2005 Fiscal Year Final Research Report Summary
On Estimation of Unburied Offshore Pipeline Stability Against Waves and Earthquakes
| Project/Area Number |
16560441
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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 | Maizuru National College of Technology |
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Principal Investigator |
TAKATANI Tomiya Maizuru National College of Technology, Civil Engineering, Associate Professor, 建設システムエ学科, 助教授 (70179448)
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| Co-Investigator(Kenkyū-buntansha) |
KATO Yoshinori Maizuru National College of Technology, Civil Engineering, Research Associate, 建設システムエ学科, 助手 (90353292)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Offshore Pipeline / Horizontal Cyclic Loading / Liquefaction Analysis / Pore Water Pressure Response / Stress-Strain Relationship / Degradation of Soil Stiffness / Simple Shear Test |
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| Research Abstract |
The offshore pipeline design is based on a lot of pipeline construction experiences in the North Sea and the Gulf of Mexico, however it may be not applied necessarily to other offshore regions in the world. The evaluation of offshore pipeline stability may play an important key role for offshore pipeline design under various ocean environments and offshore seabed conditions. The horizontal cyclic movement of pipeline under severe wave and current conditions may pose a pore pressure accumulation in the soil around the pipeline, which will reduce the effective strength of the soil and degrade the stiffness of seabed soil. In particular, a large horizontal movement of pipeline may lead to sudden break-out, which has a serious influence on the safe operation of the pipeline. It is, therefore, very important for pipeline design engineers to evaluate not only the pipeline movement but also pore pressure accumulation in the soil around the pipeline under horizontal cyclic loading condition du
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e to wave and current. Recently, many geotechnical centrifuge tests and numerical simulations under several environmental conditions and some offshore soils have been conducted to evaluate the pore pressure accumulation and the pipeline movement during horizontal cyclic loading. In summary, the following conclusions can be made based on the results presented in this paper.
1)The movement of pipeline during horizontal cyclic loading strongly depends on the ratio of horizontal to vertical load and the horizontal cyclic frequency.
2)The pipeline movement during horizontal cyclic loading strongly depends on the horizontal cyclic frequency and the material properties of seabed connected with SPT N-value and the fine grained soil content.
3)The pore water pressure buildup strongly depends on the joint element stiffness as well as the horizontal cyclic frequency f. The shear stress-strain relationship is more sensitive to the joint element stiffness.
4)The amplitude of excess pore pressure in seabed around pipeline depends on not only the distance between pipeline and measuring point but also the joint element stiffness between pipeline and seabed. The effect of the joint element stiffness to the pore pressure accumulation increases with decreasing the distance between the pipeline and the measuring point.
5)The pore pressure accumulation in the seabed due to horizontal cyclic loading of pipeline depends on the horizontal cyclic frequency f. When the fine grained soil content is larger, the pore water pressure response does not increase as the distance between the soil element and pipeline increases. Less
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Research Products
(13 results)
