Mechanism of cyclic softening of non-plastic silt and its countermeasures
| Project/Area Number |
14350250
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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 | IBARAKI UNIVERSITY |
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Principal Investigator |
YASUHARA Kazuya Ibaraki University, the College of Engineering, Professor, 工学部, 教授 (20069826)
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| Co-Investigator(Kenkyū-buntansha) |
KOMINE Hideo Ibaraki University, the College of Engineering, Associate Prof., 工学部, 助教授 (90334010)
MURAKAMI Satoshi Ibaraki University, the College of Engineering, Assistant, 工学部, 助手 (10261744)
HORIUCHI Sumio Shimizu Corp.Co.LTD, Incubate Center, Director, インキュベートセンター長
GOTO Shigeru Shimizu Corp.Co.LTD, Research Institute, Chief Engineer, 主任研究員
SATO Kenichi Fukuoka University, Civil Eng., Associate Professor, 工学部, 助教授 (20235336)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥11,400,000 (Direct Cost: ¥11,400,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2003: ¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 2002: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Keywords | Liquefaction / Post-liauefaction / Lateral deformation / Silt / Cyclic degradation / Earthquake / Countermeasure / Gravel drain / 液状化 / 剛性劣化 / 排水履歴 / 側方変位 / 鉛直変位 / 対応策 / グラベルドレーン / シルト質土 / 剛性低下 / 変状低減 |
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| Research Abstract |
Lateral flow is a large lateral movement of the ground that occurs horizontally as a result of liquefaction during and after earthquakes. Lateral flow is inferred. to cause most damage to foundations of structures and lifelines during earthquake-induced disasters. For clarifying vulnerabilities to liquefaction of silts, we require a method of forecasting the deformation according to ground liquefaction. This study proposes a method for predicting the liquefaction-induced deformation of silty soil and proposing the countermeasure to reduce damage due to post-liquefaction deformation.
Results of the present study are summarized as follows :
1)Results from post-cyclic triaxial tests on silt indicate that stiffness decreases gradually as excess pore water pressure rises. However, that rigidity decreases rapidly when a ratio of 0.8 of the excess pore water pressure is exceeded. Ground deformation after earthquakes can be decreased considerably if the excess pore water pressure is maintained b
… More
elow 0.8 using gravel drains as a countermeasure.
2)The excess pore water pressure model was adopted to predict changes in the deformation modulus after liquefaction. It was incorporated into the FEM code for predicting silt ground deformation in model tests. Using the proposed FEM code, we obtained good agreement between observed and predicted deformation of sloping silt ground.
3)In 1G model tests on sloping silt ground, deformation attributable to the liquefaction of silty soil differs depending on the ground slope : lateral flow is exceptional when the ground is severely sloping ; vertical deformation is dominant when the slope is gentle. Moreover, comparison of the actions of silt with that in sand before and after liquefaction showed remarkable delay of silt deformation in the transformation, but the amount of sand displacement is greater immediately after liquefaction. Moreover, the final amount of displacement is nearly identical to that of sand. These results emphasize that, during earthquakes, attention should be given to post-liquefaction deformation of silt as well as that of sand.
4)The tire-chip drain was adopted for reducing post-liquefaction deformation of silt ground along with the conventionally used gravel drain. Results of model tests demonstrated that the tire-chip drain method is available for reducing not only lateral displacement but also vertical displacement. These effects are almost identical to those of the cases in which gravel drains are installed in the same condition. This suggests that the tire-chip drain method can be an economical countermeasure for preventing liquefaction-induced silt deformation. Less
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Report
(4 results)
Research Products
(24 results)
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[Journal Article] Postcyclic degradation of strength and stiffness for tow plasticity silt2003
Author(s)
Yasuhara, K., Murakami, S., Song, B-W., Yokokawa, S., Hyde, A F L
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Journal Title
Journal of Geotechnical Engineering (Proc.ASCE, Aug.) Vol.129, No.8
Pages: 756-769
Description
「研究成果報告書概要(欧文)」より
Related Report
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