefaction became highest in the specimens with 5 % fines, then decreased with increasing fine content. While in the case of static triaxial compression tests pure sand speciments showed the greatest strength and the shear strength decreased with increasing fine content. The static tests on the speciments with 5 % fines, however, showed the highest dilatancy ratio in the medium strain region, which might be reflected in the cyclic behavior mentioned above.
A series of triaxial tests was also carried out on a gravel in order to study the effects of the maximum size and membrane compliance. Less
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