2006 Fiscal Year Final Research Report Summary
Study on the relationship between environments of soil sedimentation and engineering properties of the ground in Quaternary Era
| Project/Area Number |
15206057
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | Hiroshima University |
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Principal Investigator |
TSUCHIDA Takashi Hiroshima University, Graduate School of Engineering, Professor, 大学院工学系研究科, 教授 (10344318)
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| Co-Investigator(Kenkyū-buntansha) |
HIBINO Tadashi Graduate School of Engineering, Associate Professor, 大学院工学系研究科, 助教授 (50263736)
WATABE Yoichi Port and Airport Research Institute, Head of Soil Mechanics Division, 地盤構造部, 土質研究室長 (00371758)
OTSUBO Masami Kyusyu University, Graduate School of Bioresource and Bioenvironmental Sciences, Professor, 大学院農学研究院生産環境科学部門, 教授 (80112316)
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| Project Period (FY) |
2003 – 2006
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| Keywords | sedimentation environment / aging effect / marine clay / consolidation / seabed / tidal flat / wave |
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| Research Abstract |
The purpose of this study is to find a relationship between the environments of soil sedimentation and the engineering properties of the ground. The findings of the study are summarized as follow:
(1) The process of floc formation and its settling and sedimentation has an important role for the large void ratio structure of natural clay.
(2) By adding small amount of cement to clay slurry, the structure of large void ratio structure of aged clays could be reproduced in the laboratory.
(3) Sedimentation and consolidation tests of marine clay were carried out under flowing water condition. When the water flow was large, the height of the clay decreased with stair-like pattern due to repeat of the erosion and the consolidation. The shear strength of the clay consolidated under flowing water was larger than that consolidated under the stationary water condition.
(4) When soft bottom mud with high water content over the liquid limit is fluidized by the pressure induced by waves, cracks are generated in the surface of the mud. The cracks develop under the action of tensile stress and shear stress caused by the rotation of principal stress in the periodic motion of waves. The mechanism of the acceleration of consolidation of the mud by wave action is elucidated through experimental and numerical studies.
(5) When sandy soil containing 10% fines was subjected to the cyclic water pressure change, it was observed that the fines moved to the upper direction in the soil and finally reached to the surface. The upward movement of fines took place when the water pressure decreased and large excess pore pressure was observed at the ground surface. It was suggested that the occurrence of liquefaction under the cyclic water pressure change was closely related to the upward movement of fines.
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