Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Assessment of p-y Behaviors of a Cyclic Laterally Loaded Pile in Saturated Dense Silty Sand

조밀한 포화 실트질 모래지반에서 횡방향 반복하중을 받는 말뚝의 p-y 거동 평가

  • Baek, Sung-Ha (Korea Institute of Civil Engr. and Building Tech.) ;
  • Choi, Changho (Korea Institute of Civil Engr. and Building Tech.) ;
  • Cho, Jinwoo (Korea Institute of Civil Engr. and Building Tech.) ;
  • Chung, Choong-Ki (Dept. of Civil & Environmental Engrg., Seoul National Univ.)
  • 백성하 (한국건설기술연구원 미래융합연구본부) ;
  • 최창호 (한국건설기술연구원 미래융합연구본부) ;
  • 조진우 (한국건설기술연구원 미래융합연구본부) ;
  • 정충기 (서울대학교 건설환경공학부)
  • Received : 2019.10.30
  • Accepted : 2019.11.13
  • Published : 2019.11.30
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Abstract

Piles that support offshore wind turbine structures are dominantly subjected to cyclic lateral loads of wind, waves, and tidal forces. For a successful design, it is imperative to investigate the behavior of the cyclic laterally loaded piles; the p-y curve method, in which the pile and soil are characterized as an elastic beam and nonlinear springs, respectively, has been typically utilized. In this study, model pile tests were performed in a 1 g gravitational field so as to investigate the p-y behaviors of cyclic laterally loaded piles installed in saturated dense silty sand. Test results showed that cyclic lateral loads gradually reduced the overall stiffness of the p-y curves (initial stiffness and ultimate soil reaction). This is because the cyclic lateral loads disturbed the surrounding soil, which led to the decrement of the soil resistance. The decrement effects of the overall stiffness of the p-y curves became more apparent as the magnitude of cyclic lateral load increased and approached the soil surface. From the test results, the cyclic p-y curve was developed using a p-y backbone curve method. Pseudo-static analysis was also performed with the developed cyclic p-y curve, confirming that it was able to properly predict the behaviors of cyclic laterally loaded pile installed in saturated dense silty sand.

해상풍력 구조물을 지지하는 말뚝기초는 바람, 파랑, 조류 등에 의한 횡방향 반복하중을 지배적으로 받는다. 해상풍력 구조물의 안정적인 성능확보를 위해서 횡방향 반복하중을 받는 말뚝기초의 지지거동을 적절히 평가해 설계에 적용할 필요가 있으며, 말뚝 및 지반을 각각 탄성빔과 비선형 스프링으로 가정하는 p-y 곡선방법이 가장 널리 활용되고 있다. 본 연구에서는 조밀한 포화 실트질 모래지반에 설치되어 횡방향 반복하중을 받는 말뚝기초의 p-y 거동을 평가하기 위해서, 1g 모형말뚝시험을 수행했다. 모형시험 결과, 말뚝에 횡방향 반복하중 재하 시 p-y 곡선의 강성(초기기울기 및 최대지반반력)이 점차 감소했다. p-y 곡선의 강성감소는 반복하중의 크기가 크고 지표면에 가까운 위치에서 더 명확하게 나타났는데, 상기조건에서 말뚝 주변지반의 교란효과가 크게 발생해 지반의 지지능력이 더욱 크게 감소했기 때문이다. 모형시험 결과를 활용해 조밀한 포화 실트질 모래지반에 설치되어 횡방향 반복하중을 받는 말뚝기초의 p-y 곡선을 제안했다. 등가정적해석을 통해 예측된 말뚝거동을 모형시험결과와 비교한 결과, 제안된 식을 통해 비교적 조밀하고 포화된 실트질 모래지반에서 반복하중을 받는 말뚝의 횡방향 지지거동을 적절히 평가할 수 있음을 확인했다.

Keywords

References

  1. Ameircan Petroleum Institute (2007), Recommended practice for planning, designing and constructing fixed offshore platformsworking stress design: API recommended practice 2A-WSD (RP 2A-WSD), API.
  2. Baek, S. H., J. Y. Kim, S. H. Lee, and C. K. Chung (2015), "Effect of Cyclic Lateral Loads on p-y Curve for Pile Foundations in Saturated Sand", Proceeding of 25th International Ocean and Polar Engineering Conference, Big Island, Hawaii, pp.983-988.
  3. Baek, S.H., Kim, J.Y., Lee, S.H., and Chung, C.K. (2018), "Development of the Cyclic p-y Curve for a Single Pile in Sandy Soil", Marine Georesources & Geotechnology, Vol.36, No.3, pp.351-359. https://doi.org/10.1080/1064119X.2017.1318986
  4. Barton, Y.O. (1979), Lateral Loading of Model Piles in the Centrifuge, M.Phil. Thesis, University of Cambridge.
  5. Choi, J.I., Yoo, M.T., Yang, E.K., Han, J.T., and Kim, M.M. (2015), "Evaluation of 1-G Similitude Law in Predicting Behavior of a Pile-Soil Model", Marine Georesources & Geotechnology, Vol.33, pp.202-211. https://doi.org/10.1080/1064119X.2013.830165
  6. Choo, Y.W. and Kim, D. (2016), "Experimental Development of the p-y Relationship for Large-Diameter Offshore Monopiles in Sands: Centrifuge Tests", Journal of Geotechnical and Geoenvironmental Engineering, Vol.142, No.1, p.04015058. https://doi.org/10.1061/(asce)gt.1943-5606.0001373
  7. Davidson, H.L., Cass, P.G., Khilji, K.H., and McQuade, P.V. (1982), Laterally loaded drilled pier research, Report EL-2197, EPRI, p. 324.
  8. Dou, H. and Byrne, P.M. (1996), "Dynamic Response of Single Piles and Soil Pile Interaction", Can. Geotech. J., Vol.33, pp.80-96. https://doi.org/10.1139/t96-025
  9. Fleming, W.G., Weltman, A.J., Randolph, M.F., and Elson, W.K. (1992), Piling Engineering, 2nd ed., John Wiley and Sons Inc., New York.
  10. Han, J.T., Yoo, M.T., Yang, E.K., and Kim, M.M. (2010), "Evaluation of Particle Size Effect on Dynamic Behavior of Soil-pile System", J. of the Korean Geotechnical Society, Vol.26, No.7, pp.49-58 (in Korean).
  11. Heyenyi, M. (1946), Beams on elastic foundation, Ann Arbor, MI: University of Michigan Press.
  12. Iai, S. (1989), "Similitude for Shaking Table Tests on Soil-structure-Fluid Model in 1g Gravitational Field", Soil and Foundations, Vol.29, No.1, pp.105-118. https://doi.org/10.3208/sandf1972.29.105
  13. Kim, B.T., N.K. Kim, W.J. Lee, and Y.S. Kim. (2004), "Experimental Loadtransfer Curves of Laterally Loaded Piles in Nak-Ding River Sand", J. of Geotechnical and Geoenvironmental Engineering, Vol.130, No.4, pp.416-425. https://doi.org/10.1061/(ASCE)1090-0241(2004)130:4(416)
  14. KEPRI (2016), Test Bed for 2.5GW Off-shore Wind Farms at Yellow Sea, Design Basis Final Report (in Korean).
  15. Kondner, R. L. (1963), "Hyperbolic Stress-strain Response: Cohesive Soils", Journal of Soil Mechanics and Foundation Division, Vol. 87, No.1, pp.115-144. https://doi.org/10.1061/JSFEAQ.0000479
  16. Kim, T.S., Jeong, S.S., and Kim, Y.H. (2008), "A Study on the p-y Curves by Small-Scale Model Tests", Journal of the Koran Society of Civil Engineers, Vol.28, No.1, pp.41-51 (in Korean).
  17. Lambe, T.W. and Whitman, R.V. (1979), Soil Mechanics, John Wiley & Sons, New York.
  18. Lee, M.J., Yoo, M.T., Park, J., and Min, K. (2019), "Evaluation of Lateral Pile behavior under Cyclic Loading by Centrifuge Tests", J. of the Korean Geotechnical Society, Vol.35, No.6, pp.39-48 (in Korean). https://doi.org/10.7843/KGS.2019.35.6.39
  19. Meyerhof, G.G., Mathur, S.K., and Valsangkar, A.J. (1981), "Lateral Resistance and Deflection of Rigid Wall and Piles in Layered Soils", Canadian Geotechnical Journal, Vol.18, pp.159-170. https://doi.org/10.1139/t81-021
  20. Nunez, I.L. (1988), "Driving and Tension Loading of Piles in Sand on a Centrifuge", Proceeding International Conference Centrifuge 88, Paris, Corte, J.K. (ed.), Balkema, Rotterdam, pp.353-362.
  21. O'Neill, M. W. and J. M. Murchison (1983), An evaluation of p-y relationships in sands, Report PRAC 82.41-1 to American Petroleum Institute, University of Houston, Houston.
  22. Palmer, L.A. and J.B. Thomson (1948), "The Earth Pressure and Deflection along the Embedded Lengths of Piles Subjected to Lateral Thrust", Proceeding of the International Conference on Soil Mechanics and Foundation Engineering, Rotterdam, pp.156-161.
  23. Rao, S.N., Ramakrishna, V.G.S.T., and Rao, M.B. (1998), "Influence of Rigidity on Laterally Loaded Pile Groups in Marine Clay", Journal of Geotechnical and Geoenvironmental Engineering, Vol. 124, No.6, pp.542-549. https://doi.org/10.1061/(ASCE)1090-0241(1998)124:6(542)
  24. Scott, R.F. (1980), Analysis of centrifuge pile tests; simulation of pile driving. Report for the American Petroleum Institute OSAPR Project 13, California Institute of Technology, Pasadena, California.
  25. Ting, J. M., C. R. Kauffman, and M. Lovicsek (1987), "Centrifuge Static and Dynamic Lateral Pile behavior", Canadian Geotechnical Journal, Vol.24, pp.198-207. https://doi.org/10.1139/t87-025
  26. Yang, E. K. (2009), Evaluation of dynamic p-y curves for a pile in sand from 1 g shaking table tests, Ph.D. Thesis, Department of Civil and Environmental Engineering, Seoul National University.