摘要(英) |
Because the offshore wind turbine pile foundations such as that jacket and tripod are subjected to the WTG loading and long-term wind and wave loading transmitted from upper structure to lower substructure, the generated cyclic axial compression and tension, result in pile groups of difference settlement, affecting the stability of operation of the wind turbine. Therefore to investigate different pile behavior under cyclic axial load, is the destination of this study.
In this study, air pluviation method of sample was adopted to prepare a dense homogeneous dry sand specimen with a relative density of 60%, and 1-g model pile load test was conducted. When conducting axial cyclic load test, the loading which approach 1/3 of ultimate static in the axial load capacity was applied to simulate the normal conditions under safety factor of 3.In the static load tests it was, found that near bottom of the pile the sand relative density significantly affects the pile bearing capacity, the ultimate static load test total was totally 10 groups, with recording the relative density of sand layers in order to observe the variation of pile bearing capacity, and to ensure the consistent in preparation of sand samples in the future. Six unidirectional cyclic axial load test were conducted, in which three tests were under cyclic axial compression, and three tests under cyclic axial tension. The magnitude of loading were 1/3Pu, 1/6Pu and 1/12Pu, and the number of cycles were 10000, 10000 and 20000 respectively.
The results represent that the larger number of axial load cycles apply, the smaller equivalent stiffness of pile head was obtained as well as pile head displacement increases with an increasing number of cycles. Under the same condition of axial load cycles, the accumulated residual displacement of pile foundation under cyclic axial compression was larger than cyclic axial tension case. When increasing number of cycles, the pile shaft friction decreases. But the bearing capacity of pile tip increases.
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參考文獻 |
1.American Society for Testing Materials, “Standard Test Method for Piles Under Static Axial Compressive Load.” Annual Book of Standard, ASTM D1143/D1143M-07 (2013).
2.API. “API Recommended Practice 2A-WSD, Recommended Practice for lanning, Designing, Constructing Fixed Offshore Platforms-Working Stress Design(2005).
3.Chan, S. F., and Hanna, T. H., “Repeated Loading on Single Piles in Sand,” Journal of Geotechnical Engineering Division, Vol. 106, No. 2, pp.171-188(1980).
4.Li, Z., Bolton, M. D., and Haigh, S. K., “Cyclic Axial Behavior of Piles and Pile Groups in Sand,” Canadian Geotechnical Journal, Vol. 49, No. 9, pp. 1074-1087 (2012).
5.Long, J. H., and Vanneste, G., “Effects of Cyclic Lateral Loads on Piles in Sand,” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 120, No. 1, pp.225-244 (1994).
6.O’Neill, M. W., and Reese, L. C., “Drilled shafts: construction procedures and design methods.” Publication No. FHWA-IF-99-025, U.S. Department of Transportation, Federal Highway Administraion, Washington, D.C., U.S.A. (1999).
7.Terzaghi, K., “Evaluation of coefficient of subgrade reaction,” Geotechnique, Vol. 5, No. 4. pp. 279-326 (1955).
8.Tomlinson, M. J., Pile Design and Construction Practice, London (1977).
9.Jardine R. J., and Standing J. R., “Field axial cyclic loading experiments on piles driven in sand,” Soils and Foundation, Vol. 52, pp. 723-736 (2012).
10.內政部營建署,「建築物基礎構造設計規範」,中華民國大地工程學會,台北 (2001)
11.周廷韋,「以離心模型試驗模擬基樁反覆抗壓及抗拉拔之行為」,碩士論文,國立中央大學土木工程學系,中壢(2008)。
12.施國欽,大地工程學(二)基礎工程篇,文笙書局,台北(2001)。
13.黃耀弘,「超抽地下水引發地盤下陷之離心模型試驗」,碩士論文,國立中央大學土木工程學系,中壢(1997)。
14.張有毅,「以離心模型試驗及個別元素法評估正斷層和逆斷層錯動地表及地下變形」,博士論文,國立中央大學土木工程學系,中壢(2013)。
15.葉品毅,「煤灰地盤樁基礎承載行為之研究」,博士論文,國立中央大學土木工程學系,中壢(2015)。
16.黃俊鴻、楊志文,「基樁載重試驗承載力判釋方法之探討與建議」,地工技術雜誌,第八十期,第5~16頁(2000)。
17.傅哲賢,「基樁抗壓與抗拉極限承載力之差異」,碩士論文,國立中央大學土木工程學系,中壢(2006)。
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