SERBEST VE RİJİT BAŞLI AÇIK DENİZ TEKİL KAZIK TEMELLERİNİN TEKRARLI YATAY YÜKLER ETKİSİ ALTINDAKİ DAVRANIŞI

Abstract

Açık deniz tekil kazık temelleri rüzgar ve dalga kaynaklı ağır tekrarlı yatay yüklere maruz kalmaktadır. Bu yükler nedeniyle kalıcı zemin deplasmanları ve suya doygun zeminde aşırı boşluk suyu basıncı birikimi gerçekleşebilmektedir. Çalışmada serbest ve rijit başlı tekil kazık temellerinin tekrarlı yatay yükler altındaki davranışı sonlu elemanlar yöntemi ile zeminde aşırı boşluk suyu basıncı gelişimi ve deplasman birikimi dikkate alınarak incelenmiştir. Üç boyutlu sonlu elemanlar analizlerinde, zeminde aşırı boşluk suyu basıncı gelişiminin belirlenmesi amacıyla iki fazlı modele dayanan üç boyutlu elemanlar geliştirilmiştir. Böylelikle kazığın çevresindeki zeminde boşluk suyu basıncı gelişiminin elde edilmesi mümkün olmuştur. Kumlu zemin, tekrarlı yükler altındaki davranışının modellenmesine uygun olan bir hipoplastik malzeme modeli ile tanımlanmıştır. Nümerik analizlerde özellikle kazık, suya doygun zemin ve boşluk suyu basıncı etkileşimi üzerine odaklanmıştır. Analiz sonuçları, tekrarlı yatay yük etkisindeki serbest ve rijit başlı kazıkların deplasmanlarının tahmininde, suya doygun zeminde aşırı boşluk suyu basıncı gelişimini dikkate almayan mevcut modellerin yetersiz kaldığı göstermiştir.

Keywords

• Tekil kazık,açık deniz,tekrarlı yatay yükleme,sonlu elemanlar yöntemi,serbest başlı tekil kazık,rijit başlı tekil kazık,kumlu zemin,kalıcı deformasyon,aşırı boşluk suyu basıncı

Behaviour of Free and Fixed-Head Offshore Piles Under Cyclic Lateral Loads

Abstract

Offshore piles are subjected to cyclic lateral loads due to environmental loads, such as wind and waves. These loads can lead to an accumulation of permanent soil deformations and excess pore water pressures in saturated soils. Finite element analyses are performed to investigate the behaviour of cyclic laterally loaded free-head and fixed piles embedded in sandy saturated soil while considering such accumulation effects. A three-dimensional fully coupled two-phase finite element is developed and implemented on the basis of a two-phase model to consider the pore water pressure development in saturated soil. In addition, a hypoplastic constitutive model is used to describe the material behaviour of sandy soil under cyclic loading. In the numerical analyses, special attention is dedicated to interactions between the pile, the saturated soil and the pore water. The results have shown that the pile displacements caused by cyclic lateral loads are significantly underestimated for both pile head conditions by approaches which do not take into account the impact of the pore water pressure development in saturated sandy soil of the pile response.

Keywords

• Offshore piles,cyclic lateral loading,finite element method,fixed-head pile,free-head pile,sandy soil,accumulation,permanent displacement,pore water pressure,two-phase model

References

1. Achmus, M., Kuo, Y.-S. and Abdel-Rahman, K. (2009) Behavior of monopile foundations under cyclic lateral load, Computers and Geotechnics, 36, 725–735. DOI: doi.org/10.1016/j.compgeo.2008.12.003
2. API (2014) American Petroleum Institute, Recommended Practice 2A-WSD Planning, Designing, and Constructing Fixed Offshore Platforms - Working Stress Design.
3. Ashour, M. and Norris, G. (2000) Modeling lateral soil-pile response based on soil-pile interaction, Journal of Geotechnical and Geoenvironmental Engineering, 126(5), 420–428. DOI: dx.doi.org/10.1061/(ASCE)1090-0241(2000)126:5(420)
4. Bathe, K.-J. (1996) Finite element procedures, New Jersey: Prentice Hall.
5. Bauer, E. (1996) Calibration of a comprehensive hypoplastic model for granular materials, Soils and Foundations, 36(1), 13–26, 1996. DOI: doi.org/10.3208/sandf.36.13
6. Byrne, B.W., McAdam, R., Burd, H.J., Houlsby, G.T., Martin, C.M., Zdravković, L., Taborda, D.M.G., Potts, D.M., Jardine, R.J., Sideri, M., Schroeder, F.C., Gavin, K., Doherty, P., Igoe, D., Muir Wood, A., Kallehave, D. and Skov Gretlund, J. (2015) New design methods for large diameter piles under lateral loading for offshore wind applications, Proceedings of the Third International Symposium of Frontiers in Offshore Geotechnics (ISFOG2015), Norway.
7. Carswell, W., Fontana, C., Arwade, S.R., DeGroot, D.J. and Myers, A.T. (2015) Comparison of cyclic p-y methods for offshore wind turbine monopiles subjected to extreme storm loading, Proceedings of the ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2015), Volume 9: Ocean Renewable Energy, Canada. DOI: 10.1115/OMAE2015-41312
8. Cox, W.R., Reese, L.C. and Grubbs, B.R. (1974) Field testing of laterally loaded piles in sand, Proceedings of the Sixth Offshore Technology Conference, OTC 2079, Houston, 459–472. DOI: doi.org/10.4043/2079-MS

9. Cuéllar, P. (2011) Pile Foundations for Offshore Wind Turbines: Numerical and Experimental Investigations on the Behaviour under Short-Term and Long-Term Cyclic Loading, Doctoral Thesis, TU Berlin. DOI: dx.doi.org/10.14279/depositonce-2760
10. Cuéllar, P., Mira, P., Pastor, M., Merodo, J.A.F.M., Baeßler, M. and Rücker, W. (2014) A numerical model for the transient analysis of offshore foundations under cyclic loading, Computers and Geotechnics, 59(6), 75–86. DOI:10.1016/j.compgeo.2014.02.005
11. DNV (2014) Det Norske Veritas, Offshore Standard DNV–OS–J101, Design for Offshore Wind Turbine Structures.
12. Dührkop, J. (2009) Zum Einfluss von Aufweitungen und zyklischen Lasten auf das Verformungsverhalten lateral beanspruchter Pfähle in Sand, Veröffentlichungen des Institutes für Geotechnik und Baubetrieb der Technischen Universität Hamburg-Harburg, Heft 20.
13. Heidari, M., El Naggar, H., Jahanandish, M. and Ghahramani, A. (2014) Generalized cyclic p y curve modeling for analysis of laterally loaded pile, Soil Dynamics and Earthquake Engineering, 63, 138–49. DOI: 10.1016/j.soildyn.2014.04.001
14. Herle, I. (1997) Hypoplastizität und Granulometrie einfacher Korngerüste, Veröffentlichung des Institutes für Bodenmechanik und Felsmechanik der Universität Fridericana in Karlsruhe, Heft 142.
15. Jamiolkowski, M. and Garassino, A. (1977), Soil modulus for laterally loaded piles, Proceedings of the 9th International Conference of Soil Mechanics and Foundation Engineering, Tokyo, 43–58.
16. Kolymbas, D. (1988) Eine konstitutive Theorie für Böden und andere körnige Stoffe, Veröffentlichung des Institutes für Bodenmechanik und Felsmechanik der Universität Fridericana in Karlsruhe, Heft 109.
17. Martin, G.R., Lam, I. and Tsai, C.-F. (1980) Pore-pressure dissipation during offshore cyclic loading, Journal of the Geotechnical Engineering Division, 106(9), 981–996.
18. Masud, A. and Hughes, T.J.R (2002) A stabilized mixed finite element method for Darcy flow, Computer Methods in Applied Mechanics and Engineering, 191, 4341–4370. DOI: doi.org/10.1016/S0045-7825(02)00371-7
19. Niemunis, A. and Herle, I. (1997) Hypoplastic model for cohesionless soils with elastic strain range, Mechanics of Cohesion-Fractional Materials, 2(4), 279–299. DOI: 10.1002/(SICI)1099-1484(199710)2:4<279::AID-CFM29>3.0.CO;2-8
20. Pastor, M., Li, T. and Merodo, J.A.F. (1997) Stabilized finite elements for harmonic soil dynamics problems near the undrained-incompressible limit, Soil Dynamics and Earthquake Engineering, 16, 161–171. DOI: doi.org/10.1016/S0267-7261(97)00046-8
21. Potts, D.M. and Zdravković, L. (1999) Finite element analysis in geotechnical engineering - theory. London: Thomas Telford.
22. Rackwitz, F., Savidis, S. and Taşan, H.E. (2012) New design approach for large diameter offshore monopiles based on physical and numerical modelling, In: Hryciw, R.D., Athanasopoulos-Zekkos, A. and Yesiller, N. (eds.): Geotechnical Special Publication GSP No. 225 Geo-Congress 2012, State of the Art and Practice in Geotechnical Engineering, Proc. GeoCongress 2012, March 25-29, Oakland, CA, ASCE, 356–365. ISBN: 978-0-7844-1212-1
23. Reese, L.C., Cox, W.R. and Koop, F.D. (1974) Analysis of Laterally Loaded Piles in Sand, Proceedings of the Sixth Offshore Technology Conference, OTC 2080, Houston, 2, 473–483. DOI: doi.org/10.4043/2080-MS.
24. Rondón, H.A., Wichtmann, T., Triantafyllidis, Th. and Lizcano, A. (2007) Hypoplastic material constants for a well-graded granular material (UGM) for base and subbase layers of flexible pavements, Acta Geotechnica, 1(2), 113–126. DOI: 10.1007/s11440-007-0030-3
25. Tașan, H.E., Rackwitz, F. and Savidis, S. (2010) Behaviour of cyclic laterally loaded large diameter monopiles in saturated sand, Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE, Trondheim, Norway, 889–894.
26. Tașan, H.E. (2012) Prognose der Verschiebungen von zyklisch lateral belasteten Monopiles in geschichteten Böden, Bauingenieur, 87(6), 297–305.
27. Von Wolffersdorff, P.-A. (1996) A hypoplastic relation for granular materials with a predefined limit state surface, Mechanics of Cohesive-Frictional Materials, 1(3), 251–271. DOI: 10.1002/(SICI)1099-1484(199607)1:3<251::AID-CFM13>3.0.CO;2-3
28. Zienkiewicz, O.C., Chang, C.T. and Bettes, P. (1980) Drained, undrained, consolidating dynamic behaviour assumptions in soils. Géotechnique, 30(4), 385–395. DOI: 10.1680/geot.1980.30.4.385
29. Zienkiewicz, O.C. and Shiomi, T. (1984) Dynamic behaviour of saturated porous media; the generalized Biot formulation and its numerical solution, International Journal of Numerical Analytical Methods in Geomechanics, 8(1), 71–96. DOI: 10.1002/nag.1610080106
30. Zienkiewicz, O.C. (1986) The patch test for mixed formulations, International Journal for Numerical Methods in Engineering, 23(10), 1873–1883. DOI: 10.1002/nme.1620231007